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» Film-Tech Forum ARCHIVE   » Operations   » Film Handlers' Forum   » Is OBE (Optical Bass Extension) in CP500?

   
Author Topic: Is OBE (Optical Bass Extension) in CP500?
Gary A. Hoselton
Film Handler

Posts: 59
From: Portland OR U.S.A.
Registered: Nov 2005


 - posted 01-17-2015 05:34 PM      Profile for Gary A. Hoselton   Email Gary A. Hoselton   Send New Private Message       Edit/Delete Post 
On page 130 of “The Advanced Projection Manual”(2006), author Saetervadet writes that Dolby developed OBE for analog optical sound to improve on poor bass response of most cinema speaker systems, slicing off audio below what a theatre’s speakers could linearly reproduce, say below 85 or 50Hz, and sending it via a separate amplifier to a subwoofer. This might be interesting to mess with, but don’t find a reference to OBE in my CP500 installation or operators manual. What is the story here?

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Stephan Shelley
Jedi Master Film Handler

Posts: 854
From: castro valley, CA, usa
Registered: Nov 2014


 - posted 01-17-2015 07:00 PM      Profile for Stephan Shelley   Email Stephan Shelley   Send New Private Message       Edit/Delete Post 
OBE is part of the subwoofer in s CP500. Check out section 5-10 in the 500 manual about setting room SPLs. There is a separate setting for optical. You can also change the low pass filter setting between 50hz and 100 hz. Use the 100 hz if you are using unmodified voice of the theatre speakers and 50 hz for more modern ones. One drawback of using 100 hz is that lower parts of male voices can be routed through the sub and become boomy.

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Gary A. Hoselton
Film Handler

Posts: 59
From: Portland OR U.S.A.
Registered: Nov 2005


 - posted 02-12-2015 07:30 PM      Profile for Gary A. Hoselton   Email Gary A. Hoselton   Send New Private Message       Edit/Delete Post 
Thanks, Stephan. Found it in my CP500 manual, it is turned on. Turns out I didn't have subwoofer amplifier ON at the time; the little neon pilot lamp is about shot and only flickers now and then and amplifier is bottom one in rack. With gratitude, Gary

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