In this article, we will consider in detail how to make a subwoofer with your own hands, if you do not have professional knowledge in the field of electroacoustics and there is no desire to use previously unknown and incomprehensible circuits, although of course you will still have to do a few measurements.
What is a subwoofer and for what purposes is it used?
A subwoofer is popularly called simply a sub, and if you translate this word literally, it sounds quite funny - a bark. In fact, this is a real bass speaker, characterized by low frequency, housed in a special box with an extremely complex device.
Today, if you look at a photo of a subwoofer with your own hands, you will notice that they are used in a huge number of different places, ranging from simple everyday situations when it is installed at home and ending with the fact that today many people use subwoofers in their cars.
If you can find a good drawing of a subwoofer and make it correctly, then you can definitely take on almost any complexity of speakers, since low frequency reproduction is one of the most difficult moments in the world of electroacoustics.
It is only important that the subwoofer circuit fully meets your idea of ideal acoustics.
A little about bass
Reproducing different basses is, in principle, quite a difficult process. In general, the low-frequency region of absolutely any spectrum of available sound waves varies depending on its psychophysiological strong impact on several areas.
In order not to make a mistake in choosing a bass, truly high-quality speaker, and subsequently the box for the subwoofer was made quite quickly, first of all it is necessary to understand their key significance and the corresponding boundaries.
Depth
For various types of wind organs in halls specially renovated for musical instruments, the sub-bass has a significant influence on the timbre of the sound. It is for the sounds of nature and various man-made disasters, such as unexpected explosions, that quite strong sub-bass components are characteristic.
It is worth noting that most people either do not hear sub-bass at all, or they hear it, but not well enough. For example, if you filter out the fundamentally different sounds of a nuclear explosion and a strong hurricane, like a tornado in the tropics, from everything except sub-bass, then we can say with absolute certainty that it is unlikely that any of the listeners will be able to understand what is actually happening.
It is for this reason that almost everyone optimizes a home subwoofer exclusively for midbass.
How to choose a speaker?
When choosing, you should definitely pay attention to the fact that a complete calculation of the entire acoustic design is always made only according to the known Thiel-Small parameters.
When creating a good subwoofer on your own, it is only important to take into account the absolute quality factor of the head precisely at its main resonant frequency. This is due to the fact that it is used to select the ideal option for future acoustic design.
Car subwoofers
If you are interested in car subwoofers, then you should definitely keep in mind that they are most often installed either directly under the driver’s seat or in the trunk compartment.
When placed with the second option, the car subwoofer can take up quite a lot of useful space, so it is not used so often. However, even if the subwoofer is placed under the seat, there are some risks associated, for example, with the fact that in this case it is quite easy to damage it with your feet.
In addition to everything else, it is worth paying special attention to the important point that in a fairly cramped car interior you cannot do without the obligatory effect of masking various noises.
It is for this reason that almost all car subwoofers are optimized primarily for sub-bass.
In conclusion, it is worth noting that, in principle, anyone can make an amplifier for a subwoofer on their own, and this will be quite a fun activity, useful not only for the development of skill, but also the mind.
Note!
DIY subwoofer photo
Note!
Hi all! Once, sitting in a friend’s car and listening to his music, I promised him to build an amplifier for a subwoofer if he bought the sub himself. Some time passed, a friend called and said he bought a passive subwoofer - make an amplifier, there is nothing to do - I had to assemble it... There was a TDA1562 microcircuit - it fits perfectly in a car subwoofer, he etched one board for the amplifier, another for the adder and low-pass filter.
ULF circuit and board
The diagrams were from the Internet. It worked the first time. There is no need to configure anything - just solder without errors.
UMZCH case - aluminum profile from the door, drilled holes for power terminals, speaker terminal, LEDs, variable resistances.
I screwed it all together, soldered the wires, and put handles on the resistor axis. The top, bottom and side walls, from a Chinese radio - I cut them a little deep and blew them out with paint from a can. It didn't even look bad.
