Mono amps and different length speaker cables

Sometimes you're left with mismatched lengths of cable for a variety of reasons...it happens, and I've found that if it's good cable you can't hear any level differences between speakers. You simply can't. I have used differing cable lengths in the past, but find that same length cables are easier to sell when you upgrade.

You won't hear any difference.
Don't sweat the small stuff.

If you believe that cable affects the sound then longer cable should affect it more, but your cable can be so transparent that 50% difference won't be audible. I still would not do it for the reason of resale value that Wolf_garcia mentioned.

I have tried it before & yes there is a audible difference. Whether you hear the difference I can't say.

Agreed with Mustang. You're talking 3 feet for signals traveling close to light speed.

Coaxial goes about 2/3 the speed of light, so that might be a factor :)