Originally Posted by stereoforsale
I think everyone here understands that active biamping is "real" biamping, but not everyone is capable of doing it. The question is, are there any
benefits to passive biamping? Forget about the "anti-audiophile-waste-of-money" argument... assume everyone already has the equipment and cables to do it, we just want to know if it's worth all the re-wiring. Given your ample experience, where do you stand?
Honestly this is the first I've ever read about "passive biamping". If I had read it in any other context, I would have guessed that it involved a passive line level crossover. So I'm not being purposefully obtuse when I say that I'd have to have it defined. If, for example, you hooked up two unfiltered amps to the same unmodified home loudspeaker, I'm told bad things will happen. I've never wanted to waste perfectly good gear on experimenting, but I do trust my mentors. I'd count that one out.
The second possibility is hooking up unfiltered amps to raw drivers, and in that case, the drivers would be destroyed while sounding horrible. So that option isn't even to be considered.
Another possibility is defining it as an amped up form of biwiring, to be used on loudspeakers that have special passive crossovers that support biwiring, which not all loudspeakers do. In that case, the in-speaker crossovers would protect the individual drivers from out-of-band frequencies, just as they normally would. OTOH they'd still be there sucking power. In that case, true biamping can give up to 3dB more volume (barely noticeable), but the passive elements would eat up most if not all of that extra power. The power handling of tweeters is usually less than that of the low end, so there would also be some resistive attenuation to keep the highs and lows balanced, eating up still more power, or at least preventing one pair of amps to reach maximum power.
It's been a while since I've designed a system, but IIRC the main advantage of biamping PA systems was that the crossover circuitry was designed to be in a low power section, and that increased efficiency by turning less amplifier power into waste heat. It also allowed the selection of smaller (or fewer) power amps at higher frequencies, which saved on equipment and shipping costs. Some of those advantages simply aren't applicable in a home environment.
So really the bottom line is that it's a lot of work and risk for little to no practical return. Even true biamping would be a mostly wasteful endeavor unless the entire system was designed to be that way from the very start. Even then it's usually a very costly setup. I've had my eye on some ATC active triamped loudspeakers, and starting at $15,000 each they're not for saving money.
It's just one of those things that you might do once to see if it works, but not really have any practical purpose for 99% of the time. "Looks better on paper."
EDIT: Apologies. I looked over my post while reading a post on bridging, "fixed" an error that was actually correct, and then had to fix it back again. That'll teach me to try to do more than one thing at once. Biamping doubles the effective power for a 3dB bump....or something like that. I've long since forgotten why. I'm pretty sure it has something to do with divvying up the whole of the power spectral density up over two limits (amps), but don't quote me on that. I'll tackle it later.Edited by Speed Daemon - 11/23/13 at 11:43pm