A friend has it in the back of a VAZ-2109 on the shelf, the signal is connected to the rear speakers - the low-pass filter does a good job of dampening the signal if it’s from the radio.
Constant power through a 15 A fuse. And standby mode from the radio.
How much does it cost to buy a fairly high-quality low-power subwoofer, and how much does it cost to assemble the same subwoofer? Of course, it’s cheaper to assemble, and even if you have straight arms, we can build a very high-quality subwoofer for your computer at a price several times cheaper than what they sell in the store. By the way, don’t think that the stores sell high-quality equipment - this is not true at all! All boards are assembled in China, that says it all. Of course, there is “white”, better quality China, but it is not for the CIS countries. Today I will tell you how to assemble a sufficiently powerful and high-quality computer for a computer with your own hands from scrap materials.The main thing is to have a high-quality low-frequency speaker on hand, preferably an imported one, but in extreme cases, you can use Soviet-made dynamic heads, for example 25GD from S-30 radio speakers. Since our goal is to assemble only high quality, we will abandon the stereo amplifier and use the TDA2050 microchip.
This amplifier is of fairly high quality and has a decent output power of 32 watts. The article does not give the dimensions of the box, since it is important to maintain a displacement of 7 liters, and let the design be to your taste and individual design. Chipboard boards with a thickness of 0.5 mm were used, the phase inverter was designed for 35 hertz. Subwoofer circuit:
The amplifier is attached to the heat sink. As can be seen from the connection diagram, output diodes are excluded from it, since the TDA2050 has these diodes built into the microchip and there is no point in installing additional ones. The passive low pass filter circuit is shown below. The power supply is a transformer with a power of 50-70 watts, on which two windings with a voltage of 10-12 volts each and a current of at least 2 amperes are wound. You can also make a transformer yourself. To do this, we take any network transformer with a power of 50 watts or more and wind a secondary winding on it, which contains 60 turns with a tap from the middle. Winding is done with wire with a diameter of 1 - 1.5 mm. The power supply diagram is shown below.
The most important thing in designing subwoofers is maintaining tightness, so after completing assembly, you need to carefully place everything in the box, carefully attaching the power amplifier and transformer to the wall of the box, then close the subwoofer cover with PVA glue and self-tapping screws. The glue then needs time to dry, and after a few hours the subwoofer is ready for use.
It is better to make the volume control and input jack at the back. You can connect anything to the subwoofer - a computer, TV, DVD player and even a mobile phone; and remember - if we connect an amplified sound signal to the subwoofer, for example from a laptop or TV, then it plays much louder, since there is no additional amplifier in the low-pass filter and there are large losses. That's all - listen to your health! AKA
A subwoofer amplifier is an essential part of a good speaker system. Without it, it is impossible to achieve normal reproduction of low frequencies. However, it is not necessary to buy this device: if you have sufficient knowledge of electronics, you can make it yourself.
How is sound reproduced - and why do you need a subwoofer with an amplifier?
First, you should remember why you need an amplifier for a subwoofer in the first place. The subwoofer itself is a separate acoustic element (or, more simply, a speaker) designed to reproduce low frequencies. It is not a necessary part: good and large speakers are quite capable of reproducing sounds with a frequency of 20 to 120 Hz on their own. However, such speakers have two inevitable drawbacks:
- Dimensions. You can’t argue with banal physics: the lower the frequency, the larger the area of the sound-emitting element should be. By the way, this is why the ultrasound generator can be designed in the form of a keychain, but for infrasound you will need a device sometimes several meters in size. If we are talking about car acoustics, then there is usually simply nowhere to put two such speakers (for stereo sound) in the cabin.
- Price. Good speakers that optimally reproduce all frequencies cost a lot and not everyone can afford.
