Film-Tech Forum ARCHIVE: Is OBE (Optical Bass Extension) in CP500?

This is topic Is OBE (Optical Bass Extension) in CP500? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Gary A. Hoselton (Member # 3447) on 01-17-2015, 05:34 PM:

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?

Posted by Stephan Shelley (Member # 8587) on 01-17-2015, 07:00 PM:

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.

Posted by Gary A. Hoselton (Member # 3447) on 02-12-2015, 07:30 PM:

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