Help with bi-amping

There are several methods of biamping.

Horizontal biamping - This uses two different types of amplifiers one to drive the upper speakers of both channels the other to drive the woofer section of both speakers. Many folks use a solid state for the bottom and a tube amplifier for the top end so they get a tube sound on top coupled with better defined lower frequencies. This is a form of "passive biamping."

Vertical biamping - Uses two of the same amplifiers to drive both channels. You may either dedicate an amplifier to the top end on both speakers and an amplifier to the bottom end on both speakers or, as you suggest, dedicate an amplifier to each speaker. This is another form of "passive biamping."

Active biamping - This uses an active crossover to split the signal and only send the high frequencies to the channel which will be reproducing them, likewise for the low frequencies. This is the best form of biamping, but also the most costly, since not only are two amplifiers required but also an active crossover.

Horizontal and vertical biamping will have some sonic benefits, but I would test with your system to see how large they are. You can view an extensive thread on the topic at: http://audiogo5.iserver.net/cgi-bin/fr.pl?aamps&990003839
There are some wonderful and concise comments in this thread.
Another link which might interest you is:

http://sound.westhost.com/bi-amp.htm

although I personally think that the benefits of vertical and horizontal biamping are greater than the author of this does. (I use vertical biamping and it makes a big difference in my system).

The amp does not have to be biampable. For vertical and horizontal biamping, it is easier if there are two preamp outs for each channel, but I don't think very many preamps suport this so, the easy solution is to use a Y cord out of the preamp and run one leg to each channel you will use. I use a Sunfire Cinema Grand, which has two inputs to each channel, and the manufacturer recommends running into one input and then out the other input into the other channel. For active biamping, there will be two outputs from the active crossover for each channel, so you just connect a cord to each.
My experiences with the biwiring and vertical biamping are that the definition and range of the speaker improved with each change, that is, biwiring was better than single wire, verrtical biamping was better than biwirng. I also found that my speakers frequency response improved with vertical biamping. Every system is different though, so you should experiment.

Regards,
Greg

greg: very informative post & right on the mark. BRAVO!

Thanks!

First of all, Greg's thread is very good.
Personal (and limited experience):
I have owned B&W800's (quad wired) for about 9 years and love them. This year, I finally was able to actively bi-amp them (with all Krell). With everything else in the system staying the same except the addition of the 2nd amp and x-over, I experienced the biggest improvement that I have ever experience in my system, bar none.
Although Krell and others recommend that it is better to vertically bi-amp (one stereo amp per side), I have two different amps so I had to horizontally bi-amp them (one stereo amp for the bass and one for the mid/highs). There are some theories about the benifits of horizontal bi-amping such as:
1. Complete separation of the top and bottom frequencies at the amps so each amp must only "worry" about certain frequencies.
2. Complete separation of the frequencies at the speakers so there is no chance of any interaction of the bass to the mid/highs.
3. Ability to use different amps which favor top or bottom frequencies.

Everyone that I know that has gone from bi-wiring to bi-amping, either active or passive, has found large improvement, but as Creg said, much more improvement with active bi-amping, assuming it is done correctly.
Have fun!
Richard

I recently biamped my Martin Logan Odysseys using a tube amp on top and solid state on the bottom - I really liked the effect but even more after adding an active crossover - since it allows for better control of gain and frequency separation.