✅ Which box setting to choose

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How to find out the FI port setting of the box

In this video, we'll check how accurate a popular method of checking port tuning in a FI box is, which is observing the bulk materials located on the speaker cone. We will also compare this method of identifying the box settings with others. Watch the video, comment, share it with friends!

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Share with your friends by clicking on the social button! I started it sometime in 2012. This is my first box, back then it was for Orisa AMB-12. I sawed from a sheet of some old 17mm chipboard and cabinets (cabinets are our everything)). Accordingly, the box is experimental and temporary, but as we know, there is nothing more permanent than temporary. It so happened that later there were already two Oris riding in this box, both in the ZY and FI versions, and then the second hole was completely closed with a patch and the GZ took up residence.

Maybe someone doesn’t know, but measuring the FI setting is very simple. To do this, download a pack of sines onto a flash drive, or phone, or some other medium. It was enough for me to set the sines from 27 to 40Hz, well, since I knew that the setting was in any case within these limits. You can also download the tone generator application to your phone, it’s also convenient to use if your phone has bluetooth (I ran the sines one by one from the phone via BT). Next, we throw the box out of the trunk or drop it in the trunk, in short, the task is for the diffuser to take a horizontal position. We sprinkle some small crap on the diff, be it pieces of wire, beads, millet))) Then we actually drive the sines and see at what frequency these particles stop jumping - that’s where the adjustment is. Although, in principle, you can tell with your finger if you have the opportunity to chat louder.

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.

How to calculate a box for a subwoofer

The easiest way to calculate the size of the subwoofer is if it is made in the form of a closed box. There is no bass reflex or acoustic filters and the recommended volume is calculated based on the diameter of the speaker. In order to calculate liters for a subwoofer, simply multiply the width, height and depth of the box. You need to keep in mind that speakers of the same diameter, but from different manufacturers, will sound differently. This makes it difficult to independently calculate a low-frequency acoustic system. How the subwoofer box is calculated. You should know that only the “clean” internal volume is taken into account.

Self-calculation does not take into account the type of speaker, its resonant frequency and the output power of the low-frequency amplifier. All these factors influence the dimensions of the subwoofer box. If difficulties arise during the work, it is better to use simple computer programs to perform calculations. The most commonly used programs are:

JBL Speaker shop
BassBox 6 Pro
UniBox

JBL Speaker shop includes two utilities. Enclosure Module allows you to design a box for a sound system, taking into account an existing speaker, or select a loudspeaker to fit a ready-made enclosure. In the program you can calculate a closed box, a bass reflex system, or calculate a box for two subwoofers. Among the parameters needed to correctly calculate a woofer, the program takes into account the manufacturer, model number and resonant frequency. The entire list of parameters used to accurately calculate the future design includes more than ten items. Once the parameters are entered, you can select any type of housing. For a specific speaker, the program demonstrates a closed box, bass reflex or bandpass, indicating the advantages and disadvantages of each system. For beginners in acoustics, there is a training file with visual examples of calculations. The Crossover Module utility allows you to calculate all the parameters of a crossover filter for any acoustic system.

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:

Simple calculation;
Easy assembly;
Small displacement of the finished box, and therefore compact;
Good impulsive characteristics;
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.”

Assembling a subwoofer box with your own hands

You can start assembling. We use a 12-inch Lanzar VW-124 speaker.

Its diameter is 30 cm, and the first thing you need to do is cut a hole for the speaker. The minimum distance from the center of the diffuser to the subwoofer wall is 20 cm. We measured 23 cm (20 cm + 3 cm plywood width) from the edge of the panel and cut a hole with a jigsaw. Next, we cut a hole for the bass reflex slot; in our example, it has a size of 35*5 cm.

Instead of a slot, you can use a classic air duct - a tube. Now we assemble the bass reflex slot and attach it to the front panel of the subwoofer. We go along the joints with liquid nails and tighten them with self-tapping screws.

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:

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

Tips to help you set up your subwoofer correctly.

Tight, well-defined and, yes, DEEP bass is a key component of any home theater system. An active subwoofer is a must to hear thunder, explosions, and other low-frequency effects in a movie soundtrack. Many people simply place their sub in any available space, connect it to the receiver, and call it a day. But a few key points can help you set up your home subwoofer correctly. Read on to find out everything you need to know to get the most out of your subwoofer.

Where should I place the subwoofer?

As a general rule, you should try installing the subwoofer next to the front speakers. But let's be honest: most people place their subwoofer where it has the least amount of interference. And this is not always a bad idea.

