Film-Tech Forum ARCHIVE: The importance of a screen for the sound

This is topic The importance of a screen for the sound in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Antonio Marcheselli (Member # 373) on 11-23-2003, 07:57 PM:

Hi everyone.

I was wondering how important is the screen for the sound. I saw that different type of screen has different hole's size. How much this will play against the HF response of the system?

Bye
A

Posted by Sam Hunter (Member # 1119) on 11-24-2003, 09:57 AM:

Maybe you can get the info off the screen makers website [Confused]

I would think that a lot of small holes would equal the same as a screen with lesser holes but larger in size.

Posted by Dave Macaulay (Member # 813) on 11-25-2003, 07:46 AM:

My observation:
Normal cinema perf (the bigger holes) screens affect sound the same as microperf. A new b-chain alignment should be done if the screen is switched but there isn't s humungous difference. I hear more difference replacing an old heavy coated fabric screen witrh a new vinyl sheet.
Microperf has no advantage in a normal cinema. You can't see the standard perfs from the viewing distance. In a small screening room or home theatre micropoerf is required so the perfs don't become a visual distraction.
Both perforation styles have about 10% perf area.

Posted by Andrew Lee (Member # 1330) on 11-25-2003, 09:18 AM:

Actually micro-perf void area differs depending on manufacturer. It can be anywhere from 4-10%. Standard cinema perforations can be 5-8%, again depending on manufacturer. Hole diameter on a standard screen is 0.045"-0.050" while micro runs 0.020"-0.025".

There are differences in transmission readings (however slight) at the high end of the frequency band between standard and micro perforation. Speaker distance to screen and angular placement have a much more distinct affect on response with micro than with standard cinema perforation.

Posted by Gary Crawford (Member # 2038) on 11-25-2003, 11:59 AM:

Being at this awhile, I haven't really noticed big differences from big to little perfs (without test equipment at least).

However, we were restoring an old theatre some years ago and set up a speaker onstage for test purposes of the sound system. It sounded flat, actually terrible. Then I remembered what an oldtimer had told me years ago, that a speaker (on a stage) had to be centered at about 5-1/2 feet off the floor, about the height of a person's mouth. When we set the speaker on a table the sound improved like you wouldn't believe! The accoustics of the old barn were designed for live actors. Not sure if this applies to multi's, but it might be worth checking out.

Posted by Pete Lawrence (Member # 130) on 11-26-2003, 02:11 PM:

Here are a few comparison curves from MDI's web site. MDI frequency response curves Response and perf percentage will vary somewhat with different manufacturers.

Posted by Antonio Marcheselli (Member # 373) on 11-26-2003, 07:43 PM:

Thanks for the link, very intresting.

Someone noted differences between different screen's manufacturer?

Bye
A

Posted by Dave Macaulay (Member # 813) on 11-27-2003, 08:14 AM:

Stewart screens have about 10% perforation on their cineperf and microperf products. I didn't check into MDI.