RMS vs. Peak Ballistics

[Kenmillerjr]

I know visually what the differences are, I typically like to mix in Peak B. but on a technical standpoint, what is the difference? From what I have gathered, RMS seems to be more along the same metering as ProTools. When you are "clipping" in Peak Ball, that does not necessarily mean you are clipping the pre's, but when you are "clipping" in RMS, you are clipping the Pre's, correct?

[Craig F]

RMS: Root Mean Square almost the same as VU and more closely tracks the way we hear
Peak is absolute energy so Peak tracks better with digital Full Scale
RMS is about .7 of Peak

you basically have your scales backwards

[Brent Lind]

If you use the "gain guess" feature of the desk, keep in mind that it is affected by which mode you use. Since RMS is providing an average metering of the signal, versus peak which is metering the true peak level, "guess"ing based on peak is going to give you a "0" point based on peaks whereas RMS will give you a zero based on an average signal. In short, RMS will guess you a lower but probably more ideal gain level.

Take this with a grain of salt, I'm regurgitating some stuff from Scovill here, so if I've mixed it up somebody please call me out on it. In any case its worth discussion.

[Kenmillerjr]

Thanks for the info...but which do you find yourself using? What do you like better?

[Brent Lind]

Oops I said it backwards. Because peak guesses would be based off the peak level and not an average, it tends to put the gain too low, which is why I use RMS. Not that guess is that vital of a feature, but I'd rather be looking at an average metering than a peak. Using peak hold it's still very easy to see where you stand.

[Roland Clarke]

From what I have always understood, it is recommended that you mix with RMS ballistics on the meters. Even in RMS mode, peaks are still displayed. In peak mode, depending on the signal source you don't get an accurate handle on how the general level is, the problem here is that dynamic sources will give you metering information that is of little real world use in a mix situation.

It should also be mentioned, although it doesn't seem to have been discussed here in recent months, there were often threads and posts where people were having trouble with virtual sound check and tracking to Pro Tools where the levels were unusably low due to metering being switched to peak.

I'm sure that there are instances where peak metering might be useful, but for the vast majority of cases RMS is the way to go.

[rdobra]

RMS and Peak ballistics are both affecting your gain structure, an that's vital for your live mix and more importantly for any audio archiving in Pro Tools.
Luckily VENUE is metering analog style for both inputs and outputs,so we have 20 dB of headroom above the 0 dB reference point before the maximum operating level is reached ( and there are secretly another few dB's above 20 on Outputs ). If you want to run your inputs gain as hot as possible all this headroom is gone to thrash if you're metering in Peak ballistics. It will show you lots of red and the only way you can address that is to lower the gain to fit your material in the system. This way you're simply missing few important dB's, both on Inputs and Outputs, for processing and for recording in Pro Tools.
Say you've got a wildly dynamic vocalist screaming into a mic - this will create massive peaks driving mad any system in the world. Only by metering RMS you can keep the preamp set to a level that allows these peaks to happen without overloading the signal. Metering in Peak ballistics will show you red even when the preamp gain is set to very low.
Whenever you're recording in Pro Tools you have to be in RMS. It's the only way you can set the highest level possible while still monitoring the peak elements of you signals recorded in Pro Tools.The meters show you the actual RMS information as well as a single LED in the same meter that represents the peak level of the incoming signal. That is the subsequent recording level as well.

As Brent correctly mentioned, Gain Guess is not only a very quick and powerful tool to use but it will help a lot in understanding how the two different ballistics are 'fitting' the audio into your system. Gain Guess will give you a good nominal level by trimming the incoming signal to 0 dB on the input meters. But that's based on the meter ballistics setting you’ve chosen. On Peak it will set the peak energy to 0 dB.On RMS it will position the RMS energy at 0 dB.

Hope this helps.

Radu

[Roland Clarke]

There is a slight danger of confusion in this thread regarding peak level. Metering with peak level ballistics will (on very dynamic sources) encourage you to set your levels too low, RMS gives you a realistic VU style metering that tells you what the real world gain structure is like. Peaks remain peaks. If you get overs in peak metering (give or take any latitude built in by the Digidesign team) it's exactly the same as overs metering RMS. Fortunately Venue allows you to set at what reference point you want your peak to register on the meters. The consequence of overload at any point in the desk would be distortion, RMS or peak has no effect on this.