How to Bi-Amp Speakers with an external amplifier

[chris661]

The problem is that the above is NOT bi-amping. You're still driving the same passive crossover that's inside the speakers, but now you're doing it with two amplifiers instead of one.

With good amplifiers (ie, enough current to run the full set of drivers in the cabinets), there will be no measurable difference. Both amplifier channels are putting out the exact same signal, it's just that one of them passes very little current at low-frequencies, while the other passes very little current at high-frequencies. A good amplifier will be happy to pass current over the entire frequency range without any loss of quality.


The real improvement that bi-amping can bring is when it's done properly - with an active crossover.

An active crossover means you've bypassed the speaker's internal crossover, and you've got amplifiers connected directly to the drive units. Think about damping factor, and then what a 0.5ohm (DC resistance) inductor in the crossover will do to that. That's just a small part of the problems of passive crossovers. There's inductor saturation (yes, the crossover components can directly add distortion), the often fairly low-quality capacitors, and of course the limited amount of response shaping you can actually do with a speaker-level crossover.


There's plenty of reading to be done online about active vs passive crossovers, but I'll leave it with this: why do you think almost all studio monitors feature 2-4 amplifier channels per box?

Chris

 

[abacus]

Bi-amping just means using 2 amplifiers for 1 signal (The type of crossover is irrelevant) so it is correct above.
If you have a less capable amplifier and difficult speakers then using a second amp to bi-amp can give a small improvement.
The ideal scenario is replacement of the passive crossover with an active crossover between the pre-amp and amplifiers, which will make a big difference.
In the real world unless the amp and speakers are totally mismatched, 1 run of standard 2.5mm sq OFC copper cable is all you need and then save up for a better amp to drive the speakers.

Bill