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Biamping; Amps w. Different power ratings?

If a person uses two amps of differing power levels, will there be a noticeable difference in volume? I've got an Outlaw Audio 755 which is 200wpc. I'm thinking of adding an Outlaw 750, which is 165wpc also. I would use the lower power amp for the bass, and the higher for the treble.
I will have a speaker system comprising four Eminent Technology LFT-8's (biwired and biamped configuration for each of them) and will use 8 channels of amplification. The four bass drivers would be from the lower power Outlaw amp (165) and the highs from the 200wpc amp.

Or, would I be better served to make one speaker completely driven by the 165wpc, and the other by the 200wpc?

I will be sending signal to all 8 amp inputs through the same preamp - a Rogue Audio Magnum 66 (which has a selectable second main out; the signal from each pair of outs will be split and delivered to the 8 amp inputs.

So, would the difference in power cause volume discrepancies between either the bass and treble, or between entire speakers (depending on how I hooked them up).

Comments, suggestions welcome!
douglas_schroeder
jeffreybehr's avatar
jeffreybehr
805 posts
 
...and 'the same input sensitivity' doesn't mean the same number of volts for rated output, it means the same input voltage for the SAME output. If it's specified, that's usually stated for 1 Watt of output.

Since your amps have slightly different maximum outputs, I would not use them in mono; if you do, one channel will have slightly more dynamic range than the other.

The -8 uses a low crossover, and its MR/treble panels need LOTS of power, so do indeed use the 200W. channels on the planar drivers.

You'll be using the 4 speakers in a surround system?
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eldartford
4,262 posts
 
Until recently I would have agreed with Gregm about using the higher power amp for the low frequency. However, in my system, where, for each channel, a stereo amp drives high and low frequency drivers, the power required for the low frequency is much less than the high. In my case this is because the low frequency drivers are more sensitive than the Magneplanars (high frequency drivers), but, in general I don't think we can assume that, in any system, low frequency takes more power.

I would suggest that you take some simple voltage measurements while music is playing and see which amp (high or Low) is working harder. Truth to tell, the difference between 165 and 200 watts is almost too small to worry about.
piezo
304 posts
 
In sound reinforcement set ups we always use significantly more power on the bottom end than on the tops (like around 1200 wts/side or better on the subs vrs less than half of that on the tops). The bass is what drives most of the peak power requirements contrary to Eldartford's generalization. (though that could be dependant on what you are listening to...chamber music probably doesn't hit the bottom end too hard where as anything with thump most certainly will). keeping sufficient headroom keeps the sound clean and prevents clipping...clipping can be expensive. It sounds to me that you are doing the home theater thing....big amps to the bottom end no question.
eldartford
4,262 posts
 
Piezo...I am sure you do "use significantly more power on the bottom end than on the tops" and for your live pop concert application I am easy to convince that this is right. My point is that your situation does not translate directly to the home audio system situation. To get the real right answer, make some measurements. I was surprised when I did that.
piezo
304 posts
 
Again i think the measurements well be dependant on what you are listening to and the concern would be with peak responce not continuous. Looking at the VTL site their power amp recommendations are based on woofer size suggesting that bass is indeed the controlling factor. Ex. their MB185 monos (230 wt/side tetrode) are suggested for up to 10 in woofers with mb 450s suggested for 12 in. There may be some marketing in there but the trend seems to be consistant. Another thing to consider beyond having sufficient power to maintain headroom is the increased. Another thing to consider is the increased dampning factor the larger amp has which helps control the speaker as it returns to neutral (i.e comes back after it generates the wave pulse) which tends to tighten up the bass. Again i think you are right on about the two amps being too similar to tell. Maybe the easiest solution to the dilema would be trying it both ways and seeing what sounds best
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