Simple Biamp question

I vertically biamp using a TAD 150 sig to 2 SS amps. In my case though since I use one of the outputs for HT passthrough (this is how they are wired - one can serve as HT pt via resistive coupling), I use the single output and a Y-adapter at the amps (saves a long IC run).

I asked Paul Grzybek (RIP) about the impedance issue and he indicated I may lose some high end, but not likely. I haven't noticed any degradation at all and this Vert Biamp config is somewhat better than other amp setups (more expensive stereo) I have tried.

Why would my very respected audio repair shop tell me that the combination of 2 tad 60s and Allison 4s just won't work? They cite impedance and issues related tobthe Fact that the amps are stereo, not mono, amps. Any reason I am unaware of before I blow them both up?:)

I have no idea why the fact that the amps are stereo would be an issue. The fact that they said that lessens their credibility, IMO.

One conceivable issue, though, is that there are some speakers that provide two sets of binding posts for biwiring purposes, but do not have low frequency and mid/hi frequency crossover networks that are independent of each other. In those cases, although the speakers can be biwired they may not be suitable for biamping. Don't know if that applies to the Allison Fours.

Regarding impedance, it appears that the speakers have a nominal impedance of 8 ohms, and the amplifier provides 8 ohm (as well as 4 ohm) output taps. So I would expect impedance to also be a non-issue. The one conceivable concern that occurs to me, though, is that the mid/hi amplifier channel would be running essentially unloaded (i.e., into a high impedance) at deep bass frequencies, and likewise for the low frequency amplifier channel at high frequencies. It is not healthy to run a tube amplifier having an output transformer unloaded, because it creates a risk of amplifier damage from something called "inductive kickback." But I see no reason to suspect that that risk in your situation would be any greater than in any other situation where a tube amplifier is used as part of a passive biamp setup, which is commonly done.

Regards,
-- Al

Al, thank you for your valued input. Why would the absence of independent crossovers make them unsuitable for biamping?

Why would the absence of independent crossovers make them unsuitable for biamping?

It is conceivable that if the speaker is not designed to be biamped its design could be such that it would short the two amplifier channels together, either directly or through some low impedance circuit path. That could be unhealthy for both the amp and the speaker.

In that situation the risk of damage would be reduced somewhat by the fact that both amplifier channels will be putting out signals that, to a close approximation, are identical. But if you don't have a manual for the speakers, or if the manual does not address biamping, it would be prudent to do some Googling to see if others have biamped that speaker successfully.

Regards,
-- Al