When Bi-amping is there change in sensitivity

Thanks for your response, Al. The tube amp in question does have level control to try to match the gains in case of bi-amping. You mentioned active crossover, would that be a more preferable approach over the passive bi-amping? In that case I would be able to adjust the gains from the crossover itself. And if I end up doing this, would you suggest removing the crossover from the speakers?

Another question I had was if the transients in the mid-high frequencies require as much headroom as the transients in the bass region. Would a 80wpc amp be able to give enough power to provide clean high volume sound (mid-high only) with a moderately affecient speaker, say 89db sensitivity?

I'm not sure that the level control on the tube amp will be able to do the job. My suspicion would be that even with it set to its maximum setting the 500W amp would still have a higher gain. If so, you would still have to provide a means of reducing the gain of the 500W amp, such as a passive attenuator in series with its input.

Yes, an active crossover would presumably provide the necessary gain adjustment, and would also keep low frequencies out of the high frequency amp, resolving the problem I mentioned of not being able to utilize all of the power capability of the high powered amp.

I have no experience with active (or passive) biamping, but those who do generally recommend removing the crossover from the speakers, which would seem logical. However before proceeding down that path you would want to obtain detailed information on the technical characteristics of the crossover in the speakers, and make sure that the active crossover you choose would be able to emulate (match) those characteristics. Some speakers have complex crossover characteristics that may not be matchable by most or all active crossovers.

Another question I had was if the transients in the mid-high frequencies require as much headroom as the transients in the bass region. Would a 80wpc amp be able to give enough power to provide clean high volume sound (mid-high only) with a moderately affecient speaker, say 89db sensitivity?

It depends on the frequency of the crossover point. It has been mentioned in past threads here that a crossover frequency of 350 Hz will typically result in an equal division of power between the low frequency and mid/hi frequency sections. The higher the crossover point, the lower the amount of power that will be required for the mid/hi section.

Regards,
-- Al

here's the earlier thread on bi-amping that Almarg was alluding to:
http://forum.audiogon.com/cgi-bin/fr.pl?cspkr&1331402108&&&/Bi-amp-question

and here is a really good article on real bi-amping:
http://sound.westhost.com/bi-amp.htm

Issues about wether it's actually beneficial or not aside, I am intrigued by a couple of the technical matters discussed so far. Great info from Al (as always) and Drew, BTW.

Is it not true that of great importance is each amp's input sensitivity? And is there a correlation between an amp's power rating and it's input sensitivity as Al suggests? That has not been my experience.

Also, while I understand that each amp would see a full range signal at it's input, I don't understand why the amp would not still benefit from not having to DRIVE a full range signal. What am I missing?