Subwoofer with bass reflex - calculation, setup and typical mistakes

In car audio, there are many options for acoustic design of boxes. Therefore, many beginners do not know what is the best choice. The most popular types of subwoofer boxes are a closed box and a bass reflex box.

There are also designs such as bandpass, quarter-wave resonator, freeair and others, but when building systems they are used extremely rarely for various reasons. The speaker owner must decide which subwoofer box to choose based on sound requirements and experience.

We advise you to pay attention to the article on what material is best to make a subwoofer box from. We have clearly demonstrated how the rigidity of the box affects the quality and volume of the bass.

How does a subwoofer box affect the sound?

In car audio, there are many options for acoustic design of boxes.
Therefore, many beginners do not know what is the best choice. The most popular types of subwoofer boxes are a closed box and a bass reflex box. There are also designs such as bandpass, quarter-wave resonator, freeair and others, but when building systems they are used extremely rarely for various reasons. The speaker owner must decide which subwoofer box to choose based on sound requirements and experience.

We advise you to pay attention to the article on what material is best to make a subwoofer box from. We have clearly demonstrated how the rigidity of the box affects the quality and volume of the bass.

What material to use to make a subwoofer box

How to assemble a box for a subwoofer? And most importantly, what? You need to clearly understand one simple thing, the pressure created inside the case when the speaker is operating is similar to water that penetrates into any crack. The point here is that we need to prevent water from seeping in, but instead of water we have air.

First of all, you need to figure out what material the box will be made from. Only one material is ready to suit us and, of course, this is wood. The best option is plywood. Easily processed, not subject to external influences in comparison with chipboard.

Namely, swelling when exposed to large amounts of water. Of course, no one is going to pour water on the box, but this is an advantage. The most important thing is that plywood is physically stronger than particle board.

Chipboard:

Plywood:

The next option is chipboard. Plywood is sheets glued together, and chipboard is chips that are converted into a slab under a press. The fact is that such a slab is chosen because of its availability.

Firstly, it is cheap, secondly, almost all the furniture is made from it, besides, you can simply disassemble the unnecessary cabinet and use the sheets. This is an ideal option for budget systems.

In terms of sound properties, chipboard is better than plywood, but as soon as more powerful systems come into play, plywood comes out on top.

Unfortunately, the particle board bends at high power. Sometimes it breaks and crumbles the joints of the bolts that secure the basket.

The approximate power of the speakers used in chipboard boxes is eight hundred to nine hundred nominal watts. Roughly speaking, up to a kilowatt maximum.

No one can guarantee that even with such power everything will work at the proper level, so if you have plywood, it’s better to use it.

Common parameters:

The thickness of the walls is at least one and a half to two centimeters. The front part on which the speaker is located should be made double. If the box is large, and when turned on, one of the walls begins to vibrate, then spacers should be placed inside. Typically the vibration will be where the wall is not supported. Be sure to seal all joints, near the pipe (if the port is a pipe) the same.

How to fasten the walls:

Needs to be secured with screws. Before doing this, we drill a hole with a thin drill so that the screw tightens evenly. If desired, you can recess the hat.

To achieve the strength of the box, we fasten two walls: the front (front) and the back as follows as shown in the figure:

The front side consists of two walls fastened together. This is done to increase durability. If the speaker is low-power, it is permissible not to make the front side of two walls; you can get by with just one.

That's all! Happy self-building!

Closed box

This type of design is the simplest. A closed box for a subwoofer is easy to calculate and assemble. Its design is a box of several walls, most often 6.

Advantages of ZY:

1. Simple calculation;
2. Easy assembly;
3. Small displacement of the finished box, and therefore compact;
4. Good impulsive characteristics;
5. Fast and clear bass. Plays club tracks well.

A closed box has only one drawback, but sometimes it is decisive. This type of design has a very low level of efficiency compared to other boxes. A closed box is not suitable for those who want high sound pressure.

However, it is suitable for fans of rock, club music, jazz and the like. If a person wants bass, but needs space in the trunk, then a closed box is an ideal option. A closed box will not play well if the wrong volume is selected. What volume of box is needed for this type of design was long ago decided by experienced people in car audio through calculations and experiments. The choice of volume will depend on the size of the subwoofer speaker.

The most common speaker sizes are: 6, 8, 10, 12, 15, 18 inches. But you can also find speakers of other sizes; as a rule, they are used very rarely in installations. Subwoofers with a diameter of 6 inches are produced by several companies and are also rarely found in installations. Mostly people choose speakers with a diameter of 8-18 inches. Some people indicate the diameter of the subwoofer speaker in centimeters, which is not entirely correct. In professional car audio, it is customary to express dimensions in inches.

Recommended volume for a closed box subwoofer:

• an 8-inch subwoofer (20 cm) requires 8-12 liters of net volume,
• for 10-inch (25 cm) 13-23 liters of net volume,
• for 12-inch (30 cm) 24-37 liters of net volume,
• for 15-inch (38 cm) 38-57 liters net volume
• and for 18 inches (46 cm) you will need 58-80 liters.

The volume is given approximately, since for each speaker you need to select a certain volume based on its characteristics. The setting of a closed box will depend on its volume. The larger the volume of the box, the lower the tuning frequency of the box will be, the bass will be softer. The smaller the volume of the box, the higher the frequency of the box, and the bass will be clearer and faster. You should not increase or decrease the volume too much, as this is fraught with consequences. When calculating the box, adhere to the volume that was indicated above. If there is too much volume, the bass will turn out vague and indistinct. If the volume is not enough, then the bass will be very fast and “pound” the ears in the worst sense of the word.

A lot depends on how the box is configured, but an equally important point is “Setting up the radio.”

How to make a subwoofer box with your own hands

The source of powerful low-frequency sound in sound systems is the subwoofer. This also applies to car acoustics, which is why most car enthusiasts equip their cars with such devices.

You can purchase a ready-made unit, but many people prefer to buy speakers and make a box for the subwoofer with their own hands. This is not as difficult a job as it might seem, but it will require tools and certain skills.

How to make a subwoofer box correctly

Before you start making a subwoofer box, you need to choose a loudspeaker. The volume of the future structure will depend on its parameters. Most often, specialized imported loudspeakers with a diameter of 10-12 inches are used to reproduce powerful bass. Structurally, the subwoofer box can be made in three options:

• Closed box
• Bass reflex
• Bandpass

The quality of the loudspeaker and the design of the box ultimately determine the sound quality of the low-frequency sound system.

How to make a housing for a subwoofer

The easiest to make is a buried box or box. This is a completely closed structure, the manufacture of which will require a minimum of simple wooden parts. How to make a housing for a sub becomes clear when you see such a device.

Essentially, this is a rectangular box with a hole cut out in the front wall for a dynamic head. The box consists of six walls, which are easy to cut out of the appropriate material. A terminal block is mounted on the side or rear wall to connect wires from the amplifier.

The closed box (CB) is distinguished by dense and not vague bass, smooth amplitude-frequency response, but has the lowest efficiency among all designs.

The box can be in the shape of a parallelepiped or trapezoid with beveled walls. Due to its characteristics, the closed design is suitable for many musical styles.

The sealed, closed design conveys bass well in pop and rock music, classical, jazz and instrumental works.

But fans of rap and dubstep will be disappointed, as the closed box is not suitable for playing music that has a lot of heavy bass and where the low frequencies are the basis of the music.

How to properly assemble a subwoofer enclosure

It is not difficult to make a housing for a subwoofer with your own hands if you strictly follow all the recommendations. The most important thing that a closed case requires is tightness and lack of vibration. The optimal material for a low-frequency speaker is multilayer plywood or MDF. The thickness of the material must be at least 18-20 mm.

Thin walls will resonate and these vibration waves entering the car interior will greatly degrade the quality of low frequency reproduction. The most important parameter of any subwoofer is its volume. This parameter takes into account the internal space of the box without the volume occupied by the speaker.

The relationship between the volume of the housing and the diameter of the loudspeaker is as follows:

• 10 inches (25 cm) – 15-20 liters
• 12 inches (30 cm) – 25-35 liters
• 15 inches (35 cm) – 40-60 liters
• 18 inches (46 cm) – 70-110 liters

In order to increase efficiency and improve sound quality, all seams between wooden walls must be sealed. It is best to use silicone sealant for this purpose. A closed box for a subwoofer, made with your own hands, has its undoubted advantages:

• Easy to calculate volume
• Ease of production
• Small sizes
• Distinct and clean bass

There are only two main disadvantages: low efficiency, not suitable for listening to “heavy” bass. The internal volume of a closed subwoofer can be filled with padding polyester or cotton wool. If the volume is calculated correctly, then this is not necessary.

