Power requirements for biamping

[Circlotron]

I was reading the other night about how passive crossovers behave with real world loudspeaker loads, particularly as the voice coil heats up and increases in resistance. So now my mind turns to the possibility of biamping to get around this problem. So then, if you normally ran a 100 watt amp and passive crossovers, and then switched to biamping, what power split between LF and HF would be necessary to get suitable results?

GP.

[audionut]

There is a pretty good explanation of how two smaller amps equals more than thier combined wattages in a bi-amped system in the "speaker cookbook".

I recall that two 30 watt amps in a bi-amped system will equal 90 watts in a non bi-amped system.

[Bill Fitzpatrick]

For a crossover around 100Hz, 50 watts for the hi-pass and 25 watts for the low pass we be about equivalent to a 100 watt amp used full range.

[Kanga]

Rod Elliot's ESP site has chart showing power distributions by frequency, and he also talks about the joys of biamping and the additional effective power that you get from each amp. Well worth a read. If you are interested in building an Active XO he also sells boards. I'm building one at the moment for my project.

Mick

[planet10]

Different kinds of music have different distributions of energy, but on average the energy below 300 Hz is the same above. With this XO point you could use 2 x 25 w amps and be equivalent to the 100 w amp*. There is some math to back that up but i can't remember how it goes. These pictures show one of the side effects.

*(this assumes upper & lower halves of equal efficiency -- if the top was being padded down you could away with less on the top)

300 Hz is also not too bad an XO frequency (a nice 3" or even a 2" FR or ESL or Manger crossed to some extended range woofers [a pair is always nice]). If you design the baffle step to happen at the XO point you can compensate for it right in the active XO. This cooresponds to about a 15" baffle width.

dave

[navin]

300Hz = 15" hmmmm that means that one could have a 2 x 10" bass box below 300hz and a ESL panel 15" wide above 300Hz. and the active XO has the baffle step compensation.

hmm.... 2 x 10" in a 1.5 cu. ft. box (18"x12"x24" internal)..push pull...isobarik...something like that. powered by a elph.

ESL panel mounted on top of box 48"x12" i wonder where i saw designs fro this. powered by a SE tube.

this mates 2 desires of mine.
1. always wanted to do full range but 300-20k is close
2. always wanted to do an SE too.

questions.
where can i find info on home made ESLs and SEs. I wold be looking at a 20-30W SE with a ESL of 90db or so.

[planet10]

Originally posted by navin
hmm.... 2 x 10" in a 1.5 cu. ft. box (18"x12"x24" internal)..push pull...isobarik...something like that.

I'd load them push-push

where can i find info on home made ESLs and SEs. I wold be looking at a 20-30W SE with a ESL of 90db or so.

This is something you could probably build with local parts (working where you do would be an aid to). For all things electrostaic you can start at Hans Zeeuwe's ESL Circuit.

dave

[navin]

thanks for the link. gotta get back to my existing project.i got all braces cut and have assembled them. expect my first few photos tomorrow.

[Brett]

I have read in a few references that 250Hz is about the 'breakpoint', where the energy below, and the energy above this frequency are about the same. My experience with PA systems confirms it too. It will vary for different types of music, as dave mentions, but 200-300Hz is a good rule of thumb.

With all else being equal, I'd much rather have too big an amp, than too small a one.

[Brett]

Originally posted by navin
where can i find info on home made ESLs and SEs. I wold be looking at a 20-30W SE with a ESL of 90db or so.

I would suggest you borrow an amp and try this first. The real efficiency of most e-stats is less than 90dB, and they are highly reactive, so most 20W SE amps will run out of steam quickly. If you have a small room and listen softly they might be OK.