Altec,
I hear you (no pun intend) on the theory .... but there have been speakers wher i could hear a difference.
A while back, working part time in hi-fi store, i walked out of a listen session and walked back in after getting a diet coke.
I did not know that the guys in the room where going to play around.
when i came back in the same music was playing again and it sounded a little different. I thought they moved the speakers or where playing w/ room treatments....
They told me they switched to bi-wire.
It really did not make sense electrically ... but it did sound a little cleaner or slightly more open....

Just a life example.....

But i appreciate the input from you and psyprof1... thanks

Thanks for the technical clarifications. I suppose "passive bi-amping" is the correct term for what we were talking about? I have done this with receivers using the 6th and 7th channels to "passively bi-amp" the mains but never noticed much of a difference.

Whenever there is a question of whether there truly is a change, a double blind test is the only way to really sort out the truth. To properly do this in the situation you mentioned, you would have the person switch (or not switch) the configuration back and forth with you staying exactly in the same place, and without you knowing the configuration you are hearing. Score would be kept of correct identifications. Anything less than 80% correct identifications is questionable - 50% is what you would get by just flipping a coin.

The human ear is as easily fooled as the eye (ever seen an optical illusion?) and our acoustic memory is generally bad. Also, what you heard just recently (or silence) dramatically influences what you hear a minute later. A speaker for instance will sound slightly different to your ear if the thing you heard 5 minutes before was a truck verses silence, or another speaker. Also, if you drunk or ate something either hot or cold at that refridgerator, this will greatly change your hearing perception for several minutes afterward.

Personally, I've had probably thousands of instances where I think I've heard a dramatic (or slight) change from one day or minute to the next, especially after I've changed something in a system. More often than not when I've checked myself by having somebody change the system back to original and to the new configuration without me knowing which is which, I've been unable to reliably tell any difference.

Yes, passive bi-amping is what it is called when you use two identical amplifiers running the same signal in parallel, one amp feeding the HF and one the LF section of a speaker.

Active bi-amping is when the preamp line signal is fed to the input of an electronic crossover. The HF and LF portions of this crossover then feeds the inputs of two amplifiers, which then drive the speaker drivers directly with no passive crossover components in between.

I run my system with active bi-amping with a 24dB per octave Linkwitz-Riley type crossover at 500Hz. One huge advantage of active crossovers is that the two amplifiers need not be identical. You can run for instance a solid state amplifier for the woofer and a sweet sounding tube amplifier for the tweeter.

One last point (from here anyway) on biamping is that any system that sends the bass below a set frequency, e.g. 50 Hz, to active subwoofers is technically a biamped system - it's just that the two frequency bands are low bass and everything else. So lots of you are biamping right now. But if it's a mono subwoofer I guess it's just one-and-a-half-amping.

Regardless, there is still a passive crossover inside the main speakers in any configuration other than using active crossovers in a "traditional" system with a powered sub. The passive crossover is the main culprit in degrading the performance of a speaker. It's a resistive / inductive reactance / capacitive reactance mess actually.

Very good point which I forgot, and a good reason for active biamping, if you can just bypass the passive crossover built into the speaker. My Maggie 1.6's are now out of warranty and I'm almost tempted to try it, if somebody could just point me toward a high-quality active crossover for less than $500.
Get rid of performance-degrading culprits! Sounds almost like a political slogan.

Unfortunately, there are essentially no good ready built electronic crossovers on the market for anywhere near $500 or below.

Your only real option, and a very good one at that, is to build one such as this one from Elliot Sound Products, where you can use the Op-Amps, resistors and capacitors of your choice.

24dB Linkwitz-Riley Active Crossover

There are some on the market in your price range, such as one from Behringer , which is an all digital unit, but I'd steer away from these at all costs. For starters, being digital, all analog signals are converted to digital for processing, then converted back to analog. The problem is the question of how good could these converters be for the asking price of the crossover? Not very good, I'd say. Also an unnecessary digital conversion cycle is an extremely high, and totally unacceptable in my view, price to pay for a simple thing like implementing an active crossover.

Behringer also has a couple models which I believe are analog, depending on whether one is attempting to bi-amp or tri-amp:

http://www.behringer.com/CX2310/index.cfm

http://www.behringer.com/CX3400/index.cfm

I have no idea if the quality of these crossovers for critical listening. They are in common use for sound support and don’t exhibit the same issues as some users have pointed out in the digital-based DCX-2496. Sometimes used CX3400 and CX2310 show up occasionally on the classified and auction web sites at pretty good prices.

I plan to experiment with a CX3400 for tri-amp use. If the concept works well, but the CX3400 sound quality isn’t quite as good as I was looking for, then a DIY circuit may be in order. The CX3400 has variable crossover points. If I change to a DIY circuit, I will have already established the target crossover points for a particular set of drivers in an enclosure.

While I don’t like unnecessary A/D/A conversions, if I’ve read the literature correctly, beyond just crossover use, the DCX-2496 has some limited additional functions that would allow a user to EQ a set of speakers for a specific room without the need for a separate unit that might use A/D/A conversion anyway. If I were going through an A/D/A process for the sake of some EQ, I might as well perform crossover functions while I’m at it. Behringer claims that the DCX-2496 uses the ‘ultra-high resolution CRYSTAL®/AKM® A/D & D/A converter’, which I know nothing specific about.

Similar to my planned use of a CX-3400, if one used a DCX-2496 during experimentation and evaluation and learned what kind of crossover points and voicing work well with your speakers in your environment, then that would establish a target for an all-analog DIY circuit build.

I highly recommend the site Altec mentions, Elliot Sound Products , and additionally Linkwitz Lab .

If you are the type that likes to learn about these things, good reading and references:

http://sound.westhost.com/articles.htm (two-thirds of the way down the page is a section of eight articles on crossovers and filters)

http://www.linkwitzlab.com/filters.htm

http://www.linkwitzlab.com/links.htm

Behringer uses surface mount technology for it's products, which are banged out in mass quantities in China. It is extremely difficult, and impossible for the prices Behringer charges, to get high quality capacitors for use in analog-only crossovers. In a crossover, the quality of the capacitors is EVERYTHING.

I know there is tremendous temptation to use the digital crossover because of it's other "features" and price, but I would never make that tradeoff. Consider this - would a record company use the cheap digital converters in the typical Behringer product to master your CDs? I think not.

My advise for anybody interested in sound quality is to not go there, at all.