Too short means confusion and lack of coherence. Musical phrasing is smeared, timing seems subtly off, the image is out of focus. Instruments are harder to place and lack definition. Soundstage is vague. It's easy to spot the difference if you compare two lengths of the same cable.
I've never heard too long but I imagine the effect must be about the same, since the problem--timing of internal reflections--is the same.
I've never heard too long but I imagine the effect must be about the same, since the problem--timing of internal reflections--is the same.