Littledog, your answer was anything BUT inept, just not as ANAL as I tend to get (is ANYONE? Who? I vant tu talk to them...)Anyway, one of the main reasons Littledog was "rat on, dooode", is a little understood phenomenon known as "damping factor" - I don't think there is a non-technical way to put this, so either be patient or click on another thread...
We're talking about passive monitors here, driven by an external amp. This also applies to powered speakers in a lesser way, but unless you're a tech-head you won't be able to control what's already "in the box" when you buy actives.
All amplifier circuits, by the way they're designed, have a finite amount of current/power they can supply. This is a function of the power supply impedance (current capacity) and the output device impedance (current capacity into a specific "load" (speaker) - Ideally (meaning does not exist) the source impedance of the amp should be ZERO, meaning it could drive 1,000,000 amps of current through a brick wall if necessary, or through an 8-ohm speaker, if the speaker could stand it without melting. The reality is, even really well-designed amps have a finite source impedance, or current output capacity. This can be measured (by test gear you can't afford) and is usually in the range of a few thousandths of an ohm. When you hook up an 8 ohm speaker to this (typically) .008 ohm source, it means that the source has maybe 1000 times as much drive capability as the speaker can accept, so this puts the source in control of what the speaker cone does, much more than if the two impedances were matched. The ratio of amplifier impedance to speaker impedance is known as the "Damping Factor" - the higher this number, the better. The lower the damping factor, the more the speaker cone can "flop around un-controlled, and sound like shit. (That was a technical term, not to be confused with swearing, which I've also been known to do)
Where fat cables come in (thought you'd never get here, huh?) The resistance per foot of 16 gauge copper is approximately .005 ohms, which would make a 10 foot cable (20 feet round trip) come out to 0.1 ohm. The resistance of that same 10(20) foot speaker cable if it were 12 gauge, would be 0.04 ohms (2 ohms per 1000' instead of 5 ohms per 1000') So, now we have .04 ohms vs. .1 ohms, big deal, right? Remember though, our typical amp has a source impedance of only about .008 - add the cable impedance and you have either .108 ohms (16 ga) or .048 ohms (12 ga) Sooo, the ratio of 8 ohms to source, instead of 1000, becomes either 74 (16 ga) or 166, which is 2.25 TIMES better damping, or control, over the speaker cone. This is why, for best, tightest, punchiest sound, you need an amp with the highest damping factor you can find (all other things being close) and the fattest wires you can fit.
Practical, realworld experience - I once, for a brief moment, convinced my wife to put the stereo speakers in a place where I could actually concoct a balanced stereo soundfield (only lasted about a week, then she re-arranged back to "aesthetically correct", and I was screwed) - When I originally placed the speakers, they were hooked up with 16 gauge wire, 15 feet long. I had some 10 gauge (!!?!) super-flexible electrical hookup wire left over from a commercial project, so I made up some new speaker cables with it. When I replaced the wires, (same length as before), with NO OTHER CHANGES, either in level setting, program material, spkr positioning, or ANYTHING, if I had not had my eyes open I would have SWORN that I had bought new, more expensive speakers. The lows were punchier, the mids/highs were cleaner, I could hear lots deeper into the mix, etc - Up til then, I had totally dismissed the "Monster Cable crap" as just another way to extract money from un-suspecting consumers. Bear in mind, this test was with "ordinary" stranded electrical wire, NOT "oxygen free, phase-aligned, etc etc" cables. Just FAT! Needless to say, the rest of the 10-gauge wire was immediately made into speaker cables for my passive KRK monitors, and that's going to stay that way.
BTW, if you carry the above math out to whether you need the same length wire to each speaker, the answer is DEFINITELY. The differences I just mentioned would cause a noticeable difference in channel response in a studio monitoring system, unless you run a jackhammer all day for a living, and don't wear hearing protection.
I hope this wasn't too involved - the bottom line is, "size DOES matter..."
Sorry, Littledog, got a little long there, but then you KNEW that, didnt you... Steve