# Bi-Amping with Different Watts



## alexadams77 (Aug 4, 2007)

I was just wondering if anyone has tried bi-amping a speaker using different watts? Since everything under 80hz LFE goes to my PC13-U, would it be noticeable if I used 400w for the Mids/Tweets and only 140w for the woofer (Axiom m80)?


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## jerome (Apr 24, 2007)

The problem with bi-amping with different amplifiers is that it could be difficult to adjust the two amplifier gains to reproduce an homogeneous sound. You don't want the mids/highs to be louder than the lows (or the opposite).

You should also ensure that the two amplifiers have the same kind of sound and imaging. I have heard of people using one tube amplifier for the mids/highs and another transistor-based amplifier to the lows. It sounds logical for getting the best out of the two worlds but it is harder to find a good match and tune it all.


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## nova (Apr 30, 2006)

Hmm,... well, kinda. I had bi-amped my mains by using the "surround back" amps on my 3805 and connecting them to the low frequency terminals on my speakers, then assigning control to Zone 3. I know this is not really bi-amped, but it was an interesting experiment. By adjusting the Zone 3 level up or down I could boost or cut the lows,.... the high side of the speakers were still connected to the L/R mains. Kinda sorta like what you are asking about???


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## alexadams77 (Aug 4, 2007)

It was more of a question then anything. My mains are 4ohm and the rest of my speakers are 8ohm, so I was thinking of buying two different amps for the system. Probably two channel for the front and 5 channel for the rest. I was also thinking about a 5 channel amp and just bi-amp the mains and use the last channel for the center.


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## jerome (Apr 24, 2007)

Oh, I see. Sorry, I misunderstood you completely ! :sad2: I thought that you wanted to use two different amplifiers on the same speakers. My bad !

Having a separate power amplifier for the front speaker i quite common in high-quality audio systems. Typically in this case, people want a very good dedicated 2-channel system which can perform well in surround mode too.

Buying a powerful power amp for the front and using a receiver (+ optional dedicated surround amplifier) for the other speakers is one easy way to go. It's often relatively cheap too. Most modern receivers have room equalization and auto-setup which will setup the correct gain for each channel. You don't have to worry about impedance ...

Another solution, as you noted, is to buy a powerful 5/7 channel power amp to power all your speakers. It's simpler but you loose the flexibility of having a better 2-channel system than the surround system. On the other side, you can always use the unused channels to bi-amp your front speakers (and that's a cheap upgrade!)

To the end, it all depends on what you truly want to achieve and how large your budget is.


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## alexadams77 (Aug 4, 2007)

I've read a few posts where people have used a 5 Channel Amp to feed their front three (Bi-amp Mains, Center) and just run the receiver for the rear/surround channels. That way, the receiver would only be running 2 channels and the amp would be feeding the power to the front sound stage speakers.

After reading that and listening to some DVD's, I find that there's not always sound coming from the surrounds as there are from the main three. This could be another possibility as well. I think that I'm going to have to see for myself.


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## Josuah (Apr 26, 2006)

A lot of people don't put stock in audible improvements due to passive bi-amping, myself included (and I have tried it). You also can't use less watts unless you get rid of the internal crossover. If you perform the electrical circuit analysis, which Audioholics has done, and you can do even a simple model on a piece of paper, the signal that the drivers actually see should be basically the same.

Active bi-amping with no internal crossover would, however, let you use less power for the more sensitive drivers and utilize the individual amps over a smaller frequency range, both of which could result in less distortion. The problem is you need to know what the correct crossover should be, and account for any effects on phase or impedance that the speaker was designed with. Which means purchasing a speaker that was supposed to be actively bi-amped, or designing one on your own.


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## alexadams77 (Aug 4, 2007)

Josuah said:


> A lot of people don't put stock in audible improvements due to passive bi-amping, myself included (and I have tried it). You also can't use less watts unless you get rid of the internal crossover. If you perform the electrical circuit analysis, which Audioholics has done, and you can do even a simple model on a piece of paper, the signal that the drivers actually see should be basically the same.
> 
> Active bi-amping with no internal crossover would, however, let you use less power for the more sensitive drivers and utilize the individual amps over a smaller frequency range, both of which could result in less distortion. The problem is you need to know what the correct crossover should be, and account for any effects on phase or impedance that the speaker was designed with. Which means purchasing a speaker that was supposed to be actively bi-amped, or designing one on your own.


So, what did you think or what results did you notice when you bi-amped your speakers? Was it a noticeable difference and was it worth the money to try and attempt it?


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## Josuah (Apr 26, 2006)

I don't put any stock in audible improvements due to passive bi-amping.


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## alexadams77 (Aug 4, 2007)

So, are you saying that you wouldn't recommend doing the bi-amping then?


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## Josuah (Apr 26, 2006)

Yes.


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## alexadams77 (Aug 4, 2007)

Well, that's going to save me a bunch of money. I think that I may try it and see for myself, but from what I've been reading, it doesn't show any benefits unless you use an external crossover.


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## john guest (Apr 4, 2008)

I bi amp my front speakers for to use as 2 channel stereo in my 5,1 system .However the gain of all my amps is 29 top treble 100 watts bottom 60 watts ,But they have to be the same gain characteristics. ie I use a tag 5x100 amp (one channel used for front treble ) and a Tag F3 series P60 (ie 60 watt for front bass) even though they are 60 and 100 they have the same gain and sound fabulous into my Monitor audio's 8i's. Far better control at high volumes and sound much better all round.


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## xcapri79 (Jun 7, 2008)

alexadams77 said:


> So, are you saying that you wouldn't recommend doing the bi-amping then?


I found bi-amping solved the problem I had with receiver overload. I was driving 4 ohm Polk LSi front speakers with a Pioneer VSX-1014TX receiver. With high volumes during movies when bombs exploded, or with glass breaking, the receiver would cut out at higher volumes. Passive bi-amping using the surround outputs definitely cured that problem for me and I ran it that way for a couple of years.
I subsequently purchased a separate Emotiva LPA-1 amp which was a much better solution.


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## frosti7 (May 23, 2008)

Diffrent phase response would give you different sound, your best bet is to try, but i would use the stronger amp for the woofers instead of the tweeters.


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