What does a subwoofer amplifier look like? DIY subwoofer: from entry-level to high-end. Required equipment and components

How to choose an amplifier for a subwoofer

Fans of high-quality car audio are often interested in how to choose an amplifier for a subwoofer. This article will write in detail about the simple truths of choosing this device for a car.
For beginners, this is an opportunity to discover a lot of nuances, for experienced ones - to gain new knowledge. Knowing which amplifier to choose for a subwoofer, you can rest assured that the sound system in the car will be sufficiently modernized.

Amplifier and why you need it

First, let's look at this issue. Many people want the music to play loudly in their car. Of course, this requires an amplifier that will breathe new life into car audio, regardless of whether the head unit is good enough.

So, a car amplifier added to a car’s speaker system can provide the following benefits:

• Not only will the sound power increase, but more importantly, the playback quality will increase. The amplifier in this case can be compared to a pure source of energy that controls the speakers and subwoofer, with virtually no effort.

Note. The great thing about an external amplifier added to a system is that it has no limitations. In other words, music will sound good and clear at all volume levels, even the highest ones.

• Often acoustics are purchased after the head unit has been built into the car. In some cases, the car radio may already have been installed by the car manufacturer or by the former owner of the car from whom you bought it.
  If the speakers and subwoofer you purchase are high quality, they may require more power to perform at peak performance. Unfortunately, standard car radios are not able to provide this. So you have to use an external amplifier;

• Subwoofer (see) - this is generally another story. These woofers require more power anyway. And a separate amplifier, even if the last of the active ones with a built-in “amplifier”, is a prerequisite.

Standard stereo speaker systems typically provide no more than ten watts of power output per channel. And this despite the fact that the packaging says 4x50 watts. Such systems don’t even have enough power to overcome road noise, so what can we say about high sound quality?

Note. An excellent solution for upgrading your existing stereo system is factory integration with the latest amplifier. As a rule, we are talking about standard car radios specifically designed for a specific car.

More in a simple way is to update the whole thing by adding a compact 4-channel amplifier, which will take on the task of increasing the volume of the speakers and subwoofer.

Amplifier types

As you know, there are several types of amplifier:

• Mono amplifiers that are designed for low frequencies;
• 2 channel. This is needed if the car does not use rear speakers, but only front speakers. In this case, a 2-channel amplifier is the most economical and practical option, amplifying only one pair of speakers;
• A 3-channel amplifier will be an option if a subwoofer is also playing in the car;
• A 4-channel amplifier will make it possible to amplify all acoustics, including the rear one, and also the subwoofer.

Sub

The most difficult speaker to artificially amplify is the sub. It is for this reason that so many large-sized subwoofer amplifiers are produced today. They are designed specifically for amplification of low frequencies.
Here's what it's recommended to know for those who are thinking about improving the sound of a subwoofer:

• 1-channel or mono amplifiers are capable of working with wide range resistance. Such devices have special setting timbre, separate filters that help thunderous bass erupt at full power;
• 2 and 4-channel “amplifiers” are also capable of subwoofer amplifiers, but they are not able to cope with the effect of low impedance. They quickly overheat as soon as the sub starts playing at full power.

The ideal amplifier option for a low-frequency driver, which will enable the subwoofer to produce an excellently balanced sound, is a device characterized by the following parameters: 50-200 watts.

Note. It is important to know the impedance of the amplifier and subwoofer. Otherwise, buying the first one will be a waste of money as it will not be possible to integrate with the speaker due to mismatch. In principle, it will work, but it will constantly overheat.

Three opinions

Below are some more important points you need to pay attention to.
As a rule, non-professionals put forward 3 opinions about what an amplifier should be like in order to seamlessly integrate it with a speaker:

• The device should be weaker than the speaker (this helps protect the subwoofer from overload);
• The performance of both devices should be the same;
• The amplifier should be more powerful.

How do you know which opinion is correct? Where is the truth?
Here is what I would like to focus the reader’s attention on before we determine the correct statement:

• The nominal resistance of the subwoofer must be determined;
• The amplifier must be able to function under such loads;
• The "power" value will indicate the nominal value. In professional language, this power is usually called RMS.

