1) True Active Biamping: This is when you have an active crossover unit between your preamp and amplifier which splits the full range signal coming out of the preamp into a Hi and Low freq signal.
These split signals are then fed from the active crossover to 2 seperate amps (or 2 different channels on an amp) and amplified completely seperately. This way your Hi and Low stay completely seperate from the very beginning... they get amplified seperately, and passed down a dedicated speaker cable for each signal...
When these 2 signals are fed into a speaker, they must go into a speaker specially wired to accept 2 discrete signals and route them to the proper drivers in the speaker. These speakers will have no internal crossover circuitry- all signal sent to them must be "pre-filtered"- and the speakers offer direct electical connections to the components inside...
This is true biamping- and it is very rare in Home Theater applications. It is ideal as it keeps the freq discrete starting before amplification - and gives you complete control. You find this type of setup in some movie theaters, some studio monitoring situations and professional PA systems (and many PA systems are actively split 3 way or 4 ways!)
2) Passive Biamping: This is where you don't have an active crossover unit to split the signal and instead you feed identical fullrange signal into two amplifiers (or 2 amp channels).
These full range signals are amplified seperately and then fed each on their own wire into a speaker designed to accept these 2 discrete full range signals.
A passive crossover filter inside the speaker filters out the High signal from the material destined for woofer and filters out the Low signal from the material destined for tweeter.
This crossover circuit inside the speaker is not connected between the HI and LOW- so each band pass is essentially "discrete" after the amplifier: it is just filtered after it is amplified (where as in #1 above it was split before being amplified).
Is also is uncommon in HT- although more common than true biamplification. This requires that you have 2 amps (or amp channels) to drive each speaker- and that the speaker is equipped to be wired this way.
This gives a full amplifier channel dedicated to Hi and one Dedicated to low: giving more power to each driver and usually results in a sonic improvement due to added amplification (and a few other possible factors).
3) Biwiring: This is where it gets sticky.
You run 2 speaker cables from a single amp channel and hook that to 2 inputs on the speaker. If you have special speakers designed to accept this (just like the ones explained in #2 above), The passive crossover filter inside the speaker filters out the High signal from the material destined for woofer and filters out the Low signal from the material destined for woofer.
As above, this circuit is not connected inside the speaker- so each band pass is essentially "discrete" after the amplifier- however since they share a single amp channel-- they are connected at the amplifier.
I am not persoanlly a fan of Biwiring- as I believe it is of no real advantage (however some will certainly argue otherwise- you should seek these opinions out if you're interested in considering this technique).
With Biwiring the advantage of discrete signal chain is theoretcially killed when the speaker wires are connected at the amp channel... You no longer get more power to the drivers, and no longer have discrete signal. Electrically speaking, there is very little difference from this versus just feeding a single fullrange signal to the speaker and letting it split it.
Usually any improvement in sound from BIWIRING seems to be the result of the fact that you're using 2 speaker wires (thus doubling the volume of signal wire).
True biamping requires a seperates system with an active crossover.
If you wish to experiment with Passive Biamping, or Biwiring- you have to make sure you have "biwire" type speakers which allow you to remove the jumper inside the crossover and run 2 speaker lines to the speaker.
Article written by Vince Maskeeper of www.musicianassist.com . Thanks also to www.HomeTheaterForum.com
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