sub driver and crossover needed..help! (1 Viewer)

[Shankar K]

Hi All,

I'm looking for a low pass crossover (100W) that can take the input from my "speaker out" and send the filtered signal to the sub. No RCA out as I intend to use the A+B of my amp to feed the mains and the sub.

Any suggestions for a sub driver below $80 that I can build upon would be most welcome.

Thanks in Advance.

 

[Dave Milne]

Shankar,
A passive low pass filter for a sub is generally not a good idea. High quality 12dB/oct 80 Hz filters (THX standard) with, say, less than 0.1 ohm insertion loss (so as to not interfere with the Q/tuning of the sub) are very large (try 20+ lb)coils of wire and very large and very expensive mylar or polypropylene capacitors. You'll need two of each to build two filters to drive the two coils of a dual-coil sub.

And you really should put complementary high-pass filters on the mains unless your mains happen to roll off at the same frequency and slope. Otherwise, you'll have some response peaks in the crossover region and you're wasting amp power and generating distortion by sending deep bass to the mains.

I suppose you could scrounge iron-core inductors and pairs of back-to-back electrolytic caps for less than 20 bucks, but the result could be diappointing. A sub really needs its own amp.