RMS for a sub is always the power it can handle without any changes to its parameters. For an amplifier, this is maximum power.
So, now let’s look at the correctness of 3 opinions:

• An amplifier that is weaker than a sub is very bad. Of course, this is a wrong opinion, without any options. We cross it out right away;
• The same power values ​​are also not the point. As a rule, the RMS of the amplifier is normalized for a voltage of 14.4 V if the device is automotive. In real conditions, it is almost impossible to maintain such a voltage at the amplifier terminals, especially if you take into account the connection of headlights, windshield wipers, heater, and so on. Thus, an amplifier with the same power as the sub will go into the clip without reaching RMS. Overheating of the voice coil in this case is almost inevitable;
• A third opinion suggests that the amplifier power should be higher. Indeed, this should be the case. Let's say more - the amplifier should be one and a half or even two times more powerful.

Note. Of course, this option also has its drawbacks. So, if you abuse listening to “infra-low” music at high volumes, periodically pushing the sound to the limit, no speaker, no matter how high-quality it is, will not last long.

To obtain more detailed information regarding the integration of a subwoofer with an amplifier, video and photo materials will help.
You can install the purchased amplifier (see), connect it correctly with your own hands, if you have instructions on hand that indicate how to do this. The price of amplifiers varies, because it all depends on specific model and manufacturer.

In this article we will talk about making an amplifier for a subwoofer with your own hands from available materials. Upon closer examination, you will notice that such a product can be easily made in a few minutes. However, the result is influenced by the quality of sound a person needs. Even though we live in modern world, there are many admirers of the sound of tube products. The quality of such equipment is very high, but every year spare parts are becoming more difficult to find. If the amplifier is assembled on the basis of modern elements, then no problems should arise.

Main advantages of amplifiers

The most significant advantage of microcircuits is their compactness. Due to the large dimensions of the radio tube, the entire product is enormous in size. Chip has quite small dimensions. Additionally, it needs a radiator, because during operation a considerable amount of thermal energy is released. However, the most important thing is that modern devices on microcircuits are powered from a source direct current with a voltage of 12 volts.

A speaker amplifier made by hand using lamps has many disadvantages. Lamp technology requires a power supply of 150 volts. Thus, by abandoning obsolete lamps, the need for huge transformers disappears.

Tools and materials for amplifier assembly

To equip your car with a good 12-volt car radio to ensure high-quality sound, you need an amplifier and a subwoofer.

To assemble a homemade car amplifier, you need to prepare the following devices:

In order to make an amplifier for a subwoofer, you can assemble such blocks yourself or buy them in a store. Last option is more suitable for those, who does not want to waste time on assembling with their own hands. Next, we need to consider these blocks in more detail.

The pulse amplifier block is a special board. This option is optimal for an amplifier for a radio with a voltage of 12 volts. The cost of this product is not very high. It is worth noting that technical solutions This scheme allows her to cope with her responsibilities perfectly. At the output, the device is capable of delivering about 100 watts of maximum power. Such a scheme is considered single-channel, but this problem is solved relatively simply.

Powerful transistors must be provided with good cooling. In order to do this, it is better to bend the elements directly to the board, while their terminals must be at the top. Further to the contact surface you need to apply a layer of thermal paste and lay a special film that does not allow electric current to pass through. Radiators must be mounted on top of all this. It is thanks to this that you can reduce the size of the radiators and save some space on the board.

Pulse processing unit

Since the presence of a subwoofer implies the use car amplifier, then only the low frequency range will need to be separated from the incoming pulse. Considered single-channel circuit, therefore, at the input to the pulse processing unit, you need to install a channel adder, which will allow you to convert a two-channel pulse into a single-channel one.

Voltage conversion module

A car amplifier for a subwoofer requires the use of a voltage conversion module. For such a purpose, it is better to use the TL-494 circuit. You can buy other options in stores, but this one is best suited for people who do not have special knowledge for assembling amplifiers. Additional the advantage is the fact that such a circuit is ideally combined with an amplifier and subwoofer with a voltage of 12 volts in all technical specifications. It allows you to provide the highest level of power.

The switching and rectifier unit consists of the following elements:

1. A switching unit is needed to notify a person about the state of the amplifier. The notification process is carried out using red and green LEDs.
2. The rectifier block is needed to stabilize the pulses that arrive at the main control module.

