I second that. I have one 8 ft speaker cable and one 6 ft cable, and can't hear any effect. Given the speed at which the signal runs through cables, the mismatch would have to be on the magnitude of many a difference of several times the length of the shorter cable and then, it would be probably noticeable only for someone with great hearing (which I've not had for many years) if the cable lengths were many times longer than the 1 to 2.5 meters most folks use.
In other words, relax and enjoy.
In other words, relax and enjoy.