David Farber wrote:



It's amazing a movie could be so loud that it caused structural damage to a
building but not cause hearing damage to the moviegoers!


** The sound was all very low frequency so excited standing waves in the room.

The system was developed by speaker maker Cerwin-Vega and called "Sensurround":

https://en.wikipedia.org/wiki/Sensurround

Cerwin-Vega also supplied high powered amplifiers for the system, mostly models A3000 and A1800 which later turned up on the second hand market and were bought for use in PA systems for live music in the 1980s.

One of my customers acquired a number of them and they were constantly coming in for repair. They were never built well enough to go touring in the back of a truck.


..... Phil