It is recommended to listen to the work of the subwoofer, both with and without filler, and choose the best option.

At different air temperatures, the pressure inside a closed volume changes and to equalize it, a small hole of no more than 1.5-2.0 mm is sometimes left in the subwoofer housing.

Making a box for a subwoofer with your own hands

Making a do-it-yourself subwoofer housing is simple and takes a minimum of time. After the speaker has been selected and the internal volume of the closed box has been calculated, you need to prepare the material, fasteners and tools. With your own hands, the subwoofer body is usually made from the following materials:

Moisture-resistant multilayer plywood is considered the best material for making a subwoofer box. There are some difficulties with this. Plywood is the most expensive material and it is difficult to find plywood with a thickness of 18 mm or more.

If the volume of the subwoofer is too large, then the plywood walls will emit a “ringing”, which can be eliminated by installing internal stiffeners. A good choice would be to use MDF. It is cheaper than plywood, easy to process and has good moisture resistance. Chipboard has become widespread.

It can be found at any furniture company. There the slab will be cut to the specified dimensions. The disadvantages of chipboard structures include very low rigidity, when strong low-frequency vibration at the fastening points causes the material to collapse.

In addition, it absorbs moisture well and if water gets into the trunk of a car, the box may simply crumble. This material can be used to make a housing for a home subwoofer. It will not be used in extreme conditions and will last a long time.

The right subwoofer box

The correct body means a more complex, but also higher quality design. This could be a body with a bass reflex or an even more complex system called a bandpass. Assembling a subwoofer enclosure with your own hands will take more time, but the result is worth it. The bass reflex can be slotted or in the form of a pipe. This design is a small “tunnel”. It rotates or inverts the phase of the signal with its further radiation into space, as a result of which the efficiency of the subwoofer doubles. A bass-reflex subwoofer is distinguished by strong and rich bass, and on its amplitude-frequency characteristic, at the tuning point, there is a large protrusion and At this frequency the volume increases. The tuning peak is regulated by changing the size of the port and the ratio of the working volume of the subwoofer to the size of the bass reflex. This subwoofer design is well suited for playing music with fast and powerful lows. How to assemble a subwoofer box largely depends on its design.

Making a housing for a subwoofer with a bass reflex

As with making a closed box, work on a more complex design begins with choosing a loudspeaker. How to make a box for a subwoofer depends on the type of material and fasteners. Multi-layer plywood is the strongest recommended material.

To assemble the subwoofer housing with your own hands, you can use any self-tapping screws. When connecting elements from MDF, and especially from chipboard, you need to use only white self-tapping screws. Black ones do not provide such a strong connection. Sometimes the caps break off when screwed in.

The bass reflex subwoofer must be well sealed. To do this, a layer of sealant is applied to all seams on the inside. The cutting lines must be very even, so it is better to do the work on a special machine, if possible.

When making a slotted bass reflex, you need to ensure that all internal partitions do not have through holes. If the dimensions of the speaker and the box are large, then stagnant zones may appear in the turns of the slot port.

To avoid this, all right angles of the bass reflex are smoothed out by installing additional wooden plates. Do-it-yourself subwoofer box assembly is completed by installing external contacts for connecting the amplifier.

These places must also be sealed.

Small subwoofer box

Some motorists do not strive for powerful bass, but want to slightly improve the sound picture in the cabin. A small subwoofer is suitable for this. 8" speakers are suitable for this design. Some companies make 6-inch speakers, but they are hard to find. How to make a subwoofer box correctly. A subwoofer for a small loudspeaker has a small displacement, therefore, it will take up little space in the luggage compartment of the car. There is no need to reduce the size of the structure too much, but you also shouldn’t increase it. Increasing the size of the box will lead to the fact that low frequencies will “spread” and the bass will be unclear. If the volume is less than what is needed for a speaker of a certain diameter, then the lows will be too fast and will literally hit the eardrums.

How to make a housing for a subwoofer with your own hands

If you need to make a good box for a subwoofer, then it is best to focus on the most complex design. This system is called a bandpass. It comes in fourth order and sixth order. The fourth-order system is a two-chamber box, where one chamber is a closed box, and the other plays the role of a bass reflex.

A sixth-order bandpass is a design with two bass reflexes. The most difficult thing here is the calculation of the second port and the relative relationship of the settings of each bass reflex. The two chambers have different sizes and are capable of limiting the frequencies reproduced by the loudspeaker.

The box for two subwoofers is the most difficult to design, but it has the maximum efficiency. To determine all sizes of such sound systems, special utilities are used. The universal WinISD program is suitable for calculating any subwoofer design. It does not have a Russian-language interface, but it is not difficult to understand.

To make a drawing of a box for a subwoofer, just load the parameters of the speaker you are using into your computer.

Subwoofer housing drawings

If you don’t have the time and desire to calculate the subwoofer box yourself, you can take ready-made calculations and drawings. If you need to make the bass very deep and powerful, you can make a subwoofer box for two speakers. In this case, the design can be in the form of a closed box or bass reflex.

Both speakers must be of the same type and with the same resonance frequency, otherwise it will be difficult to adjust the bass reflex. If you have no experience working with car acoustics, then it is better to make your first subwoofer using a closed box design. A bass reflex subwoofer with one loudspeaker is also easy to make with your own hands.

You should not, without experience, take on a system such as a bandpass. In any case, the result will not be satisfactory.



Bass reflex

This type of design is quite more difficult to calculate and build. Its design is significantly different from a closed box. However, it has advantages, namely:

1. High level of efficiency. A bass reflex will produce low frequencies much louder than a closed box;
2. Simple calculation of the body;
3. Reconfiguration if necessary. This is especially important for beginners;
4. Good speaker cooling.

The bass reflex also has disadvantages, the number of which is greater than that of the ZYa. So, the cons:

• FI is louder than ZY, but the bass here is not so clear and fast;
• The dimensions of the FI box are much larger compared to the ZY;
• Large displacement. Because of this, the finished box will take up more space in the trunk.

Based on the advantages and disadvantages, you can understand where FI boxes are used. Most often they are used in installations where loud and pronounced bass is needed. The bass reflex is suitable for listeners of any rap, electronic and club music. It is also suitable for those who do not need free space in the trunk, since the box will occupy almost all the space.

The FI box will help you get more bass than from a small-diameter speaker. However, this will require much more space.

What volume of box is required for a bass reflex?

• for a subwoofer with a diameter of 8 inches (20 cm) you will need 20-33 liters of net volume;
• for a 10-inch speaker (25 cm) – 34-46 liters,
• for 12-inch (30 cm) – 47-78 liters,
• for 15-inch (38 cm) – 79-120 liters
• and for an 18-inch subwoofer (46 cm) you need 120-170 liters.

As with ZY, the numbers given here are imprecise. However, in a FI case you can “play” with the volume and take a value less than recommended, finding out at what volume the subwoofer plays better. But do not increase or decrease the volume too much, this can lead to loss of power and failure of the speaker. It is best to rely on the recommendations of the subwoofer manufacturer.

What does the FI box setting depend on?

The larger the volume of the box, the lower the tuning frequency, the bass speed decreases. If a higher frequency is needed, then the volume must be reduced. If your amplifier's rated power exceeds the speaker's rating, then it is recommended to make the volume smaller. This is necessary in order to distribute the load on the speaker and prevent it from exceeding the stroke. If the amplifier is weaker than the speaker, then we recommend making the volume of the box a little larger. This compensates for the volume due to the lack of power.

Setting the speaker size

Enter your receiver's settings menu and find the speaker setting. There should be a setting for the size of your front left and right speakers. Actually less has to do with the physical size of your speakers. It's more about bass management.

