very simple, your amps don't like the speakers and are unstable into the load they present for whatever reason. Either impedence/effeciency of the speakers or design of the amp/input impedence-output sensitivity. This is a guess though as I am not stating this from my own knowledge but from what I have recently read in Listner. Go ahead and correct me anyone if this sounds wrong.
tube amp/flutter in speakers?
i have a nice pair of mono blks that are making my woofers flutter. when i adjust the hum bal it gets stronger or softer depending on which way i turn the adj. my interconnects are good. i am using an old pair of ess monitors with the heil driver. the amps are sansui HF V60. rated at 15wpc i belive?. thanks to all who help.