First move the subwoofer; Then buy a subwoofer flat power amplifier; Connect the wire of the flat-panel amplifier to the connector; Fix the flat-panel amplifier on the box.
Subwoofers can generally be divided into active subwoofers and passive subwoofers.
Active subwoofer has power amplifier, passive subwoofer has no power amplifier, only speaker unit and frequency divider, and some need to make a box. The passive subwoofer must be driven by a power amplifier.
And it is generally better to add a low-pass filter. It can also be directly driven by power amplifier, but signal selection and volume control are not above. A passive subwoofer, like a passive speaker, has no integrated circuit and power transformer inside.
Extended data:
Advantages and disadvantages of active subwoofer and passive subwoofer;
(a), active subwoofer:
Advantages:
1, the workmanship is smaller and it is easier to install.
2, the speaker comes with a power amplifier, which can be directly connected to the audio source.
3. The price is cheaper.
Disadvantages:
1, the output power is relatively small, and the musical expression is not very strong.
2. The circuit structure is simple.
(2), passive subwoofer:
Advantages:
1. The horn unit has complex mechanism and excellent materials.
2, the output power is relatively large, and the musical expression is relatively strong.
Disadvantages:
1, which is large, heavy and takes up more space.
2. The price is more expensive.
How to change passive speakers to 5. 1 bluetooth?
Bluetooth itself is a wireless tax bureau transmission protocol, which originally realized short-distance data exchange between devices. Bluetooth uses 2.4G box frequency band, which was proposed by Ericsson in 1994. The biggest advantage is that the Bluetooth protocol supports the connection of multiple devices.
With the development of Bluetooth technology, the Bluetooth Technology Alliance now has more than 20,000 member companies, covering communication, computer, personal digital products, audio and other fields. It first appeared in the communication between mobile phones, and later both industrial products and consumer products adopted Bluetooth technology. When it was first used for audio transmission, the Bluetooth protocol version was low. At that time, it was mainly used for mobile phone wireless headphones. At that time, it only supported mono, with poor sound quality (low decoding accuracy) and high power consumption, so until now, some stubborn old audio lovers have always thought that Bluetooth is not high fidelity when used for audio transmission. In fact, the current Bluetooth version 4.2 has greatly improved the sound quality, the transmission distance has reached more than 1 meter, and the power consumption has also decreased.
Because it is easy to use, and at present, mobile phones are standard, because it is convenient to connect various consumer electronic products, such as bracelets, headphones, sphygmomanometers, balance cars and so on. If you have a Bluetooth stereo at home, it will be much more convenient to connect. As a sound source, the mobile phone can take your favorite songs with you at any time and play them at any time.
It is also very simple to turn ordinary audio into Bluetooth audio. There are two ways.
First, buy finished products
At present, there are many such products, such as Xiaomi's Bluetooth audio receiver, which costs tens of dollars each and has a built-in battery, so don't worry about introducing AC noise. As long as the stereo is connected with a 3.5mm audio cable, the stereo will be upgraded to a Bluetooth stereo, which is very convenient.
Second, DIY
Do-it-yourself (DIY) can have fun in the production process and enrich your knowledge and skills. Science and engineering men must try. Below is a Bluetooth receiver and two audio Bluetooth modules I made.
1, manufacturer of Bluetooth audio receiver
We need to prepare the following materials: two RCA sockets, a 1200mAh lithium-ion battery, a Bluetooth 4.0 protocol stereo transmission module, a switch, a MicroUSB interface, and some necessary resistance and capacitance components.
Find a small plastic box, punch holes and install various connectors.
The battery, module and plug are firmly installed and bonded, and all kinds of wires are welded.
The stereo we use is Joan amplifier and bookshelf HIVI speaker.
2. The light cavalry M7 is equipped with Bluetooth module.
This is the light cavalry M7 speaker, using active mode. The so-called active mode means that the speaker contains a power amplifier unit, which can emit sound as long as there is external signal input, while the passive speaker needs to be equipped with a power amplifier (hereinafter referred to as power amplifier) to promote the speaker's work. The advantages of active mode are high integration, convenient installation and low user input cost. Disadvantages are transformers, circuit boards, etc. Inside, it occupies a certain space, which leads to the reduction of the effective volume in the box and the simple power amplifier circuit, which leads to the loss of sound quality. Therefore, active mode is usually adopted in the design of small speakers.
In order to upgrade, we have prepared a 4.0 Bluetooth stereo module, including a blue LED status indicator and a power decoupling capacitor.
The internal power amplifier is composed of LM 1875, and the circuit is relatively simple. Now we connect the Bluetooth 4.0 stereo module to the circuit: weld the original signal input line from the power amplifier to the audio input end of the Bluetooth module, and then weld the audio input end of Bluetooth to the input end of the power amplifier, so that when there is a Bluetooth connection, the Bluetooth output signal will be played, and when there is no Bluetooth connection, it will be automatically switched to the original audio input end.
Because the working power supply of Bluetooth module is 3.3-5V and the working voltage of speaker is 18V, it is necessary to assemble a DC/DC buck module to reduce the main power supply of 18V to the working voltage of Bluetooth.
Then we use 704 to glue the Bluetooth module to the top of the speaker and the Bluetooth antenna to the front.