How to make a high-quality case with your own hands

Before assembling a simple amplifier for a subwoofer, you need to make the main element of this product, which is the housing. Such an element is necessary to accommodate all the details of the product diagram. Good the body can be made of plywood or buy in a store. The choice depends on the preferences and financial capabilities of the person. For example, the device can be connected to the casing of a car player. Such a device has suitable dimensions, a stylish design, and its connections can be converted into a car subwoofer.

The most suitable option would be to use a solid aluminum body, which will perform cooling functions. When the circuit operates, all elements heat up, so if a wooden case is used, it is necessary to make a cooling system. Similar system must be of the highest quality. Sometimes you need to use active cooling, so using an aluminum case is considered the simplest option.

How to make a homemade subwoofer amplifier

You need to start making a homemade amplifier for a subwoofer after preliminary preparation of the main parts. 12 volt product can be done by connecting all of the above components and placing them in a special housing. Due to the voltage of the conversion unit, a simple small fan can be installed on the product body. It will ensure good air circulation in the system, which will help cool the circuit components and protect them from overheating and further breakdowns.

When connecting blocks, you need to use wires protected by cambrics. When wires come into contact, there is a risk of formation short circuit or burnout of circuit components. All details must be placed in the housing so that air can circulate well between them. The circuit components must be secured very well, otherwise the manufactured amplifier will vibrate when driving and when the subwoofer is operating.

You must be extremely careful when performing all work. If errors occur, parts will quickly break. Worth taking on amplifier assembly only if you have the necessary skills in the field of electronics. If you have no experience working with electrical diagrams You should entrust the assembly of the product to a specialist.

Everyone loves to listen to music, but not everyone can listen to music in good quality with bass and at a sufficient volume. But this can be achieved by purchasing an amplifier for your car. Although you can not buy, but make an amplifier for a subwoofer with your own hands, however, for this you will need to purchase some parts, as well as have some knowledge in electronics and physics. I'll help you with the latter.

So, first we need a high-power amplifier and a 12/40V voltage converter (for automotive voltage). You can make these parts yourself (this is a topic for a separate article, so let’s consider the second option), or you can buy them in specialized stores.

Having acquired these two parts, we begin the process of manufacturing the entire amplifier for the subwoofer. To do this, these parts must be coordinated with each other and protected from overload and interference.

And in order for our amplifier to increase the stereo signal, we should install a module for processing and filtering the audio signal. Let's deal with that now.

We are making an audio signal processing module.

A car radio subwoofer amplifier requires two channels, but our amplifier is currently single-channel. To correct this nuance, you need to merge two radio channels together. The adder will help us with this. The block diagram for processing the audio channel can be found on special websites or forums.

Diagram of the subwoofer audio signal processing unit:

After connecting the adder, the audio signal will be filtered, and therefore frequencies less than 16Hz and more than 300Hz will disappear. After the adder, the signal will go into a filter, which will remove frequencies from 35 to 150 Hz.

And in order for your subwoofer to better match the overall acoustics and volume control, the output should have a smooth phase control.

Important points:

• When assembling a sound processing module, it is best to use the board diagram for this module;
• To power the processing module, you need a bipolar current source stabilizer with a voltage of +/- 15V.

We create the next block - stabilization and communication of the power circuit.

Switching block diagram:

When the car is idling, the amplifier requires a current of 1-1.5A, which is produced by the battery. Therefore, to prevent the latter from sitting down, a relay is installed in the car (a separate terminal called “REM” is made for it) with a voltage of 12V in the coil and a current of at least 20A.

REM is connected to a separate output of the car radio with a voltage of +12V. So, the subwoofer will turn on together with the radio.

We will also install two LEDs to control turning on and off, and to obtain bipolar power supply to the unit - transistors, zener diodes and integral stabilizers(to reduce the voltage and stabilize it to 15 V).

Assembly of all parts.

When all the individual modules are prepared, all that remains is to assemble the amplifier together, i.e. place them all in the amplifier housing and connect them to each other.

Before I start my article, I want to say that if you have strong nerves, a lot of free time, certain skills in electronics, like to listen to very loud music in the car, powerful bass and are willing to spend a lot of money on such a project, then this article is just for you !

