Home subwoofers: types, operating principle, best manufacturers

Speakers and a subwoofer are integral elements of a modern acoustic system. The first ones are responsible for sound reproduction in different frequency bands, and the second one enhances the bass. The only purpose of the subwoofer is to add lower frequencies, which are actively used in club, rock and other types of music. Anyone who has been to concerts can imagine this device in the form of a huge box with large speakers. Home models are somewhat different from professional ones. The material is precisely intended to help with the selection of subwoofers for the home.

How the subwoofer works

There is no need to delve into the principle of operation; it is enough to understand that a subwoofer is a low-frequency speaker. It is responsible for converting the frequency of the incoming signal into sound. Bass reproduction occurs using a coil, which, under the influence of a signal from an amplifier and a magnet, affects the emitter diffuser. As a result, the speaker creates low frequencies (LF) of sound.

Important! Subwoofers always include large drivers. Their diffuser diameter is always larger than that of speakers. There is a pattern: the more impressive the size of the speaker, the cleaner the low frequencies are. Models with a small diffuser reproduce high and mid frequencies better.

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Subwoofer for home, for family. Part 1 - general information

Author: Kostyan Published 01/01/1970

Comrade Kostyan ( [email protected] ru

), who ate the dog (frrr!, meow) in building subwoofers and amplifiers for them, shared with us some basic information regarding his craft. In fact, he knows much more, but not a single threat of being brutally scratched broke his persistence and forced him to give up all his secrets...

Assembling a home subwoofer will require you to:

1. FREE TIME CAR (from a week to a month)
2. MONEY (the cooler the sub, the more)
3. PATIENCE AND ACCURACY - I.E. WISHES

This is quite enough!!!!!!!!!!!

Let's get started

Driver selection

First, you need to successfully select a dynamic head (popularly called a speaker). We select according to the following criteria:

1. The diameter of the speaker is at least 20cm, otherwise the bass will not be enough, and the price for them goes through the roof for 5-6 thousand rubles.
2. We choose a speaker with a rubber suspension, which should ensure that the diffuser moves FORWARD by 1.5-2 cm (more is possible) without any overtones.
3. The resistance should not be less than 3 ohms. If it is 2 ohms according to the passport, then problems may arise with the selection of an amplifier.
4. We determine the power of the speaker. For an apartment, you need to keep within the range of 80-150 watts.
5. You must not forget about the sensitivity of the speaker, it should be at least 90 dB. The sensitivity of the speaker determines how effectively it manages the power given to it by the amplifier. In other words, the sound pressure created by the driver at a distance of 1 meter when a 1 W signal is applied to it.

However, sometimes the sensitivity indicator of a speaker indicated in its passport is not entirely adequate to the real state of affairs. The thing is that power is created by voltage depending on the rated resistance of the driver. If it is equal to 4 ohms (which is typical for car speakers), then a voltage of 2 V is supplied. But 8-ohm home speakers already require 2.83 V. You can play on this difference, which many manufacturers do, indicating the absolute sensitivity of the woofer head, that is, measured with an input signal of 2.83 V. The acceptable sensitivity for a subwoofer is 90 dB, but, as they say, the more, the better. Better, higher output speakers place lower demands on amplifier power. This is clearly illustrated in this table

Sensitivity	Required amplifier power
87dB	200W
88dB	158W
89dB	126W
90dB	100W
91dB	79W
92dB	63W
93dB	50W

As you can see, a difference of even 3 dB is very significant and allows you to save twice as much on amplifier power. But don't rush to rub your hands. There are also pitfalls here. Subwoofers with high sensitivity often suffer from higher cutoff frequencies, which means that while saving on amplifier power, you can easily lose on the deepest bass frequencies. I have a sub with a sensitivity of 91dB

6. it is necessary to determine the equivalent volume i.e. with a volume body.
7. Make sure that when moving the diffuser, the wires from the coil to the terminal block do not touch the frame.

Based on these criteria, you can choose a high-quality speaker for your subwoofer.

Subwoofer Types

What the acoustic design of the woofer head should be depends on many factors. Each type of subwoofer box, be it completely sealed, ported or band-pass, has its own advantages and disadvantages. In addition, a lot depends on the specific platform for building an audio complex. Still: is there an absolute best type of bass enclosure? The answer is negative. Agree: if there was, then why are all the others needed? On the contrary, closed boxes are installed with approximately the same regularity as bass reflexes.

