Bi-amping with or without active cross-over? - diyAudio
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Old 23rd December 2005, 10:07 AM   #1
klitgt is offline klitgt  Denmark
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Default Bi-amping with or without active cross-over?

My B&W 803 speakers have separate terminals for the low and high frequency sections, for use with bi-wire setup.

My preamp can feed two power amps and I wonder whether it might be an idea to let one power amp drive the low frequency section and another (identical brand/model) drive the high frequency section, but without active cross over.

The built-in passive cross over in the speakers will take care of the cross over task.

Pros & cons in this bi-amp setup without active cross over?

Rather go for one 2x200W amp with biwiring than two 2x100W amps in a bi-amp setup without active x-over?
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Old 23rd December 2005, 10:28 AM   #2
sreten is offline sreten  United Kingdom
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Hi,

the main advantage of the active c/o is the increase in dynamic range
that you get. e.g. 2 100W amplifiers actively c/o @ ~ 300Hz will have
the dynamic range of a 400W amplifer driving a normal c/o.

Of the options you mention, 2 x 100W or a single 200W bi-wired,
IMO the 2x100W option will sound better most of the time.

/sreten.
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Old 23rd December 2005, 01:53 PM   #3
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Another benefit of bi-amplification is a reduction in intermodulation distortion.

An informative website with an article about this is here:

http://sound.westhost.com/bi-amp.htm

Be sure to check out the rest of the website for more information and the second part of that article. The general conclusion I got from the article was that with passive crossovers it is probably a better buy to get a bigger amp instead of two smaller ones.

Just don't leave that jumper installed if you Bi-amp!
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Old 23rd December 2005, 02:10 PM   #4
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Default Re: Bi-amping with or without active cross-over?

Quote:
Originally posted by klitgt
Pros & cons in this bi-amp setup without active cross over?

Rather go for one 2x200W amp with biwiring than two 2x100W amps in a bi-amp setup without active x-over?
You'll clip up to 3dB (the power supply should sag less so you won't loose all that output) sooner since both power amps have the same input and output waveforms as the single 200W amp.

Not much point to that unless you're selling amplifiers (two 100W amps cost more than one 200W amp).
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Old 23rd December 2005, 03:05 PM   #5
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Hi Klitgt,
You have a good opportunity to test two different amp :
one big solid state on the bass + one "kind"little tube amp ( or something like Pass Zen,Aleph,etc.) on the mid-high.
Obyouvsly one must be have an input level control due to the different
gain.
Cheers,
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Old 23rd December 2005, 04:56 PM   #6
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Quote:
The built-in passive cross over in the speakers will take care of the cross over task.
I dont get it. You are spliting the frequencies out of the reamp and driving 2 seperate amps into separate drivers.

What work does the crossover in the speaker do?

If you connect to the "high" and "low out puts, wouldn't the x-over be isolated?

I don't understand the question.
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Old 23rd December 2005, 08:53 PM   #7
Tweeker is offline Tweeker  United States
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Theres no point in biamping without an active, or passive line level XO.

The later being an option with relatively simple xos and baffle step compensation where power amp input impedance and preamp are suited to deal with the insertion loss.

Without a line level / active XO, the amps are just parallel.
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Old 23rd December 2005, 09:01 PM   #8
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Hold up. I get it;
Your Bi-amp plan involves running both amps at the full range with the presumption that the speakers' crossover will sort it out.

If you have "hi" and "low" out on your pre amp, isn't that already crossed over?
If you have Hi and Low speaker inputs, I presume that they would bypass the crossover. If they don't, i would think that you have a risk of correcting your amps in parallel. Scary!

In any case running your amps full range negates most of the advantages of biamping.

crossover - amps - Drivers
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Old 23rd December 2005, 09:35 PM   #9
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By the way, Thats a great link Joe, but I can't understand how the output from 2 amps adds up to twice as much as a single large amp.
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Old 23rd December 2005, 10:17 PM   #10
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Quote:
Originally posted by Pbassred
By the way, Thats a great link Joe, but I can't understand how the output from 2 amps adds up to twice as much as a single large amp.
Because we're adding voltages and an amplifier which can deliver twice the voltage into a given load will need 4X the power rating because power = V^2 / R.

When you split the signal before the amplifire you don't need that extra current+power reserve that you're not going to use on a musical signal.
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