TC Electronic DB4 MKII - Manual (Page 92)

LM6
88 DB4 / DB8 MKII Algorithms
Stereo or 5.1 Integrity
In this mode, Integrity is given when either Ste-
reo or 5.1 Integrity are detected. This means that
the LED is lit when neither valid Stereo nor 5.1
signals are detected.
Off
The Alert indicator is disabled.
LM6 algorithm – stats page
LM6 algorithm – stats page
The Stats page gives an overview of essential
descriptors.
Note! The Reset button resets the meters and
the log file.
Level versus Loudness
When level normalization in audio distribution is
based on a peak level measure, it favors low dy-
namic range signatures as shown in Fig 1. This is
what has happened to CD.
Quasi-peak level meters have this effect. They
tell little about loudness, and also require a
headroom in order to stay clear of distortion. Us-
ing IEC 268-18 meters, the headroom needed is
typically 8 to 9 dB.
Sample based meters are also widely used, but
tell even less about loudness. Max sample de-
tection is the general rule in digital mixers and
DAWs. The side effect of using such a simplistic
measure has become clear over the last decade,
and CD music production stands as a monu-
ment over its deficiency. In numerous TC papers,
it has been demonstrated how sample based
peak meters require a headroom of at least 3 dB
in order to prevent distortion and listener fatigue.
The only type of standard level instrument that
does not display some sort of peak level is the
VU meter. Though developed for another era,
this kind of meter is arguably better at presenting
an audio segment’s center of gravity. However, a
VU meter is not perceptually optimized, or ideal
for looking at audio with markedly different dy-
namic range signatures.
Unlike electrical level, loudness is subjective,
and listeners weigh its most important factors –
SPL, Frequency contents and Duration – differ-
ently. In search of an “objective” loudness mea-
sure, a certain Between Listener Variability (BLV)
and Within Listener Variability (WLV) must be
accepted, meaning that even loudness assess-
ments by the same person are only consistent
to some extent, and depends on the time of day,
her mood etc. BLV adds further to the blur, when
sex, culture, age etc. are introduced as variables.
Because of the variations, a generic loudness
measure is only meaningful when it is based on
large subjective reference tests and solid statis-
tics. Together with McGill University in Montreal,
TC Electronic has undertaken extensive loud-
ness model investigation and evaluation.
The results denounce a couple of Leq measures,
namely A and M weighted, as generic loudness
measures. In fact, a quasi-peak meter showed
better judgement of loudness than Leq(A) or
Leq(M). Even used just for speech, Leq(A) is a
poor pick, and it performs worse on music and
effects. An appropriate choice for a low com-
plexity, generic measurement algorithm, which
works for listening levels used domestically, has
been known as Leq(RLB).
Combined loudness and peak level meters exist
already, for instance the ones from Dorroughs,
but BS.1770 now offers a standardized way of
measuring these parameters.
In 2006, ITU-R Working Party 6 J drafted a new
loudness and peak level measure, BS.1770, and
the standard has subsequently come into ef-
fect. It has been debated if the loudness part is
robust enough, because it will obviously get ex-
ploited where possible. However, with a variety
of program material, Leq(RLB) has been veri-
fied in independent studies to be a relatively ac-
curate measure, and correlate well with human
test panels. It therefore seems justified to use
Leq(RLB) as a baseline measure for loudness,
especially because room for improvement is also