It’s amazing what you can learn about the short-comings of your studio setup when you take the extra step of calibrating your monitors and console. After a long several months of integrating an analog console (Soundtracs PC-MIDI 16) into my DAW setup, including installation of patch bays, cabling, and new audio interface (Lynx Aurora 16), and some nice used Genelec 8040a monitors, I finally got around to running some fairly simple and standard calibration tests.

So what is calibration for anyway?
When you are mixing an audio project you make decisions based on the frequencies and loudness of various tracks. Due to psychoacoustic factors (how the brain perceives audio) we are often led to make decisions based on loudness (louder often sounds better) that don’t always contribute to the overall quality of a mix. Many audio engineers agree that listening to mix at high loudness levels is not only bad for your ears, but may not result in a balanced, pleasing mix.

Bob Katz, the renowned mastering engineer (www.digido.com) has advocated the K-System of metering, and this involves among other things having a well-calibrated audio system where the maximum loudness of your monitoring system is set to a known value. Here is what I did last night to get my loudness levels set correctly.

1. Downloaded the -20 DB pink noise wave file from his site (www.digido.com).
2. Turned the volume control on my Central Station monitor controller all the way to the right (to zero db), and turned down the trim controls for my main monitors so I would not damage my speakers and ears.
3. Turned off the right speaker, so I would be calibrating one at a time.
4. Loaded the pink noise file into Wavelab (any DAW would do), and set it to loop continuously.
5. Pulled out my trusty Radio Shack digital SPL meter, set it to C-weighting and slow response (per Mr. Katz’s recommendations), and sitting in the listening position, pointed the SPL meter at the left speaker.
6. Adjusted the trim on the monitor left channel louder and louder until SPL read +83 dB. This becomes the calibrated listening level for maximum loudness, when my monitor controller is set to zero dB.
7. Turned off the left monitor, turned on the right one, and repeated steps 5 and 6.

The Results, Please!

OK, this was pretty loud, although pink noise is a random noise, and 83 dB is quite tolerable. But I neglected to do one thing. I forgot to disconnect my subwoofer! OK, I have a KRK sub patched in line with the main monitors, and realized that the considerable amount of bass noise I was hearing came of course from the sub, which sits on the floor underneath my workstation.

So I disconnected the sub and hooked the output from the Central Station Monitor A directly into the Genelecs (there is no way to otherwise bypass the sub, unfortunately). Then I reran the calibration again and found that my SPL’s were down considerably, to about 72 dB max. The subwoofer was adding a fair amount of low frequency audio to the mix. This may or may not be a good thing, depending on what you are mixing, but I decided that it would be better to start clean, without the sub.

So I recalibrated and reset the trim levels on the CS so that now I am back to 83 dB for each monitor. Life is good. Loaded a mix I had been working on, and began to immediately notice some ickiness in some of the synth bass lines, violin etc. I had been using plug-in EQ to play with this sound, and now it sounded pretty bad. So I disabled the plug-ins, and basically decided to remix the project from scratch. I noticed that the Genelecs now yielded a more “accurate” mix. I did not need to monitor at 83 dB, I actually preferred setting it the level about 10 dB lower, but when I want to hear it louder, I can now be reassured that my level won’t exceed 83 dB. This will hopefully add more consistency to my mixes, as well as protect my ears…

Next up – calibrating the console.