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The best solution here is to separate the low frequencies into a separate element that can be placed anywhere. The physiology of human hearing is such that sounds from a subwoofer are not recorded in direction, and stereo sound will not be disturbed.
Subwoofers themselves are divided into two types:
- passive, powered from the system's audio outputs, like regular speakers;
- active, equipped with their own amplifier, where the playback system only needs to send a signal - and the energy to “drive” the diffuser will come from a separate source.
The first type is good because it does not require additional devices - however, a massive low-frequency diffuser “eats off” a fair amount of power. As a result, either the bass is not properly reproduced, or the high frequencies begin to “fail” and sound dirty. That is why for high-quality sound it is best to use active subwoofers with an amplifier.
Types of amplifiers suitable for installation in a car
In practice, an amplifier for a subwoofer in a car can be one of the following types:
- Mono – powers one speaker, that is, only the subwoofer itself. The remaining speakers are content with the signal from the audio output of the radio.
- Two-channel - energy goes to two regular speakers and one subwoofer.
- Four-channel – supplies two low-frequency and four regular speakers.
More complex systems designed for a large number of sound elements, like a car
Subwoofer power amplifiers are impractical and almost never used.
In addition, you can select the amplifier power for the subwoofer. In relation to the power of the subwoofer itself (RMS), they are divided into the following types:
- Less power. Not recommended as it will not allow full use of the acoustics.
- Equal RMS. Safe for a sub, but not for a car. The fact is that the voltage of a regular on-board network with 12 volt outputs can change. If some other electrical appliances are turned on while the amplifier is running, the system will easily go into the clip. This term refers to a situation where they are trying to get more voltage from the amplifier than is available in the power system. A clipped signal is the quick death of a speaker.
- Exceeding RMS. There are pitfalls here: if you constantly listen to “heavy” music with an abundance of low frequencies at high volume, such an amplifier will also burn the subwoofer. However, if used carefully, this option is still the safest.
Is it possible to make a simple amplifier for a subwoofer with your own hands?
Typically, a sound amplifier for a subwoofer is purchased in specialized stores. However, this is completely optional. Having certain knowledge in electrical engineering and skills in working with a soldering iron, you can assemble almost any structure yourself. With the modern availability of microcircuits and transistors, it is not difficult to purchase any parts.
In order to make a subwoofer amplifier with your own hands, you will need:
- chip;
- resistors;
- capacitors;
- transistors.
Depending on the circuit used, additional elements may be required (for example, a ready-made or home-made transformer), but these parts should be enough for a simple subwoofer amplifier.
12 volt car amplifier circuit
In order to assemble an amplifier, you must first decide on the circuit for it. There are several options here:
The simplest option based on the TDA1562 chip. Its advantages:
- ease of installation;
- low power consumption.
The disadvantage of the circuit is that you cannot get more than 50 watts of power out of it.
A more complex amplifier circuit for a subwoofer is a variant based on the TDA7294. It includes a subwoofer converter and a low-pass filter mounted on a common printed circuit board.
Finally, here is a circuit that allows you to assemble an amplifier for a 1000W subwoofer based on the TDA2500. Two channels of approximately a kilowatt each. However, this option is recommended to be used only in extreme cases: in order to use such a powerful amplifier for a subwoofer, you will have to additionally solve power problems.
Finally, a slightly simpler 800w subwoofer amplifier. Here is its power supply diagram:
How to assemble an amplifier?
For reliability and compactness of assembly, installation must be done on a printed circuit board. To do this you will need:
- Computer.
- “Sprint-layout” program (or similar) for calculating and designing boards.
- Laser printer.
- Foil-coated textolite.
- Ferric chloride solution.
The sequence of actions here will be as follows:
- The program creates a board diagram.
