Central physical location of Multiplex movie power amps

[robertbartsch]

We went to a movie at a nearby multiplex cinema yesterday. This movie house has 7 or 8 flicks that are played at the same time in separate viewing rooms. As you enter the cinema, there is a large air conditioned room with windows that shows 7 or 8 large stacks of power amps and each power amp stack has a separate controller with a small digital screen. Each power amp stack has 5 or 6 stereo power amps, a single controller and a keyboard.

It is obvious that the sound for all 7 or 8 theaters is being powered and controlled centrally from this single location. This seems weird to me since many of the theaters are two hundred or more yards away from the speakers which are physically located behind the movie screens and along the theater walls.

Question: Is this a good design and why? Do they use transformers to get the power signals from the power amps in the central room to the drivers [speakers] that are located 200 yards or more away? Given the current designs of most sound reinforcement applications that are designed with the power amps located physically in the same cabinet with the drivers, I would not have guessed that this movie theater design would work very well.

I thought transformer based sound systems are often used in larger outside menus like sports arenas, car racing stadiums, etc but these are generally not known for quality sound.

Please comment. ...just wondering.... Thx...

[Ed Zeppeli]

Yes this does seem like an inefficient way to transfer power. I suppose that there is a benefit in putting all the amps in the same location though.

My understanding of distributed systems (transformer 70v) is that their primary benefit is the ability to daisy chain multiple speakers. They're usually mono but other than that I don't believe there is any major sound degradation.

I wonder what guage of wiring this cinema is using to its furthest subwoofers.


Regards,

Warren