Production of multimedia subwoofer active speakers

Circuit diagram of this subwoofer active speaker. The core device of this circuit is IC1, that is, T1.072JFET dual op
amp port op amp IC l-a, capacitors C2 and C3, and resistors R2 and R3 together form a high-pass filter, while ICl-b and
(., 4, c 5, C6 and R7 form a low-pass filter. The cut-off frequency of this type of filter can be calculated by the following formula:
    , -11 (27rRC)
    According to the value shown in the figure, the cut-off frequency of the high-pass filter can be calculated to be about 3. 4Hz , and the cutoff frequency of the low-pass filter is about
150Hz. The gains of the two filters are set separately, that is, the high-pass filter stage is set by R4 and R5, and the low-pass filter
gain is set by R8 and R9. Plug
    U xsl and xsz are connected in parallel so that the subwoofer active speaker can be installed between the left and right satellite speakers
.
    As mentioned above, this installation allows the active speaker itself to control the subwoofer Volume. Resistor R15 and potentiometer
R l 6 constitute...a 'r' divided into three devices, M to adjust the volume of this subwoofer . Providing this adjustment allows us to
install it again, so that the The playback system is balanced.
    The amplification part of this ultra-low active loudspeaker uses a 20W power amplifier integrated circuit IC2. The capacitors (, 6
and C7 are used as input couplings). Here two electrolytic capacitors are used instead of one. Non-polar capacitors are used to save costs.
The gain of this amplifier is adjusted by resistors R11 and R12.
    The quiescent current consumed by this amplifier can be up to lOOmA D. Therefore, it generates a lot of heat when no load is used, so it is
very . Although this circuit has used internal thermal protection, a heat sink and silicone grease must still be installed. The
    power supply of this machine consists of a 3fiV, center-tapped transformer T!, a bridge rectifier BR1 and two filter capacitors
The DC output obtained after rectification and filtering is about ±25V. Note that the power supply of the op amp is provided
by Zener diodes VDl, VD2, and resistors R13 and R14. Stable at ±15V