Homemade active subwoofer

Due to the active mode, the size of the power amplifier circuit
is required to be as small as possible, but the output power should be able to reach]. 0 0w. After repeated research, we decided to use the thick film power amplifier circuit ST K 6153 as the power amplifier
. The high frequency response of STK 6153 is not satisfactory, but its performance in low frequency power is well known. As shown in Figure 9-2 9 is the RP1 volume potentiometer of the subwoofer power amplifier circuit
port composed of STK 6153 and low-noise return op amp TI,074 . RP2 is a high -end response (cutoff frequency) adjustment potentiometer, which can continuously adjust the port A1 between 40Hz and 160Hz to form an input buffer, which is composed of Rl, R2, and RP1. , R channel signal is mixed and divided. A2, C2, C3.R4.R5 together form a two-phase active high-pass filter of 12c113 per octave . R6R7 determines the gain and Q value of the filter. Cl. R3 is actually a c- per octave ; dB RC high-pass filter, the cut-off frequency is about 20Hzn A3. C, 4~C5 and R8, R9.RP2 constitute a second-order active low-pass filter of 12dB per octave , and its cut-off frequency is at 12dB per octave. It is adjusted from 40Hz to 160Hz. RlO and Rll determine its gain and 0 value. Therefore, A1~A3 actually form an adjustable band-pass filter, as shown in Figure 9-30 for its amplitude-frequency characteristic curve A4 and STK. 61 -53 together form the power amplifier output stage. R12 R13 determines the gain size. STK 615 3 should be installed on a 5cm×8.5cm fork-shaped aluminum radiator. The output power of the power amplifier is greater than lOOWoR16, C.7.C8 and Vl-V3, K] , etc., which together form the speaker protection circuit. Each time the power is turned on, R17,09 delays for about 5 seconds before activating relay Kl to protect the speaker from current impact . When the midpoint voltage of ST K 6153 drifts seriously, it is rectified by VD1~VD4 and controlled VI saturated conduction. V2 and V3 are cut off, the relay Kl is released, and the normally open contact Ki-l is disconnected to prevent the speaker from burning out.