Hello everyone, I just bought a pair of Klipsch KG 4's and I've been having a few problems with them. I've noticed that whenever I have the bass at a reasonable level, the mid range drivers and the passive radiator in the back begin vibrating and pulsing and it is not part of the song. This is my first foray into vintage speakers so I have no idea if the crossovers are bad or something is blown. I'm hoping you folks here can help me. The speakers are running out of a Kenwood KR-3130 receiver from 1971. Any help would be greatly appreciated. Thank you!