Film-Tech Forum ARCHIVE: Sound AMp Location

This is topic Sound AMp Location in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Jason M Miller (Member # 2597) on 04-20-2006, 04:31 PM:

Just thinking, why do most theaters place there sound amps in the booth? (now I know that it is easier to turn off and on and for quicker access) but I am talking in a techinical stand point, whouldn't having the amps (at least for the front speakers) be better so there is less resistence in the wire between the amp and the speaker?

Posted by Richard Hamilton (Member # 321) on 04-20-2006, 06:28 PM:

What is your question?

Posted by Bob Koch (Member # 1062) on 04-20-2006, 06:35 PM:

Dr Hare who made the first solid state amplifiers for 3 panel cinerama thought they belonged backstage also and actually had his way in several theaters. After quite a few thrills in backstage handleing by ancient stagehands and others the idea was given up.

Posted by Sam D. Chavez (Member # 1841) on 04-20-2006, 06:39 PM:

Placing the amps behind the screen is better audio practice but there are a couple of practical reasons why it does not work very well. The first reason is theft, the second reson is access for service. The backstage area tends to collect old seats, popcorn machines, lobby standees, etc.

Posted by Steve Guttag (Member # 268) on 04-20-2006, 07:13 PM:

Don't forget that the air behind the screen is normally FILTHY with all those leaf-blowers and other garbage that gets behind the screen...with amps that blow air, it is short order before they are clogged.

However, in theory, yes, behind the screen offers many advantages from an electrical standpoint. With the price of metals nowadays, it even makes some financial sense to consider building a small lockable "amp closet" for them.

With technology like Cobranet, one can send the audio via Cat 5 and save a bundle on that part of the materials an installation. QSC has done this with their Basis line of products...they also afford the exhibitor the ability to monitor the amps from anywhere. To some degree, one could set the system up such that if the Ethernet cable becomes unplugged...the system calls the cops or at least alerts some form of security. I know this is starting to happen in colleges where many of the A/V systems have Ethernet connections...if the unit fails or becomes out of touch, the system automatically dispatches someone to investigate.

That said, I like my amps in the booth...aside from the dirt issue, it makes troubleshooting a lot easier.

Posted by Richard Hamilton (Member # 321) on 04-20-2006, 07:47 PM:

Do any Cinema processors support Cobranet yet?

Posted by Louis Bornwasser (Member # 3063) on 04-20-2006, 08:48 PM:

Kintek found out (with the KT-90 subwoofer) that many codes require "supervision" (people) if the amp was remote located backstage.

Too bad, technically it is a good idea. Louis

Posted by Gordon McLeod (Member # 33) on 04-20-2006, 08:52 PM:

I like keeping it all in the booth from a troubleshooting point of view

Posted by Frank Angel (Member # 248) on 04-20-2006, 09:03 PM:

We use SoundWeb to control system audio channels from the booth as well as a main mixing console in the center of the orchestra and a backstage mixing console. The amps are all in a separate room backstage. Since cinema and live sound events require different configurations between the systems, the SoundWeb allows instantanious changing between all three systems with all the parameters from eq to delay automatically preset.

Our amps have always been located in close proximity to the speaker clusters in a separate air-conditioned "amp" room even be for the SoundWeb installation. This location allows for short amp-to-speaker runs (HH amps to the JBL clusters) of less than 75ft.

[ 04-20-2006, 11:54 PM: Message edited by: Frank Angel ]

Posted by Steven J Hart (Member # 2340) on 04-20-2006, 10:27 PM:

We put our amps behind the screen simply because it was well over 100 feet from the booth and we couldn't fit all the heavy guage speaker wire into the existing conduit. I ran an 8 pr snake (plus an additional control pair to remote control the AC to the amps via a low voltage relay) through the existing conduit.

Steve

Posted by Richard Hamilton (Member # 321) on 04-21-2006, 07:35 AM:

quote: Steven J Hart
we couldn't fit all the heavy guage speaker wire into the existing conduit. I ran an 8 pr snake (plus an additional control pair to remote control the AC to the amps via a low voltage relay) through the existing conduit.

An 8 pair snake? Must be a good 3/4 inch of cable. How much does a good 100 to 150 feet of snake cost? How do you run that through conduit?

Posted by Steven J Hart (Member # 2340) on 04-21-2006, 08:09 AM:

quote: Richard Hamilton
An 8 pair snake? Must be a good 3/4 inch of cable. How much does a good 100 to 150 feet of snake cost? How do you run that through conduit?

Its a snake made for installations, not heavy duty floor use - I don't think it was much bigger than 1/2 to 5/8 inch. Don't remember the exact cost, but I don't think it was too bad. We pulled it through the 1" conduit with the old wire using LOTS of lube.

Steve

Posted by Steve Guttag (Member # 268) on 04-21-2006, 09:19 PM:

We use a fair amount of "8-snake"...Belden 1410R, I believe is its number. Anyway...it will fit a standard 25-pin Dsub shell so it is in the 1/2" range in diameter. It also not only provides 8 individually shielded pairs (numbered and color coded) but also an 18awg overall shield.