Set your speakers to "small" even if you are using floorstanding speakers. Because the setting for a “small” speaker will send low frequencies to the subwoofer. This is useful for three reasons:

1. This relieves the front speakers so they are focused on the mids and highs.

2. This will allow your receiver to allocate more power to the mid and high frequencies.

3. It can prevent low frequencies from damaging the speakers.

Crossover Settings

Once you set your speakers to "small", you may not need to fine-tune the crossover. But if you want to tune it more precisely, you can set the crossover cutoff, measured in Hertz. All signals below the cutoff point will be sent to the subwoofer. For bookshelf speakers, you will need a higher crossover frequency - around 120 Hz. For floorstanding speakers, use 60 Hz. Most receivers have default settings somewhere in the middle, usually around 80Hz.

Finishing your subwoofer placement

If you have several accommodation options, you are now ready to choose the perfect location. Play some music with good bass. Then sit in your main seat and listen. Weak bass? Or maybe too strong?

Go to a couple different places in the room and listen. You'll probably notice that the bass may sound completely different when you change its location.

If you used Auto Calibration to set up your home theater system, be sure to re-run it every time you move the subwoofer.

To tune the bass to the "ideal point", use a popular method known as "scanning". Start with the subwoofer by placing the subwoofer at or near your listening position. Then move it to different places that suit the placement and listen to your chosen section of music again, listening carefully to the bass. Once you find a place where the bass sounds right, that's where you should place your subwoofer.

Final Settings

Phase switch. If your subwoofer seems to be muted or not producing rich bass, the subwoofer may be working out of phase with your main speakers. Most powered subwoofers have a two-position phase switch on the rear panel. Switch it to a different position and listen to see if the bass has changed for the better.

Level control. Most powered subwoofers have independent volume controls. It's an easy way to get a little more "boom, boom, boom" or reduce the bass on a particularly loud soundtrack. You may have to make these adjustments from film to film.

Place the subwoofer on the platform. If your floors, walls, and ceiling vibrate to the beat of your sub, you'll get unwanted resonances that will color your sub's bass. To stop vibrations, place your subwoofer on a sound-absorbing platform.

What if my AV receiver does not have a subwoofer output, or my subwoofer does not have an LFE input?

Don't worry - you can still connect your subwoofer using one of the following two options:

Wiring diagram for pre-out/main input.

Or you can use speaker cables to connect to the speaker inputs of your subwoofer:

Not enough bass? Try two subwoofers.

If you have a very large room and need a lot of bass, we recommend adding a second subwoofer. This is the best option for evenly distributing bass in a large space. Most new AV receivers have two subwoofer outputs. Or you can just use a Y adapter.

Bass reflex tuning frequency

Introduction

When calculating the port, you need to choose your preferred music genre. If you are rock fans, then a low port setting will not suit you, and vice versa, when listening to blacks, a high port setting will not suit you.

For beginners, it is better to choose something universal and preferably on a pipe, since the slot box cannot be simply remade to change the setting.

Music genres:

• Low setting
  - frequency 25 - 29 Hz. For fans of flex, the car shakes, the windshield blows up and the most important thing is the wind, a lot of wind. The bass with this setting is deep and soft, which does not hurt the ears. — With this setting, the subwoofer will not play strawberry, electro, rock and pop music. — Not all subwoofers are capable of reproducing such frequencies normally.
• Everyday setting
  is frequency 30 - 35 Hz. The most common and popular port setting. For fans of blacks and dub step, where there is body flex. The bass with this setting is more pressing to the ear.
• Musical setting
  - frequency 36 - 40 (42) Hz.
  Universal setting or, more correctly, BALANCE
  between all genres. The bass with this setting is more pronounced, fast but hard. Flex, accordingly, is minimal. — Short-throw subwoofers are more suitable. — Option aside sound quality.
• Sport setting
  - frequency above 45 - 55 Hz.
  This setting is used for sound pressure measurements at competitions. People call such a box a COMBAT box
  . The bass with this setting is very hard and it is impossible to listen to music. — We do not recommend using this setting for everyday listening.

How to determine the bass reflex tuning frequency?

1. The easiest way to check the bass reflex tuning frequency is using the Frequency Tone Generator. At the box tuning frequency, the speaker cone stroke is minimal. We start the tone generator, set the approximate frequency and, in 1 Hz steps, determine at what frequency the stroke is minimal.
2. The second method is no less simple, similar to the first. It is necessary to place the subwoofer with the diffuser up and pour cereal or something small and light onto it. We start the tone generator, set the approximate frequency and, in 1 Hz steps, determine at what frequency the material remained motionless, and at frequencies higher or lower it jumped noticeably. This frequency will be the bass reflex tuning frequency.

Recommendations

We advise you to choose the acoustic design of the box, specifically on the pipe, if you need precise tuning, or to get the desired result from measurements.

If you don’t like the port setting, you can simply change it to a longer one or cut off the pipe.

• The shorter the pipe, the higher the setting;
• The longer the pipe, the lower the setting.

Don’t forget, there is no exact port tuning frequency by calculation; plus or minus 2 Hz deviation is the norm.

Subwoofer with bass reflex - calculation, setup and typical mistakes

Excessively separated resonances of the FI and dynamics. Speaker resonance – 58 Hz, bass reflex – 27 Hz. Everything is understandable: at lower frequencies, the rear side of the speaker emits weaker, and the resonator swings weaker. The greater the frequency separation, the lower the peak of the FI resonance in relation to the overall frequency response (the one that is higher than the dyne resonance).

I draw your attention: the frequency response of the FI (resonance FI) seems to slide up and down along the descending inclined frequency response of the speaker, as if on a hill. This is the essence of choosing the FI resonance frequency in any subwoofer. When you change the length of the FI pipe (or its diameter), this is exactly how the frequency response of your subwoofer will change. Whatever resonance frequency of the FI you choose, that’s how it will play.

Example.

The Chinese (and not only them) sometimes put a cheap speaker with a high resonant frequency in the sub (I have seen Fs = 65 Hz). When installed in a housing, its resonance increases to 85 Hz. Of course, such a sub won't give you any bass. And then they put a FI in the sub, tuned to a frequency of, say, 30-35 Hz. What an advertisement: 30 hertz!

What happens? Below the resonant frequency, the speaker operates as if in a closed box, that is, below 80 Hz its sound pressure smoothly drops at a rate of 12 dB/octave, which means that at 40 hertz it will play 4 times quieter than at 80. What does a normal person do? That's right, it adds subwoofer volume.

And this is where the tricks begin. I'll tell you what it looks like.

A person turns on music music, an orchestra, for example, there are very few low-end sounds, and he adds them to the level he needs. That's it, the orchestra starts playing, the person is enjoying himself. And suddenly, at some unpredictable moment, one of the notes hits the resonance of the bass reflex. In reality, it looks like this: against the backdrop of smooth music, your ears suddenly become blocked, your floor and liver begin to tremble: FI’s pipe began to sing. At the same time, the sound is practically inaudible, only the trouser legs clap and the dishes rattle. After 1-2 seconds, the note ends, the tremors disappear, and the orchestra continues to play as if nothing had happened. Until the next note like this. You don’t listen to music, but sit and wait for it to Whoop again.

Guys, no jokes, I heard this with my own ears, and on branded acoustics. It’s just that, unlike normal people, I know what’s going on and why it’s like this. The above example is, of course, rare, but it is an example. Much more often, although less pronounced, this effect can be observed in mass-produced budget subwoofers. When the resonances of the speaker and the FI are too far apart, then the resonance of the FI will stick out out of the blue, like a penis in a clearing, in the form of a hum on one note. The resonance frequency of the FI should be no more than 33% lower than the resonance of the speaker in the same enclosure with a closed FI. This should be just a continuation of the damped frequency response of the speaker, BUT IN NO WAY DEFINING from it.

Why am I scribbling this?

At least explain to our “craftsmen” how it all works. This is what they do: they completely thoughtlessly lower the resonance frequency of the FI, lengthening its pipe, and thereby spreading the resonances even further. They also boast about their experience on the forums: do as I do and the lower classes will be trampled. They will trample, of course. On one note, albeit a very low one. It turns out that it’s like two separate subwoofers in one housing: an inferior ZYa, and a separate, separate 2-3 notes in the FI.

More advanced “audiophiles” use specialized programs to calculate new ones on their computers and recalculate ready-made subs with FI. But the computer is stupid, it will calculate whatever numbers you give it. There’s a catch here: in no program will a window pop up with the inscription “boy, I, of course, will calculate everything the way you want, but you’re doing something stupid, and the sound will be bad.” There are no such programs.

