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Active vs. Passive biamped speakers

Flint

Prodigal Son
Superstar
This was a longer article at the old forum, but I found the images I used back then and will slap together a quick description with pros and cons for the various methods of bi-wiring or active/passive bi-amped speakers.

First off, here's the various methods of wiring a speaker with separate connections for high & low (bi-amp posts):

This is a diagram of what you are doing when you use two sets of wires from a single amp channel to drive the "low" and "high" (woofer and tweeter) terminals on a traditional two way home speaker:

Bi-Wired Speaker
BiWired_Speaker.jpg


As you can see, all you are doing is using more copper to connect to the crossovers for the speaker. You still have just one amp and same current and voltage is still going to the high pass crossover for the tween and the low pass crossover for the woofer at the same time. No real difference from using a single wire of similar gauge as the two separate wires combined. This is not a practical thing to do and really offers no tangible benefits at all.


Here's a diagram of a Passive Biamped Speaker.

Passive_BiAmp_Speaker.jpg


In this case you are using two amplifiers, both putting out the same signal, with one driving the low input (woofer) and another driving the high input (tweeter). The amps must be identical, or at least offer identical power and gain structure. This approach does introduce some modest improvement in performance because the frequency related impedance each amp will effective reduce the current going to the range outside of the crossover's bandpass range and thus lighten the load a bit on each amp and allow it to perform better in the range it is operating in. However, the passive crossovers in the speaker, which inherently introduce their own distortions in phase, THD, IMD, and dynamic variation, are still there.


The ideal setup is an actively biamped system:

Active_BiAmp_Speaker.jpg


With an active bi-amp setup you remove the passive crossover altogether and replace that function with an electronic active crossover which sits in front of the amplifiers. The crossover filters the signal between "low" and "high" before it is sent to each amp an then each amp is directly coupled to its own driver, the woofer and tweeter, to deliver the highest damping, lowest THD, and the least amount of passive signal artifacts possible. Also, each amp can be chosen for the best performance being asked for. The tweeter, for example, could be driven by a great 10W single-ended triode tube amp and not have to worry about having enough power and "oomph" and the woofer could be driven by a large 150W digital amp, or PA amp, to get the greatest dynamic range and power. However, this approach takes great skill to setup and operate.
 
Timely!! Thanks, Flint! :handgestures-thumbup: :handgestures-thumbup: :handgestures-thumbup:
 
And, after reading this, what I was thinking about doing isn't any of the above.
 
Can't do an electronic drawing easily here, so will try to verbalize it:

- The "red" line of "Channel 1 of Amplifier" and "Channel 2 of Amplifier" would have been connected together, then sent to the speaker over ONE line;
- Same with the "black" line of both;
- The input into both "Channel 1, and 2, of Amplifier" would be identical, both HF and LF information;
- Red and Black lines into the speaker would go into the "non-biamped" position of the speaker, (the "HF" inputs in my case) and be split by the speaker's crossover to the woofer/tweeter.

and, I now understand: no that won't work.
 
Yeah... that won't work. Connecting the outputs together will destroy the amp.
 
Yeah. That configuration, assuming you can split the source input to both amps, will cut the impedance to each amp in half... not good
 
could be driven by a great 10W single-ended triode tube amp


:scared-eek: I'm having trouble believing those words came out of your mouth, Flint!!!




:teasing-neener:

Soundhound would be proud. Or at least not as pissed off as usual.
 
PaulyT said:
could be driven by a great 10W single-ended triode tube amp


:scared-eek: I'm having trouble believing those words came out of your mouth, Flint!!!




:teasing-neener:

Soundhound would be proud. Or at least not as pissed off as usual.

Naw, he's already said the same before. I remember when he was putting together his current rig he would have liked to have been able to buy a DIY tube amp for his tweets.

Which, I'm surprised there isn't out there someplace actually...
 
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