Bass Blockers Won't Work

the resistor is intended to put a load on the amplifier, and thats it. if the speaker is 4 ohms, and a resistor in series with it is 10 ohms, the resistive load would be approximately 14 ohms. That would stabalize the amp. if the bass blocker is a small value (high crossover point)  putting it in series with a 4 ohm speaker could cuase the impedence to change drastically think about it. if you put two 4 ohm subs in parallel with each other. you get two ohms, right?  But a woofer and a tweeter together in parallel would still be 4 ohms even if each is 4 ohms. that is becuase the capacitor used to cross the tweeter over raises the impdence up to the point that the amp doesnt even notice its there.   So by putting a resistor in parallel with the bass blocker, and then running that network in series with the speaker, it returns somewhat of a load to the amp, which will stabalize it.   I would bet almost anything that a lack of load on the amp is the problem. Its just like how you need SOME back pressure on your exhaust.   And as for changing the frequencies, the resistor is most definately going to change the slope of the filter. It will be less steep, I dont feel like doing the math, but since a cap by itself is 6dB/Octave, we can assume it would change the slope to around 3dB or so..  This isnt really a great thing, in fact it would be best if it didnt happen, but it will still cut out a fair amount of the deep bottom end thats causing the speakers to woof too much.

Good luck. I promise that my info is correct.