I love KLH 9's. I did notice an improvement upgrading the power cords to twisted silver over copper conductors with braided shield for the ground connections. Replace ALL rectifiers and capacitors. Rectifiers should be high speed silicon variety. Check and upgrade all connections points, silver or gold. These are 50+ years old most likely. They sound fantastic even compared to newest technology.
KLH model 9 electrostatic Speakers
I just bought the above speakers, I like them a a lot , I am thinking if it’s possible to replace the power cord on the power supplies. On this speakers? Thanks B