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.
Mono amps and different length speaker cables
Wondering if there is any noticeable negative effect from using say a 3 meter pair of speaker cables to one set of binding posts on the amp and speaker and using a 2 meter pair of the same brand and model of cable to different binding posts on the amp and speaker. I am using solid state mono amps.