The idea of ​​​​creating a high-power amplifier has been around for a long time, but due to lack of time and finances, the project was postponed. And then summer... vacation... It was decided to turn the idea into reality and exactly 3 months were spent for this, since there were big problems with the parts, but despite this, the amplification complex was successfully assembled and tested.

To begin with, I would like to clarify the meaning of the expression “enhancing complex”. The fact is that it was decided to collect high quality amplifier, which could power the entire car audio system. The entire power section (power amplifiers) had to be combined “under one roof”, the result was 5 separate amplifiers with a total power of 680 watts, do not confuse with Chinese watts, there is a pure 680 watts of rated power, the maximum power of the system reaches 750 watts.
The requirements for the complex were as follows.
1) High quality sound
2) High output power
3) Relatively simple design
4) Low costs compared to the prices of factory systems of this kind
5) Ability to power 10 -12 speakers + subwoofer
To implement this idea, 5 separate power amplifiers were used, including a high-quality Lanzar amplifier to power the subwoofer channel.

Below are the parameters and series of microcircuits that were used in this amplifier.
TDA 7384 - 4x40W (2 pieces, total power of microcircuits 320 watts or 8 channels, 40 watts per channel)
TDA 2005 - 1x20W (2x10W) (2 pieces, total power 40 watts or 2 channels 20 watts each)

The above microcircuits are designed to power front speakers. This solution is the most economical; to create an amplifier of this kind, you can find out about the monetary costs at the end of the article.
The most difficult part in any amplifier of this kind is the voltage converter, it is designed to power the subwoofer amplifier, perhaps we’ll start with it.
Voltage transformer

It took me exactly two weeks to create.

The voltage converter pulse generator (from now on PN) is built on a traditional TL494 microcircuit. This is a high-precision push-pull PWM controller, a domestic analogue of 1114EU3/4.
The microcircuit does not contain an additional output amplifier. The additional stage is built on low-power transistors, the signal from them is fed to the gates of the field switches.

The circuit is known as a push-pull or push-pull converter. The circuit is not new, but I had to change some of the circuit values ​​to suit my needs. On each shoulder there are two powerful field workers of the IRF3205 series. Through heat-conducting gaskets they are mounted on heat sinks that were removed from computer power supplies

In the rectifier part, KD213A diodes are used, they are just for such purposes, since they can operate at frequencies of 70-100 kHz, and the maximum current reaches 10 amperes; in this circuit, the diodes do not need additional heat sinks, I did not notice any overheating.

I used 2 relays for power supply, 20 amperes each, but it is advisable to install a relay for 50-60 amperes, since the converter draws a considerable current. The remote control system (REM) is implemented in the PN, i.e. No powerful switches are needed to turn on the subwoofer. By applying plus to the remote control, the relays are instantly activated and power is supplied to the converter.

I especially struggled with winding the transformer, since the transformer was of my own design. Unfortunately, I could not find ferrite rings, so I had to go for an alternative solution.
We got several computer power supplies for free, and large transformers were soldered out of them.

The ferrite halves are tightly glued to each other, so they need to be heated with a lighter for 30 seconds, then carefully removed from the frame. As a result, the standard windings were unwound from the transformers, and the terminals were cleaned.

At the end the frames are attached to each other. The result is one elongated frame onto which we can freely wind the windings we need

Through experiments, the required number of turns in the primary winding was found. Eventually primary winding contains 10 turns (2x5vit) with a tap from the middle.

Winding was done immediately with 5 strands of 0.8 mm wire. First, 5 turns are wound along the entire length of the frame, then we insulate the winding and wind another 5 turns on top identical to the first. We wind the windings IN THE SAME DIRECTION, for example clockwise.

After winding the wires, we twist them into a pigtail, not forgetting to remove the varnish in advance, then we tin them and cover them with a layer of tin.
Now you need to phase the windings. In fact, there is nothing difficult here, you just need to find the “beginning” and “end” of the windings and connect, for example, the beginning of the first winding with the end of the second or the beginning of the second with the end of the first, the connection point is a tap to which the plus from the general power supply is supplied ( see diagram).
After phasing the windings, we wind a test secondary winding; it is needed so that if the phasing is incorrect, we do not wind the entire secondary winding. The test winding can contain any number of turns, for example 3 turns with 0.8 mm wire, then we assemble the transformer by inserting the core halves.