But what beautiful frequency response the computer draws! A sight for sore eyes. This reminds me of the 80s: on the face of any Soviet speaker there is a nameplate with a straight line.

All you need to do is bring the resonances of the speaker and FI closer together to the required level and equalize the volume. Either replace the crappy speaker with a good one with a lower resonance, or increase the resonance frequency of the FI by reducing the length or, better yet, increasing the diameter of the pipe. Yes, increasing the resonance frequency of the bass reflex increases the lower operating frequency of the subwoofer, but what do you want with a shitty speaker?

What should the bass reflex resonance frequency be?

The resonance frequency of the bass reflex (in general) should be 2/3 octave lower than the resonance frequency of the same speaker in the same box with the FI hole closed.

Example:

Fres. dynamics in GZ = 60 Hz. An octave of 60 Hz = 30 Hz, 2/3 of 30 = 20 Hz. 60 – 20 = 40 Hz

Or in other words, the resonance frequency of the bass reflex (in the general case) should be 1/3 (33%) lower than the resonance frequency of the same speaker in the same box with the FI hole closed.

Example:

Fres. dyne in ZY = 60 Hz. 60 x 0.33 = 20 Hz. 60 – 20 = 40 Hz

The calculated resonant frequency of the FI in this example should be 40 Hz.

For this frequency, and NOT FROM THE BALDA, the diameter and length of the bass reflex are then calculated for the volume of a given box. If this results in a small hump in the frequency response (error 1), you can always muffle it with synthetic padding (or, although this is more difficult, slightly reduce the resonance by lengthening the FI). If you get “ragged bass” (error 2), you will have to shorten the FI pipe.

I repeat once again for the dashing “craftsmen”: an arbitrary choice of the resonance frequency of the phase inverter “FROM THE LANTERN”, like, I want to make FI at 30 hertz and I will do so... well, do it, but it will not lead to anything good. At least in the sub for music. The FI resonance frequency cannot live on its own; it is tied to the resonance of the dyne and the volume of the box, and not to your desire.

I remembered an old joke about this:

Two friends meet, one to the other: “Are you out of breath?” - Yes, I ran for the tram and saved on the fare. - What a fool. If I had taken a taxi, I would have saved more.

If you don't care at what frequency your FI will perform poorly, make it at 15 hertz. Still, 15 hertz is steeper than 30. Run for a taxi, at least you'll have something to brag about.

Advice:

Before you grab a saw, wallet or calculations, first try to muffle the bass reflex with a piece of padding polyester and listen, maybe this will be enough. As a last resort, a FI-sub with a good speaker (Fs no higher than 35-40 Hz) can be easily converted into a VZ, you just need to insert a tight plug into the FI pipe instead of a sock, and - goodbye hum. Foam ones are sold specifically for ugly subs.

Note.

It is impossible to make a good subwoofer on a crappy or simply low-quality speaker, just like any speakers. But you can try. If you are free, please try. True, you still need to be able to do this, that’s why I’m writing. I outlined some things about improving subwoofers in the next article: https://samlib.ru/m/makeew_l_a/1806.shtml.

Error 3

This is not even a mistake, but some kind of general craze for stupidity.

When independently designing and calculating a subwoofer box with FI, a speaker with many accurately measured parameters is usually carefully selected. All these parameters are measured in open space, in air.

As soon as you put the speaker in the box, you can safely forget all the parameters of the speaker that were previously measured with fucking accuracy. The parameters of the dyne in the box will be very different from its parameters in open space, and the smaller the volume of the box, the greater the differences, up to 20-40-60%. After installing the speaker in the box, all further calculations should be carried out based on the new parameters of the speaker.

All computer programs for calculating subwoofers are built according to the same scheme: they recalculate Thiel-Smol parameters taken in the open air into speaker parameters for a closed box (or box with FI) of a given volume. And they do this with significant mistakes. That is why not a single computer program will help you calculate a subwoofer with FI so that it immediately starts singing properly. Everyone then fucks and brings the sub to mind manually, individually.

Before using a program to calculate subs, it is advisable to know who wrote it and for what purposes. All these programs were written by sub manufacturers for SERIAL production. For example, a company decided to release a sub in a certain price category on specific speakers with specific Thiel-Small parameters. The sub is calculated by the program, and then its parameters are polished and perfected in a prototype. And only then the sub is put into production, and only on these speakers. To debug and bring a prototype subwoofer to condition, reputable companies have laboratories, control rooms, and the necessary measuring instruments. You will never have such equipment, you don’t even have to twitch.

These programs are intended for PRELIMINARY and approximate calculation of subwoofers. And each company has its own program; they know better the errors of their programs. Unlike you.

Thus, a great many programs for calculating subs with FI lying on the Internet are not intended for individual use by audiophiles on God knows what speakers. Especially in the final version, without debugging and modifications.

Some features of the bass reflex operation

Group delay – group delay time

– the parameter means nothing. About the same as the average temperature in the hospital. The phase shift at different frequencies in the PI passband changes by one and a half to two times. The immediate conclusion is that the clock lag time of the bass drums will not be constant. It will change depending on the nature of the drum sound. What fidelity of sound transmission of a complex musical signal can we talk about?

Transients.

When the signal is initially applied or the frequency of the bass signal changes, these are the first few periods when the FI resonator adapts to the speaker oscillations imposed on it from outside, different from the resonant frequency of the bass reflex (the so-called “imposed oscillations of the resonator”), which also passed through elastically - viscous medium of sub-air. At the time of adjustment, the FI pipe, in addition to the signal delay, produces large nonlinear distortions, the so-called “transition distortions”.

When a constant sine wave is applied to the speaker in the operating range of the FI, an equilibrium is established between them. When the frequency of the signal on the speaker changes, this balance is disrupted and some time (sometimes significant) is required to establish a new equilibrium point between the FI and the speaker. This is transient distortion. On fast bass lines they are quite significant.

Because these distortions are short-term in nature, they are difficult to measure. In the static mode of operation of a subwoofer with a sine generator, there are no such distortions.

Thus, the group delay is more or less constant, and the distortion of transient processes increases proportionally at a high tempo of playing bass and drum instruments.

In addition, after the end of the bass note and the speaker cone stops, the air in the resonator continues to oscillate for some time, the so-called “aftersound”. But, since the speaker is silent and there are no vibrations imposed on the resonator, the bass reflex tube continues to produce a damped sound with its own resonance frequency, such as a tuning fork at 30-40 Hz. To the ear, this is perceived as the sound of a subwoofer on one note. Always on the same one. And in any case of bass music, the Phase Inverter will ALWAYS strive to return to its own resonance: mumbling on one note. Its own resonance is closer to FI than the vibrations of some speaker, its own shirt is closer. Louder or quieter, it will always be bugged. Well, you understand, since these vibrations occur in the FI pipe, and not in the wires and circuit, no equalizer or processor will filter them out or suppress them.

I still hope that this text is read by more or less prepared people, so I will explain the after-sound effect in a little more detail.

Power amplifiers have this parameter: damping coefficient. It shows how quickly the PA output stage can dampen the vibrations of the speaker cone at its resonant frequency. And the higher this coefficient, the better, in expensive amplifiers up to 1,000. The time of free oscillation of the diffuser after the signal stops is very short, a few milliseconds.

But no one in the world produces even expensive subwoofers with a damped bass reflex tube, since its output decreases and efficiency decreases. Therefore, air vibrations with the resonance frequency of the FI after the signal is stopped continue in its pipe for a long time, up to 60 - 80 milliseconds. There has been no signal for a long time, but the pipe keeps buzzing and buzzing. And the whole world is listening to this bullshit. They also praise.

Another incredible thing, “a fairy tale about a white bull”

A subwoofer with a bass reflex produces less nonlinear distortion than a subwoofer. Allegedly, in FI resonance, the speaker has a very small cone stroke, so it produces less distortion.

Who could argue? But in the operating band of the Phase Inverter, the speaker makes virtually no sound, and, one might ask, why measure distortion near a diffuser that is silent? The SOI of the speaker and bass reflex must be measured separately, in the frequency band in which they actively emit. But not the other way around. In the working band of the FI, near its resonance, all sounds are emitted by the FI pipe, port, hole. It’s near the hole that you need to measure distortions: transient and nonlinear, and others. According to some data, at frequencies near the FI resonance, at increased volume in the hole, nonlinear distortions reach 3-5%. In this case, the FI is no longer just an acoustic emitter of sound waves, but an air duct, a pipe with a high air flow rate. Like a vacuum cleaner. Here the nonlinear PNEUMATIC resistance of the pipe has a dull effect.

