Film-Tech Forum ARCHIVE: Intentionally wrong installation and setup

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Posted by Antonio Marcheselli (Member # 373) on 02-26-2003, 04:26 PM:

Hi,

Over my 4 years experience, I saw many sound system in many theaters. I don't know if it is just an Italian behaviour, but do you found in USA too systems that aren't enough for the room with some "trick" to make them working with no problems?
Let me explain.
I made my first equalization few weeks ago. It was my friend's theater, a little theater with poor sound system and analog capability only. But the sound was horrible.
Let's ignore the stage and surround eq. Let's concentrate on SW.
The theater, initially, didn't have a subwoofer. When my friend started managing it he asked for a subwoofer and a tech brought to the theater an "hand made" subwoofer.
When I check the SW eq on my RTA, I found that the subwoofer... wasn't a subwoofer since there was a dramatic roll off under 75Hz. Then I realized that I didn't flat the current equalization: the cut trim was at maximum, so that the sw was, really, cut under 75Hz. With no equalization the subwoofer freq. response was at about 40Hz. I made a little cut on 100Hz to have the response flat.

The subwoofer is clearly not enough for that theater, despite the analog only decoder. I had to think that the tech, to seel the subwoofer, used the cp65's parametri eq as an "high pass" filter so that it will never break.
Do you want to know more? Try to guess where the CP65's low frequency cut frequency was set... Yes, 50Hz (with a roll-off at 75Hz). What was the purpose of that subwoofer?? [Smile]

Another situation: a 1000W subwoofer powered with a 1000W amp with clipping limiter. The sub is clearly not enought for the screen.

Is it a common situation outside Italy too?

Bye
Antonio

Posted by Paul G. Thompson (Member # 655) on 02-26-2003, 08:32 PM:

I have seen some "spend a dollar to save a nickel" sound systems in my day. I just shake my head, mumble to myself, and walk away. If the theatre does not want to spend the money to do it right, there is not too much you can do about it.

Posted by German Marin (Member # 918) on 02-26-2003, 11:35 PM:

The aditorium could has certain characteristics that doesn't help to the low fq, as big space that absorbe it (The last aud. I EQ has a big space over the screen that "eat" frequencies between 63Hz and 100Hz).
I've seen people with capacity of making good installations but they are irresponsible.

Posted by Paul G. Thompson (Member # 655) on 02-27-2003, 12:56 AM:

I think it is time to buy a sub-woofer built for the theatre industry. By the way, how big is the speaker, is it horn loaded or a direct radiator? What are the auditorium dimensions? What is the efficiency of the speaker?

I think John Allen would probably be your best bet for advice.