mike_mccue


This is still the best thread ever for 2011!!!

By what scale of reference?

Thanks Mike for your kind words about this thread. It is very kind of you. I am quite interested in level subjects. You can get quite into it when you start looking into it a bit more. It is one of the most basic requirements of using a DAW well. Understanding levels of signals both back as analog electric signals hitting our audio interfaces and leaving them and also everything that is going on inside our DAW.

drewfx1 back in post #27 mentioned the concept of a square wave being used as a test signal. He was implying that the rms and peak values of the wave will be the same.

This is what I discovered looking a little deeper into this.

A square wave that also only reaches a digital level of -14 db FS shows +3db up on the VU meter (compared to a sinewave) so it may be incorrect to use it as a test signal. Interesting thing here is that the Sonar meters show rms and peak at the same value eg -14 db as suggested with a square wave created at -14 db FS. But not on the Blue Cat meter. It shows rms being +3db up compared to peak which is line with the VU is doing. I am more inclined to agree now with the Blue Cat and stick to sinewave test signals.

Any ideas here on waveform shapes for test signals? (Note my Yamaha digital mixer outputs a test tone and it is only sinewave selectable.

Here is what looks like a fairly serious article on how to set up and calibrate your DAW:

http://www.msr-inc.com/do...al_your_system_daw.pdf

They refer to the test signals definitely being sine wave. But note here. It is using the -20 db FS as a reference and that is fine. But I like K system because there are three ref levels instead of one. And -14 db FS happens to match my digital mixing console rather well. If you create music down at -20 db FS and you need to master it way up to say -6 db on average you have got a long way to go (14 db) But if you create something at K -12 FS then you only have to push things up 6 db instead and that is quite a lot easier to do in mastering. But if you also leave -20 db FS alone it will sound fantastic up loud. Pray the day will come!

Bob calls the K -12 level the broadcast standard and it is probably a good title for it. It is as loud as he thinks you should go. It is also a great level to start at for a client who wants a pretty loud master at the end of the day. K -20 is the pristine album standard. The good thing is that K -20 has come from the film industry where there is a form of a standard at least with -20db FS being a ref level and supposed to equate to 85 db SPL in a movie theatre. Cool that there is 20 db of headroom and they can take an explosion up to 105 db SPL if they need to! And they do it don't they!

Jeff Evans

This is what I discovered looking a little deeper into this.  

A square wave that also only reaches a digital level of -14 db FS shows +3db up on the VU meter (compared to a sinewave) so it may be incorrect to use it as a test signal. Interesting thing here is that the Sonar meters show rms and peak at the same value eg -14 db as suggested with a square wave created at -14 db FS. But not on the Blue Cat meter. It shows rms being +3db up compared to peak which is line with the VU is doing. I am more inclined to agree now with the Blue Cat and stick to sinewave test signals.

Jeff I don't have Blue Cat, but I looked at their online docs, and it looks like they have a parameter you can set. From http://www.bluecataudio.com/Doc/Product_DPeakMeterPro/#Parameters:

RMS Boost     3dB offset for the RMS value. It allows the peak and RMS levels of a pure sine wave to be equal. Used for K-System scales.

Any ideas here on waveform shapes for test signals? (Note my Yamaha digital mixer outputs a test tone and it is only sinewave selectable.

I would definitely use sine waves. But you have to figure out first how each meter's RMS value relates and calibrate yourself accordingly.  My recollection is that on analog style VU meters it will always be sine=0dB RMS, whereas most DAW's it will be square=0dB RMS.

The Peak and RMS value of a sine wave ARE NOT THE SAME!
Of course, we all know that.
So am I to gather from this that Katz is trying to prevent "overs" with the K system?
(I have the book, I guess I could look it up)
I'm going to have to have a "look" (send it out to the scope) at some sine waves with "overs" in the box,
and see what really happens when some plugs are "pushed".
I'm still not convinced that we don't have some "louder" = "better" going on...

As far as digital is concerned the amplitude of a sinewave and a squarewave can be the same. But it sounds like there is quite a difference in rms levels.

Yes the K system generally prevents overs. If you apply it at track level and use it there it means you are adjusting your input gain level while the signal is being generated and you use the meter of choice to show the rms value. If working at K -14 for example is used then the average part of the signal will be around this level and the VU shows a healthy 0 db VU. It is easy to get right because you have the whole VU FSD to fine tune it. Having  real VU meters makes it a little easier and nicer too.

Get a musician to play hard and as loud as he is going to be and still trim for a nice -14 db FS and 0 db VU. Now there is 14 db of headroom above it so it is very unlikely an over will occur. What are the chances of a very loud signal that is set at around -14db FS likely to jump another 14 db and go through 0 db FS. Very little.

Setting levels with very fast attack sounds such as drums still takes some skill in my opinion. The VU is less important and your peak metering comes into play. VU's can still allow you to set drums that are more open and have slightly longer sustains. Without much effort you can get all the material on each track to sit nicely at the chosen ref level without any overs anywhere.

Groups of tracks tracked at K -14 can be sent to a buss or the master buss. You aim to achieve a total mix of any buss or master to also average K -14 db. With 14 db of headroom above it. Lesser amounts of the individual tracks plus the mix positions you want for each fader result in total buss or master buss level of the chosen ref still with no overs even with all the parts present.

So tracks, busses and the final stereo master buss can all be at the chosen K ref level and with healthy transients and still clear of 0 db FS. And with the VU showing a total stem or mix just hitting 0 db VU.

Naturally the K -20 ref level gives that more headroom with the possibility of even higher transients.  24 bit recording is good when you go into K -20 db FS ref. The K - 12 level is good for loud masters and wanting to go into heavier mastering mode to get louder tracks again. (When tracking for a K -12 ref level one tends to track at a lower ref eg K -20 in order to catch any high transients. I then usually go into an editing program and limit very high peaks down and then raise the overall level of a track to bring it up to K -12 level. From that point on you are working at K -12. As long as there are no overs on those individual K -12 tracks then you won't see any from then on if you keep an eye out)

Bob suggests we perhaps treat the K ref levels as far as we should perhaps go but of course modern mastering techniques are lifting the average level well above K -12. I like to think now simply how far above K -12 is any commercial CD mastered. Easy to measure. When the average level of a CD gets to say -8 db then things are getting loud at this point. That is only 4db above the K -12 level and easy to achieve in mastering.

The monitor gain in the room is also adjusted to suit the chosen K ref level. The music will always sound the same volume. That is part of the K system process too.

All this is very timely as there a very interesting article in the latest Audio Technology Magazine here in Australia on LKFS loudness Metering for DAW's There are some quite expensive plugins that do it but it is going to become more important. It is more about perceived loudness over time and it is supposed to more in line with how the human ear and brain interpret sound.