bi amp imrpoving?

Active biamping is simple with as little a Dahlquist DQLP-1(still used by Marchisotto, to biamp the Alón Exotica Grand Reference system). I used (and modded in a number of ways) one over the course of almost 25 years, with a variety of systems, and excellent results. I might still have it, were it not for the present acoustic nightmare of a listening room a divorce stuck me with. A TacT RCS 2.2 has rectified the situation quite nicely though. There's an LP-1 for sale on AudiogoN now: (http://www.audiogon.com/cgi-bin/cls.pl?misceqal&1283407862&/Dahlquist-DQ-LP1-electronic-cr)

Once again, I say thanks to the experts who are willing to take the time to educate the rest of us. I haven't read the links in detail yet, but I surely will. I have a NAD C162/C272 preamp/amp combo driving a pair of Aerial Acoustics Model 7s. I have been considering bi-amping the Aerials with two Monarchy SM-70 Pros thinking that would be an upgrade over the NAD C272. It appears I need to learn more about bi-amping first.

Keep in mind that it is not REALLY necessary to bypass, or delete, the existing crossovers in your speaker system, to experience most of the benefits of active biamping. Those are primarily gained though the elimination of highs and lows being fed to the amps that don't need to reproduce them, via the low/high pass filter of the active crossover. That's providing that your speakers are equipped with a network that can be split by removable jumpers. Happy listening =8^)

"Keep in mind that it is not REALLY necessary to bypass, or delete, the existing crossovers in your speaker system, to experience most of the benefits of active biamping."

For MOST of the benefits of bi-amping, yes it is necessary to go to an active crossover. For one thing, by connecting the drivers directly to the amplifiers the speakers present a nearly perfect resistive load, which is much easier for an amp to drive. Bi-amping via passive crossovers has some benefit, but using an active crossover puts you in another world as far as engineering benefits.

Active crossovers are seldom used though, because an active crossover costs A LOT more to build than a passive crossover, you need multiple channels of amplification (perhaps as many as eight for two speakers), and it's better if the amps are engineered to the speaker system, with more watts in the lower frequency connections, etc. All of this conspires to relegate 99% of commercial products to passive crossovers, which are inferior.

07-10-10: Mhedges
Kal - why do you need a custom crossover? What's wrong with a of the shelf active crossover like the NHT X2?

That is because a crossover from a textbook (as must be all off-the-shelf designs) cannot compensate for the parameters of each and every set of drivers and cabinets. Even a choice of crossover slopes is inadequate to match the inherent variables of every hardware set.

For example, from the X2 page:

The X-2 is a general purpose active, electronic crossover. It mates with the NHT A-1, but can be used with any stereo or monaural amplifier. The X-2 is stereo/mono switchable and has a feature set designed to shape bass frequencies for optimizing room response. Note: The X-2 will not work properly with the NHT U2, iWS, or any Evolution series product,....

Kal