Before we turn to subwoofer enclosures, let's talk about what they are needed for in principle. The problem is that the rear of the speaker generates the same amount of sound as the front, but with the opposite direction. Purely hypothetically, if these two components affect the auditory organs with equal intensity, then they will be neutralized, and you will not hear anything at all. In practice, speakers lacking proper acoustic design will emit high and mid frequencies, but not the bass we need. This happens because the sound wave emanating from the rear of the head must travel a longer path to the listener's ear. As a result, high and mid frequencies are enhanced, while low frequencies are weakened. In a word, we cannot do without “corporation”. What are the boxes made of? The preferences of experienced installers are very different, but most agree on one thing: without wood in one form or another, good bass cannot be achieved. The two most common materials today are medium-fiberboard (MDF) and plywood. These materials have optimal acoustic characteristics, are quite durable, easy to process and are affordable. Chipboard is even more affordable, inferior in its characteristics (sound insulation, density, strength) to the two previous materials. Various types of plastic or plexiglass are more often used when there is a lack of space or for demonstration purposes, but this is already a certain concession on the part of the music.

Completely sealed boxes

A type of subwoofer enclosure that is quite effective in preventing the propagation of sound waves emanating from the rear of the loudspeaker. The “stagnant” air inside the box in this case acts as a spring, controlling the vibrations of the diffuser. Completely enclosed boxes are easier to design than, say, bass reflex and bandpass subwoofers. They are not too picky when it comes to calculating the working volume required for optimal driver operation, and are more lenient with erroneous data provided by the manufacturer in the accompanying product documents. The air cushion protects the speaker from low-frequency impulse noise that sometimes occurs when the system is turned on, when infrasound energy is applied to it, or when simply driving on uneven roads. This is the most preferable option if you need to take up minimal space in the trunk or cabin, since it is believed that in order to reproduce “deep bass” the volume of a completely closed case may be insignificant, although in this case you need to know when to stop. When the volume decreases below acceptable limits, significant losses of the low-frequency component occur. With increasing volume, the output in the region of infrasound frequencies will increase, but then the space-saving effect will be neutralized. In any case, in terms of output, such a subwoofer will be inferior to its larger counterparts of the bass-reflex or bandpass variety. At the same time, in comparison with them, the frequency response of closed cases in the roll-off region is smoother.

Bass reflex subwoofers (ported)

Bass-reflex enclosures, unlike completely closed ones, use the sound emanating from the rear of the speaker for the benefit of powerful bass, since the resulting sound pressure is the sum of the emissions of the diffuser and the port. Accordingly, the use of this acoustic design makes it possible to increase the efficiency of the woofer head. At the same time, bass reflexes are more complex to manufacture and more picky in terms of calculating the working volume, setting the port to the optimal frequency, matching the radiation resistance of the diffuser and the bass reflex pipe, etc. Therefore, it is better to double-check the parameters specified by the manufacturer. But competent work, as a rule, is rewarded according to its merits. It is believed that a bass reflex subwoofer is capable of reproducing bass a whole octave below the cabinet. True, there is one “but”: in this case the box itself should be five times larger. So the use of a case with a bass reflex is often due to the customer’s willingness to part with a certain volume of the cargo compartment.

Bandpass subwoofers

This type of acoustic design can be called a hybrid of the previous two, since its design has characteristic features of both. A typical bandpass sub consists of two chambers, one of which does not have access to the outside, and the second is designed in the form of a bass reflex tunnel. Through it, the bass is concentrated and supplied outward. In a concentrated mode, because the speaker is mounted in a wall separating two air-filled volumes, and the vibrations of the diffuser encounter resistance from both the front and the rear. As a result, the energy supplied to the loudspeaker is not dissipated, but is spent more efficiently than in closed and bass reflex boxes. This cunning structure of the bandpass determines, on the one hand, its higher sound pressure (up to 6 dB compared to closed enclosures), and on the other, its tendency to operate in a narrow low-frequency band. But the good thing about bandpass drivers is that they give you the right to choose, since by changing the volume of the chambers you can either increase the amount of sound pressure created by the low-frequency head or expand the boundaries of the frequency range. However, in order to successfully manipulate volumes, as well as adjust the bass reflex tunnel in accordance with acoustic conditions, you must have extensive installation experience. Here, the “young fighter course” will clearly not be enough. We evaluate our experience and decide how we will design the speaker.

