A look at logic's meters

Digital metering is apparently not easy to get right, because every piece of software does it differently. Most digital meters are peak meters: they respond quickly to transients (very useful to see exactly what's going on), but they do not show the 'average' level of the audio, which is what our ears perceive as volume.

The golden rule for setting levels is: 0dBv =-18dBFS . 0dBv is the analog standard of RMS (average, loudness) level for audio - the right level of output of a preamp, the output of a compressor, the optimal input for a tape recorder etc... However, RMS is a slow response measure, and peaks will always go above this. Analog equipment often has +24dB of headroom before clipping to cater for the peaks. In digital land, if you aim to record levels at around -18dBFS, you have 18dB of headroom before clipping at 0dBFS.

Therefore, -18dB is the centrepoint for recording audio, it is the loudness that things can move either side of. So it makes sense that is in the centre of the meter, no?

Apple's Logic Pro comes with two types of meters in the mixer window:

a) Exponential meter:


b) Db sectional linear:


Both these meters are displaying the same signal, a keyboard peaking at around -12dB on the digital scale. On the exponential meter, it seems like a very weak signal, even though it is above our centre mark of -18dBFS and is a very healthy level indeed!

The Db sectional linear meter is far superior. The -18dbFS mark is about halfway up (the centrepoint!), and there is great resolution between -40 and -18 - the major chunk of the working dynamic range of a lot of instruments and if you were recording classical music, much of the quiet passages would be in this zone. The exponential display shows the -40 to -18 range as only the bottom %15, a seemingly useless twittering at the bottom of the scale.

For some silly reason logic's default is the exponential meter, but this can be changed in Preferences -> Display.

For interests sake, check out the REAPER meter:

Very well designed, and is even more generous in it's placement of -18dBFS high up the scale. The designers of this program obviously understand the huge dynamic range digital recording has, and it's meters show that.

Protools meter:

Better than the default (exponential) logic meter certainly, but still places the centrepoint too far down for my tastes, and devotes the whole top half of the meter to only the top 10dB of dynamic range, making one believe they are tracking too quietly when in reality it may be a fine level.