You also hafta remember that when we designed the old Acoustic bass amps, there weren't many bass amps around that could fill a stadium or keep up with the guitar amps. The introduction of my D130F and D140F started a lot of companies thinking about new speaker designs for increased output.
The Altec 421 was basically Altec's answer to the D130F and D140F. I used the 421 in the Acoustic 261 simply because JBL wouldn't sell us the D130F (that I designed). After Acoustic became somewhat successful, JBL offered to sell us JBL's, but I turned them down, gleefully.
The form of the Acoustic speakers basically followed function: light shows were the usual thing those days, so notched knobs (you could find in the dark) made sense. The Acoustic blue color came about because early color TV cameras couldn't handle pure white. The built in hand cart, and feet into cup holders, were cheaper that the Fender amp-to-cabinet mounting arrangement.
It's nice to know that people are still talking about some things I designed 40+ years ago, so I guess I musta done something right back then.