—Part 2—>>

Types of subwoofers

The biggest difference between low-frequency devices is the amplifier. By type of construction they differ in:

• Active. They have a pre-installed amplifier located directly in the subwoofer housing. The design also includes an active crossover, which allows filtering high frequencies and improves the interaction of the subwoofer with the rest of the speaker system. Good models have additional functionality for setting up playback: changing the frequency response, rotating the phase, etc.;
• Passive. There is no amplifier, therefore, the device can be connected in parallel with conventional speakers. It also supports a separate connection. A pass-through device is rarely used, because the system creates unnecessary load on the channel output amplifiers. In practice, the technology leads to a drop in sound volume and dynamics. The connection also negatively affects the sound quality, due to the passive crossover.

Which speaker is better for a subwoofer in a car?

There is no big difference when choosing a low-frequency dynamic head for home and car. When choosing a speaker for a subwoofer, you need to take into account the diffuser material, which has a significant impact on the sound quality. Diffusers made of pressed paper pulp with polymer impregnation have high sound characteristics. Such speakers have a smooth and even frequency response without pronounced peaks and dips. Low frequencies are reproduced very smoothly and naturally. The disadvantage of such designs is their low mechanical strength, which limits the power of the low-frequency channel amplifier, and low moisture-proof properties. Therefore, speakers with paper cones are not used in car sound systems.

Polypropylene diffusers are widely used in the production of speakers for consumer goods. The best polypropylene diffusers approach the quality of reproduction of bass frequencies to paper products, which are accepted as a high standard. The disadvantage of polypropylene diffusers is less detail in musical parts at low frequencies. Diffusers made of carbon composites have an uneven frequency response with sharp peaks and dips. To level and smooth it, you have to use complex filters with a high cutoff slope and correction chains. Speakers with Kevlar diffusers have approximately the same characteristics. Loudspeakers with metal cones in woofers are used to produce huge output power, while reducing sound quality. Which speaker is best for a subwoofer. For a home sound system, it is best to use a speaker with a paper cone. For a car speaker, speakers where the moving system is made of polypropylene, carbon composite or Kevlar are suitable. Such structures are not susceptible to moisture and are able to withstand a large range of movement without damaging the moving system.

How to choose the right subwoofer for your home?

To successfully select a subwoofer model, you need to take into account the size, configuration of the room and even the arrangement of furniture. All of these factors are individual and cannot be determined in absentia. Despite the lack of input data, I would like to give some basic tips for choosing.

Recommendations for choosing a good subwoofer:

• High quality and durable case. Plastic models do not fit this description. During operation, the flimsy material creates vibrations that undesirably affect the quality of the bass. It is better to give preference to a case made of MDF. True, it is not completely protected from distortion; powerful systems can lead to rattling of the case. The best option is a wooden base. You can determine the quality of a material by weight; wood is always heavier than its substitutes.
• Price and model type. Closed design models are much more expensive than open ones, but have a richer and clearer sound. Bass reflex devices (without speaker protection) cannot show similar sound dynamics, although they still produce good sound and are much cheaper. However, they are not characterized by a sharp change in volume, unlike the closed type.
• Power. For small rooms and apartments there is no need to take a powerful subwoofer. Instead of high-quality audio, there will be unnecessary rattling of objects and an unpleasant hum. For home use, it is optimal to use models with a power of 5-8 W per 1 m2.
• Frequency range. Numbers will help you understand the issue. Frequencies in the range of 20-40 Hz are responsible for deep bass, frequencies from 40 to 80 Hz are responsible for mid-bass, and high frequencies are considered to be 80-160 Hz. Subwoofers operating in the 40-200 Hz range are widely used and do not support low frequencies. For home, the optimal value is 30-60 Hz.
• Depth and realism of sound. Apart from the frequency range, there are no characteristics that allow you to determine the quality of audio in absentia. Before buying, you should listen to how well the device copes with its task - reproducing low frequencies.

Important! Not all characteristics are listed above; you also need to focus on the availability of settings, additional options, ergonomics, ease of control, etc. All of these parameters play a minor role and affect the final result.

