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Today someone - let's call him Phil (not his real name) - attempted to explain a calibration technique that he claims is regularly used by “all the best engineers”. As I am having difficulty following the logic behind this technique, I present it to you for discussion. The technique he conveyed is as follows:

As an engineer would set up a session, he would calibrate the trim on the console for each channel of each mic to be used by sending tones from a tone generator, through a speaker placed a specific distance from the mic. The engineer would then, using the meter for that channel adjust the trim until it reads 0db. “Phil” claims that this is an accurate way of adjusting the trim on each channel to optimize the gain and headroom of that particular mic and to ensure the the mic will produce optimum signal without clipping. When I asked what the specific output level and/or distance from speaker-to-mic was, and if it is adjusted based on each microphone's specs, such as max SPL or impedance, “Phil” said “no it is the same for all mics, you send a 0db signal from the tone generator and adjust to 0db using the trim”. He also could not provide information as to which frequencies and waveform types would commonly be used.

Though I am familiar with methods using a signal generator plugged into various devices as a calibration and gain structuring technique, I have never heard of using this method that “Phil” describes, nor does it make any sense to me as an accurate way of adjusting a mic channel's input gain based on the information he provided. I have alway been under the impression that the mic's channel trim is adjusted according to the sound pressure level of the instrument/voice being recorded. And that the trim adjustment was made to get best signal-to-noise ratio without clipping - unless of course you like the sound of your console channel clipping (see: Trent Reznor).

While “Phil” is a “nice guy”, appears to be somewhat knowledgeable about recording techniques and claims to have recorded in “high-end” studios, I question the validity of this calibration technique that he purports is so often used. Moreover, “Phil” has convinced a friend of mine and his band mates that this is the “proper way” of setting up a mic. As they are recording their current album at home and are new to the recording process, I would hate to see them led astray by “junk science” that could diminish the quality of their recordings.

I was wondering if any of the kind folks here could substantiate “Phil's” claI'm regarding this technique, and if so please shed some insight as to the proper technique and theory behind it. If it is, as I suspect, misinformation please reveal it as such so that I may pass this new information along to friends who are recording.



RemyRAD Thu, 10/12/2006 - 20:58

As a fairly accomplished engineer/producer myself, I think your friend "Phil" has been partaking in too many natural combustibles, which is a fairly important part of the recording process.

His technique is absolutely ridiculous! Having designed, built and maintained many consoles over the years, I can tell you that is not the way to set microphone gain trim.

Most consoles offer a "solo" or "PFL" (pre-fader listen) feature which is generally a pickoff point right out of the microphone preamp, that generally also appears on a meter on the console. It is there that you will observe the microphone preamp gain structure. If you are a good engineer, you will adjust this with the actual signal source, not a stupid signal generator. I think he was just pulling your leg? I know a lot of engineers who think their technique is so special, they won't share anything with anyone else and if they do, it's usually like what your friend described, just to throw you off.

Discussion over.
Ms. Remy Ann David

JoeH Thu, 10/12/2006 - 21:04

Keep Phil away from all sharp objects, and don't let him near any firearms or combustibles. You've been listening to the ramblings of a looney tune or having your leg pulled.

Stick to what you know, and send "Phil" out for coffee. Give him a dead channel when he comes back, and tell him that his job is to ride gain on the "Talent enhancer" knob. 8-)

anonymous Thu, 10/12/2006 - 22:48

Unfortunately "Phil" is not simply pulling anyone's leg, he appears to enjoy sharing his recording and music industry "experience" with with some of the less experienced local musicians who buy into his stories and "techniques". It infuriates me that "Phil" is spreading misinformation about the recording process to impressionable musicians who happen to be friends of mine. He was probably a snake oil salesman in a previous life! I intend on showing my friends this thread in hopes that they will discontinue taking "Phil's" advice.

I'll bet "Phil" might go as far as to claim he owns a whole rack full of Rane PI-14's (! :wink:

JoeH Thu, 10/12/2006 - 23:49

Seriously, Phil's misconception is that what he's doing is fine for "in theory" applications or perhaps to do mic comparisons in a static environment, but no one sings pure sine waves, no one stands precisely where he puts the tone generator(s); nor do tone generators breathe, spit, wheeze and cough. They don't inhale, exhale, put plosives on the mic capsule, or deliver transients that would overdrive the inputs anyway. It's rather pointless, really.

What Phil's trying to do is set it all up clinically, as in a lab, but as anyone who's ever worked in a real-world situation will tell you, it ain't necessarily so. His approach might work for baseline mic or speaker testing, or simple general calibration to get the session started, but I'm sure it mostly goes out the window as soon as you start a real session with real people. It's about as useful as polishing the cymbals on the drums. It'll look nice, but it won't do much in the long run when it's time to set real-world levels.

Perhaps what he's trying to do is to optimize the gain structure from the preamp through the input channels, the way one would with test tones from a calibration tape. That's fine for known playback levels, but again, it's going to have to be re-adjusted the moment a singer or an instrumentalist actually uses the mic. (He'd be better off using his ears, and watching the input level & overload LEDs once the session starts, on a track by track basis.)

He's going to get three possible results doing it his way:

1. MAYBE get lucky and set it properly.
2. Set it too low and have too much noise and wasted dynamic range.
3. Set it too high and it'll clip and overload.

Best to get it in the ballpark, and then use one's ears the moment the session actually starts.

Thomas W. Bethel Sun, 10/15/2006 - 06:39

Maybe Phil is just trying to be a real audio engineer and trying to do things in a laboratory setup.

If you are trying to set levels in the "real world" you have to do it with "real world" levels coming off a vocalist or instrumentalist and not from a speaker at a set level.

I ran into a "Phil" one time when we were doing concert sound and he plugged in a tone generator into each microphone line on stage and set the trims on the house and monitor console according to the tone he was generating. This took a very long time and when we were though it was all for naught since when the musicians came on stage and started their rehearsal everything changed and he had to reset all of his carefully set trim levels. The one good thing about what my "Phil" did was it confirmed that all of the microphones were plugged in correctly to the corresponding inputs on the splitter and the house and monitor consoles. Other than that it was a lesson in futility.

Sounds like he needs to get some "real world" experience under his belt and not from the pages of Mix magazine.

MadMax Sun, 10/15/2006 - 17:16

Re: Silly calibration techniques of the technologically insa

anim8r wrote: Today someone - let's call him Phil (not his real name) - attempted to explain a calibration technique that he claims is regularly used by “all the best engineers”.

I must REALLY stink then... as do Joe, Thomas and Remy... NOT!!!

You're "Phil" has never touched a console in a live setting I'm willing to bet. Man, if ONLY that's the way it worked!!??!! My life as a live FOH and Monitor AE would be Soooooo much easier! And when I wear my tracking AE hat, I could just sit back and watch the cash roll in, too.

As everyone here, whom BTW I really respect, has mentioned... this ain't how it really goes in the real world.

When tracking, I'm usually bumpin' up and down the console riding gain by everything from tweeks to wholsale twists. That's just the nature of the beast.

Ask Capt FOS to prove his theory out by allowing you to come in on a session and assist... Calmly explain that you don't quite understand his explaination and that it works best for you to "see" hands-on some things... and this is one of em'. I think he'll probably find a myriad of excuses why you can't help him on a session... This kind of crap really is bad for the industry's reputation.

Twistin' and Pannin' the night away!
(Forgive me Remy?)