unequal cable lengths

Do unequal lengths of speaker cable adversely affect
the sound. I need 15' for one speaker and only 4' for
the other. Should I use the same length or does it matter?
Ag insider logo xs@2xdave43
In my experience, I was able to hear the difference between different lengths, especially when the difference was as great as you are talking about.

"adverse" and "different sound" are subjective terms, in my opinion, and better decided by you in your own system.