Speaker for subwoofer characteristics

To select a speaker for a subwoofer, you first need to know the power of the low-frequency amplifier. This parameter is used to select the power of the dynamic head. An important parameter is also the resonant frequency of the loudspeaker. The optimal natural resonance frequency for a low-frequency channel loudspeaker is considered to be in the range of 25-40 Hz. Speakers with a frequency below 20 Hz are rare, and those with a frequency above 40 Hz are not suitable for high-quality and powerful low-frequency speakers. Loudspeakers for the low-frequency channel can have voice coil impedances of 2, 4 and 8 ohms. A loudspeaker with a 2 Ohm coil needs a special amplifier, since with a bridge connection, each channel of the amplifier will have 1 Ohm and not every ULF model provides operation in this mode. A resistance of 4 Ohms is considered optimal for both a home speaker and a car low-frequency channel. Each loudspeaker has its own amplitude-frequency response. Correct calculation of the acoustic speaker allows you to eliminate some nonlinearity and smooth out peaks and troughs. Since any low-frequency speaker reproduces a wide frequency band, a passive LC filter is placed at the input of the low-frequency speaker system, which “cuts” or greatly limits the level of those frequencies that the speaker should not reproduce.

Among the companies producing loudspeakers for low-frequency speakers are the following:

• Alpine
• Hertz
• Focal
• Pioneer

The speakers of these brands are distinguished by high build quality, reliability and durability. They can be used in any low frequency channels.

Best Home Subwoofer Manufacturers

The following brands are at the peak of their fame and enjoy the love of users:

• Yamaha. The company comes from Japan. It is a benchmark in the world of musical equipment. A company with more than a century of history began producing acoustics in 1971, when it invented the first integrated circuit of its own manufacture. It produces subwoofers for various purposes, including household models.
• Pioneer. In terms of popularity and quality of products, it is practically not inferior to the leader. The company is focused on developing all kinds of acoustics, but the greatest emphasis is on receivers, speakers and subwoofers, including automobile ones.
• JBL. The world leader has its head office in America. It is distinguished by the production of advanced, multifunctional subwoofers. Mainly engaged in the production of high-end systems, but there are also budget analogues in the range.

TOP 3 subwoofers for small rooms

This includes models with power up to 80 W. They best reveal their potential in small spaces up to 20 m2.

YAMAHA YST-SW012

The compact bass reflex subwoofer has a cubic shape and a laconic design. The body uses wood to prevent unwanted distortion and maintain high sound quality. The power of the device is 100 W with a radiator diffuser diameter of 20 cm. The listed characteristics are sufficient to create rich and pure low frequencies. The subwoofer is a universal type that can be included in a home theater, music center or any amateur equipment.

Pros:

• stable wooden body;
• neat assembly;
• compact dimensions;
• powerful bass.

Minuses:

• there is no cutoff frequency regulator;
• There is no auto shut off feature.

Price: 7990 rubles.

YAMAHA YST-FSW050

The low but wide body allows you to place the subwoofer on any flat surface without the risk of tipping over. The basic controls are located on the front side and are located next to the air intake hole. In small rooms it shows good results both in terms of volume and quality of low frequencies. However, it practically does not produce low bass frequencies, covering only 35-160 Hz, which is due to the small 165 mm speaker. It is made of durable fiberboard, which is ideal for a power of 100 W.

Pros:

• deep bass for its characteristics in rooms up to 20 m;
• durable body;
• There is no unpleasant hum in inactive mode, typical of most models.

Minuses:

• there is no automatic switching on and off;
• There are no additional settings, only a volume control.

Price: 9990 rubles.

YAMAHA YST-SW216

An active subwoofer classified as a bass reflex type. The shape resembles the YST-SW012 model, but has a kind of platform-stand. Blends perfectly into home systems with clear, distortion-free bass. A speaker 25 cm in diameter with a power of 270 W is responsible for deep low frequencies. Covers a large frequency range - from 20 to 160 Hz and has the ability to more accurately adjust the sound using controls on the body.

Pros:

• power is optimally selected for rooms up to 20 m2;
• first-class assembly;
• wide range of supported frequencies.

Minuses:

• wheezing may occur at high volumes;
• the varnished surface quickly becomes dirty.

Price: 24,990 rubles.

