Monitor Calibration: Pink Noise, RMS vs Peak Real World Findings

Robert Katz Leave a Comment

Curt Wrote:

Dear Bob,

Thought I’d relay my K-System escapades from yesterday… it may prove interesting, and I’d like to confirm that I went about it the right way.

First of all, I had a hell of a time with the pink noise. I work in ProTools, and as you’ve probably heard, the Signal Generator plug-in creates a very odd pink noise… I knew about this and avoided it.

I used a plug-in called Generator X, which made a very nice looking, flat pink noise. Only problem was — as I later figured out — pink at -20dB FS is a based on peak, not RMS… so the resulting pink noise is very light. If you calibrate to this type of pink noise (as I did), you end setting your monitoring volume A LOT louder than you should. I have some of the CDs listed in your Honor Roll, and even after I compensated for your recommended attenuation, they all ripped my head off. I thought either you were deaf or crazy, or I was doing something wrong (I assumed the latter). 

I was using Waves’ PAZ Meters, which exacerbates the problem (I’ll explain in a minute), so I decided to download a Spectrafoo demo. This was VERY crucial. First of all, when I created a pink noise file with Spectrafoo, I noticed the option to check off “RMS”. This RMS-based pink was of course much louder. I know you mention “Pink Noise at -20dB FS RMS” several times in your article, and you even reminded me about “RMS calibration” in your e-mail, but I wrongly assumed most generators would handle it the same. I found out just how crucial this RMS distinction is! I wonder how many people out there are calibrating to any old pink noise?? If the main purpose of pink noise is for calibration (and room tuning), then I don’t really get why every generator wouldn’t just make it RMS only. 

So now that I have the correct pink level (I do, right?), I checked it out on Spectrafoo’s meters. While I was comparing your K-System presets to the Factory Default, I noticed a discrepancy in the VU level… and found the culprit to be the “AES Standard RMS level” box checked in the K-System presets. Finally, -20dB RMS pink showed 0 on the “VU” meters, using K-20. Yahoo! 

My point here is that I don’t think you can overstate the importance of using pink noise based on RMS levels. People will need the difference to be clear. Second, this “AES Standard for RMS” is so crucial, there’s no way to calibrate properly without it (actually, now that I have a proper pink noise file, I guess I can, but…). I also wonder if this is something new you’ve come up with, which IS probably better, and if the rest of the world has been calibrating without this AES calibration. 

As an aside, the Waves’ PAZ meters are totally off the wall in regards to this. If you set the meter to RMS, you get a non-AES readout. So my -20 RMS pink shows something like -23dB. If you set the meter to peak, you get a PEAK RMS meter, only NOW it corresponds to the AES standard, matching Foo’s Peak RMS metering. Hmmm. 

I am VERY happy to say that after years of trial and error with calibrating, everything seems right in the pocket now. I’m convinced I’m hearing playback at the same levels you are, and it feels perfect (mildly loud at times, but not too much). The K-meters are jibing with the music and what I’m hearing. I hope this was of some value to you, and that if you get a moment, you’ll give me thumbs up or down on whether or not I followed the methodology correctly. 

Final notes: From the Honor Roll, I was able to check out Nightfly, Aenima, and Dark Side of the Moon. Nightfly at -2 and Aenima at -9 feel perfect. Dark Side, however, seems a little out of control. I wonder if you used the same version I have, mastered by Doug Sax in 1992? This CD felt better at -5 or 6. Also worth mentioning is that I was using the ubiquitous and somewhat flawed Radio Digital SPL meter. For Aenima, calibrating -20dB RMS pink to -74dB (9dB down) sounded a little louder than when I left my monitors calibrated at -20 and lowered it in ProTools by 9dB — which felt right. Probably the meter. At this calibration for Aenima, the ‘Shack meter showed 
average levels of 88 to 92dB, C weighted, slow.  That looks high but sounds right. Again, thank you for making your techniques available to everyone. 

Take care, 
Curt A. Cash

 

Dear Curt:

Many thanks for your comments. A lot of people are learning about the K-system. At the least, calibrating your monitor so you know how far down it is set is going to be an excellent start. I am definitely advocating adjusting on a per speaker basis (per channel). And remember: RMS calibration.

May I suggest you pick up a copy of my new book, which really goes into detail on the subject (and so many others).  Also, the Honor Roll at digido.com will help you to get into sync on using the system.

Very best wishes, and thanks again,

Bob

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