Bi amp pros out there I could use some help! First time Bi Amping...

I have been an advocate of passive vertical biamping forever, because, speakers such as the Dunlavy line, easily show sonic differences between amplifiers, and to maintain coherence, it is the only way to go. Not to mention, the amplifiers maintain much better control in this configuration. I urge the OP, to seek out another exact Pass amp, and vertically biamp the Dunlavys, because it has been my experience, he has not heard what the Dunlavys are capable of. Understanding how difficult it would be to attain another Pass amp, it would be worth seeking out anyway, or, finding another pair of high quality stereo amps and vertically biamp. Of course, this could lead to another thread, as to finding a pair of amplifiers to replace the sonics of his Pass, but passive vertical biamping has been most impressive for me over the years. Just my final thoughts on the matter, understanding this thread has come to an end. Enjoy ! MrD.

haywood310:

 I'm gonna stick with the Pass for the Dunlavys and try to Swarm (mutil sub) the bass.

Smart move. Massively more bang for the buck this way. The reviews on the Hsu ULS-15 MkII sound like you add another one or two of these and you will have AWESOME bass probably beyond your wildest dreams. Four of those in your room should go flat to subsonic with hella headroom. 

Bdp24 you are completely missing the point. The OP wanted to use the bi-amp feature designed into his speakers. In other words, the way they are supposed to work. The jury is still out on power ratio as far as I’m concerned. Bottom line is that the optimal configuration for his speakers is bi-amp. 

I am little late for the game and may have missed some fine points in comments, but wanted to add 2 cents. I have 4 way crossover with identical amplifiers (except for subs) and one of the issue I had not figured out was speaker impedance matching. The woofer (in parallel) had 3.5 ohms and midrange (in series) had 8 ohms. All experts told me that would not cause problems but every time, I increased the volume, the sound stage would move forward. Once I matched all speaker impedance, sound stage is stable. 

In the spirit of KISS as others have, here is a simple way to have more control and get as complicated as your OCD allows, add a Mini DSP 2x8 Active Crossover. It makes bi-amping super simple and you can integrate your sub swarm by ear, or get sophisticated and use room correction. The computer interface (connect via USB only while tuning) is clean and intuitive with visual on screen crossovers (start with what the manufacturer recommends) and adjust levels to match your amps. 

I had horizontally bi-amped for years with matching amps and it sounded good but recently vertically bi-amped my set up and it has much more punch. So I recommend finding another like model Pass amp to do it and you’ll love it. 

I am happy to discuss how to set it up if interested. To illustrate how far you can go: I’ve gone off the deep end with four subs (two in stereo) integrating seamlessly with my vertically bi-amped 20.1 Maggies. There are 12 bi-quad filters in each speaker created by Multi Sub Optimizer from data captured with Room EQ Wizard. The  crossovers look crazy and the result is jaw dropping.