I was going to say JBL as well. '66, eh, Tom? I thought maybe even a little earlier.
Might be worth perusing www.lansingheritage.org docs and/or www.radioshackcatalogs.com in the late 1950s/early '60s (R/S sold Altec and JBL in those days...)
Mach speakers used 15" drivers, eliminating any need for passives. This is an interesting thread.
Mach speakers used 15" drivers, eliminating any need for passives. This is an interesting thread.
I wouldn't be surprised if Harry Olson at RCA built one or at least described the practice before anyone used them commercially.
Damned if he didn't. A quick google just showed that Olson patented a PR system in 1935 and presented more work in an AES paper in 1954.
Olson knew everything.