Best Of

Passive crossover networks found in consumer speakers waste an enormous amount of power. The often complex network is made up of large coils, chokes, capacitors and resistors. The circuit splits the full range signal into different frequencies (low, mid and high) appropriate for the different drivers in the speaker. Further, a crossover network compensates for efficiency differences in the drivers; woofers demand mode power than midrange drivers which in turn demand more power than tweeters, etc. Further, each of the drivers has different sensitivities, with some requiring far more (of far less) power than other drivers in the same speaker system. In a passive crossover, the excess power not required is dumped into resistors and burned off as heat. This makes for an incredible waste of power.

in addition, passive crossovers do much to degrade the signals that pass through them, and wastes a good deal of amplifier power, so bi-amping is an attractive idea. But there are pitfalls to be recognized before one embarks on that journey.

As we have seen, the key part of the equation is the electronic crossover. Splitting the signal at line level allows us to bypass the lowly passive network. So, buy another amp, an electric crossover and you are off to races. Ah, but it's not that simple. Now comes the task of calibrating the crossover to your speakers; making sure that the drivers are sent the specific frequencies their designers intended, and that slopes (the rate at which the transition between the frequencies occur, and how much they overlap) are correctly set. These adjustments are key to not only optimum performance, but system safety; operating a driver beyond its range will likely result in its failure. Maybe you've read the book, "Poof the Mangled Driver"?

Ok, so what about just using two amplifiers and forgetting about the electronic crossover? Simply using two amplifiers is not true bi-amping and does not offer the same advantages; we still face the limitations of the passive crossover. What about the notion that bi-amping reduces stress on the amplifiers since they are powering only limited frequency ranges? That would be true in a true bi-amp configuration where the frequencies are split ahead of the amplifiers, but in a passive environment both amplifiers receive a full range signal from the preamp and dump that power into the speakers, regardless of whether one is connected to the tweeter or woofer inputs. The only benefit (and it marginal at best) is simply the additional power offered by the second amp.