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Simple Biamp question

I know there have been dozens of biamp threads, but my question is so simple that I'm sure someone can answer it instantaneously.
I have a preamp with 2 pairs of outputs and 2 identical stereo amps than cannot be bridged into mono status. So I wish to biamp my speakers (Allison 4s with biwire posts)
1. Can I vertically biamp with the left leads of both outputs going to one amp and the left speaker and vice versa with the right leads? I have heard from some Audio people that I cant do this. Why? Something to do with crossovers and imaging and soundstage....
2. Is it better to horizontally biamp witjh both amps sending single wires to lower frequencies and both amps sending single wires to upper frequencies?

I would prefer the verical, as it's neater and easier, but are therte drawbacks? Is there a reason both left and right outputs from the preamp cannot go into one amp and use it as a mono?

Amps : TAD 60
Prreamp: TAD 150 Signature

Thanks very much for your help.
springbok10
rrog
1,958 posts
 
Give it a try. Vertical biamping should give you a big effortless sound.
bdgregory
1,710 posts
 
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.
springbok10 OP
711 posts
 
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?:)
almarg's avatar
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almarg
9,670 posts
 
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
springbok10 OP
711 posts
 
Al, thank you for your valued input. Why would the absence of independent crossovers make them unsuitable for biamping?
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