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What’s the Right Power Amp Ratio For Bi-Amping?

Is there a “golden rule” or rule of thumb when selecting amplifier power in a bi-amp setup? It seems to me that the power should be apportioned according to the demands. Since most of the energy consumption  in sound reproduction is by lows, it stands to reason I should use a much more powerful amplifier for lows than highs, but what ratio of power? 2:1? 10:1? Is there a wrong answer?
128x128sleepwalker65
georgehifi's avatar
georgehifi
10,312 posts
 
Bridging seems too extreme by the way, as I’d end up with the capability to produce 400 watts per channel, probably ten times what I’d ever
Not only that, but also sound quality is worse. As everything measured parameter that makes an amp a good one takes a hit when you bridge. The only plus you get is the extra wattage when you bridge, and if you don’t need it, then you actually go backwards in sound quality.

EG: Bridging Amps
CON’s:
Higher distortion
Lower current
Lower stability
Inability to drive as low impedances
Lower damping factor
Higher output impedance.

PRO’s:
Higher wattage.

Cheers George
rich200
9 posts
 

I have bi-amped a100 watt Yamaha receiver with a 100 watt Kenwood separate amp with very satisfying results. The sound warmed up nicely IMO. The Kenwood had trim control so I could match the levels. I connected the receiver to the high side of my bi-amp able speaker posts and the separate amp to the low side speaker posts.

Your power ratios sounds workable to me 40/150 or the 150/150, with the trim to help match.

I have also bi-amped other combinations of amps with no improvement.

I would try bi-amping then compare to only using one 150 watt amp and see if there is improvement.

Agree with you could try bridging but would not expect that to sound better. However, it would not take much time to try it and satisfy the question and I have been surprised before.

sleepwalker65's avatar
sleepwalker65 OP
832 posts
 
Well, I received the second NAD 2700 amplifier this week, and wired it up with the other 2700 to vertically bi-amp my speakers.

Love the newfound benefits of not being power-deficit anymore. There seems to be substantially more detail in the midrange, which is handled a little differently by my Energy Reference Connoisseur 30 speakers. They have a three way design even though they have two identical woofers and one tweeter, designating one of the woofers as a midrange driver. 

Now getting back on topic, checking heat output of the two halves of each amplifier, the sides that drive the woofer / midrange is *much* warmer than the sides that drive the tweeters. That unscientific evaluation suggests there is a distinctly greater amount of power dissipated by the low frequency side of the bi-amp split. I haven’t yet figured out how to empirically measure this, but the first stab will be using my infrared thermometer. 

In the meantime, I’m no longer power hungry 😋 
mijostyn's avatar
mijostyn
8,518 posts
 
There is not one. Just go for quality, best low end, best treble etc. You like tube high end, but maybe you like SS bass. Forget about power although the more you can afford the better.
knighttodd
199 posts
 

Im bi-amping a pair of Tyler Acoustics Halo Extreme with an Parasound A21+ into the low end and an Prima Luna Evo 400 feeding the top. Rocket 88 carbon x speaker wire. The gain on the amps are within 3 db of each other. The sound and imaging space between the instruments is phenomenal. Im using an Cambridge Audio Cxn v2 into a Audio GD r7he mkii dac and Audio Research LS 28se preamp. Im loving it. 

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