Freaky speaker experience:

Hi Greg --

Biamping, as you no doubt realize, is simply a whole different thing compared to either biwiring or single-wiring from a single amp. It has lots of potential benefits, and a search of this and other forums will turn up lots of interesting reading on it. Although, of course, some of the advantages that are often mentioned for biamping only apply to active biamping, where an electronic crossover ahead of the amplifiers replaces the passive crossovers in the speakers. But "passive biamping," which I suspect is what you are doing, has lots of potential advantages, too, which biwiring doesn't provide.

Not sure if you are doing it "vertically" (one amp driving the highs and lows of one speaker, and the other amp driving the highs and lows of the other speaker), or "horizontally" (one amp driving the lows of both speakers; the other amp driving the highs of both speakers). The noted designer Steve McCormack has made the point in posts here that the vertical arrangement is probably preferable because in that arrangement each amplifier sees an identical signal at both of its inputs. That eliminates possible interactions within the amplifier between channels, via power supplies, grounds, and other paths, that can impact the sound when a single amp is handling two different input signals for two different channels.

In either arrangement, biamping reduces or eliminates the possibility of interaction between highs and lows in the amplifier output stages; it provides more total power; it presents each amplifier channel with a less complex load; and there are undoubtedly other advantages which I'm not thinking of right now. As I say, its a whole different thing compared to bi-wiring, which just basically separates the highs and lows so that they travel through different wires.

Best regards,
-- Al

very interesting, thanks for the info Al, the amps in my system are set up horizontally, i will have to try setting them up vertically one day to see what it sounds like.
greg

In the second of my posts dated today (July 11) in the other current thread on essentially the same question, I propose the following explanation of what I think is going on here:

Here's a theory I just thought of: You are not really losing bass in the bi-wire configuration; you are just getting better bass damping (meaning tighter, more well-controlled bass), for reasons I'll explain below. That would very conceivably produce the slight measured loss in bass response that you have found (I presume using test tones), and on musical material could very conceivably produce a subjective impression of less bass.

The reason that may be happening is as follows:

In the bi-wire configuration, back-emf from the low frequency drivers is conducted directly (and only) back to the amplifier, which in your case has an extremely good damping factor (i.e., an extremely low output impedance). So the back-emf is absorbed there very effectively.

In the single-wire configuration, some small fraction of the back-emf from the low frequency drivers is conducted through the jumpers into the mid-frequency drivers, where it will not be effectively damped (because the impedance is much higher than at the amplifier output), and, more significantly, WHERE IT WILL PRODUCE SOUND THROUGH THE MID-FREQUENCY DRIVERS, ADDING TO THE SOUND PRODUCED BY THE LOW FREQUENCY DRIVERS.

So you may indeed be getting measurably more bass in the single-wire configuration, but bass which is the result of back-emf effects and is therefore less accurate!

And of course that loss of accuracy in the single-wire configuration (relative to the signal going into the speakers) may be subjectively preferable if it offsets inaccuracies which may exist elsewhere in the system, the room, or the source material.

Regards,
-- Al