I had a pair of ESS Heil AMT 1b's new from about 1978. They sounded great especially for Rock music. I drove them at the time with a HK PM660 integrated. From a audiophile standpoint there was a bit of a rough spot in the crossover from the mids at the bottom end of the air motion transformer unit to the bass cone driver but, back then, who cared?! The Heil tweeter was so fast that nothing really mates with it seamlessly. These Speakers made it through my college days. They were bullet proof.
Happy Listening!
Happy Listening!