- The board is printed using a laser printer. It is highly advisable to use photo paper and a branded cartridge - refilled ones may have too low toner density. It should look something like this:
- The resulting pattern is carefully cut out along the contour and applied to a textolite blank. Before this, the workpiece must be sanded with fine sandpaper (to remove oxides) and degreased with acetone. Then the piece of paper laid down with the design is ironed with a hot iron. This is the most important operation; the quality of the board depends on it. If done correctly, you will end up with a blank with a wiring pattern applied to it with toner. The temperature must be set to the maximum so that the toner re-melts and sticks to the foil.
- The workpiece, which has cooled after ironing, is soaked in water, after which the soaked paper is carefully removed.
- The drawing is checked. If some elements are not printed, you can complete them with a permanent marker. However, you should not abuse this: the marker is not as reliable as toner.
- The workpiece is then etched in ferric chloride. The result is pure PCB with copper preserved only where it was protected by a layer of toner or marker.
On the resulting board it is already possible to mount a microcircuit and other parts in accordance with the chosen design. But before that you need to decide on your diet. Here again you will need a computer and a program for calculating transformers: it is necessary to convert the on-board 12 V to at least 80. After the calculation, the winding is mounted on the core with insulation of each layer. An excellent option for a homemade car subwoofer is to use old transformers from a TV with a corresponding recalculation of the winding.
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Lastly, a low-pass filter is installed. Without it, high-frequency signals will go to the sub - and then the very use of the subwoofer is pointless. The filter is mounted in the same way as the rest of the amplifier, and after that you can proceed to testing on the on-board network and radio.
Important: when testing an amplifier, you must connect it only through resistors and an incandescent lamp! Otherwise, there is a risk of burning the parts before the structure is ready.
Installing the amplifier in the case and using wires
Once the electronics are ready, you need to think about the housing and wires for power and signals. There are many options here depending on what materials are available. In particular, you can use:
- plywood;
- aluminum profile;
- Fiberboard, etc.
Separately, you need to take care of the wires. They must be well insulated to avoid electromagnetic interference and signal distortion.
- About computer calculations
- What is this and why?
- What kind of speaker do you need?
- System structure
- Decor
- Car subwoofers
- It couldn't be simpler
- It's also simple
- Powerful 6th order
- 4th order
- Electronics
- How to calculate a subwoofer?
In this article we will look at how to make a subwoofer with your own hands, without delving into the depths of electroacoustics, without resorting to complex calculations and subtle measurements, although you will still have to do some things. “Without any special difficulties” does not mean “slap on a brick, drive away, grandma, mogarych.” These days, it is possible to simulate very complex acoustic systems (AS) on a home computer; See the end for a link to a description of this process. But working with a finished device on a whim gives something that you cannot get by any reading or viewing - an intuitive understanding of the essence of the process. In science and technology, discoveries at the tip of a pen are rarely made; Most often, a researcher, having gained experience, begins to “gut” understand what’s what, and only then looks for mathematics suitable for describing the phenomenon and deriving design engineering formulas. Many great people recalled their first unsuccessful experiences with humor and pleasure. Alexander Bell, for example, initially tried to wind the coils for his first telephone with bare wire: he, a musician by training, simply did not yet know that live wire needed to be insulated. But Bell still invented the telephone.
About computer calculations
Do not think that JBL SpeakerShop or other acoustics calculation program will give you the only possible, most correct option. Computer programs are written using established, proven algorithms, but non-trivial solutions are impossible only in theology. “Everyone knows that you can’t do this. There is a fool who doesn't know this. He is the one who makes the invention."– Thomas Alva Edison.
SpeakerShop appeared not so long ago, this application was developed very thoroughly and the fact that it is used very actively is an absolute plus for both developers and amateurs. But in some ways the current situation with him is similar to the story with the first photoshops. Who else used Windows 3.11, remember? - back then they just went crazy with image processing. And then it turned out that in order to take a good picture, you still need to know how to take photographs.
What is this and why?
