What I'm about to write may be regarded as total heresy by almost any audiophile who knows anything at all about the conventional wisdom of speaker cable usage, but here is my recent experience anyway. I too am faced with the necessity for a longer run than is usually considered acceptable, albeit more for aesthetic and financial reasons than Richm53. In fact for the past two years I've been using 28' of QED Qudos-dirt cheap by audiophile standards, but first rate-in a single wire configuration on my bi-wirable Audio Gem speakers. I never tried to bi-wire, largely because the dealer had told me there would be little or no improvement, a position which suited my essentially cheapskate nature perfectly. Within the past six months, however, I've managed through judicious bargain hunting (Well, relatively, as these things go!) to upgrade my electronics significantly to a Joule Electra preamp & Bryston 3B-ST amp. This made me curious to see if bi-wiring might not be beneficial, but to test it out on the cheap, I went to Home Depot and bought 120' of 10 gauge copper appliance wire for a total cost of less than $17.00. I've connected this wire, cut into 30' pieces, to the tweeter posts. The difference is incredible: Sweeter highs, especially for strings; improved soundstage depth and delineation of instruments within the stage; an overall delicacy & airiness which I had never noticed before; better mid-bass definition, etc., etc., etc. In fact it's hard to find fault with the results.
So what does this mean? That you have to be crazy to spend big dollars for cable? That the usual theory about long cable runs is myth? That my system might sound even better were I to try an expensive audiophile wire (Admittedly this is a real temptation, although I've lately become increasingly convinced that interconnects play a much larger role than speaker cable.)? That bi-wiring alone, even with the cheap Home Depot stuff, is sufficient to create a significant upgrade in sound, contrary to the dealer's suggestion (I keep thinking there has to be a reason for the manufacturer to include this capability.)? That-Heaven forbid!-I'm hearing what I want to hear, because the change was so cheap?
Frankly, the answer(s) may be all, some, or none, of the above. I really don't know, nor am I inclined to speculate a whole lot on this (very pleasant) phenomenon, for which I'm sure some talking head out there has an explanation. I for one simply intend to enjoy the results, now that I've passed on my experience.