Most of the traditional active subwoofers use large resistance resistors to obtain audio signals from the preamplifier. This will inevitably lead to crosstalk between the left and right channels. Some fans have disadvantages in obtaining signals from the output of the amplifier.
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This article describes a mini subwoofer made with wireless transmission. It is suitable for small rooms with low volume requirements.
Circuit principle:
The speaker adopts the stereo transmitting integrated circuit BA1404, and transmits the mixed signals of the left and right channels with the carrier of 76~100MHZ, which is received by the FM receiving circuit and sent to the input end of the power amplifier through the low-pass circuit to drive the speaker to sound. The wireless transmission method can save the trouble of connecting the signal lines, and the speaker is placed more casually.
The BA1404 peripheral circuit is simple and ready to install. At height, you only need to adjust the inductance of L so that the transmission frequency is the same as the frequency of the receiving circuit. L in the circuit is wound around 3 cylinders of 5, which is connected in parallel with the capacitance of 47PF to make the transmission frequency 76. Choose between -~100MHZ. The transmitting circuit is shown in Figure 9-43; the receiving circuit is shown in Figure 9-44.
The power amplifier circuit can also be used as a "fool" 155 or 175.
The low-pass filter cut-off frequency of this circuit is about 150HZ, and the low-range speaker uses the Feile YD103-33 four-inch speaker. The speaker size is shown in Figure 9-45.
If you use a larger speaker, the bass effect will be better.
The front speakers that work with them can be made with active speakers, such as Dibo 2000 speakers, or by yourself. This paper adopts a small speaker produced by Feile Factory. The speaker adopts an elliptical full-band speaker with a frequency response of 150~15000HZ and a nominal power of 2*5W. It can be successfully promoted by TDA1521.
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