Cable Connectors
Short lengths of speaker cables with high current capable interconnects is your best bet to not "hear" your cabling. All it takes is a little bit of contact corrosion or a loose connector termination to make things sound terrible. If possible, choose Speakons or EP connections over banana and phone connector options to minimize contact resistive losses (count those milliohms). Also invest the time and materials to wipe the connector contacts with a light coating of contact cleaner. I use cotton swabs and the CAIG Labs two-step process of "DeoxIT" and "PreserveIT" on cabling periodically. Old soundmen will know these chemicals as Cramolin red and blue, and they have been around since the birth of the vacuum tube.

from Mark Amundson's column, Theory and Practice, FOH Magazine