TOP 3 subwoofers for rooms up to 30 sq. m

The models listed above are not best suited for rooms with an area of ​​20-30 m2. In such rooms it is better to use more powerful devices.

YAMAHA YST-SW215

Comes with built-in amplifier. The subwoofer has a power of 150 W, which is enough for medium and relatively large rooms. Provides rich bass across almost the entire frequency band. Impulse parameters and sound purity are maintained down to the lower octave. Equipped with exclusive Q-Bass technology. Its essence comes down to the direction of the speaker down. This solution improves the uniformity of sound propagation over 360°. There is no need to worry about distortion, because the body is based on wood.

Pros:

• crisp, clean sound;
• there is a system for independent transition to sleep mode;
• manual phase and volume adjustment function.

Minuses:

• auto shutdown can occur even when operating at minimum volume;
• Dust is clearly visible on the coating; you will have to wipe it often.

Price: 16,490 rubles.

PIONEER S-51W

One of the inexpensive and advanced subwoofer models, covering the frequency range from 26-900 Hz. It has a laconic design in the shape of a cube with legs. It has good dynamics and bass depth. Characteristic hums and ringing are not typical for the device; it works quietly and without unnecessary sounds. The only drawback of the device is its sensitivity to overloads, which can cause wheezing. Under normal conditions it works properly, for which a 20 cm emitter with a power of 150 W is responsible.

Pros:

• voluminous, clear and powerful bass;
• handles very low frequencies perfectly;
• Self-on/off technology.

Minuses:

• something needs to be done with the sharp corners of the body if there are children in the house;
• At high volumes, wheezing appears periodically.

Price: 18,390 rubles.

VELODYNE IMPACT-10

A floor-standing bass reflex subwoofer with an amplifier inside can produce high-quality sound in low and mid-bass frequencies. In HF it also shows acceptable results, but does not cover the entire range, because it works in the range of 32-140 Hz. It has an optimal power of 165-275 W for halls with an area of ​​25 to 30 m2. It is made of high-strength MDF, the material is only slightly inferior to wood. To prevent possible violations of sound purity, all seams are sealed and treated with sealant. The model is based on one speaker 25 cm in diameter.

Pros:

• juicy, clear sound;
• there are sound adjustment functions;
• stylish design.

Minuses:

• the direction of the sound flow is slightly felt;
• slight hum in passive mode.

Price: 29990 rubles.

TOP 3 subwoofers for rooms from 30 sq. m

In large rooms, the following subwoofers are clear favorites.

JAMO SUB 210

Available in different colors: black, wood, white, dark wood. Manufactured in a classic design with a long-throw driver for low-frequency reproduction. The model is characterized by clear and rich bass, for which the amplifier is responsible. The power at moments of maximum load can reach 200 W. The sound is produced by a 203 mm bass reflex driver, directed downward. The solution helps to increase sound pressure and ensure proper distribution of audio in all directions.

Pros:

• small size and light weight;
• assortment of colors;
• voluminous, bright bass without distortion.

Minuses:

• excessively bright LED;
• Smooth adjustment knobs impair sensitivity.

Price: 25,990 rubles.

JBL STUDIO SUB 260P

The bass reflex subwoofer from the USA is characterized by high functionality and a power of 300 W. Peak values ​​can reach 600 W. Despite the simple design, the model remains stylish thanks to the black color of the wood and plastic inserts. To prevent plastic elements from degrading the sound, they are treated with insulating materials. The active subwoofer covers the range of 32-150 Hz, that is, this includes almost the entire low-frequency spectrum.

Pros:

• huge power, suitable for full-fledged cinemas;
• there is a system for manual adjustment of parameters;
• high-quality and clear sound throughout the entire low-frequency range.

Minuses:

• there is no remote control;
• The controls are located on the rear panel, making them difficult to use.

Price: 37,910 rubles.

BOWERS&WILKINS ASW608

The junior model of the well-known series of subwoofers has a number of unique properties. This includes an unusual design based on Kevlar, paper and special resins. The material is characterized by high strength and mobility. The 20 cm speaker with an easily bending diaphragm produces rich and deep bass. There is no need for a separate amplifier, because the built-in device can output 200 W. The bass extension and equalization system is adjustable using toggle switches on the back cover of the subwoofer.

Pros:

• dynamic and deep bass;
• supports many connection methods;
• allows you to adjust the cutoff frequency and volume;
• automatic sleep mode.

