Hi there,

I guess you could try it a couple different ways. If you want to bi-amp, then that precludes the bridging method. The bridge method, by definition, is only a single channel, and then you are no longer bi-amping, but rather bi-wiring.

If you really want to bi-amp, and your A500 doesn't have the run in parallel option (sounds like it doesn't), then you will have to split the output of the 990 and feed both inputs of the A500. Each output of the A500 is then isolated from the other, and you will be passively bi-amping. Of course, you will remove the jumpers on the speaker wire inputs of the speakers themselves.

I see what Altec is saying, but I've never tried it. I see that he's making an assumption about while channel maintains uninverted polarity ("usually the left"), so it's possible that you will run into polarity problems with respect to your other speakers. In general, I see how this implementation could work, but I wouldn't personally do it without understanding exactly what's going on. You could figure it out empirically if you have an oscilloscope.

If you're worried that you're underpowering your center, I think you'll get the quickest and easiest mileage out of simply briding the amp and single-wiring the speakers.

There is a slight electrical advantage from passive-biamping. However, I really doubt how audible it is. I'd say that some people might be able to hear it in fine musical recordings. While the center channel is an extremely important component for home theater, I think its fidelity is reliant upon much more basic things that separating the high pass and low pass internal crossovers. If you find your amp is running out of gas power-wise when driving the center, using bridge mode will generally get you the same amount of power as bi-amping.

Bottom line: 1) bridge the amp and single-wire for maximum power to the speaker; 2) split the input from 990 to A500 and run each channel independently if you want to passively bi-wire (see if you can hear a difference in blind testing!) and 3) do the bridge mode with one channel inverted if you want to do the bi-wire thing with a twist.

Good luck!