bi amp imrpoving?

Some of the above responses seem to imply that when "passively" biamping (i.e., using two amps on a biwirable speaker with no external line-level crossover added, be that active or passive -- "passive" biamping is actually a misleading/confusing term in that sense!), you don't get the benefits of relieving the upper-frequency amp from having to deal with the bass frequencies. Although passive attenuation (by the speaker's crossover) after the power output isn't exactly the same as filtering out those bass frequencies before feeding the signal to the treble-range power amp in the first place, there is still worthwhile benefit to be gained (at least in theory) by not requiring that amp to drive a woofer. The amp inputs may "see" the full frequency range, but the output section of the HF amp is not being called upon to deliver much current in the LF. This is of course in addition to the other theoretical benefits, like doubling the available amp power (assuming the top and bottom amps are identical).

I've only ever done passive biamping, but my feeling is that the main benefits of "active" biamping (again in theory - in practice, as has been pointed out above, all bets may be off under the wrong circumstances) are mostly in implementing the frequency-divider network at the low-power line level instead of the high-power speaker level. (Which, as was also pointed out above, relieves the power amps from having to deal with the more reactive load of a speaker's crossover -- in addition to eliminating the high power-handling requirement so the crossover can be miniturized, and removing it from the highly vibrational environment inside the speaker cabinet.) My guess is that this factor is much more significant than any benefit gained from restricting the frequency range seen at the power amp inputs per se. After all, to my knowledge no one has postulated a benefit in relieving the system preamp from handling the full frequency range by dividing the signal after the source and using two preamps...

BTW, I also have to disagree about the wisdom of using different and possibly dissimilar amps for the different frequency ranges (subwoofer amps excluded) -- in my (albeit limited ) experience, using identical or very similar amps (and cables) top and bottom is necessary for the sound not to risk becoming discontinuous, at least with speakers that are coherent/consistent top-to-bottom to begin with.

Hi Al, although I think a potential increase in headroom of up to 3dB is nothing to sneeze at (and although I happen to be one one of those who feels that, other things being equal, more power -- and a realistic playback level -- is better for lifelike reproduction), it needs to be said that the audible benefits of increasing power capability, whether via biamping or just moving to a more powerful single amp, are not necessarily directly related to whatever is conferred in terms of sheer ability to play louder. One may never listen more loudly than before (and never bump up against the system's clipping or dynamic headroom limits) and yet still hear benefits from so-called "passive" biamping. My own feeling is that this results mostly from the (doubled number of) output devices having a more advantageous grip on an easier load combined with an effective doubling of the power supply (as well as the effective doubling of the cable guage and the elimination of possibly inferior jumpers, as in simple biwiring). Assuming your statement about the unchanged voltage output swing when the input remains identical is accurate (and granting that my technical [in]competence to discuss such matters is likely below the chart relative to yours), I'm not sure what bearing this actually has on amp performance or audible results, at least as compared to current output demands.

Ngjockey wrote:

Don't see the point of using identical amps to biamp. Ya, it makes it easy but you're not taking advantage of mixing different characters. The result may be schizo but it's entertaining.

The point, at least in my case, is that biamping can get somewhat more and better sound out of the speakers, as compared with single-amping.

[My case: 88dB, 48" tall dynamic/reflex 3-ways having paired 6.5" woofers, in a mid-sized room, where the amps in question are a pair of 400w monoblocks (top) plus a 500wpc stereo amp (bottom) from the same (audiophile-quality) manufacturer, each with power supplies and SS output sections which are sufficiently beefy on their own. As you can see, a relatively modestly-scaled setup where there was certainly never any putative power deficit without biamping, yet improvements were still there to be had with it.]

My guess is that you and I are probably just after different things, sonically speaking, and/or may have very different kinds of speakers. I also find that doubling-up on physically more managable, more affordable (but good-sounding) amps is an easier way to go for increased power than jettisoning them in favor of much pricier and difficult to deal with gargantuan tanks.

Almarg wrote:

Under typical circumstances, passively biamping two 50 watt amplifiers will result in little more than the equivalent of a single 50 watt amplifier, in terms of the peak volume level that can be generated.

At the risk of repeating myself or seeming a jerk, IMHO the peak volume level that can be generated is largely beside the point. (And in any event that is, as you suggested, not only a function of amp power but also speakers and room, any and all of which may limit the max level. Conversely, where distortion isn't perceived as a negative, ear-splitting levels can be acheived with relatively "low" wattage, as proved by my 40w Fender Super Reverb 4 x 10" tube guitar amp.) In the scenario you describe, I would expect distinct sonic improvements at typical room-filling listening levels to be not only possible but entirely probable.

