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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
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
eldartford
4,262 posts
 
Piezo...If Peak is your concern, the High frequency amp is more critical, because the peak/rms ratio is higher.

I know that "everyone knows" that the LF amp needs the most power. And that includes VTL. It used to include me until I actually measured what was going on in my system.
Of course, other systems and other music might be different, but I bet a lot of people would be surprised.
piezo
304 posts
 
First time i heard about the peak/RMS ratio for high end, interesting. Was that based on your measurements? What about overall power demand? For my home unit i just use one mono per side and for live stuff it's usually moot as well because 2 to 4 18's a side are the obvious power sucks verses a couple of 12s and 10s per side. You have my curiosity though. For smaller club set ups i wonder if putting more power to the high/mid boxes would smooth out the sound (still a room battle in a lot of cases)
eldartford
4,262 posts
 
Piezo...
1. With regard to the peak/rms (voltage) ratio, this would be 1.414 for a pure sine wave. High frequency waveforms are more jagged than low frequency, and the "spikes" will go much higher relative to the rms. Suggestion...look at some waveforms with a scope if you have one.

2. In general, I suggest that you measure what your high and low amps are delivering in your real world situation. If you are using high frequency horn drivers with very high sensitivities your HF amp may indeed be loafing.
douglas_schroeder OP
3,281 posts
 
Well, guys, you're waaay more knowledgeable and technical than I am. I appreciate your insights! I thought I'd just try wiring it both ways and seeing which I prefer.
I've thought the bass was a bit strong with a single pair of LFT-8's biwired at 200wpc, so I thought that maybe I'd "lighten it up" with 165wpc and putting the power more on the mid/tweet.
As you can see, I'm not scientific about this. Hopeful is more the word. I've got an ad in for an additional Outlaw 755 to match my setup if the 750 doesn't perform as hoped. But I'm going to peek at the sensitivity ratings of the different Outlaw amps to see what I can ascertain. Very helpful posts!
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