matching different amps for bi-amping

[kenshone]

Hello forum,

Can someone with some EE/electronics knowledge help me understand how I would match the output levels of two different amps, so that when bi-amping a speaker (amp 1 to the tweeters, amp 2 to the mid/bass) the sound remains balanced regardless of the power of the input signal to the amplifiers?

I imagine that setting both amps to unity could be an easy way, but I'm not sure.

I'm sure there are more sophisticated ways to approach this -- hopefully short of setting up an active crossover. Pointers to articles and wikis are highly welcome!

 

[Speedskater]

Using a cal mic or SPL meter (some cell phones have these functions) use a tone at crossover frequency.

 

[SIY]

An easy alternative is to use test tones and a voltmeter. Set the volume on a moderately low setting. Without changing the volume, run a test tone an octave or two below crossover and measure the woofer amp output voltage. Then run a test tone an octave above crossover and measure the tweeter amp output voltage. Adjust so they're equal.

If you have a couple of resistors laying around of equal value and greater than, say, 4R (and they can be as large as you like assuming you have solid state amps), then use them in place of the speakers, run a test tone at, say, 100 Hz (not critical), and adjust for equal voltage outputs of the power amps. Then you can hook your speakers back up and enjoy. (This assumes you're not using an electronic crossover)

 

[Sokel]

It's also usefull to adjust and match the input before the amps (both between amps and channels),don't take the balance for granted ,it will make things a lot easier on the other end.

 

[GIEGAR]

-- hopefully short of setting up an active crossover.

Unless you are setting up an active crossover, I don't know why you'd go to the trouble. Passive bi-amping (filter network after the amps) makes no net electrical difference in routine use.

Assuming your use case is still that outlined in your other passive bi-amping thread, you're not achieving anything worthwhile with this because the system's output capability is still limited by the less powerful HF amp clipping as both amps are being sent identical pre-amp signals. The only way to increase system output capability by any meaningful amount in this scenario is to send the amps band-limited signals - i.e. active bi-amp.

Here's the first of two articles on bi-amping by Rod Elliott. (To be clear, Rod's laying out the advantages of active bi-amping; these advantages don't accrue with passive bi-amping.)

BiAmp (Bi-Amplification - Not Quite Magic, But Close) - Part 1

ESP - The Audio Pages. How to biamp or triamp your hi-hi speaker system for greatly improved sound, and higher sound levels with less distortion.

sound-au.com

 

[HarmonicTHD]

Some more info.

Bi-amping 101

This article provides a quick look at how bi-amplification works. The conventional scheme is to split the signal into two frequency bands before the power amplifiers that drive the speakers. The bass (LF) amp sees only LF signals and drives only the LF driver (woofer). The treble (HF) amp sees...

www.audiosciencereview.com