A subwoofer (simply a sub) in its literal translation sounds funny: a burr. In reality, this is a bass (low-frequency, woofer) speaker that reproduces frequencies below approx. 150 Hz, in a special acoustic design, a box (box) of a rather complex device. Subwoofers are also used in everyday life, in high-quality floor-standing speakers and inexpensive desktop ones, built-in and in cars, see fig. If you manage to make a subwoofer that reproduces bass correctly, you can safely take on any speaker, because LF reproduction is perhaps the fattest of the whales on which all electroacoustics stand.
It is much more difficult to make a compact low-frequency section of the speaker system than the mid-range and high-frequency (mid- and high-frequency) parts, firstly, due to an acoustic short circuit, when sound waves from the front and rear radiating surfaces of the speaker (loudspeaker head, GG) cancel each other out: lengths LF waves are meters, and without proper acoustic design of the GG, nothing prevents them from immediately converging in antiphase. Secondly, the spectrum of sound distortion in the low frequencies extends far into the best audible region of the midrange. In essence, any broadband speaker has a low-frequency section into which midrange and high-frequency emitters are built. But from the point of view of ergonomics, an additional requirement is imposed on the subwoofer: a subwoofer for the home should be as compact as possible.
Note: All types of acoustic design of LF GG can be divided into 2 large classes - some dampen the radiation from the rear of the speaker, the second reverse it in phase by 180 degrees (turn the phase) and re-radiate it from the front. A subwoofer, depending on the properties of the GG (see below) and the required type of its amplitude-frequency response (AFC), can be built according to a circuit of one class or another.
People can distinguish the direction of sounds below 150 Hz very poorly, so in an ordinary living room a sub can be placed basically anywhere. MF-HF speakers (satellites) of acoustics with a subwoofer are very compact; their location in the room can be selected optimally for the given room. Modern housing is, to put it mildly, no different in terms of excess space and good acoustics, and it is not always possible to “stuff” at least a couple of good broadband speakers into it correctly. Therefore, making a subwoofer yourself allows you not only to save a very significant amount of money, but also to still get a clear, true sound in this Khrushchev, Brezhnevka or modern new building. A subwoofer is especially effective in full surround sound systems, because... putting 5-7 columns on a full page each is too much even for the most sophisticated users.
Bass
Reproducing bass is not only technically difficult. The generally narrow low-frequency region of the entire spectrum of sound waves is heterogeneous in its psychophysiological effect and is divided into 3 regions. To choose the right bass speaker and make a subwoofer box with your own hands, you need to know their boundaries and meaning:
- Upper bass (UpperBass) – 80-(150…200) Hz.
- Average bass or midbass (MidBass) – 40-80 Hz.
- Deep bass or sub-bass (SubBass) – below 40 Hz.
Top
Middle
For midbass, the main task when creating a subwoofer is to ensure the highest GG output, a given shape of the frequency response and its maximum uniformity (smoothness) in the minimum volume of the box. The frequency response, which is close to rectangular towards lower frequencies, gives a powerful but harsh bass; Frequency response, uniformly falling - clean and transparent, but weaker. The choice of one or the other depends on the nature of what you are listening to: rockers need an “angrier” sound, while classical music needs a gentler sound. In both cases, large dips and spikes in the frequency response spoil the subjective perception with formally identical sound technical parameters.
Depth
FI
Note: a passive radiator (PI) is equivalent in all respects - instead of a pipe with a port, a bass speaker is installed without a magnetic system and with a weight instead of a coil. There are no “tuning-free” methods for calculating PI, which is why PI is a rare exception in industrial production. If you have a burnt-out bass speaker lying around, you can experiment - the adjustment is made by changing the weight of the load. But keep in mind that it is better not to make an active PI for the same reason as a closed box.
About deep crevices
Acoustics with deep slots (items 4, 6, 8-10) are sometimes identified with FI, sometimes with a labyrinth, but in fact this is an independent type of acoustic design. There are many advantages to a deep slit:
The deep slot has only one drawback, and only for beginners: it is not adjustable after assembly. As it is done, so it will sing.