The low-frequency waves we hear and call "bass" are less directional than the higher frequencies generated by full-range speakers. This means that even if the subwoofer is not installed near the TV, it will be quite difficult for you to understand where exactly it is located.

Some manufacturers recommend placing the subwoofer in a corner. Walls can help reflect more low-frequency waves into the room. If you're a fan of very full, exciting bass, this is a good option.

If you have several options for placing the subwoofer in a room, just experiment with different placements before making the final connection. So, connection.

How to connect your subwoofer

All subwoofers require two connections: power and signal. For power you just need the nearest outlet. We strongly recommend connecting your subwoofer to a power protector to protect against surge voltages.

There are three options for connecting to a signal source. Let's start with the most common connection.

Connecting LFE to a Home Theater Receiver

This is the simplest and most common connection. It is relevant for any AV receiver or amplifier with a separate subwoofer output. Use a subwoofer cable to connect your receiver's subwoofer output (usually labeled SUB OUT or Subwoofer Out) to the subwoofer input (usually labeled LFE or LINE IN). Many stereo receivers and amplifiers also have subwoofer outputs and are connected in the same way.

Crossover – “regulator” of your system

You need to make sure that all the bass and sub-bass frequencies are sent to your subwoofer. This will allow your front, center, and surround speakers to only reproduce the frequencies they can reproduce without distortion. Crossover allows you to determine which frequencies go to specific speakers.

You will find crossover settings both on your subwoofer and in your receiver's menu. We usually recommend using the crossover that is on the receiver. But before you dive into your AV receiver's system menu, follow these steps first. They can solve this problem easier and faster.

Auto calibration

Your receiver most likely comes with a calibration microphone to optimize the sound of your speakers. Typically, these automatic room correction systems do a very good job of adapting the sound to your environment.

But what if your receiver doesn't have automatic calibration? Or have you tried it and are still not impressed with the bass? You can perform manual setup.

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?

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.
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).

Fb – dyne resonance in the box (in the box)
Vb – volume of the box (box)
Fs – dyne’s own resonance
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:

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

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.).

The diffusers of subwoofers, as well as midbass speakers, have this oscillation frequency. Conventionally, fluctuations up to 50 Hz are low bass, 50-100 mid-bass, 100-150 upper bass. So, correctly setting up a subwoofer in a car can significantly expand the dynamic range.

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.

It is best to configure LPF on the head unit. If this is not possible, then the cutoff is adjusted on the amplifier itself. At the same time, it is not recommended to use the filter on the amplifier and the PG at the same time.

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 practice, subsonic is needed so that the subwoofer speaker does not try to reproduce frequencies that fall outside the audible range (20 Hz and lower). Working at such frequencies, the diffuser stroke increases noticeably, the coil can come out of the gap and be damaged.

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.

Let us add that to fine-tune the subwoofer in the car, it is optimal to use an oscilloscope. This solution allows you to adjust the levels flexibly, eliminating even subtle distortions.

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.

So, amplifiers often have a phase regulator (phase shifter). When choosing an amplifier, it is advisable to purchase one that has a similar function. The phase can also be changed on the GU, which also often has this option. If there is no phase control on the amplifier and radio, then you can swap the “+” and “-” wires on the speaker itself.

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.

We also recommend reading the article on how to connect a subwoofer in a car. From this article you will learn about which subwoofer to choose, as well as what circuit to use to connect a subwoofer in a car and what to look for when connecting a subwoofer with your own hands.

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.

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.

How to calculate the volume of a subwoofer box

To calculate the displacement of a box for a subwoofer, you need to choose the design of a low-frequency device. Powerful low-frequency systems are divided into three groups:

Closed case
Bass reflex
Bandpass

A closed box is the easiest to make. It can have the shape of a cube, rectangular parallelepiped or trapezoid with a beveled front or back wall. The closed box, in its dimensions, is smaller than other structures. A reduction in volume, while maintaining acoustic characteristics, is achieved by filling the internal space with some kind of damping material. Correctly calculating a subwoofer with a closed box is quite simple. It has only one characteristic, volume. Even an untrained amateur can cut blanks for the “closed box” design from the appropriate material.

Despite many advantages, the closed box has one significant drawback. This is the lowest efficiency of all designs. In order to get maximum sound quality from a closed box, the speaker needs to be loaded as much as possible. Only in this case the acoustic characteristics of the product will be at a high level. You can calculate the box for a closed subwoofer based on the diameter of the speaker.