When turning on the circuit, the transformer should not emit a “buzz”; the transistors should not overheat if the converter is idle. We connect a 12-volt incandescent lamp of a couple of watts to the secondary winding, which should light up with almost full heat, while the transistors should be cold and only after a few minutes of operation you can feel a slight heat release. If everything is normal, then remove the test winding and wind in its place a normal one, which is wound according to the same principle as the primary.

This time the winding is wound with two strands of 0.8-1mm wire and contains 30 turns (2x15 volts). Two identical windings are wound, each with 15 turns and stretched along the length of the entire frame. After winding the first half, we insulate the winding and wind the second one on top. The windings are phased according to the same principle as the primary.

After winding the secondary winding, the wires at the ends are twisted and tinned. At the final stage, the core halves are strengthened. The transformer is ready!

IMPORTANT! In converters of this kind (push-pull) there should be no gap between the halves of the core! Even the slightest gap of a fraction of a millimeter will lead to a sharp increase in the quiescent current and overheating field effect transistors! It was because of my clumsiness that I burned several field-effect transistors. Make sure that the ferrite halves are pressed against each other as tightly as possible. Such a transformer is capable of providing the required voltage and current to power the subwoofer amplifier.
We solder the transformer onto the board and begin winding the chokes.

Throttle
The circuit uses 3 chokes. They are designed to filter out RF noise and interference that can form on the power lines. The main choke is used on the positive power line of the converter. It is wound with 4 strands of 0.8 mm wire. The ring used those in computer units nutrition. The number of throttle turns is 13.

The remaining two chokes are located after the diode rectifier in the PN, they are also wound on rings from computer power supplies and contain 8 turns of 3 cores of 0.8 mm wire.

To be honest, I didn’t expect that such a high-quality voltage supply would be obtained, the quiescent current of the circuit does not exceed 200 mA, this is normal for such a monster, the output voltage is +/-63 volts, the slope is insignificant, only half a volt. The maximum power of the converter would allow powering two of these amplifier, but here it works with a large margin.

Amplifiers based on TDA2005, for low-power heads

Assembling this block took only 2 hours. During this time, two identical power amplifiers were assembled. The amplifiers were chosen as the cheapest option for low-power speakers; they can be used to power speakers located on the front panel of the car. Each microcircuit develops 20-24 watts of power and has very good sound quality.

Each microcircuit is connected via a bridge circuit; with a stereo connection, one microcircuit is capable of delivering up to 12 watts into a 4 ohm load

The microcircuits are installed on the heat sink through an insulating gasket. The volume is adjusted in advance using a regulator. At first, another board was planned, amplifiers were assembled from this one, then a general board was invented, which was entered into the project archive.

TDA 7384 for front speakers

For more powerful speakers, TDA 7384 quadraphonic microcircuits are used. Each microcircuit is capable of delivering up to 40 watts of power per channel into a 4 Ohm load. The result is 8 channels of 40 watts, sounds very good.

Such microcircuits are used in car radios; if you are too lazy to buy them, you can get them from non-working radios.

Microcircuits have different filters independent of each other; if you use a common filter, then noise and excitation are possible.
Both amplifiers start working when +12 volts are supplied from the battery to the REM pin. The amplifiers were assembled on one board, but later the blocks had to be rearranged, so each amplifier was implemented on a separate board.

Subwoofer amplifier

The famous Lanzar circuit, full description, assembly, circuit and configuration are described here, so there is no need to talk about this amplifier. The amplifier is completely assembled on transistors, has a very good quality sound and increased output power. I made some changes in the diagram and below is the diagram I used to assemble it, the original diagram in the same forum thread.

Since I could not find some of the circuit ratings, I had to make some changes, in particular the emitter resistors were replaced with 0.39 Ohm 5 watts. The BD139 transistor was replaced with a domestic analog KT815G, in addition, the low-power transistors of the differential stages and pre-output stages of the circuit were replaced.