About anti-acoustics
Bandpasses
BandPass means band pass, which is the name given to speakers without direct radiation of sound into space. This means that bandpass speakers do not emit midrange due to its internal acoustic filtering: the speaker is placed in a partition between resonating cavities that communicate with the atmosphere through pipe ports or deep slots. Bandpass is an acoustic design specific to subwoofers and is not used for completely separate speakers.
Bandpasses are divided by order of magnitude, and the order of a bandpass is equal to the number of its own resonant frequencies. High-quality GGs are placed in 4th-order bandpasses, where it is easy to organize acoustic damping (position 5); low- and medium-quality - in 6th order bandpasses. Contrary to popular belief, there is no noticeable difference in sound quality between the two: already at the 4th order the frequency response at low frequencies is smoothed to 2 dB or less. The difference between them for an amateur is mainly in the difficulty of setting: in order to accurately adjust the 4th bandpass (see below), you will have to move the partition. As for 8th order bandpasses, they obtain 2 more resonant frequencies due to the acoustic interaction of the same 2 resonators. Therefore, 8th bandpasses are sometimes called 6th order class B bandpasses.
Note: idealized frequency response at low frequencies for some types of acoustic design are shown in Fig. red. The green dotted line shows the ideal frequency response from the point of view of the psychophysiology of hearing. It can be seen that there is still enough work in electroacoustics.
Amplitude-frequency characteristics of the same loudspeaker head in different acoustic designs
Car subwoofers
Car subwoofers are usually placed either in the cargo compartment, or under the driver’s seat, or behind the back of the rear seat, pos. 1-3 in Fig. In the first case, the box takes up useful volume, in the second, the sub works in difficult conditions and can be damaged by feet, in the third, not every passenger will be able to tolerate powerful bass right next to their ears.
Recently, car subwoofers are increasingly being made of the stealth type, built into the rear fender niche, pos. 4 and 5. Sufficient sub-bass power is achieved by using special auto speakers with a diameter of 12” with a rigid diffuser, which is little susceptible to the membrane effect, pos. 5. How to make a subwoofer for a car by molding a wing niche, see next. video.
Video: DIY stealth car subwoofer
It couldn't be simpler
A very simple subwoofer that does not require a separate bass amplifier can be made using a circuit with independent sound emitters (IS), see fig. In fact, these are two channel LF GGs placed in a common long housing installed horizontally. If the length of the box is comparable to the distance between the satellites or the width of the TV screen, the “blurring” of the stereo is hardly noticeable. If listening is accompanied by viewing, it is completely unnoticeable due to involuntary visual correction of the localization of sound sources.
Using the scheme with independent FMs, you can make an excellent subwoofer for a computer: a box with speakers is placed in the far upper corner under the tabletop. The cavity underneath is a resonator tuned to a very low frequency, and an unexpectedly good sub-bass comes out from the small box.
FI for a subwoofer with independent FIs can be calculated in the speaker shop. In this case, the equivalent volume Vts is taken twice as large as measured, the resonant frequency Fs is 1.4 times lower, and the total quality factor Qts is 1.4 times higher. The material of the box, as elsewhere below, is MDF from 18 mm; for subwoofer power from 50 W – from 24 mm. But it is better to place the speakers in a closed box; in this case, it can be done without calculation: the length inside is taken at the installation site, ranging from 0.5 m (for a computer) to 1.5 m (for a large TV). The internal cross-section of the box is determined based on the diameter of the speaker cone:
- 6” (155 mm) – 200x200 mm.
- 8” (205 mm) – 250x250 mm.
- 10” (255 mm) – 300x300 mm.
- 12” (305 mm) – 350x350 mm.
In the worst case (an under-table computer sub with 6” speakers), the volume of the box will be 20 liters, and the equivalent with filling will be 33-34 liters. With a UMZCH power of up to 25-30 W per channel, this is enough to get decent midbass.
