Speed has nothing to do with it. Equal length speaker cables are suggested for the same reason one needs to use larger wire for longer AC runs...resistance. Twice the length of wire has twice the resistance. Don't believe me? Connect 200 feet of wire to one speaker and 2 feet to the other, then try to convince yourself that you can't hear a difference. Output will be noticeably reduced from the speaker connected to 200 feet of wire. That said, with a more reasonable difference in cable length (like 10 feet to one speaker and 8 feet to the other) and decent quality speaker wire, anyone would be hard pressed to ever hear a difference. Of course, everyone knows what insane perfectionists we all are (grin).