Passive bandpass input filter followed by adjustable 20Hz - 150Hz active low pass filter, then amplifier output.
power amp input looks like 1k impedance, input line goes through 4.7uF then 1kΩ.
Replaces the original circuit that overheated and died; it had a pair of 1W resistors on the board to divide the supply voltage down.
Still doesn't sound as "punchy" as the original. On the bench it has excellent low frequency response even at subhertz ranges, but when I put it back into the system it just doesn't sound as impressive.
gain tweaks to try:
change output filter resistor from 1.5k to 10k, or chop it.
change output divider lower resistor from 20k to 4.7k.
current in place is 10k
reduce the 10uF stage coupler; possibly the very low frequencies are holding the cone too long, limiting it's range?
Need to read up some more; look into a bandpass to attenuate the very low frequencies below ~15Hz to reduce excursion