Filters
In this case, it is better to use LC filters of type K. They require more coils, but in amateur conditions this is not essential. K-filters have low attenuation in the stopband, 6 dB/oct per link or 3 dB/oct per half-link, but have an absolutely linear phase response. In addition, when operating from a voltage source (which, with great accuracy, is the UMZCH), the K-filter is little sensitive to changes in load impedance.
At pos. 1 pic. Diagrams of K-filter sections and calculation formulas for them are given. R for the low-frequency GG is taken equal to its impedance Z at the low-pass filter cutoff frequency of 150 Hz, and for the high-pass filter equal to the satellite impedance z at the high-pass filter cutoff frequency of 185 Hz (formula in position 6). Z and z are determined according to the diagram and formula in Fig. above (with measurement diagrams). Working diagrams of filters are given in pos. 2. If you prefer to buy additional capacitors rather than wind coils, exactly the same parameters can be made from P-links and half-links.
Data and circuits for making filters for a simple subwoofer with independent emitters
The attenuation of the low-pass filter in the stopband is 18 dB/oct, and the attenuation of the high-pass filter is 24 dB/oct. This frankly non-trivial ratio is justified by the fact that the satellites are unloaded from the low frequencies and give a cleaner sound, and the remainder of the low frequencies reflected from the high-pass filter is sent to the low-frequency speakers and makes the bass deeper.
Data for calculating filter coils are given at pos. 3. They need to be positioned mutually perpendicular because K-filters operate without magnetic coupling between the coils. When calculating, the dimensions of the coil are specified and the number of turns is determined using the inductance found in the order of calculating the filter. Then, using the laying coefficient, the diameter of the wire in the insulation is found; it should be at least 0.7 mm. It turns out less - increase the size of the coil and recalculate.
Settings
Setting up this subwoofer comes down to equalizing the volumes of the bass and satellite speakers, respectively. cutoff frequencies. To do this, first prepare the room for acoustic measurements, as described above, and a tester with a bridge and transformer. Next you will need a condenser microphone. For a computer one, you will have to make some kind of microphone amplifier (MCA) with bias applied to the capsule, because a regular sound card cannot simultaneously receive a signal and emulate a frequency generator, pos. 4. If you can find a condenser microphone with a built-in MUS, even an old MKE-101, great, its output is connected directly to the primary (smaller) winding of the transformer. The measurement procedure is simple:
- The microphone is fixed opposite the geometric center of the satellites at a horizontal distance of 1-1.5 m.
- Disconnect the subwoofer from the UMZCH and apply a 185 Hz signal.
- Record the voltmeter readings.
- Without changing anything in the room, they turn off the satellites and connect the sub.
- A 150 Hz signal is supplied to the UMZCH and the tester readings are recorded.
Now you need to calculate the equalizing resistors. The volumes are equalized by muting the louder links in a series-parallel circuit (item 5), because it is necessary to keep the previously found values of Z and z unchanged modulo. Calculation formulas for resistors are given in pos. 6. Power Rg – not less than 0.03 of the power of the UMZCH; Rd – any from 0.5 W.
It's also simple
Another option for a simple, but real subwoofer is with a paired low-frequency generator. Pairing woofers is a very effective way to enhance their sound quality. The design of a subwoofer based on a pair of old 10GD-30 is shown in Fig. below.
The design is very perfect, 6th order bandpass. Bass amplifier - TDA1562. You can also use other high-quality GGs with a relatively small diffuser stroke, then you may have to make adjustments by selecting the length of the pipes. It is produced at control frequencies of 63 and 100 Hz. way (control frequencies are not resonant of the acoustic system!):
- Prepare the room, microphone and equipment as described above.
- 63 and 100 Hz are supplied to the UMZCH alternately.
- Change the lengths of the pipes, achieving a difference in voltmeter readings of no more than 3 dB (1.4 times). For gourmets - no more than 2 dB (1.26 times).