Electrolytic capacitors can be removed at the input if the input is replaced with 2.2 µF or more.

It is advisable to do the first start-up of the amplifier with one pair of output transistors with the input shorted to ground, so that in case of breakdowns the transistors of the final stage do not burn out; they are the most expensive thing in this amplifier.

Pay special attention to the installation of the circuit, monitor the pinouts of the transistors and the correct connection of the zener diodes, the latter when incorrect connection They work like a diode. I installed a regular quiescent current regulator, I don’t advise anyone to repeat my mistake, it’s better to install a multi-turn one, it can be used to accurately adjust the quiescent current of the circuit, it’s also convenient for tuning.

The output stage of the amplifier operates in AB mode, this is essentially a fully symmetrical circuit, the level of nonlinear distortion is reduced to a minimum. Due to its high performance, this amplifier belongs to the Hi-Fi category; getting 300 watts from this amplifier is not a problem. It is also possible to connect a 2 Ohm load at the output, i.e. you can power as many as two subwoofer heads by connecting them in parallel. In this case, you cannot raise the amplifier voltage above 45-50 volts.

You can increase the power of the amplifier by adding one or two more pairs of output transistors, but do not forget about increasing the power supply, since the output power of the amplifier directly depends on the power supply.

AC protection

Despite the fact that the power amplifier is quite reliable, sometimes problems can occur. The output stage is the most vulnerable part of any amplifier; due to the failure of the output transistors, a constant voltage is formed at the output. The constant disables the expensive dynamic head. Any amplifier of this kind has protection that will protect the speakers from constant voltage.
When the amplifier is turned on, the relay closes, including the head, when constant voltage at the PA output the relay opens, keeping the head

Protection has relatively simple diagram, contains 3 active components (transistors), a 10-20 ampere relay, the rest is small stuff. When the PA is turned on, the relay closes with a slight delay. Power for protection is supplied from one arm of the converter, through a limiting resistor of 1 kiloohm, select a resistor with a power of 1-2 watts.

Low-power transistors can be replaced with any others whose parameters are similar to those used. The relay is connected to the collector more powerful transistor Therefore, the final transistor needs a more powerful one. From the domestic interior, you can use transistors KT 815.817 or more powerful - KT805.819. I noticed heat generation on this transistor, so I mounted it on a small heat sink. Protection and output signal indicator are mounted on one board.

Stabilization block

Bipolar voltage stabilizer provides the necessary voltage to power the filter unit and audio signal indicator. Zener diodes stabilize voltage up to 15 volts.

This unit is assembled on a separate board; it is advisable to use zener diodes with a power of 0.5 watts

Audio level indicator

I won’t go too deep into the operation of the circuit, since the circuit of such an indicator is described in one of my

The indicator uses LM324 microcircuits. It is advisable to use an operational amplifier for these purposes, since the microcircuits cost only $0.7 (each). The indicator uses 8 LEDs; you can install any LEDs that are at hand. The indicator operates in the "column" mode. The indicator is powered by a voltage converter, then the voltage is stabilized to the desired value and supplied to the level indicator. The indicator is connected to the output of the power amplifier, using a trimmer we adjust the indicator to the desired level of LED response.

Adder and low-pass filter block

The adder is designed to sum the signal of both channels, since we have only one subwoofer. After this, the signal is filtered, frequencies lower than 16Hz and higher than 300Hz are cut off. The regulation filter cuts off the signal from 35Hz - 150Hz.

Assembly

After a thorough check of all blocks, you can begin installation.

Unfortunately, I couldn’t find a case from a DVD player or anything else convenient. I attached indicator LEDs to the front panel, where the display used to be located. All boards are attached to the bottom of the amplifier through insulating washers, which in turn were removed from domestic equipment

All microcircuits and transistors are screwed to the heat sinks through insulating gaskets. It is advisable to use thermal paste; unfortunately, we do not sell it, but even without it everything is not so bad.
The input connectors of the amplifiers were soldered out of the DVD, and a connector from the car radio was used as output terminals.

My design uses only one cooler, it is designed to cool the heat sinks of the PN and TDA7384 power switches; the subwoofer amplifier does not need forced cooling, since for it I selected a huge heat sink that practically does not heat up.
The power wires of each amplifier are connected to common power terminals. REM control allows you to turn off any of the amplifiers (for example, a pair of TDA 2005) at the right time. Each amplifier is powered through relays, which are activated when positive is applied to the REM pin.