And what are the advantages of FI over ZY?

The listed processes occur in the subwoofer with FI not just on their own, but also superimposed on each other. If you combine all this in one subwoofer, you have a bucket. And if this bucket is enhanced with high efficiency (Fig. 3), then you can even choke. All the tricks for calculating and debugging a subwoofer with a Phase Inverter are nothing more than pathetic attempts to reduce the undesirable consequences of physical phenomena arising from the use of a resonator in a subwoofer. Like, no matter how hard you try, the grave will correct the “hunchbacked FI”. In a subwoofer of the ZYa type, the described phenomena are absent in principle, due to the absence of a hole with a pipe.

WARNING to DIYers

The most favorite subwoofer parameter among craftsmen is frequency response. She is leveled and licked to perfection. But, an ideal frequency response is not a guarantee that a bass instrument will be similar to itself when performed by a subwoofer with a Phase Inverter. Much more often this is not the case at all, because FI gives a lot of small dirty tricks and a smooth frequency response will not get rid of them.

Before you sit down to calculate the subwoofer, decide what is more important to you: a loud FI sound, or high-quality bass in the ZY. You are unlikely to be able to combine this, the processes are too different. My advice: if you decide to make a sub with FI, calculate it so that by plugging the FI port (fully or partially), you can get at least an average ZY. You'll see, then you'll have a choice.

And don’t point at me about Aldoshina. Acoustics is a small, small part of physics, CONCEPTUAL science. And what is the concept of women, sir, everyone knows. Me too, Sklodowska-Curie. It's funny, sir.

For lovers of high efficiency, I recommend a horn loudspeaker: efficiency 15 - 20%:

Well, I got angry and that’s enough. Since you are impatient with FI, let’s get down to business.

Primary simplified calculation of the volume of the box for an indoor floor-standing subwoofer with FI. In reality, for the initial calculation of the internal volume of the box, taking into account the quality factor of the speaker, only the dyne resonance Fs and its equivalent volume Vas are needed. That's all.

The internal volume of such a box should be equal to the equivalent volume of the speaker Vas. In this case, the resonant frequency of the dyne Fs (in a box with a closed FI hole) should increase by 1.4 times. From this increased dyne resonance the FI resonance should be calculated. That is, according to the above calculations, in this case the resonance frequency FI is approximately equal to the resonance frequency of the speaker in open space Fs. (Yes, and one more thing: it is advisable to select a speaker with a not very high or low quality factor, average so.)

Setting up FI is described above. If necessary, subsequent adjustment of the speaker quality factor is carried out by damping the subwoofer with a sound absorber (see the adjacent article: https://samlib.ru/m/makeew_l_a/1806.shtml).

Advice: don’t get carried away with subwoofer volumes exceeding 50-60 liters. If you don’t know Vas, look on the Internet, they describe ways to determine the equivalent volume of speakers. There are even simple ones. I'm lazy. If you are also lazy, make a sub in the box you have. Put a din in it, measure the resulting resonance and calculate FI from this. Get the best you can get out of this box. Well, okay, so be it, I overcame laziness, here you go:

Rice. 7 – chart-cheat sheet, scale respected:

An approximate graph of the increase in the resonance of the woofer (Fb) by several times, while the volume of the real box (Vb) decreases relative to the equivalent volume of the dyne (Vas), also by several times. For example: if the actual volume of the box Vb is 3 times less than the equivalent volume of the speaker Vas, then res. The speaker frequency Fs will increase by 2 times and will be called Fb. The quality factor of the speaker will also increase by 2 times.

You can calculate more accurately. Formula for the dependence of speaker resonance on the volume of the box (volume change method).

1. Fb – dyne resonance in the box (in the box)
2. Vb – volume of the box (box)
3. Fs – dyne’s own resonance
4. Vas – equivalent dyne volume

We measure Fs and internal volume Vb of the first box we come across. We put the speaker in a box (outside is possible) and measure Fb. We substitute the resulting numbers into the formula and find Vas. Then, without grabbing a saw and plywood, but simply playing with numbers and a formula, you can calculate the resonant frequency of the speaker in the planned volume of the subwoofer. Simple as a turnip. It is desirable that the volume of the measuring box Vb be approximately similar to the volume of the future subwoofer.

Calculation of the size of the FI for a given (calculated) frequency of its resonance.

The classical formula of the Helmholtz resonator for a round hole FI:

All dimensions are given in the SI system:

1. F – specified resonant frequency of the bass reflex [Hz];
2. S – hole area FI [m2];
3. V – internal volume of the box [m3];
4. L – length of the bass reflex pipe (you can add 10-20% just in case) [m];
5. C – speed of sound in air = 344 [m/sec];
6. π = 3.14.

Which box setting to choose

Hi all. Please tell me, my friend and I decided to make a FI box for 12 din and chose the 35 hertz setting. We thought it would play softly and low, but it turned out that there was more pressure than bass. We tried to put both Kix and Mystery there. They play the same way, there is not enough softness and elasticity of the bass.

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WATCH THE VIDEO ON THE TOPIC: How to make a box for a subwoofer + BONUS: KILLING a URAL subwoofer

What materials do we need to assemble the subwoofer?

The material for making the subwoofer box must be durable, dense and well insulating sound. Multilayer plywood or chipboard is perfect for this . The main advantages of these materials are their affordable price and ease of processing. They are quite durable and provide good sound insulation. We will make a subwoofer from 30 mm thick multilayer plywood.

To make a subwoofer box we will need:

• Wood screws (approximately 50-55 mm, 100 pieces)
• Soundproofing material (Shumka)
• Drill and screwdriver (or screwdriver)
• Jigsaw
• Liquid Nails
• Sealant
• PVA glue
• Carpet, approximately 3 meters
• Klemnik

How to choose the HF box setting for a subwoofer

The recommended net volume of a closed box, based on one 8-inch speaker, is from 8 to 12 liters.

The recommended net volume of a closed box, based on one 10-inch speaker, is from 13 to 23 liters. The recommended net volume of a closed box, based on one 12-inch speaker, is from 24 to 37 liters. The recommended net volume of a closed box, based on one 15-inch speaker, is from 38 to 57 liters. The recommended net volume of a closed box, based on one 18-inch speaker, is from 58 to 80 liters.

The recommended net volume of the bass reflex box, based on one 8-inch speaker, is from 20 to 33 liters. The recommended net volume of the bass reflex box, based on one 10-inch speaker, is from 34 to 46 liters. The recommended net volume of the bass reflex box, based on one 12-inch speaker, is from 47 to 78 liters. The recommended net volume of the bass reflex box, based on one 15-inch speaker, is from 70 to liters. The recommended net volume of the bass reflex box, based on one 18-inch speaker, is from up to liters.

You can also use our box volume calculator. The internal “dirty” volume of the box, which includes the clean volume of the box and the volume displaced by the speaker. The internal “dirty” volume of the box, which includes the clean volume of the box, the volume displaced by the speaker and the port. The volume displaced by the speaker elements located inside the box.

Plywood

Plywood (laminated wood board) is a multilayer material that is made by gluing prepared veneer. To increase strength, layers are applied so that the wood fibers are strictly perpendicular to the previous sheet.

The most popular material for making your own subwoofer. It happens: construction, industrial, packaging, furniture and structural. It’s better to use furniture; if you’re lucky enough to find a structural one, it’s generally great.

Plywood has high strength, is easy to process, and with sufficient thickness gives good rigidity to the body, but can delaminate during assembly.

Medium Density Fiberboard (MDF) - made by dry pressing small wood chips at high pressure and temperature. It is very well suited as a material for subwoofer housings and acoustic speakers in general, as it has a homogeneous structure, absorbs sound well and is easy to process. It has a high density and holds screws well. An MDF box of sufficient thickness is dull, durable, and has no resonances.