The tuning of the resonators is interdependent, so the pipes need to be moved according to: pulled out the short one, pushed the long one in by the same amount, in proportion to its original length. Otherwise, you can completely upset the system: the peak of the optimal setting at the 6th bandpass is very sharp.
- A dip between 63 and 100 Hz – the partition needs to be moved towards the larger resonator.
- Dips on both sides of 100 Hz - the partition is shifted towards the smaller resonator.
- The burst is closer to 63 Hz - you need to increase the diameter of the long pipe by 5-10%
- A burst closer to 100 Hz is the same, but for a short pipe.
After any of the adjustment procedures, the subwoofer is reconfigured. For its convenience, complete assembly with glue is not done at first: the partition is tightly smeared with plasticine, and one of the side walls is placed on double-sided tape. Make sure there are no gaps!
Pipes for resonators
Ready-made elbow pipes for acoustics are sold in music and radio stores. You can make a telescopic acoustic pipe with your own hands from scraps of plastic or cardboard pipes. In both cases, across the inner mouth, you need to firmly glue 2 pieces of fishing line: one with tension, the other with a loop protruding outward, see fig. on right. If the pipe needs to be moved apart, press on the tight line with a pencil, etc. If you shorten it, pull the loop. Tuning a resonator with a pipe is thus speeded up many times.
Powerful 6th order
Drawings of the 6th order bandpass for 12” GG are given in Fig. This is already a solid floor-standing design with a power of up to 100 W. It is configured like the previous one.
Drawings of a 6th order bandpass subwoofer under 12? speaker
4th order
Suddenly you have a 12” high-quality GG at your disposal; on it you can make a 4th order bandpass of the same quality, but more compact, see fig; dimensions in cm. However, setting it up will be much more difficult, because Instead of manipulating the pipe of a larger resonator, you will have to immediately move the partition.
Subwoofer bandpass 6th order under 12? speaker
Electronics
The bass UMZF for a subwoofer is subject to the same requirement as filters, the requirement of complete linearity of the phase response. It is satisfied by UMZCHs made using a bridge circuit, which also reduces the nonlinear distortions of integral UMZCHs with a non-complementary output by an order of magnitude. UMZCH for a subwoofer with a power of up to 30 W can be assembled according to the diagram in pos. 1 rice; 60-watt according to the circuit on pos. 2. It is convenient to make an active subwoofer on a single chip of a 4-channel UMZCH TDA7385: a couple of channels are sent to the satellites, and the other two are connected via a bridge circuit to the sub, or, if it has independent amplifiers, they are sent to the woofers. The TDA7385 is also convenient because all 4 channels have common inputs for the St-By and Mute functions.
According to the diagram at pos. 3 makes a good active filter for a subwoofer. The gain of its normalizing amplifier is regulated by a variable resistor of 100 kOhm over a wide range, so in most cases the rather tedious procedure of equalizing the volumes of the subwoofer and satellites is eliminated. Satellites in this version are switched on without a high-pass filter, and volume preset potentiometers with slots for a screwdriver are built into the mid-high frequency amplifiers.
You may want to design a slot sub from scratch rather than mess around with reconfiguring prototype subwoofers to fit your speaker. In this case, follow the link: http://cxem.net/sound/dinamics/dinamic98.php. The author, we must give him his due, was able to explain at a “for dummies” level how to calculate and make a high-quality subwoofer using modern software. However, in a big deal there are some mistakes, so when studying the source, keep in mind:
And still…
Making a subwoofer yourself is a fascinating task, useful for the development of intelligence and skill, and besides, a good bass speaker costs one and a half times less than a pair of a lower class. However, during control auditions, both seasoned experts and casual listeners “from the street”, all other things being equal, clearly prefer sound systems with full channel separation. So first think about it: won’t you still have to deal with a couple of separate columns on your hands and your wallet?