TC Electronic Radar Meter Bundle TDM - Manual (Page 8)

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6 / LM5/LM5D & AM6
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Current Loudness: Outer Ring
The outer ring of the Radar page displays current loudness. The 0 LU point (i.e.
Target Loudness) is at 12 o’clock, and marked by the border between green and
yellow, while the Low Level point is marked by the border between green and blue.
The “0 LU Equals” and “Low Level Below” parameters are found on Prefs page. Keep
the outer ring in the green area, and around 12 o’clock on the average. Excursions
into the blue or the yellow area should be balanced, and not only go in one direction.
LKFS, LUFS and LU
The units used on loudness meters from different vendors may vary, so it’s important
to be aware of the differences and similarities between these units. First of all, LKFS
(Loudness ‘K-weighted’ Full Scale) and LUFS are interchangeable and both denote
an absolute measure of the loudness of a digital signal. For instance, -24 LUFS is
precisely the same as –24 LKFS.
LU, on the other hand, is a relative measure of loudness. When displaying loudness
level on an LU meter, a certain Target Loudness is explicit. For instance, if the target
loudness level of a station is –24 LUFS, the radar meter can be configured to show
that number as ‘0 LU’ which causes a level of –27 LUFS to be shown as –3 LU, while
one of –20 LUFS will be shown as +4 LU.
In other words, it’s merely a question of preference whether an absolute or a relative
display of loudness level is preferred. See Fig 4 as an example of the same program
shown on the LU scale and on the LUFS scale.
Fig. 4 - LU vs. LUFS
In both cases, Target level is set to -23 LUFS. Some users find it easier to use LU as
it gives an indication of the number of dB you’re too hot or too soft on the average,
but the measurement remains exactly the same regardless of the LUFS vs. LU
selection.
Switch beteeen LUFS (the same as LKFS) and LU viewing styles on the Prefs page.