Sorry Al, I suppose I worded that poorly. I didn't mean that max volume levels are prima-facie beside the point -- I'm a big believer that realistic volume levels, and good sound at those levels, are required for convincing reproduction. (In fact I termed a phrase I call "absolute volume distortion" to describe listening at unrealistically loud or soft levels -- we all do it, but it's a form of playback distortion just the same). I meant that a relatively small potential increase in max volume capability (as you pointed out) is not the main reason for biamping, at least not for me. And lest my Fender amp analogy lead you to think I'm insensitive to uncompressed acoustic music's dynamic range, although I do listen to a lot of electric rock (a lot of it pretty lo-fi at that), and maintaining image independence within a group or massed context at high levels is important to me, in my view a critical test of whether additional power actually benefits a system's natural fidelity would not only be acoustic, but something like solo piano, or even solo acoustic guitar (a relatively quiet instrument at realistic volume settings, but one with which I am intimately familiar) and/or voice. If you screw these things up rather than making progress, then the ability to crank a little more in the bass is worthless to me. Besides which, now you've started making my argument for me! ;^)

Hi Ngjockey, in reference to your response, one of the reasons I go with very similar amplifiers (having basically the same gain) is that I prefer not to have to introduce outboard attenuators into the system, in addition to wanting as uniform sound as possible with seamless transitions between drivers. (I also use the same power cords and interconnects all around in addition to identical speaker cables.) I don't know from personal experience if this is as critical with an active outboard crossover (I do know that some have found it to be so), but as far as I can see I'm probably gonna stay 'passive' and never try going that route, for some of the reasons (among others) mentioned by various posters above. Not that I doubt the benefits of active multi-amping if done properly -- in fact, I've always found it somewhat surprising that there haven't been more high-end manufacturers designing complete integrated crossover/amp/speaker systems where each driver gets its own dedicated amplifier.

The question Psag poses could be taken, or rephrased, either of two ways: 1) Is there any advantage in going to biamping (by doubling up on identical amplifiers) if the single amp already in use is high-powered to begin with and the speakers are of average difficulty to drive (and let's also stipulate that the room size and listening volumes desired are around average)? Or, it could be taken to say: Is there any advantage to biamping (using identical amps) over just single-amping using a similar model (let's say from the same manufacturer) but whose construction and output specs are nominally twice that of the smaller amps?

Or put most simply: For an average system and listener, is there nearly always an advantage (in absolute terms and cost-effectiveness aside) in biamping where the power is doubled, regardless of how high it was to start with -- and is there an advantage in biamping where the power remains constant?

Putting aside for the moment the additional and important questions of whether we are talking about "passive" or "active" biamping (and assuming we don't screw it up if it's the latter), and also whether the amps are stereo or monoblocks (not to mention whether the cables in the starting condition are single- or bi-wired), based on my experience (again, limited!) I'd say the answer in the first instance would probably be yes -- even if the original amp or amps are high-powered to begin with and the demands are average, there may very well be an absolute advantage to be gained by doubling-up (amps + power). But then again, I'm an advocate for the notion that, other things being equal (which they won't necessarily always be), more power is better.

The second instance I can't address from experience, but I'd hypothesize that yes, even though the total power doesn't increase, there could still be some advantage to be gained in divvying up the duties so that the HF amp or amps don't 'see' the LF driver(s) -- much the same way most audiophiles believe that a pair of monoblocks can exceed a similar stereo amp of equivalent power per channel in part because an amp dedicated to each channel doesn't 'see' the demands of the other channel.

So, my opinion taken to its logical conclusion: In a multiway system, the best scenario would be to have an independent mono amp dedicated to each driver (I personally don't, and likely won't, have this), and you basically can't have too much total power, even with 'average' speakers and room/listening demands. Fire away...

My tests with double runs of cable vs. various types of jumpers lead me to agree that one of the main (but often glossed-over) benefits of biwiring lies simply in the elimination of jumpers which are inferior to the cable being used. (FWIW, I never used to biwire before I started experimenting with biamping, and wouldn't call myself an advocate of it.) Another variable when single-wiring with jumpers can be which set of binding posts to connect to the amp -- right now I own two sets of speakers whose manufacturers recommend the opposite connections to the amplifier, one to the woofer binding posts and one to the tweeter, and my findings have confirmed that both are right for their own speakers and wrong for the other.

BTW, though I've never used or even heard a Spectron, my own amplifiers (both mooblock and stereo) do happen to be of fully-balanced/bridged topology (and are fed via balanced connections from a fully balanced preamp and DAC). These amps are always in this mode regardless of whether I'm biamping or single-amping, and I still find benefits in biamping.