Sounds like a bad panel-
i owned Crosby moded ESL-63 for >20 yrs, with Entec LF20 Subs- sold quads wished i hadn't & bought 988's- traded 988/entec LF20 4 yrs ago as i live in HI with no AC & got tired of the humidity affecting the panels every few yrs & having to replace em after hearing noise, spitting, etc- got my rebuilt panels from Ken at ES solutions & had local guy who knows quads install panels-
Finally traded quads/Entec for mint pair of older Watt/Puppys with new drivers, etc. There not quads but i can rock em out & don't worry about replacing panels..
i owned Crosby moded ESL-63 for >20 yrs, with Entec LF20 Subs- sold quads wished i hadn't & bought 988's- traded 988/entec LF20 4 yrs ago as i live in HI with no AC & got tired of the humidity affecting the panels every few yrs & having to replace em after hearing noise, spitting, etc- got my rebuilt panels from Ken at ES solutions & had local guy who knows quads install panels-
Finally traded quads/Entec for mint pair of older Watt/Puppys with new drivers, etc. There not quads but i can rock em out & don't worry about replacing panels..