When assembling, there is an led on the panel. When flashing, it means waiting for pairing or link, and when it is always on, it means that the Bluetooth link is successful.
3. Old tape recorder with Bluetooth module.
This SHARPGF777, known as the "king of tape recorders", is huge in size and does not lag behind in terms of frequency parameters even today. I used to listen to FM today, and the sound quality is quite satisfactory. Unfortunately, the tapes that were popular in those years have been eliminated. It would be a pity if it was only used to listen to FM.
Through analysis, this circuit board is the PCB of line input circuit, and this single-row 9P IC is the amplifier circuit of record player, so we won't touch it. Find these three pads, which are the output points of the amplified circuit of the line or phonograph. We need to connect the Bluetooth decoding module here.
Prepare a Bluetooth decoding module. Prepare another 2.4G antenna.
This is a welded Bluetooth module. Now we need to find a suitable place to put it in the tape recorder. I'm going to stick the antenna on the top of the inner wall of the recorder.
This is what it looks like after bonding, with the decoding module on the left and the Bluetooth antenna on the right.
Finally, add a power supply, then cover the shell, turn on the power supply and search for the Bluetooth module. After pairing, it will be renamed as "SHARPGF777". As a result, a tape recorder with Bluetooth decoding function was transformed.
Play the tape and put the function switch on the tape and radio. If you want to connect your mobile phone, please put the function switch on Linein. At this time, if there is a Bluetooth-paired mobile phone, the music in the mobile phone will be played. Because this Bluetooth module can pair two devices, we will also pair the laptop, which device is turned on first, giving priority to the signal of that device. If both devices are not turned on, the signal will realize the input function of the Linein terminal behind the recorder.
I have an abandoned old passive speaker. How can I turn it into an active speaker?
1. Buying electronic components according to the characteristics of the speaker, using flying wires with holes as amplifier boards and frequency dividing circuits, connecting transformers, and digging holes in the box as radiators for power amplifier chips all require strong circuit knowledge, speaker manufacturing knowledge, hands-on ability and patience. Not recommended!
2. If it is an anti-box, disassemble the speaker to see the impedance and power of the speaker and the width of the bottom plate or back plate of the speaker (the circuit board can be put down). According to these parameters, the finished amplifier board (including transformer and heat sink) is purchased online or in the local electronic city and fixed with wood screws or glue. The back plate of high-power speaker must have holes to expose the heat sink, and the edge must be sealed with glue or other materials, so as not to leak; Low-power speakers, such as those within 10w, can put heat sinks in them. A fixed terminal or small hole in the drill hole leads the wire directly to the auxiliary box.
Because the main box has a power amplifier and transformer, the volume and reflection have changed, so the auxiliary box needs to be stuffed with some sound-absorbing cotton to balance the timbre of the two speakers. The volume of sound-absorbing cotton is about 2-3 times that of the main box.
If the output of the amplifier board has only two left and right (L, R) channels, regardless of the treble and bass, it is a board without frequency division. It is necessary to connect a non-polar capacitor between 2.2 UF and 4.7 UF in series on the tweeter (horn), and it can withstand 50v electrolysis.
3. If it is a closed box, it is not recommended to build an amplifier board and a transformer, because most closed boxes are filled with sound-absorbing cotton, and the temperature is too high, which is dangerous. Must be built-in, the box should be made into an anti-box. The length and diameter of the nozzle need to be calculated according to the characteristics of the horn and the volume of the box, which is very troublesome. Moreover, the original closed box is made in the opposite direction, and the speaker parameters are definitely inappropriate, and the sound will be very strange.
You can use the finished Bluetooth game board (module) to improve your hands-on ability, and kill two birds with one stone with old things. But the final cost and appearance will be different from the finished Bluetooth case. The finished Bluetooth speakers mostly use small-caliber, long-stroke speakers and digital power amplifiers, and the sound sounds heavy, which is actually a kind of rendering. Small-caliber speakers can never compare with large-caliber speakers. However, because of its small size, exquisite appearance, rechargeable, portable and even intelligent system, it is deeply loved by the public.
If the speaker at hand is an active speaker (built-in amplifier), then you only need a simple Bluetooth player board. If it is a passive speaker (there is no power amplifier inside), then choose a Bluetooth board with power amplifier. The picture below shows the Bluetooth module without power amplifier.
The picture above shows a USB flash drive, FM radio, App control and external sound card function. It can be said that it is a fully functional motherboard. It is also very simple to use. The power supply port can be directly powered by mobile phone charger or 5v, and the audio output is output by 3.5mm socket. If you are too lazy to start welding, buy a recording cable and connect the audio input of the active speaker. I have to say that with the development of science and technology, the price of electronic products is getting lower and lower! And many circuits are sold with finished boards, which are simpler and more convenient to use.
The picture above shows the Bluetooth player board with power amplifier module, which is suitable for refitting passive speakers. Open a hole in the appropriate position of the speaker, bring your own panel and embed the speaker.
Easy to use, simple wiring. Because the power amplifier is slightly smaller (5 watt digital power amplifier), it is suitable for speakers with high sensitivity, and the impedance is preferably 4 ohms, so the power can be higher. The voltage of the card in the above picture is wide, which can be used for 4-40v, and can also be used with the idle lithium battery of the mobile phone to realize the portable function.