Each of the amplifiers has a separate remote control system, which is located on the contact platform on the side of the housing.

Subwoofer box

A couple of months after the start of assembly, I managed to buy a SONY XPLOD XS-GTX120L subwoofer head, the head parameters are below.
Rated power - 300 W
Peak power - 1000 W
Frequency range 30 - 1000 Hz
Sensitivity - 86 dB
Output impedance - 4 Ohm
Frequency range - 30 - 1000 Hz
Diffuser material – polypropylene

Since stores only sold laminated chipboards, and we don’t have MDF at all, we had to choose from what was available. Fortunately, we were lucky with the material. Chipboard from USSR times was perfectly preserved in the attic, thickness 22 mm.

The diameter of the FI port is 14 cm, the length of the pipe is 7 cm.
A hole with a diameter of 28 cm was cut for the head. After making all the parts of the box, it was time to assemble it. It is convenient to start assembly by joining the bottom and front of the box. First, holes for the screws were made with a drill (with a small diameter drill), and only then the screws were screwed on. Before this, the fastening points were covered with PVA glue.
There is no need to spare glue, so as not to complain about whistling later. I got a pretty good box, I worked as neatly as possible. At the end the seams were covered with silicone on the inside of the box (silicone has bad smell, so this work should be done in a garage or outdoors). After assembling the box, I couldn’t resist, put the head where it was supposed to be and turned it on

I cannot convey this in words or even in a video, because it needs to be felt, not heard. You can feel the full volume of the box, the scope of the head, the power and quality of Lanzar, and all this is embodied in the pressure on your chest.... It’s impossible to describe in words and only then you begin to understand that everything around you is collapsing and falling apart, the glass is moving on the table by itself, the glass is starting to "swell" from pressure. In a word, everything in the house was under a “dose” of vibration.

We sold special glue for carpet, but a can of aerosol costs $25, so we had to use PVA glue. To begin with, I sanded the box; this process took me 4 hours. Apply PVA glue to the already cut carpet. After this, the box needs to be “rolled” over a pre-cut carpet. We wrapped the box, now in order for the glue to dry properly, we hammer small nails along the edges, then after drying they can be removed or left.

Then we cut out the holes for the head and the bass reflex. The head is attached to the box with ten self-tapping screws, this ensures tight contact, no additional gaskets are needed.

This alternative solution is again caused by a shortage of factory connectors.

It turned out well. A separate hole was cut for it.
On the inside, after sealing the wire, the connector hole was sealed with silicone sealant to avoid whistles and unwanted noise.

Total construction costs

Voltage transformer:
BC557 3pcs - $2.5
TL494 1pc - 1$
IRF3205 4pcs - 10$
Diodes KD213A 4pcs - $4
Polar capacitors - $10

Resistors - $2
Chokes and transformers - from old PC power supplies
Relay - from voltage stabilizer

Lanzar amplifier:
Transistors
2SA1943 2pcs - 6$
2SC5200 2pcs - 6$
2SB649 2pcs - 2$
2SD669 2pcs - 2$
2N5401 2pcs - 1$
2N5551 2pcs - 1$
Resistors 5 watt - 4 pcs - $3
Other resistors - $4
Non-polar capacitors - $3
Polar capacitors - $5
Zener diodes - 2 pcs - 1$

Other amplifiers:
TDA7388 2pcs - 15$
TDA2005 2pcs - $2.5
Resistors - $2
Non-polar capacitors - $4
Non-polar capacitors - $6

Filter block:
TL072 1pc -1$
TL084 1pc - 1$
Non-polar capacitors - $3
Resistors - $2
Regulators 3pcs - 4$

Indicator block:
LM324 2pcs - 2$
LEDs and everything else - $2

Stabilizer block:
Transistors 2$
Zener diodes 13 volt 6pcs - $1.5
Stabilizers 7815 2 pcs - $1.5
Zener diodes 7915 1 piece - $0.7
The rest is $2

