Why passive bi amplifying exists???

[TLS Guy]

Yeah when I wrote some older "upscale Onkyos" I was referring to their flagships and Integra line.

According to one of the world experts on bi-amping (the legit variety) the main benefit to the use of an active crossover over passive is they effectively provide full amp power with no waste. In a normal single amp scenario the loudspeaker's passive crossover elements are never 100% efficient so they gobble up, let's say, 5% of the incoming amplifier power and wastefully turn it into heat instead of music signal to send to the drivers. But in active biamping instead an amp goes straight to the voicecoil (because there is no speaker crossover) so nearly all of the power amp's signal gets there intact (assuming the speaker cable being used is adequately thick). Still these gains are rather modest. He said he measured it as being around 1dB in real world use or at the very best 2dB, tops. Far better is to simply get a fundamentally doubly powerful single amp and wire it conventionally with one wire, which achieves a solid 3dB greater maximum potential output. [And it may cost less than buying those two lesser power amps.}

The loss of power in a passive crossover is much higher than you think and generally 3db per order. So in most passive speakers at least half the amp power is wasted and usually more. In addition in many commercial speakers the components are undersized, with too narrow a gauge of wire in the inductors. This results in the wire heating and dynamic compression, which also changes the crossover point to an extent depending on the power demands. The lower a crossover point, the larger this problem becomes. It is much less of a problem the higher the crossover point, due to lower power demands as frequency rises.

So, my practice is to use active crossovers in the lower crossover points in my reference systems. I have trouble justifying an amp to drive a tweeter. In my passive designs I use far more expensive and larger inductors than would normally be found in commercial speakers.