built-in Xover during active bi-amping.

As I mentioned, you will not see the full benefit nor will you lower your speaker's resale value unless you remove the crossover. This approach will always generate debate much like vertical biampping, since it uses ideas from both active and passive biamping. I would say there is a continuum of sound quality/cost which runs along these lines.

1) Standard setup, one channel per speaker
2) Vertical biamping, two channels per speaker Need more amps
3) Active/Vertical biamp approach (This one) Need more amps and a unusual crossover.
4) True active More amps, crossovers and speaker mods.

There are a few who stoutly maintain that passive biamping has no effect and will not improve your sound, since I've heard it improve sound, to the point where I bought another amplifier for that improvement, I disagree with them.

There are two main advantages to an active biamp over other forms of biamping.

1) "Getting passive filters out of the way" and thereby getting rid of all the nastiness like phase shifts and frequency response problems which passive crossovers are noted for.

2) Reducing the frequency range of the signal each amplifier channel is seeing. With a vertical biamp, the amplifier still sees the full frequency spectrum and attempts to reproduce it even though the portion of the spectrum which is outside of it's section of the speaker does not produce power since it is driving infinite resistance.

You will not get the first benefit with the approach I suggested, however you will get the benefits of reducing the frequency range each amplifier is seeing, and keep it from trying to reproduce the singal which will not be heard. Exactly how much of a benefit you will see is somewhat system dependent, since it relies on the original crossover.
Greg
BTW - The Bryston I was referring to is the 10B, it's up on Bryston's web site at www.bryston.ca.

Hi Mar:
I agree with Rich that you have to know what's going on but you do NOT have to be a mod superstar ala D'Agostino or
something to bi-amp your system. Like Rich, typically your low pass passive filter remains.

I'm not certain what system Greg is referring to and I am not familiar with the Bryston unit he talks of but, in any event, I do not see how you can "get away not removing the crossover" for the mid to high frequencies. Getting the passive filters out of the way at that point (between amp and speakers) is the main advantage of bi-amping. Whatever system you have you cannot keep the entire passive XO system in (and working) and get the advantages of bi-amping. There is a good general discussion of bi-amping at Rod Eliot's web site. I suggest you read that Mar. It is a great improvement when done properly.

Rod Eliot's article on bi-amping is @ www.sound.westhost.com/bi-amp.htm

Maybe Sean or some biamp guru will pipe in.

Sincerely, I remain

The answer is definitely system dependent.

I actively bi-amped my B&W800's. I removed the bass low pass filter completely, and rewired my mid/high filter network. The design was done for me by Dan D'Agostino of Krell fame.

YOU SHOULD KNOW WHAT YOU ARE DOING BEFORE MAKING CHANGES TO A GOOD SPEAKER SYSTEM. I didn't, but Dan D'Agostino did.

Richard

If your crossover has separately adjustable crossover frequencies like the Bryston, you can probably get away with not removing the crossover although the net effect will not be as good as removing the crossovers, it will preserve the resale value. If not you need to remove the crossover.

If your crossover does have separately adjustable crossover frequencies, you can set the high frequencies to extend below the crossover point and the low frquencies to extend above the crossover point and let the passive crossover filter out the portion of the frequency spectrum above or below it's crossover point. The advantage is that the amplifier channels will no longer see the portion of the signal above or below their crossover points. The disadvantage is that you still have the passive crossover in there sorting out the frequencies around the crossover point.

To answer your question about the effect of leaving both in, think of it in these terms. Let's say you both have an active and a passive crossover which both attenuate the signal at 6 dB per octave (just to make up a number). The passive crossover was designed so that with it's 6 dB per octave the speakers would blend together and give you a flat frequency response. With the two crossovers in the picture you now have a 12 dB per octave rolloff. Looking at the situation from the woofers point of view, originally it was counting on the help of the midrange speaker to produce part of the frequencies below the crossover point. Since these frequencies are being rolled off more quickly that the designer intended, less of those frequencies are being produced by the midrange than required for flat response (assuming it was flat to begin with). The same thing applies in reverse to the upper end. The net result is a reduction of output around the crossover point.

Greg

How's the poetry coming.

Depends a little on what you are doing but the typical bi-amp will only eliminate the bass to mid-high network in the speaker. Generally you retain the passive crossover for the higher frequencies and you by-pass/remove the passive low pass filter. The crossover frequency for the electronic XO should be close to the original.

Not good to leave in as your not really bi-amping if the passive XOs stay in the circuit.

Sincerely, I remain