Minuses:

• no remote control;
• The power LED is too bright.

Price: 39,490 rubles.

FAQ on designing subwoofers for those who want to make their own subwoofer with understanding.

(click on the picture to enlarge) 4) When assembling, you need to put it on glue - IMHO, PVA is best, but the plates should be pressed tightly during gluing - this can be done with the help of clamps, but if they are not there, you can first make holes and plant them on self-tapping screws. (for those who have never done this, let me remind you that the self-tapping screw must fit freely into the hole for the screw in the attached surface, and the hole in the attaching surface must be of such a diameter that the self-tapping screw does not break chipboard/plywood/mdf (i.e. on 3mm thinner than a self-tapping screw (approximately)). It is better to tighten this thing with an electric screwdriver or, as I do, with a drill with an attachment for a self-tapping screw (and you can press it harder with a drill, but you should be careful because you can get a dislocation), because manually twisting - it won’t work out very well; if it’s possible to twist it in half in chipboard, then in plywood or MDF - it will be real torture. 5) Bass reflex - sewer pipes are usually used, they can be found on any market for building materials of various calibers, then if the pipe is long then it’s better to strengthen it in some way, perhaps fabric + epoxy as an option. As an option, you can also use pipes on which linoleum is wound in stores, thick pipes are excellent in general, and you won’t have to pay for them, come up and ask - they’ll give you at least 20 of them. 6) how to cut a hole for the speaker and FI - if there are many ways: The most correct one is with a milling cutter - it will work out neatly and accurately. You can use special files for jigsaws, which allow you to cut in a circle, You can also use a drill. Make holes along the contour next to each other (but not protrude beyond the circle required for the speaker) and then finish the job using a jigsaw, after which you can level it manually or using something else - it’s whatever you think of. 7) The case must be sealed; I strongly recommend that all internal joints be coated with silicone sealant. Now let's move on to finishing. I won’t dwell much here. Only your ingenuity and perseverance decide here. I'll tell you a couple of points: 1) The case must have smooth walls! At the junction of the sides, one should not go beyond the other; if it does, it must be removed, usually this is done with a grinder. 2) Next, I can offer an option for the lazy: (it only requires that the walls be basically even) the use of laminated fiberboard (it is only 2 times more expensive than regular fiberboard, and one sheet (one meter by 3 meters) is enough for the entire subwoofer (price question about 10 USD per sheet (well, at least here in Belarus)), or use regular fiberboard and then stick a film on it. Along the edges, as necessary, you can stick so-called corners. 3) For those who decide to paint the subwoofer and then varnish it, I can say that you will have to work very hard with the surface, I don’t know the full technology because I didn't do this, but used option 2. If you have already decided on this feat, don’t be too lazy to search the Internet yourself. Fortunately, there is enough material about this. 4) There are all sorts of different materials, on the forum I saw how a person used something like granite film as a finishing material, or I don’t even know what it’s called, it looks like granite (but this is not an ordinary film that is sold in rolls), so what are you looking for...

What else are we missing? — that’s right, amplifier. I’ll point out a couple of points that are very often of interest: 1) Power. The power of the amplifier should be selected based on the power of the speaker, you should focus on the specified RMS power, and make (order, buy) an amplifier of approximately this power. It is possible with lower power 2) What class of amplifiers should I use? there is no definite answer, you can give preference to class D, for reasons of ease of use. Here you can read about amplifier classes https://www.soundhousepro.com/articles.php?id=16 3) the use of microcircuits (TDA 7293( 4) LM 3886, etc.) it is reasonable to use only with low-power speakers such as 35GDN, or at least with 75GDN (by the way, so you know that 75GDN stands for dynamic low-frequency 75-watt head, and similarly with other speakers... gdv - dynamic head high-frequency and so on...), they are clearly not enough to drive car subwoofer speakers, you need to look at home subwoofer speakers individually, but it is better to use transistor amplifiers, one of the most mature is the Holton amplifier, this is an industrial design, so it is the easiest and simplest to set up can tolerate a lot. Here is the material on it https://www.sibaudio.ru/?id=30&pid=32&cid=7, https://audio.micronet.lv/diy/soldering/fjedor.html 4) the subwoofer also needs filters and other paraphernalia here is some interesting material: https://audio.micronet.lv/diy/soldering/control.html here is more, simpler https://www.bluesmobil.com/shikhman/arts/subfil.htm

