From: “Timothy P. Stockman”
Organization: Integrated Electronic Solutions
Your essays on digital audio are GREAT! It’s the first time I’ve seen this much useful information all together in one place. Although I’m presently engaged mainly in custom microprocessor hardware/software design (PIC/8051/HC11), I spent several years in the broadcast, PA and recording fields. I got my first exposure to digital audio with a Sony PCM-701ES in the mid 80’s (as a matter of fact I mixed a couple CD’s on it back in those days).
In the mid’s I was working at WXUS-FM (now WKHY), and as I was renovating the production studio I installed a set of Sifam PPMs in the board. I had Sifam make custom scales for them marked in dB (similar to the “NPR” PPM scale), except I had a yellow warning zone included starting at the “0dB” mark (6 on the BBC scale). I did NOT have the reference level (4 on the BBC scale, “-8dB” on my scale) identified, since I did needed some experience with program material to come up with a good reference level.
I finally settled on -4dB (5 on the BBC scale), which corresponded to “0dB” on the VU meters on the recorders (250 nW/M). When I made dubs to the PCM-701ES, I used -15dBFS (as was marked on the 701’s indicators). These levels might not have left enough headroom for today’s digital recording studio, but they worked out great in a broadcast production environment. I should say that my experience with PPM’s is that their integration time and ballistics are very well suited to analog tape recorders (because of the inherent “compression”), but less so to digital recorders. My goal was to equip all the analog cart machines with dbx, but I could never convice the management to spend the money, so I don’t know how my levels would have worked out then, but my hunch is that they would have been OK.
I finally gave up on the broadcast industry about 1990, out of my growing frustration with the “loudness war”. My conclusion was that it was caused by the “louder sounds better” illusion that happens in A-B tests. Thus the louder station *would* sound better when compared with the competition.
But this effect *only* happens in the comparison, not if you actually stop to listen to either station. But it’s such a powerful illusion that I was never able to convice the management!
Tim Stockman Integrated Electronic Solutions
Dear Tim: The old analog QPPM (Quasi PPM) was a GREAT meter for recording to analog tape, superior to VUs or anything else out there at the time. I used SIFAM QPPM meters aligned to -10 dB at 320 nW/M for 15 IPS Dolby SR with great success. It reallly wasn’t very good for radio broadcasting (despite all those Europeans using it) because it did not reflect program loudness.
So—- those were the old days and these are the new days. A true loudness meter corresponding with the EBU/ITU standard is the current standard, and broadcasters are moving to that rapidly. They’re abandoning their old QPPMS, Nordic or BBC in favor of the new standard, and the U.S. side is abandoning their VU meters and broadcast peak modulation meters as well except to satisfy FCC modulation requirements. So I suggest everyone bone up on the EBU tech standard, which you’ll find at our links page in the tab under “Media”.