So a question for the other 'ol timers-how well did they actually work? The horn mouth is very small for the pattern-and I suspect there would be lots of interference.
I suspect the "masher" part widened the pattern-but at what sonic expense.
About 10 years ago I bought a collection of old JBL horns and drivers which included one potato masher.
Being a single, it didn't sell (plus they never did get a big following) four years ago I cut off the throat at the point where it fit a 2" exit and used it with a spare EV DH1A driver on top of what had been a drum sub.
The response is actually pretty amazing- there are no horns of that depth and size that load as low (312 Hz is the same level as 4-10 kHz) that I am aware of, though there is a huge "scoop" in the 2000 Hz range. The masher's loading also corrects the falling HF response of the driver.
The charts below are the raw response with the masher and driver in a 11.25" x 11.25" x 11.25" box, and the same with a passive crossover, which IIRC only uses a capacitor, coil and two resistors for the HP section.
Took a lot of parts juggling, never would have got it that smooth with what I knew in the late 1970's when these were (somewhat) popular.
The sensitivity works out so the nominal 16 ohm HF masher/crossover is about equal to a 15" which is about 98 dB midband.
The measurement distance was about 2 feet, the distance the potato masher is from a drummer's ear sitting on top of the angled 15" speaker cabinet.
As others have mentioned, these are "short throw" devices, the sound does not hang together too well outside a relatively small "bubble".
Hey Jeff- want to buy a drum monitor?