12" subwoofer box

The recommended net volume of a closed box, based on one 8-inch speaker, is from 8 to 12 liters. The recommended net volume of a closed box, based on one 10-inch speaker, is from 13 to 23 liters. The recommended net volume of a closed box, based on one 12-inch speaker, is from 24 to 37 liters. The recommended net volume of a closed box, based on one 15-inch speaker, is from 38 to 57 liters. The recommended net volume of a closed box, based on one 18-inch speaker, is from 58 to 80 liters. The recommended net volume of the bass reflex box, based on one 8-inch speaker, is from 20 to 33 liters. The recommended net volume of the bass reflex box, based on one 10-inch speaker, is from 34 to 46 liters.

Glass fabric

Fiberglass is used to make stealth subwoofers or to give non-standard shapes to parts of the housing. The mold is covered with fabric, impregnated with polyester resin. Using such material it is quite difficult to achieve the required thickness, so additional stiffening ribs must be used. In general, making such a case is a labor-intensive process, but the result is aesthetically worth it.

The question is often asked: “Does it make sense to remake a factory subwoofer enclosure?” If you remake the factory housing of a budget sub, there will be an improvement and it will be audible. But since the speaker is most likely bad, it will limit the degree of improvement.

For a high-quality subwoofer, choose the right material. Good luck with your builds!

How to choose the HF box setting for a subwoofer

By Jendoss, November 19, in Subwoofers. Your BMW has a very low interior resonance, so you can safely tune it to Hz; there will be a lot of wind. That's how you do it. There's nothing to invent. Not only the settings, but also how people do the volume, what is the area of ​​the port. This is how I understand this every day, and you recommend a 40 hertz setting. Nobody needs a buzzer, in my opinion it’s much more pleasant to feel a lot of wind in the cabin than a headache! Jendoss, Try it, cut a couple of cm, listen. Where you like it most, leave it at this length.

How to calculate the displacement of a subwoofer housing

To correctly determine the volume of a subwoofer enclosure, you need to take into account one important quantity. This is the transfer function of the car interior. It is defined very simply. You need to multiply the longest seat in the cabin by two and divide the speed of sound in air by this value. If the length is 2 m 45 cm, then the transfer function of the cabin will be equal to 343/4.9 = 70. The interior PFS is the frequency in hertz. This value is entered as a parameter when calculating the subwoofer box using computer programs.

The more parameters are entered into the speaker system design program, the more accurate and correct its volume will be calculated.

Phase reflex tuning frequency

You've probably at least heard something about quarter-wave resonators. This type of enclosure is not so widely used in the construction of subwoofers and low-frequency sections of acoustic systems compared to, say, a bass reflex and a closed box. But why? After all, a quarter-wave oven provides undoubted fat advantages: Perhaps the widespread use of CV is also limited by the somewhat laborious nature of its calculations. Although the calculation itself is not that complicated, usually while you are designing a box, you have to go through several options, recalculating everything again each time.

How to make a housing for a subwoofer

The easiest to make is a buried box or box. This is a completely closed structure, the manufacture of which will require a minimum of simple wooden parts. How to make a housing for a sub becomes clear when you see such a device. Essentially, this is a rectangular box with a hole cut out in the front wall for a dynamic head. The box consists of six walls, which are easy to cut out of the appropriate material. A terminal block is mounted on the side or rear wall to connect wires from the amplifier. The closed box (CB) is distinguished by dense and not vague bass, smooth amplitude-frequency response, but has the lowest efficiency among all designs.

The box can be in the shape of a parallelepiped or trapezoid with beveled walls. Due to its characteristics, the closed design is suitable for many musical styles. The sealed, closed design conveys bass well in pop and rock music, classical, jazz and instrumental works. But fans of rap and dubstep will be disappointed, as the closed box is not suitable for playing music that has a lot of heavy bass and where the low frequencies are the basis of the music.

Secrets of the musical bass. A guide to setting up a subwoofer for beginners. Subwoofers.

In car audio, there are many options for acoustic design of boxes. Therefore, many beginners do not know what is the best choice. The most popular types of subwoofer boxes are a closed box and a bass reflex box. There are also designs such as bandpass, quarter-wave resonator, freeair and others, but when building systems they are used extremely rarely for various reasons. We advise you to pay attention to the article on what material is best to make a subwoofer box from. We have clearly demonstrated how the rigidity of the box affects the quality and volume of the bass. This type of design is the simplest.

Subwoofer housing. Shapes and materials

The subwoofer housing must be strong enough, otherwise its vibration will generate frequencies that will give undesirable coloration to the sound. In this article we will tell you what material is best to make a subwoofer enclosure from, as well as what types of enclosures there are for a woofer.
Multilayer plywood . There are many grades of plywood, many of which are not suitable for speaker cabinet construction. Regular plywood is not dense enough and will distort the sound. Multi-layer plywood is an excellent material for building small cabinet systems. This plywood is quite dense and lighter than chipboard and MDF. It is easy to work with, screw in screws without fear of delamination. The disadvantage of plywood is that large cases made from it begin to ring. To do this, when making cases for powerful subwoofers, plywood with a thickness of at least 18 mm is used; sometimes the walls of the box consist of a double layer of plywood. And in order to finally get rid of resonances, guy wires and amplifiers are installed inside the case. For more details about building a case from multilayer plywood, see the article: how to make a case for a subwoofer with your own hands. Chipboard . There are several types of slabs on sale, but chipboard of the highest density is recommended for cabinets. Although high-density varieties weigh more, they are easier to handle and sound better. High-density 16mm chipboard is perhaps the best choice for a higher-power low-frequency speaker system because it has the highest density and weakest resonant qualities. The disadvantage of this material is that it absorbs moisture easily and is difficult to cut with a saw. Chipboard cabinets should be painted to prevent swelling due to moisture. Medium Density Fiberboard . Essentially a form of compressed paper, it has a high density and is easy to cut. The disadvantage of fiberboard is that it is difficult to work with due to its tendency to delaminate when held together. It absorbs moisture a lot and quickly. As with chipboard, careful design must be taken both in terms of fastening and in preventing the effects of moisture. Sealed enclosures (closed box) . Perhaps the most common form of enclosure today is the sealed enclosure.
It is preferred due to the relative ease of development and construction. A sealed enclosure is an enclosure that completely seals the subwoofer's internal airspace from the external airspace. The air inside the box supports the speaker membrane and acts as an additional suspension for it. This allows the speaker to handle more power.

The range of emitted frequencies of the subwoofer depends on the volume of the enclosure. If the volume of the box is less than optimal, then the pressure inside the box will increase, which will lead to cutting off some frequencies and enhancing others. Instead of pure deep bass, the subwoofer will produce a booming, 'failed' bass. By increasing the volume of the box, the bass improves, but again to a certain level. The main task of designing a box is to determine its optimal volume for the selected woofer.

In practice, it often happens that a box is first designed based on the limitations of free space in the trunk of a car, and then a speaker is selected to fit the internal volume of this box.
The following figure shows a graph from which you can determine the approximate volume of the internal space of the housing for a given speaker diameter. Phase-inverted subwoofer enclosures are widely used in home speaker systems.
Currently, phase-inverted or ventilated enclosures are widely used in car audio systems. This body shape is unique in that the bass reflex (ventilation duct) helps in reproducing the lowest frequencies in the audible range. The bass reflex actually becomes a sound source that contributes to the overall sound of the subwoofer system. Phase inverted systems produce more bass with less power than sealed systems.

A properly designed vent will produce increased output at the tuned frequency. The sound of phase-inverted subwoofers is cleaner, but their volume is larger than that of sealed subwoofers for the same speaker.

The disadvantage of this type of subwoofer is the possibility of distortion when reproducing frequencies from a range below the design one.
Calculations of the parameters of a ventilated enclosure are more complex, and even small errors may not justify the effort and time spent. Errors in the design and configuration of the bass reflex can cause the speaker system to 'mumble' or the bass to be 'smeared'. The isobaric design of the case is a box in which two identical speakers are installed.
This design is based on the idea of ​​having constant air pressure between the membranes of the two speakers. As a result, two acoustically coupled speakers function as one speaker. The advantage of this design is that it saves box volume.
The disadvantage of this design is that if there are two voice coils, only one membrane remains actually working. The overall output of an isobaric subwoofer is approximately 3 dB less than that of other subwoofers at the same input power. Structurally, a pair of speakers is located inside the housing on the same axis, membrane to membrane, magnet to magnet or magnet to membrane. Bandpass enclosures consist of two chambers between which a speaker is mounted.
One of the chambers is sealed, and the second chamber is phase inverted. This design provides very high quality low bass compared to other subwoofers, making them very popular in the car audio market. However, their acoustic output is relatively low. When designing bandpass boxes, one should take into account this relationship between the frequency response and the sound pressure that the housing develops. The lower and better the bass, the lower the acoustic output and power of the subwoofer. And vice versa, the more powerful the bandpass subwoofer, the higher and worse the bass it produces.

