Q. What are the rules with matching loudspeaker cable lengths?
Answer:
The longer the length of speaker cable, the more impact the length has on the resistance and general quality of the signal transmission. In our own testing and general reports (probably the same ones you have been looking at) it was found that under 5m, the human brain finds it very difficult to detect phase differences in the signal if the cables are of different lengths, for example 1.5m one side and 1m the other side. The impact however does become more so the longer the length of the cable so, in instances of over 5m, we would recommend the same length of cable either side.
We always tend to recommend this regardless of length, whether it is 1.5m/2m/3m etc or longer, that you use the same length either side to ensure that the cable parameters of resistance, inductance, capacitance etc are kept constant on both sides of the stereo signal.