8 inches – 10-12 liters
10 inches –13-25 liters
12 inches – 26-36 liters
15 inches – 38-58 liters

The larger the speaker diameter, the greater the volume dispersion. Calculating the volume of a subwoofer for powerful speakers is more difficult than for compact products. This is due to the individual characteristics of different models.

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.

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.

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 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.

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Checking the subwoofer box settings

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How to find out the FI port setting of the box

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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.

What's the result?

As you can see, setting up a subwoofer in a car is an important and crucial step. At the same time, you need to understand that even if all the components are selected correctly (amplifier, subwoofer, wires, etc.), without the appropriate settings the subwoofer may sound too quiet or loud.

We also recommend reading the article about. From this article you will learn about the features of connecting a radio in a car with your own hands. It may also not play the entire frequency range, reproduce bass with distortion, do not fit well with front speakers, etc. To get high-quality sound, above we looked at how to set up a subwoofer, paying attention to frequency cuts, phase, filter settings, etc. Sources used:

https://autobryansk.info/proverka-nastrojki-koroba-sabvufera.html
https://m.audiomania.ru/content/art-3997.html
https://krutimotor.ru/nastrojka-sabvufera-v-mashine-kak-nastroit-sabvufer-pravilno/

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%.

Making a stealth subwoofer with your own hands

Tired of carrying a huge box in your trunk? Then the stealth subwoofer is just made for you. This unique type of case is more practical than the classic box. It doesn't sit in a square box in the middle of the trunk and takes up less space. Often, stealth is installed in the inner part of the wing, sometimes in a niche instead of a spare wheel. The minimum volume of the box that requires a 10-12 inch speaker for normal operation is 18 liters.

To make a passive stealth subwoofer we will need:

subwoofer;
protective grille and socket for connection to the amplifier;
wire for connecting the speaker to the outlet;
multilayer plywood or chipboard (thickness 20 mm);
a small piece of fiberboard;
epoxy adhesive;
brush;
fiberglass;
mounting tape;
polyethylene film;
wood screws;
drill, jigsaw.

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After choosing the place where the stealth will be installed, we empty the trunk and begin manufacturing the body. You can remove the trunk trim where the subwoofer will be installed to place it even closer to the fender. First of all, lay a plastic film on the floor of the trunk. It performs two functions at once: it protects the trunk lining from epoxy glue and allows us to make a mount to which we will screw the bottom of the subwoofer. Next, we cover the inside of the wing with mounting tape in two layers.

We cut the fiberglass into small pieces, approximately 20x20 cm. We place pieces of fiberglass onto masking tape and glue them with epoxy glue. It is better to overlap the fiberglass fabric so that there are no obvious joints and seams.

We sculpt layers of fiberglass on top of each other, simultaneously lubricating them with epoxy glue, until the thickness of the sheet reaches 10 mm (about 4-5 layers).

The material will harden in approximately 12 hours. To speed up the process, you can use a lamp. Now we cut out the bottom of the subwoofer and glue it to our body. The joint is treated with sealant or glued with epoxy resin.

In this particular case, the shape needs to be adjusted to the trunk hinges so that our homemade subwoofer does not interfere with its closing. After we cut off all the excess, we cut out the side walls and the top cover from chipboard. We make the rounded part from plywood, we did it “by eye”.

Chipboard sheets must be glued with epoxy glue or sealant, and then fastened with self-tapping screws. We also glue the fiberglass box using epoxy resin, and when it dries, we fasten it with self-tapping screws.

For better sealing, you can glue the seams again . We applied another layer of epoxy glue and pressed the structure with sand to help the glue adhere better.

Next we can measure the front panel and cut it out. Using a jigsaw, cut out a circle for the speaker. In order to securely attach the front panel to the body, you need to tighten it with self-tapping screws on all sides. That is, you need to install bars on the entire inside of the panel, at a distance slightly greater than the thickness of the plywood (in our case, we attached the bars at a distance of approximately 25 mm from the edge of the panel). Thanks to this, we will be able to secure the front part at the top, bottom, sides, and most importantly, securely attach it to the rounded element.

Cut a hole in the end for the socket.

In the end, it was decided to add two more layers of fiberglass and epoxy glue to the curved part of the body for the stealth subwoofer.

We carry out the final assembly: install the socket and connect the speaker to it, but do not screw it yet. Then there are two options - paint the subwoofer, or cover it with carpet. Painting is a little more difficult, since you must first level the surface. For this we used universal putty.

We level everything with sandpaper, prime and paint. The subwoofer is ready!

What awesome advice about an amplifier with less power than the speaker itself. You are fucked up, delete this crap, don’t embarrass yourself