The disadvantage of this type of housing is the high complexity of calculations and relatively large dimensions compared to sealed or phase-inverted housings.

Subwoofer installation

I’ll disappoint you right away, there is no correct design for a subwoofer and there never will be, because it’s different for everyone. Which one is right for you depends on your musical preferences and the space you can sacrifice in the trunk. The most compact of all designs and the easiest to manufacture is ZYA. But it has the lowest efficiency. The sound of this performance is soft and not particularly loud.

What frequency should you set the bass reflex to? The frequency of the phasic port can be selected based on your preferences in music. With this setting, the ears do not suffer - it is a soft bass! Usually they think that if the hair blows out, it means there is pressure on the ears and how it sits there. With such a setup, you can forget about strawberry, electro, especially pop music.

Switch to English registration. Phone or email. Another's computer. Flea market of AutoSound Ukraine.

Subwoofer volume

How to find out and calculate the volume of a subwoofer in liters. The most labor-intensive calculations will be for structures with a bass reflex or bandpass. Despite the high user parameters, the bandpass design is rarely used in cars. Calculation and production of an acoustic system with a slot bass reflex requires more parts and carpentry work. It is necessary to accurately calculate the area of ​​the bass reflex port, and after manufacturing and assembling the structure, all internal corners must be carefully rounded to avoid air vortex waves. It’s easier to calculate a box for a subwoofer on a pipe.

The pipe is made of plastic and consists of two segments, one of which can move inside the other. Such a device is sold in specialized stores. The movement of the pipe components changes the effective area of ​​the bass reflex, which allows you to tune the structure to a specific frequency.

Which box to choose for a subwoofer is determined by the type of speaker and location of the bass speaker. If the luggage compartment is empty and not used for transporting cargo, then it is best to place a low-frequency speaker system there. If part of the trunk is needed for any purpose, then it is better to choose a closed box, since it has minimal dimensions. When the trunk cannot be used, the bass speaker is mounted on a shelf behind the backs of the rear seats. In this case, the “Free Air” design is selected.

Choosing a box for a subwoofer. Types of boxes

Here we will look at the three main types of boxes (boxes) used in subwoofers (as well as in other speakers). But first, a little about the purpose and function of any box. The acoustic head emits sound not only “forward” but also backward, while the front and rear sound waves are opposite in phase. In this regard, there is a term “acoustic closure”, in which the waves on both sides of the diffuser add up and (if they are opposite in phase) cancel each other out. In this case, ideally you will not hear anything at all, but in practice the sound will be very far from the original. The acoustic system box allows you to eliminate this short circuit and give the sound the required characteristics in terms of power and frequency.

Midbass and subwoofer adjustments

As practice shows, the subwoofer setting should be done so that the woofer fits well with the front speakers, there are no frequency dips, etc. In other words, it is not enough to adjust the subwoofer, since the midbass speakers will also require adjustment.

For proper tuning, you will need to make the frequency response section smooth by slightly changing the cutoff frequencies LPF and HPF. This is done both by ear and with the help of an RTA analyzer. The main thing is to achieve dense and spacious sound so that there is no “dropout” in frequencies.

Closed box (ZY) - sealed box

This is the easiest type of acoustic design for speakers to manufacture. The vibrations in such a box are in a closed volume and are eventually damped. But since a sound wave is energy, when it decays it turns into heat. And although the amount of this heat is small, it still affects the characteristics of the acoustic system. (warmer air expands and increases the rigidity of the system). To prevent this effect, the core is filled from the inside with sound-absorbing material, which, while absorbing sound, also absorbs heat. The increase in air temperature becomes much smaller and it “seems” to the dynamics that there is a significantly larger volume behind it than in reality. In practice, in this way it is possible to increase the “acoustic” volume of the box compared to the geometric one by 15-20%.

Materials for making a subwoofer

The choice of material for construction is an important step in the construction process. On this page we will look at what is the best material for a subwoofer enclosure and how to choose it correctly. The main requirements for the box are that it must be rigid, airtight and free of resonances. For example, premium home speakers are very heavy for their type, this is precisely to enhance these three qualities.

The ideal material for a subwoofer would be granite or something similar, but of course car audio cannot afford this - this concerns the weight and complexity of processing. Therefore, the materials used are: chipboard, plywood, MDF, fiberglass. The thickness of the material should be selected based on the volume of the case - the more, the thicker to maintain strength, while for sheet material take 18 mm as a minimum. An exception may be the CV, in which, thanks to a large number of partitions, good rigidity is gained; for it, material from 16 mm can be used.

Bass reflex (FI) - vented box

A bass reflex is the next most common type of acoustic design. In a bass reflex, part of the energy that is “put against the wall” in a closed box is used for peaceful purposes. To do this, the internal volume of the box communicates with the surrounding space through a tunnel containing a certain mass of air. The size of this mass is chosen in such a way that, in combination with the elasticity of the air inside the box, it creates a second oscillatory system that receives energy from the back side of the diffuser and radiates it where needed and in phase with the radiation of the diffuser. This effect is achieved in a not very wide frequency range, from one to two octaves, but the efficiency is within its limits. increases significantly.

In addition to higher efficiency The bass reflex has another important advantage - near the tuning frequency, the amplitude of the diffuser oscillations significantly decreases. This may at first glance seem like a paradox - how the presence of a hefty hole in the loudspeaker housing can restrain the movement of the cone, but nevertheless. In its operating range, the bass reflex creates completely greenhouse conditions for the speaker, and exactly at the tuning frequency the oscillation amplitude is minimal, and most of the sound is emitted by the tunnel. The permissible input power is maximum here, and the distortion introduced by the speaker is minimal.

Above the tuning frequency, the tunnel becomes less and less “transparent” to sound vibrations, due to the inertia of the air mass contained inside it, and the loudspeaker acts as if it were closed. Below the tuning frequency, the opposite happens: the inertia of the speaker gradually disappears and at the lowest frequencies the speaker operates practically without load, that is, as if it had been removed from the housing. The amplitude of oscillations quickly increases, and with it the risk of spitting out the diffuser or damaging the voice coil from hitting the magnetic system. In general, if you do not take precautions, going for a new speaker becomes a real prospect.

A means of protecting against such troubles, in addition to being careful in choosing the volume level, is the use of infra-low-pass filters. By cutting off part of the specAvtozvuk Kirovtra, where there is still no useful signal (below 25 - 30 Hz), such filters prevent the diffuser from going into disarray at the risk of your own life and your wallet.

The bass reflex is much more capricious in the selection of parameters and settings, since three parameters are subject to selection for a specific speaker: box volume, cross-section and tunnel length. The tunnel is very often made so that with a ready-made subwoofer it is possible to adjust the length of the tunnel by changing the tuning frequency.

Subwoofer settings in the car

First of all, it is important to understand that the sub is an element for reproducing low frequencies. Simply put, the subwoofer produces bass. In fact, the woofer has a cone that vibrates, creating compression and release of air.

In the case when vibrations occur with a frequency of 16-20 times per second. (16-20 hertz) up to 14-18 thousand times per second. (14-18 kilohertz), a person perceives it as sound. In this case, bass represents the lower range of such sound vibrations (from 20 to 150 Hz.).

In fact, fine-tuning the subwoofer begins at the stage of designing the box where the woofer is placed. The characteristics of the subwoofer speaker, the style and type of music that will be listened to most often, the features of the amplifier for the subwoofer, etc. are also taken into account separately. One way or another, if the sub is designed from scratch or already comes with a ready-made solution in the housing, the right approach allows you to get good sound.

Subwoofer frequency

Let's move on to the settings. Once the subwoofer is properly connected to the amplifier, the first thing to start with is setting the LPF filter (low pass filter). To do this, you need to turn on the LPF filter on the amplifier on the sub or on the main unit. Simply put, this filter allows you to feed only low frequencies to the woofer, while cutting off the mids and highs.

As an example, the cutoff frequency for subwoofers is often set to 50 to 63 Hz. The filter must be set to the specified frequency, after which additional adjustments are made.

