"I have a set of B&W CM4 speakers and a center CMC speaker. They all have 2 sets of terminals; my dealer did not explain anything to me about "bi-wiring," [SIC] he just said that "true audiophiles" (?!?) just use the lower terminals..."
Sounds to me as if your dealer wouldn't know a true audiophile if one walked in the door. It's a cinch the dealer isn't one.
"From what I have read here, though, it would appear that my speakers are set up for bi-wiring [SIC] - is this correct?"
Yes. One pair of terminals drives the lower-frequency part of the crossover*; the other drives the high-frequency part of the crossover.
"My receiver is not set up for bi-wiring [SIC]..."
Amplifiers never are; they don't have the crossovers networks in them.
"..., but I reckon I can just use one terminal for 2 cables.:
Yes, one terminal pair.
"And, could anyone clarify whether or not bi-wiring makes a sonic improvement? Newbee said he didn't feel there was a meaningful difference, while Bgrazman said he thought it could make a pretty big difference. I realize it all depends on ones own ears and system, but I am curious, and would like to know if its worth the expense to experiment with this."
OF COURSE it's worth experimenting with it...or so many of us believe. (Do remember, Oak, that opinions about sound, music, and audio are like as......; everybody's got one and most of them stink. :-) ) Read Audioquest's blurb about it, here http://www.audioquest.com/ . ENTER, Cable Theory, page 5/10. Remove the jumpers between the 2 input-terminal pairs when biwiring.
"Also, if you use two cables to each speaker instead of the special - and expensive - biwire cable, I assume that both cables have to be the same brand and type."
Not so and probably not the best way to do it. Using identical cables gets you only the benefits of separating the 2 magnetic fields. (Read the AQ blurb.) Using different conductor sizes and/or different materials can gain you other audible benefits...and cost you a lot of money, too, maybe... READ more of this subject before playing much with biwiring.
* A 2-way speaker combines bass and mid frequencies in one driver and crossover section, while the 3 octaves of treble are handled by the tweeter. A 3-way speaker divides the frequencies, GENERALLY, with the bottom 3-4 octaves going to the woofer (and this is the lower part of the crossover), 2-3 octaves to the midrange, and 3 octaves to the tweeter. Most biwirable 3-ways combine the latter 2 sections and drive them with one pair of terminals and drive the woofer with the other pair of terminals.
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