No, You Cannot Bi-Amp

"Eldartford:
...True biamping means that you use a line level (sic) crossover."

WRONG. There are at least 2 types of biamping, and both are 'true'. Each has advantages and disadvantages.

"Subwoofers are almost always biamped."

WRONG again. In the last few decades, subwoofers are usually powered, but a powered SW is NOT biamped. Did you mean that by adding a powered SW to a system, the SYSTEM then becomes biamped?
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"Macrojack:
Bi-amping (sic) provides more flexibility in circumstances where more flexibility is warranted. While that flexibility MIGHT provide improvements, it can provide problems. The Nigels of the world read this forum and will take advantage of the fact that the electronic crossover goes to eleven--or twelve.

...

I have owned and used actively bi-amped (sic) systems at least 3 times over the years. To me, they have held great potential that I never felt I fully realized. I even went so far this last time around to hire a professional sound man to come in and set it up for me. The results were very good--far better than what I was able to accomplish on my own, but in the end, I commissioned Bill Woods to design passive crossovers for my system. ...

My experience supports the KISS principle. There is way too much fantasy out there about DIY and mods. Some of us have the skills to know what's an improvement and what's just a way to spend money kidding ourselves. Most don't."

VERY well said, jack. Designing passive crossovers or even configuring active crossovers is NOT easy, at least not if you want to get it corrrect. The best passive crossovers include impedance- and phase-correction networks that are required for the system to sound correct, and when some amateur eliminates them to use an active crossover, the relationships between/among drivers is left uncorrected.

I built an open-baffle line-array system that used active filtering and biamping; the whole project turned out to be too complicated for this amateur to get right, and I simply gave up.

What's a 'Nigel'?
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Elizabeth, you crack me up! Though I got to be honest, your comment about your "top burners being good for popcorn" got me thinking some unpure thoughts. James Brown needs to take it the bridge before I get myself in trouble.

Jeffreybehr - Nigel Tufnel is (was?) the immortal lead guitarist from the mythical British rock group, Spinal Tap. He reached an amazing level of fame for being the owner of a guitar amp that went to ELEVEN. As he pointed out repeatedly, other guitar amplifiers only went to ten and were therefore inferior to his.
Last November we celebrated Tufnel Day on 11/11/11.

Isn't that Guy Fawkes day?

I don't remember....remember