Let us also add that LPF does not cut off the sound sharply. In practice, if the sub is set to 60 Hz, there will also be sound at 61 Hz, but the frequencies will be weakened, a smooth decline appears. In this case, the smoothness of the decay depends on the order of the filter. Some GIs allow you to choose the order.

For example, a 4th order filter produces a smoother rolloff, while a 1st order filter means a sharper rolloff. This filter allows you to combine the subwoofer and midbass speakers well.

Subsonic: setup

Without going into too much detail, a subsonic is a high-pass filter that operates in the low-frequency region. Simply put, sabsonic cuts off infra-low frequencies while letting higher ones through. Please note that subsonic is not present on all amplifiers. If the system is assembled independently, it is advisable to immediately select such an amplifier for the sub, which has the specified filter.

In turn, the subsonic cuts off ultra-low frequencies, which does not allow the speaker to exceed the permissible stroke. As a result, the service life of the speaker increases, and the quality of reproduction of the audible bass range improves; the sub begins to play cleaner and louder.

Subsonic tuning is done by cutting 5 Hz below the bass reflex port tuning frequency. As an example, if the tuning frequency is 35 Hz, the subsonic is tuned to 30 Hz. To adjust, you need to enable this option and scroll the knob to obtain the desired values.

Setting Gain or Level

Setting the subwoofer input sensitivity level and adjusting it is carried out on the amplifier. As a rule, this is a regular regulator with numbers (often from 0.3 to 5 V). Please note that many people assume that this is the volume level on the amplifier.

In fact, this is not true. The Level or Gain regulator allows you to match the level of the radio or head unit with the amplifier. Settings can be done in different ways, but the general gist is the following:

• an audio signal with a configured frequency is supplied to the subwoofer from the radio;
• in this case, the amplifier first sets the input sensitivity level to a minimum;
• then the volume on the GU increases until distortion appears;
• then the volume knob must be turned back until the distortion disappears;
• then begin to rotate the “GAIN” knob until distortion appears;
• then the control is moved back to make the sound clear.

Subwoofer acoustic phase and delay setting

Let's start with phasing. In some cases, you can notice that the subwoofer plays separately from the front speakers; the sound of the subwoofer can clearly be heard from the trunk. This setting is incorrect.

Simply put, subwoofer phase allows you to “shift” the sound of the subwoofer forward. As a result, the sub sounds seamless and uniform along with the front speakers.

Having dealt with the phase, you should then move on to setting the delays. Please note that delays can only be set on processor-based radios or if there is an external processor.

This setting is needed if the impulse response is insufficient and the bass “lags”. In practice, this manifests itself in such a way that the front has already played the note, while the subwoofer plays a little later, that is, with a delay. It is for this reason that delay adjustments are needed to allow the front speakers and subwoofer to play in sync.

Bandpass loudspeaker - Bandpass

The third type of subwoofer, quite often used in car installations (although less frequently than the previous two) is a bandpass speaker. If a closed box and a bass reflex are high-pass acoustic filters, then a band-pass filter, as the name implies, combines high- and low-pass filters. The simplest bandpass loudspeaker is a single 4th order (single vented). It consists of a closed volume, the so-called. rear chamber and a second one, equipped with a tunnel, like a conventional bass reflex (front chamber). The speaker is installed in the partition between the chambers so that both sides of the diffuser operate in completely or partially closed volumes - hence the term “symmetrical load”.

Of the traditional designs, the bandpass loudspeaker, in any version, is the champion in efficiency. Moreover, efficiency is directly related to bandwidth. The frequency response of a bandpass loudspeaker has the shape of a bell. By selecting the appropriate volumes and frequency tuning of the front chamber, it is possible to build a subwoofer with a wide bandwidth, but limited output, that is, the bell will be low and wide, or it can be with a narrow bandwidth and very high efficiency. in this strip. At the same time, the bell will stretch in height.

The bandpass is a tricky thing to calculate and the most labor-intensive to manufacture. Since the speaker is buried inside the case, it is necessary to go to some lengths to assemble the box so that the presence of a removable panel does not violate the rigidity and tightness of the structure. The impulse characteristics are also not the best, especially with a wide bandwidth.

How is this compensated? First of all, as stated - the highest efficiency. Secondly, the fact that all sound is emitted through the tunnel, and the speaker is completely closed. When assembling such a subwoofer, considerable opportunities open up for installing it in a car. It is enough to find a small place at the junction of the trunk and the passenger compartment where the mouth of the tunnel can be placed - and the path is open to the most powerful bass. Especially for such installations, JLAudio, for example, produces flexible plastic tunnel sleeves with which it offers to connect the subwoofer output to the cabin. Like a vacuum cleaner hose, only thicker and stiffer.

Which box you choose for your speaker is of course up to you. And our auto studio will make this box for you.

What material can be used to cover a subwoofer?

For high-quality sound, the subwoofer must be sheathed. How to choose a material to cover a subwoofer with? There are many materials, but carpet is mainly used. To do this, it is enough to know a few rules and have several tools. Knowing this information, you will be able to properly process your box and you will not be ashamed to open the trunk.

Preparation of materials and tools

First of all, you need to list a list of tools and materials to get started:

• scissors;
• stationery knife with blades;
• spray paint (matte black);
• ruler;
• roll of self-adhesive carpet;
• soldering iron (for processing carpet around the edges of holes).

Paint is necessary to paint the port so that it does not stand out against the background of the box. You can also paint the joints where the sheets will be connected. It will be enough to paint these places with a small strip. Once you have prepared all the tools and materials, you can begin covering the subwoofer box.

How to cover a subwoofer box with carpet

After preparing the workplace, we begin pasting. First of all, you need to decide on the joint. Where will it be located? It is usually placed on the back wall, since it is least visible.

A very important point: all surfaces must be cleaned before pasting, otherwise the film will not stick tightly and will eventually come off the surface. We identify half of the back wall of the box by eye and begin work. Carefully seal all the walls around the perimeter until it reaches the back wall again.

After this you will need to make a nice, even joint. To do this, paint the line with black paint at the overlap site and glue the carpet with an overlap onto the old layer.

Next, we apply a ruler to the box and, using a utility knife, cut the carpet in a straight line and tear off the excess material. Thus, you should get a beautiful, even joining of sheets.

For durability, you need to take a hard cylindrical object and walk it along the joint. Roll and press the carpet at the point of contact.

In this case, it will not shrink in the future and an unsightly and unesthetic gap will not appear.

This joint is not the most difficult part. The most difficult work is the top and bottom walls. First you need to wrap up the remnants of the carpet that remain along the edges of the back wall and this perimeter.

To do this, select the middle of the corner and cut a straight line. Afterwards, we carefully bend the remains and glue them to the finished surface. After gluing, you need to cut another line diagonally and remove excess material.

This procedure must be repeated 7 more times, for each remaining angle.

Features of a bass reflex for a subwoofer

The next step is to tape the top and bottom of the box for the subwoofer. If you chose not a self-adhesive carpet as a material, but a simple one, then you only need to coat the plywood with glue. The glued carpet cannot be coated with glue.

If you are using adhesive-based material, you can simply lay a piece the size of the bottom or top side of the box and cut out the missing part in the center. Then we cut lines diagonally from the corners of this piece to the edges.

Don’t worry that you won’t be able to cover the subwoofer with carpet the first time. Carpet material is inexpensive, so you can perform this procedure again without any special financial costs.

We try on the resulting blank and partially glue it to the bottom or top side of the box. Then, using a ruler, cut off the unnecessary carpet along the edges.

The utility knife must be pressed firmly to cut through the decorative material evenly. After this, we remove the excess adhered material and glue our workpiece. The same procedure must be repeated with the remaining wall.

On the lower and upper walls you will get smooth and almost invisible joints.

There are two final steps left - the speaker port and the hole in the box to install the speaker itself. We need to make sure that the carpet in the port area does not shuffle over time. To do this, you need to cut a hole for the port and cut off excess material. Take a heated soldering iron and carefully run it along the edges of the material around the holes. In this case, it will never lint on you.

At this point the work can be considered completed. As a result, you will get a smooth, beautiful box for the subwoofer, which you won’t be ashamed of. In the article, we examined in detail the process of covering a subwoofer with carpet and highlighted all the nuances that are worth paying attention to. All you have to do is install your speaker and enjoy your favorite music.