FALKEN said:mshilarious,
forgive me if this is not correct...but aren't decibels measured in *relative* volume? i.e., shouldn't you be hearing the full range at any volume level?
Fletcher-Munson curve.FALKEN said:mshilarious,
forgive me if this is not correct...but aren't decibels measured in *relative* volume? i.e., shouldn't you be hearing the full range at any volume level?
AAAHHHHH!!! It's a sign of the Apocalypse! Next thing there'll be a snowball fight in Hell!FALKEN said:for once I actually agree with Glen (what is the world coming to?). For my ears, 85 is way too loud. maybe the response is flatter but with that much air coming at me I can't even think.
Track Rat said:Fletcher-Munson curve.
Aviel said:How Can i know the level (i mean db)? i have a meter" on the mixer, but it depends on the monitors level too, so how can you know that?
mshilarious said:That depends on your hearing. 0dBSPL is defined as the lowest level a normal human can hear, most males over the age of twenty will have substantially worse hearing than that. Of course hearing is frequency-dependent, too. But there is a very real possibility of a noise existing at -80dBFS that a teenager can hear on headphones, but a middle-aged engineer would miss monitoring at a calibrated 75dBSPL.
I assume I am "the rest" ....bennychico said:Out of curiosity, a question for FALKEN and the rest who are saying 85dBSPL per channel is too loud...where is your 0 reference point when mixing? Where do you try and keep RMS and peak levels at? Similarly, where are you running pink noise at both RMS and peak levels?
The "theatre standard", Proposed SMPTE Recommended Practice: Relative and Absolute Sound Pressure Levels for Motion-Picture Multichannel Sound Systems, SMPTE Document RP 200, defines the calibration method in detail. In the 1970's the value was quoted as "85 at 0 VU" but as the measurement methods became more sophisticated, this value proved to be in error. It has now become "85 at -18 dB FS" with 0 VU remaining at -20 dBFS (sine wave). The history of this metamorphosis is interesting. A VU meterwas originally used to do the calibration, and with the advent of digital audio, the VU meter was calibrated with a sine wave to -20 dB FS. However, it was forgotten that a VU meter does not average by the RMS method, which results in an error between the RMS electrical value of the pink noise and the sine wave level. While 1 dB is the theoretical difference, the author has seen as much as a 2 dB discrepancy between certain VU meters and the true RMS pink noise level.
The other problem is the measurement bandwidth, since a widerange voltmeter will show attenuation of the source pink noise signal on a long distance analog cable due to capacitive losses. The solution is to define a specific measurement bandwidth (20 kHz). By the time all these errors were tracked down, it was discovered that the historical calibration was in error by 2dB. Using pink noise at an RMS level of -20 dBFS RMS must correctly result in an SPL level of only 83 dB. In order to retain the magic "85" number, the SMPTE raised the specified level of the calibrating pink noise to -18dB FS RMS, but the result is the identical monitor gain. One channel is measured at a time, the SPL meter set to C weighting, slow. The K-System is consistent with RP 200 only at K-20. I feel it will be simpler in the long run to calibrate to 83 dB SPL at the K-System meter's 0 dB rather than confuse future users with a non-standard +2 dB calibration point.
It is critical that the thousands of studios with legacy systems that incorporate VU meters should adjust the electrical relationship of the VU meter and digital level via a sine wave test tone, then ignore the VU meter and align the SPL with an RMS-calibrated digital pink noise source.
Boy, Ben, to be honest, I never bother delving into it that deeply. I just don't remember what flavor of pink noise I used back then (I have since changed computers and hard drives because of a crash and all my original files were lost), and frankly couldn't even tell you for sure if I knew back then.bennychico11 said:Glen-
Basically what I was trying to figure out is if people who are running their RMS pink noise at a certain level (-20, -18, -14, -320...whatever) are calling that RMS point their 0VU level.
...
Basically I think their should be a standard. I agree that you maybe don't have to use 85dBSPL as the standard, but picking one and saying "this is where the bulk of my mixing is going to be at" will help create constant mixes. And letting other engineers at other studios know where your monitoring level is at will help them adjust accordingly...much like the reference tone on tape.
But I still don't get the whole point of mixing at 83 db for sound when most listeners will be listening much lower than that.
play this pink noise on a per-speaker basis, and measure the SPL at the listening position. Check the SPL for each speaker, but don't worry as long as they're within 1/2 dB. Don't try to make it equal on a per speaker basis because the exact position of your microphone is too critical to be that repeatable. Mark this position of your monitor control as 0 dB (the reference).
Now, play the non-correlated pink noise test signal out of both (front) channels simultaneously, and confirm the level goes up about 3 dB to 86. That's an indication your speakers are in polarity with eachother. Then play the correlated pink noise test signal and put your ears between the speakers and confirm you have a nice, tight center image. The level with the correlated pink noise will be anywhere from 87 to 89 dB, depending on how correlated your loudspeakers are to eachother, room reflections, and so on. This is pretty hot for ear fatigue, so you're welcome to turn it down and check the center image at a lower volume if you wish. If the pink noise is not centered, then slightly tweak the gain of one of the speaker/amplfiers until it is centered. It's also good to ride the pot up and down and confirm the noise stays centered within the normal travel of the control.
Next, turn down the monitor gain 1 dB at a time (Instead of using the pink noise, you might prefer to find the rest of the points with the speakers off and with a simple sine wave oscillator and decibel meter on one of the cables to the amplifier). Mark the position of the pot at each 1 dB position until you get to -12 dB, at which point even Red Hot Chili Peppers won't be too loud. Especially mark the -6 and -8 positions (put 'em in red). If you shoot for -6 for the vast majority of your pop and jazz productions, you will be making material that probably has an excellent crest factor, and whose loudness will in the ballpark with the vast majority of pop music ever recorded. -8 will be a good position to try for more limited range material that you will be sending direct to broadcast. It will cause you to tend to use more compression, but won't be so bad.
YES---The 0 dB gain IS HOT. It will only be suitable for wide dynamic-range material, symphonic material, my Paquito recording, and some material that was recorded with little or no compression or limiting. But we have to have a reference somewhere, and the 83 dB reference, your mark at 0 dB on the control is the best one we have.
bennychico11 said:Here's another explanation by Katz in how to properly calibrate the monitors at 83/85dBSPL and why he agrees that it IS way too hot for most stuff. It looks like he considers the 83dBSPL limit as an UPPER limit for mostly dynamic pieces. Which is why Dolby, SMPTE and THX were the ones to standardize it...for movies.