And for last I left such a concept as a subwoofer in the room. Remember at the beginning of the article I talked about the length of sound waves in the area of ​​​​the subwoofer? - so the fact is that at these frequencies the wavelength can be comparable to the size of the room, and because of this, wave interference occurs (wave superposition, in which they are mutually amplified at some points in space and weakened at others. The result of interference depends on the phase difference of the overlapping waves taken from Wikipedia.) i.e. when reflected from the walls, areas in the room with weakened sound and areas with enhanced sound will be created, and not the entire frequency spectrum is amplified/attenuated, but certain frequency sections of the subwoofer operating range, and that beautiful frequency response that we drew in the program is mercilessly deformed, with a rise near walls will be at those frequencies whose length is 2 times greater than the longest side of the room, while in the middle of the room, on the contrary, there will be attenuation, in a standard room of 5x4 meters this is a frequency of 50 Hz (this is the strongest mode, there will also be less pronounced modes for frequencies the length of which is twice the height and width of the room), the sound becomes booming and loses its structure, so you need to choose the location of the subwoofer very carefully and exactly for the place where you will usually sit when listening to music. There is also one more point, although it concerns more the physiology of the human ear. The fact is that a person has different sensitivity of the inner ear (with which we generally “hear”) and therefore if you take a speaker that has linear (in the specified range it should have absolute linearity (i.e. at any of the frequencies the volume will be the same

but in life there is no such thing, unfortunately) (and not what the manufacturers indicate on the speakers (they indicate the frequency response with a possible blockage at the edges of the frequencies (those who are conscientious in terms of the level are -3dB, those who are not conscientious can indicate in terms of the level - 40 dB (-3dB is about 2 times quieter, when we say -10 dB it will be quiet relative to the rest of the range, and -40 so nothing will be heard at all)))) Frequency response let's say from 20 Hz to 5000 Hz, We will take 40 Hz and 3000 Hz as control points, and apply sinusoidal signal of the same amplitude (voltage), and what will we hear? - when we apply a signal at a frequency of 3000 Hz (mid frequencies) then we apply a signal at a frequency of 40 Hz, then 40 Hz will be heard noticeably quieter, for reference I will say that subjectively we will not hear 20 Hz at all if it is quieter than 100 dB (decibel ) and this is not at all quiet, at mid frequencies at this level we will try to turn it off as quickly as possible. Also, as the volume increases, this difference between sensitivity at different frequencies evens out a little. There are also many questions about where the speaker should be directed. There can only be 1 option - as you like, i.e. There is no optimal solution for all cases. the speaker can be directed towards the room, towards the wall, towards the floor or the ceiling, etc. ... by directing the speaker in a certain direction, we can use the room as a kind of equalizer and adjust the sound. Of all, I will dwell in more detail only on the option of directing the speaker to the floor. Questions arise about what height of the legs to use, and here again I am powerless - this is all selected solely by ear, but usually 5-10 cm, but I want to note that very strong vibrations go to the floor and everything can ring, and I don’t think it’s a problem for the neighbors either cool, you can use some other dissipative surface between the speaker and the floor, but it must be very hard, for example a 5 cm plate of granite or a 6-7 cm plate of solid wood or glued plywood. those. the gap between the plate and the floor is not important, it can be 1-2 cm, or as much as you like, but only the gap between the speakers and this plate is adjusted. When orienting to the wall, the same rules apply, but I don’t see the point in this, of course, if orientation to the wall is not an element of finding the correct location of the subwoofer (when the distance to the walls is more than 50cm) Questions are also asked about the relative position of the speaker and bass inlet - unfortunately here similar to the previous one - you can direct the speaker downwards, for example, and the phasic towards the room, I do not recommend pointing the phasic towards the floor. its setting will change.

The article is not yet completely ready, it will be supplemented and edited, for your comments and suggestions, please contact the forum, nickname Gorilin

Good luck in your endeavors!

(click on the picture to enlarge)
my sub
Discussion https://forums.overclockers.ru/viewtopic.php?t=249580 https://www.vegalab.ru/forum/showthread.php?t=15672

Comparing models

The main characteristics of the considered subwoofers in one place.