Active Crossover Recommendations

Whoops - I guess I've been offline for a couple of days. Jeffreybehr - thanks for your suggestions. In about a month I'll have a preamp that has 2 sets of RCA outputs: 1 with caps that are selected to roll off at 80hz into my 100kohm Cary SLM70 monoblocks, and one without any filters. I will try it both ways: 1) passive filter on the high frequencies and active filter built into the subs, and 2) active filter (Bryston) on both. For now, I can only work with the Bryston, until I get my other preamp.

The sub options include: 1) a pair of TBI Magellan VII's, and 2) a single ACI Titan. The TBI's only have phase reverse whereas the Titan has fully adjustable phase. I'm not looking forward to moving the subs around, but it has to happen! The TBI is very fast, which is why I bought them (to keep up with the Quads). I needed 2 because they aren't that powerful, plus I believe in stereo subs. If the single ACI works, I would likely buy a second.

Thanks all for your comments. Check back on this thread in about a month for a summary of my results (I hope).

By the way Jeff, what is the equation for calculating the capacitance for a passive crossover frequency based on the input impedence of the amp?

Thanks, Peter

does anyone have the equation for calculating required capacitance for use in a crossover (given amplifier input impedance)? this thread stalled just when it got handy...

tia

Rhyno, I assume you;re referring to a passive line level low-pass? If so, 1st order Butterworth is C= 1/2pi(F)(Ramp)(1+a). F= xover frequency, Ramp is the amp's impedance, a is the relation between amps' gain.
I.e. if a=1, the amps to be used have identical gain. If not, give a the appropriate value to balance the gain. For a much better take on this, check out Art Ludwig's site (sorry don't have it handy).

hi greg, so if i understand correctly, this is 6db per octave, yes?

and, if the high freqency amp had a gain of 20db, and the subwoofer amp had a gain of 10db, then "a" would be 2, and pi would be 3.1417, correct?

the cap would of course go in series w/ the high freq amp, while the low freq amp (the sub) you could simply rely on its own internal crossover to filter out higher freq info?

best