Remove and re-insert or twist banana connectors once in awhile to restore a possible "filmy" contact (oxidizing or just general atmospheric hazing on metal surfaces). Also rotate any hi/mid controls built into the speakers. this will help keep the contact wipes cleaner. Also, I have found that elevating the speaker's tweeters higher then ear level seems to improve the sound stage (but may reduce bass output). Also, id you preamp or receiver has lots of tape monitor buttons or things that might be in the signal path, push them in and out many times monthly to remove possible oxidation from not being used.