The difference is not due to timing but in loudness. The longer cable is a bit weaker in loudness due to its higher resistance. Moving that speaker a bit closer to the listener makes it a bit stronger in loudness.
Odd length speaker cables
Given the considerable cost of most high end speaker cables and corner equipment placement in a non dedicated room I am in need of 18 foot run and a 5-6 foot run. How much detriment coiling 12 feet of cable on one side will have for signal path versus difference if one obtains 2 cables of different length?