Two different amps to horizontal bi amp?

The biggest potential problem that i see is that the amps might have different levels of gain. As such, applying the same drive level from your preamp to both amps at the same time may not result in equal output from each of them. This could result in a very noticable lack of continuity between the frequency ranges, shifts in imaging and soundstage, etc...

In order to do something like this without getting complicated, you really need to run identical amps that have been gain matched. Otherwise, you'll need some way to measure the output of each amp individually and adjust the drive levels accordingly. This can be done using some type of attenuation device between the preamp and highest gain amp of the two or via the use of an active crossover.

By the way, it's obvious that you are NOT a "Bozo". You have very nice taste in electronics : ) The speakers i'm not that familiar with. Sean
>

Sean is right - gain is one problem. Another is time and phase errors introduced by mixing and matching amps. Unless you use exactly the same amp (and I do mean the same model - not just the same manufacturer because some manufacturers are not consistent from model to model) you will introduce time and phase anomalies which will totally destroy the coherency of your speakers.

The two prior posts raise excellent points. The third element that I think is relevant is that different amps can also have different audio "qualities" -- somewhat like the voices of people differing. I have bi-amped with two amps before, but I have always used amps of the same brand.

All of the above posts are correct and their warnings should be taken into consideration. However, I will tell you I horizontally bi-amp with Levinson Reference 20.0 (top) and Krell KMA 160 (bottom) on modified Martin Logan Monolith IIs with an external (active) cross over. It's almost impossible to use two different amps without the flexibility of an active cross over, but this combination has really worked well--it was not easy to find the right combination though due to the above mentioned concerns, but I was actually looking for slightly different amps in this application.

Dr. Sean,

I'm curious as well, Is it better to have two mono block amp, two identical stereo amp that horizontally bi-amp , OR using the the
same two stereo amp in bridge mode? Thanks for your help on
this Doc.

I have 2 NAD S200 running in Horizontal bi-amp mode driving
the Sony SSM9ED and is thinking of upgrading to the pass lab
x350 or the x600 mono block someday, but I still need to learn alot about high end audio before I can spend my money wisely. I'm a new baby to the high end stuff.

I personally think THE ONLY THING TO CONSIDER FOR YOUR BASS AMP is the Parasound stuff!!!! Not only are those amps RENOUNED for their dynamite bass impact,speed, and weight, but they are great value, and HAVE GAIN CONTROLS ON THE BACK FOR LEVEL MATCHING!!!...something your other amps won't! why spend bigger bucks on a higher end amp that will not surpass what the very flexible, well built, super strong bass performing, excellently priced PARASOUND'S will do!?!
I was using the Threshold T200(better amp) for a long time, and it was excellent! However for a BASS amplifier, I don't see using ANY OTHER AMP on the bass woofer than the Parasound! They're dynamite for that!
Anything from the HCA1500, HCA1200,HCA2200, HCA3500, or other bridged models should be excellent!
good luck

If you've got the opportunity to try before buying...
From one, whose experiment in bi-amping with different amps, failed.

foreverhifi: How do you feel about Parasound amps for bass? I wasn't sure, be clear now--and don't hold back:)

With regard to the question of monoblocks vs. bridged stereo amps.

Generally speaking stereo amps do not increase current output when they are bridged into mono. You may see an increased wattage spec but the current output is typically not much higher.

I say generally speaking because there are some amplifiers which, either because they are dual differential or truly balanced or whatnot, will be able to effectively double their current output when bridged into mono. You should research your particular amp and find out.

In most cases I am not a big fan of bridging amps into mono and prefer to bi-amp instead. I had a customer who was using two big 600 wpc. McIntosh amps bridged into mono and we unbridged them for him and set them up as vertically bi-amped stereo amps. He could play _much_ louder and the bass was much deeper. More current - that was the trick.

Any thoughts regarding a Bryston 4B3, bi-amping (horizontal vs vertical) vs bridging into a monovloc? 

In most cases I am not a big fan of bridging amps into mono and prefer to bi-amp instead. I had a customer who was using two big 600 wpc. McIntosh amps bridged into mono and we unbridged them for him and set them up as vertically bi-amped stereo amps. He could play _much_ louder and the bass was much deeper. More current - that was the trick.

+1, vertical bi-amping = shorter speaker cable, less crosstalk.