There are lots of probally's, could have, may have, etc in this thread. if you need all you tubes tested pm me for my address and I'll test them for you. then at least you will know if it is or is not probally, maybe, perhaps, could be, the tubes.
Welcome to the Klipsch forum.....hope you stick around.
This hobby began in 1966, when I figured out how to disable my dads stereo by swapping out the driver tubes for RF tubes. He used to like to blast the stereo during the school week til 1 in the morning.
my first crossover network project came in 1972.
my first DIY khorns came in 1986. I built as set of khorns using 18inch drivers, enclosed backs, and used them at an air force base in Germany during all army day.