In theory, paralleling the outputs of a stereo amplifier (with both channels being driven by the same signal) will double the current available to the load. This would seem like a simple way to make a high-current, mono amplifier. In practice I do not trust or recommend this technique. I feel that there are too many opportunities for things to go wrong, become unsymmetrical, and end badly (with a lot of smoke). It might work well for a while, but I just don't trust it.
Hi Din -
Passive vertical bi-amplification is defined as using one amp per speaker, while horizontal bi-amping uses one amp for the highs of both speakers, and another amp handles the lows. The "passive" part refers to using the speaker's own internal crossover network to do the range splitting and signal conditioning, rather than an external electronic crossover.
Passive vertical bi-amplification is easy to do (and works well in my opinion) so long as you use a matching pair of stereo amps, along with matching interconnects and speaker cables (4 separate lengths required). The trap that many audiophiles succumb to is to start mixing-and-matching different cables with the thought that some are better for highs and others are better for lows. This may seem like a good idea, but it usually just messes-up the system coherence. This is actually the reason why some high-end speaker designers refuse to provide bi-wireable inputs - it gives the user the opportunity to screw things up.
In my opinion, passive horizontal bi-amping will never work as well as the vertical option. Ok, why? Let's assume you are using a matching pair of stereo amps. In the vertical approach, both channels of each amplifier see the same input waveform, and the only difference in the output is the amount of current vs. frequency. There is no difference crosstalk across the common power supply and ground system, and that's a good thing.
In the horizontal approach, each amplifier sees a different left channel / right channel input (just as it would in a normal full-range setup) so you do have the usual crosstalk and signal interference across the power supply which degrades performance to some degree (unless you have a perfect amplifier - good luck!).
Ahh, but you have the solution! Just use 2 different amps - one chosen for the highs, and another that has great bass. That should do the trick! Well, sorry - we're right back to that whole "loss of coherence" problem, and we've complicated the issue by adding the need for separate level controls to match the amp's volume. This simply doesn't work well (or very rarely) with speakers whose crossover point is usually somewhere in or close to the midrange. This is not to say that it can't be done, but having it turn-out well and actually conferring an advantage is difficult and unlikely in the extreme. But this has not stopped a lot of folks from trying. Hey - it's a hobby after all, and monkeying around with this stuff can be a lot of fun and a worthwhile learning experience. You've been warned ;-)
Best regards,
Steve McCormack
SMc Audio
