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Is bi amping really a trade off?

First a little background. My very modest system consists of a NAD T744 receiver that I'm running as a pre-amp to an old HK PA5800 amp. My speakers are a pair of B&W 685s. I do have a Paradigm PW2200 sub, but don't like to use it, preferring 2.0 stereo.

Just on a whim, I decided to bi amp my speakers, using two more channels from my amp. I had them running bi-wired (a remnant from my Studio 40s) so bi amping them took me all of ten minutes.

The result? The bass tightened up a LOT and went deeper. Although the sound stage stayed about the same, I got a lot more depth. Listening to some Sade, I could not only tell that her sax player was standing to her left, but I could now tell that he was also standing a good bit behind her.

Another observation that I made, though, was relative to the volume level. My usual listening level is at -30. When I turned it up, after bi-amping, I noticed that I had to go to -20 to get to my usual level. Now, I'm not real sure about this because I never really paid much attention, but this is just what I thought.

Anyway, it just got me to thinking. My amp is spec'd as putting out 80W on an 8 ohm load and something around 120 on a 4 ohm load. I wondered how splitting the tweeter from the woofer affected the overall load of the speaker components.

Just to keep things simple, I'll assume that each component in the speaker is running in parallel to the other. If that is right, then (to keep things simple) can I say that each component has a resistance of 16 ohms so that when I run the components in parallel I have a speaker that presents an 8 ohm load?

If all of this is right, then by bi-amping, I've effectively made it so that each channel of my amp is driving a 16 ohm load. Again, if this is true, then I've taken my 80 wpc amp and turned it into something around a 50 or 60 wpc amp, due to the greater load.

Am I making any sense? Or am I just imagining things? Did I trade off power for better sound?
tonyangel

Showing 2 responses by tonyangel

tonyangel OP
309 posts
 
Al, I really appreciate your taking the time. Like an idiot, I completely forgot about the crossover and the affect that it would have on the load, or its distribution. You really cleared things up for me and now I almost regret having posted. I could have answered my own question (or gotten pretty close to it) with a little more digging.

As for the volume level, it could be all in my head. That tends to happen to me sometimes.

In the end, I do know that MY system sounds better in this configuration and would have accepted the trade off in power (had there been one) for the better sound.
tonyangel OP
309 posts
 
Of course, a lot of this is over my head, but I really can't see (due to ignorance?) how the load can be divided equally. I only did that in my model for simplicity's sake.

What leads me to believe that the loads are not equal is my one experience with active speakers. In my case, it was a pair of Paradigm Studio 20s. If I remember right, the highs had a 50 or 75W amp on them and the lows had a 100 or 125W amp on them.

What I've gathered from the information that you guys have provided so far is that getting the better sound is about the lack of distortion that is brought about by not having to stress the amp.

What I'm hoping all of this is telling me is that if I get an amp with some nuts, I won't have to worry about bi-amping in the future.
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