Monitor Calibration : What is this “Dolby 85” thing

Robert Katz Leave a Comment

From: Brad Sarno

My comments are: Hi. Bob, I checked out some of the CD’s you recommend for listening to mastering and levels and compression. I don’t understand the “-4db below Dolby 85” or whatever. Please explain.

Thanks, Brad

Hi, Brad. Dolby Laboratories has established a standard for monitoring gain for the large theatre which can be our reference. The first step is to have a monitor gain control that is marked in 1 dB steps. Every production engineer and mastering engineer should have a calibrated monitor control. Then, using a pink noise test signal that is -18 dBFS (you can obtain this test from TMH corporation, for example) you adjust your monitor gain until the SPL from each speaker (individually) is 85 dB SPL (c weighted, slow setting). Mark this monitor gain as 85 on your control.

The lower you have to set your monitor gain, the more compressed the CD is likely to be. There are some overcompressed CDs that are so loud, they monitor 14-15 dB BELOW the Dolby standard. I’ve found and made lots of clean CDs that monitor about 6 dB below the Dolby standard. My goal is to bring some sensibility into this, so that the production personnel (us!) producing masters work with a calibrated monitor, so that we are very aware of the apparent loudness of every master we make.

In addtion, I have written a report published in the September 2000 Issue of the AES Journal, “How to Make Better Recordins in the 21st Century, an Integrated Approach to Metering, Monitoring, and Leveling Practice”. This article takes you through the whole rationale of calibrated monitoring, and suggests how it can be adopted to improve our recording and listening experience in the 21st century. I’ve revised and improved the article since, and it may be found Here .

That’s it in a nutshell,

Bob

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