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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
erik_squires
5,268 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
ivan_nosnibor's avatar
ivan_nosnibor
782 posts
 
Ok, gotcha I believe. This then is the problem unless the active crossovers (or filters that you guys were talking about above) are applied at the input, yes?...not the output. And if they were applied at the input, then all 10V would be available for whatever portion of the frequency spectrum the amp was being fed, do I have that right? Just making sure.

IOW it all depends on whether the filtering is being applied after or before the input...(which is apparently how it is for my own amps or otherwise I might have run into this problem already, since my system active tri-amped).

Regards
dprincipato OP
2 posts
 
Thanks to all for the insights.  Nekaudio, interesting articles, thanks for the links.  Erik, I’m inclined to agree with you, and if I were to go down the road of actively crossing and leaving the passive crossovers in place, the active cross point should be at least an octave away from the passive’s crossover point. I’m thinking now that the best move would be to keep eyes pealed for bargians that fit the future scheme for active three-way, with speakers that I build, designed with no passive, or very minimal passive crossovers. I really like the Triangle Volantes, although they can be a bit bright on some recordings. And I definitely don’t want to blow up thier resale value by digging around inside them. As far as I can see right now, it would be a Marchand crossover, three-way, with 24dB slopes, that allows signal attenuation for the frequency bands. Now, amps for this scheme are an area I could definitely use some ideas on, I love my JC 1’s, would consider them good choices for bass, but could use suggestions regarding mids and highs, amp-wise.  I’m thinking of tubes for the highs, and I have a Bob Latino ST-120 tube kit that may fit the bill for the highs quite nicely.  Any thoughts are appreciated, and thanks again to all for th fine information..
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