Metering in Mastering: RMS vs. LUFS

WAVES DIGITAL VU METER

iZotope Ozone 7 Advanced Mastering

Before Mastering you should familiarize yourself with your meters. In this article we will review a VU meter and a LUFS meter and how to read/use them to create a well mastered track.

The VU meter

The VU meter was/is the analog meter built into large format consoles made by companies such as SSL, API, and Neve. VU meters are also found in classic analog compressors/limiters but is not limited to such. A VU meter responds to a source similarly to how our ears respond to sound. VU meters read in terms of RMS which means real mean square. In simple terms, this means that the VU reads an "average level" compared to just peaks- (think a loud transient like from a snare). The benefit of a VU meter in analog systems is to be able to record, mix, and master with proper gain staging and have a well summed (combined) signal- one that does not overload. In a digital domain, a VU can still be used to gain stage, measure RMS, and peaks. A rule of thumb to keep in mind is that a signal hovering around -18dB (analog) according to a lot of classic analog engineers, converts well to digital and sums in a desirable way. When compressing, a VU meter is very useful for seeing an average level and knowing whether to thicken (bring up the average level) or limit (bring down the average level.) In mastering, the rule of thumb is to master around -7 and -9 dBFS on a VU meter (or a meter set to RMS which functions as a VU meter). RMS measures average loudness across whatever source material you are using (i.e. song, dialogue etc.). NOTE: generally a song with a higher average loudness will be perceived as louder or fuller. A higher average RMS typically correlates to a smaller dynamic range (or difference between the softest and loudness signals).

LARGE FORMAT SSL DUALITY CONSOLE

LUFS Meter

A LUFS meter is a meter created to measure how loudness is perceived. This meter's goal is to imitate how different sound sources are perceived subjectively. it is possible to have two sources both reading at the same RMS level but also one that is perceived louder. Note: Generally material with more high frequencies are perceived louder than ones with less of them. A LUFS meter will help you read the perception of your material's loudness such as -14LUFS (*integrated) (Loudness Units Full Scale) not in dB, or dBFS. Note: LUFS, dB, and dBFS are not the same units. Streaming services have certain requirements for LUFS for your mastered audio. The closer you are to their standards, the less processing they do to either bring up your material- if it's too quiet or bring it down- if it's too loud.

Dorrough LUFS or Loudness Meter

LUFS Meter vs RMS (VU)

RMS: Reads average levels across a signal

LUFS: Reads perceived loudness across a signal (when set to integrated)

General Uses:

RMS: Used for analog systems i.e. transferring to tape

LUFS: Digital systems i.e. to release to Spotify

How to Use in Mastering:

Balance signal to set RMS or/and LUFS standards

Read perceived and average loudness of your material and adjust material to those standards

Control transients/peaks

Broaden or shorten dynamic range

Make sure your materials meets broadcast standards such as the ones set by Pandora or Spotify.

We generally recommend using both meters in mastering to achieve a great RMS readout plus hitting the loudness standards for digital platforms like Spotify.

THE BALANCING ACT IN MASTERING: WHY IS MASTERING SO HARD?

The challenges presented in mastering are:

Making source material as loud as possible

Maintaining a "healthy" dynamic range

"Sonically" fitting into your genre

Separating your frequency bands where less clashing is presented (i.e. clearly defining the low end, vs. lower mids, vs. midrange, vs. upper mids, and highs).

Note: The way you achieve target loudness will vary per source. Sometimes EQ does the job, sometimes a compressor, sometimes a limiter, sometimes an imager, sometimes an exciter. It all depends. There are many ways to get to the targeted finish line.

Thank you for reading. If you have questions, feel free to reach out.

© 2021 Avery Blue Productions