AC protection:
Transistors - $2
Relay - for free
everything else is 1$
Fortunately, plugs, sockets and connectors were in stock

Subwoofer box:
Self-tapping screws 50 pcs - $0.5
Sealant 2 bottles - $2

Chipboard - for free
PVA glue - for free
Head - $65
Carpet - $15

Results

That's all. I'm pleased with the results, very pleased! It is not possible to buy such an amplifier; amplifiers of similar power cost from $400! Although Chinese manufacturers offer it for significantly little money, quality and reliability.... In general, the amplifier turned out to be a thrice-bang success! Everything works great, all that remains is to buy a car and enjoy the man-made amplifier, and for now the amplifier will work at home, from powerful block 12 volt power supply.

The thing that we will now talk about, as is clear from the title of the article, is homemade amplifier for a subwoofer, popularly called “Sub”. The device has an active low-pass filter built on operational amplifiers and a combiner that provides signal input from the stereo output.

Since the signal for the circuit is taken from the outputs on Acustic systems, there is no need to interfere with a running amplifier. Receiving the signal from the speakers has another advantage, namely, it allows you to maintain a constant volume ratio of the subwoofer to the stereo system.

Naturally, the subwoofer channel gain can be adjusted using a potentiometer. After filtering high frequencies and highlighting low frequencies (20-150 Hz), the audio signal is amplified using the TDA2030 or TDA2040, TDA2050 microcircuit. This allows you to customize the bass output to your liking. Any woofer with more than 50 watts of power per subwoofer will work successfully in this project.

Filter circuit with UMZCH subwoofer

Schematic diagram of low-pass filter and UMZF subwoofer

Description of the operation of the amplifier circuit

The stereo signal is fed to the In connector via C1 (100nF) and R1 (2.2M) on the first channel and C2 (100nF) and R2 (2.2M) on the other channel. It is then fed to the input of op-amp U1A (TL074). Potentiometer P1 (220k) operating in circuit feedback amplifier U1A, the gain of the entire system is adjusted. Next, the signal is fed to a second-order filter with elements U1B (TL074), R3 (68k), R4 (150k), C3 (22nF) and C4 (4.7 nF), which works as a Butterworth filter. Through circuit C5 (220nF), R5 (100k), the signal is supplied to repeater U1C, and then through C6 (10uF) to the input of amplifier U2 (TDA2030).

Capacitor C6 ensures separation of the DC component of the preamplifier signal from the power amplifier. Resistors R7 (100k), R8 (100k) and R9 (100k) serve to polarize the amplifier input, and capacitor C7 (22uF) filters the offset voltage. Elements R10 (4.7 k), R11 (150 k) and C8 (2.2 uF) operate in a negative feedback loop and have the task of forming the spectral characteristics of the amplifier. Resistor R12 (1R) together with capacitor C9 (100nF) form the output characteristic. Capacitor C10 (2200uF) prevents DC current from passing through the speaker and, together with the speaker resistance, determines the lower cutoff frequency of the entire amplifier.

Protection diodes D1 (1N4007) and D2 (1N4007) prevent voltage surges that may occur in the speaker coil. The supply voltage, in the range of 18-30 V, is supplied to the Zas connector, capacitor C11 (1000 - 4700uF) is the main filter capacitor (do not skimp on its capacity). Regulator U3 (78L15) together with capacitors C12 (100nF), C15 (100uF) and C16 (100nF) provides a 15 V supply voltage to the U1 chip. Elements R13 (10k), R14 (10k) and capacitors C13 (100uF), C14 (100nF) form a voltage divider for operational amplifiers, forming half of the supply voltage.

Subwoofer assembly

The entire system is soldered to . Installation should begin by soldering two jumpers. The installation order of the remaining elements is any. At the very end, capacitor C11 should be soldered in because it must be installed lying down (the legs need to be bent accordingly).

Printed circuit board for the device

The input signal must be connected to the In connector using twisted wires (twisted pair). The U2 chip must be equipped with a large radiator.

The circuit should be powered from a transformer through a diode bridge rectifier; the filter capacitor is already on the board. The transformer should have a secondary voltage in the range of 16 - 20 V, but after rectification it should not exceed 30 V. A subwoofer with good parameters should be connected to the output - a lot depends on the head.