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Bi-amp benefits with active crossover

Hello All,

What are the benefits of an active crossover from the amplification point of view?  Will a given amplifier sound better if it's input is of a limited frequency spectrum?  Is there an assumption that if an amplifier is driving a limited spectrum, and therefore not working as hard as it would in driving full spectrum, it will drive the limited spectrum "better" than it would if it was driving the full spectrum?

What I am considering is bi-amping, with speakers that have separate terminals for lows and mid/highs, and whether or not there would be a benefit in actively crossing over the frequencies before they get to the respective amplifiers.  This scenario would NOT include bypassing the passive crossovers in the speakers in any way.  I want to retain the speaker designers intent regarding the speaker as a whole.  My focus is whether or not there is an advantage to actively crossing over as opposed to simply using separate amplifiers for the lows and mid/highs, with all the amplifiers driving the same full spectrum signal.  My initial thoughts were that it seems a shame to make the amps work that hard, only to have the spectrum limited by the passive crossover.  But then, in crossing over actively there's all those extra cables and connections and circuits that the signal needs to go through to consider.

The equipment I'm using:
Triangle Volante 260 speakers
Parasound JC 1 mono block amps (would need to add two more channels of amplification, obviously, but the particulars on that are in the next questions: tube? Solid state? Matching levels?  Input sensitivities?  etc.)
Sonic Frontiers Line 1 preamp
Arcam UDP 411 universal disc player
Pro-Ject Carbon Debut w/Ortofon 2M Red cartridge, soon to be 2M Blue.

Thanks All!


dprincipato

Showing 3 responses by erik_squires

erik_squires
15,615 posts
 
Hi @Ivan_nsnibor

Instead of thinking of amplifiers as amplifying power, think of them as amplifying voltage, as indeed, the ideal amp is a voltage amp with infinite power.


So, take an amplifier that can produced a maximum of 10V rms. In music, most of that will be used by the bass, below 200 Hz. A lot of it. Maybe 8 V rms. If the bass takes all 8, you are left with 2 V for the rest.


If you put a high pass filter before it, the amp is now able to reserve all of the 10V for mid to treble.


Does that help?

Best,
E
erik_squires
15,615 posts
 
@ivan_nosnibor
No, that's not correct.
Consider a speaker with the woofer section (crossover and driver) removed.

The amp still produces the complete voltage swing. However, there is very little current flowing at low frequencies. So, power is greatly reduced. However, the dynamic range of the amp is not affected by much.
By eliminating bass from the amp intput, you greatly reduce the voltage swing, allowing greater dynamic range in that amp.

Put another way, you could run around a 30 watt top amp and 200 watt bottom amp, and have balanced dynamic range, and more of it. :)
erik_squires
15,615 posts
 
If you are going to keep the original crossover I'd suggest then is you bi-amp at points far from the speaker's crossover.

For instance, if the speaker is designed with a 2 kHz, set the high pass at 500 Hz, and low pass at 5 kHz. Your high amp will eliminate most of the power hungry bass.

Otherwise, the crossover slopes will get altered.
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