TC Electronic DB6, User Manual

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Loudness Wizard
DB6 English Manual (2014-10-07) 107
Loudness Wizard – Limit page
Fig. 45.: DB6 Loudness Wizard – Limit page
The Limiter uses true-peak detection exceeding
the oversampling requirements of BS.1770.
Loudness normalization based on “perceived
loudness” can lead to peaks that might overload.
That’s why DB6 employs True-Peak limiting.
Your signal gets upsampled so that even inter-
sample peaks are detected. True-Peak limiting
handles these transient peaks seamlessly, keep-
ing your audio at its finest.
Pre Limit Gain section
Use the Trim parameters for Target transcoding
e.g. to mobile platforms with 7-8 dB of static gain
to bring the output up to -16 LUFS/LKFS.
Center Trim
Range: -18 to +18 dB (Default: 0 dB)
Use the Center Trim parameter to apply static
gain control to the Center channel after the ALC
section, but before the output limiter.
Lateral Trim
Range: -18 to +18 dB (Default: 0 dB)
Use the Lateral Trim parameter to apply static
gain control to all the Main channels, except for
Center, after the ALC section, but before the out-
put limiter.
LFE Trim
Range: -18 to +18 dB (Default: 0 dB)
Use the LFE Trim parameter to apply static gain
control to the LFE channel after the ALC section,
but before the output limiter.
True-Peak Limit section
Threshold parameter
Threshold
Use the Threshold parameter to set the true-
peak Limit Threshold for all limiters.
True-peak detection makes overload of down-
stream devices, such as data reduction codecs,
sample rate converters and DA converters, less
likely. Though digital samples may go to full
scale, it is recommended to use a conservative
Limit Threshold, even in digital transmission. Re-
serve the top of the digital scale for occasional
peaks in wide range material (feature films, clas-
sical music), so don’t go above -6 dBFS in HDTV
for normal broadcast programming. This way,
down-mixing or bass management at the con-
sumer will also not generate unexpected distor-
tion.
The distance between the Target Level of the
ALC section and the Limit Threshold is an impor-
tant audio quality defining factor – the so-called
headroom. Analog TV only had around 10 dB of
headroom, but DTV should have at least 15-16
dB of headroom for a chance of conveying audio
of a decent quality.
Raising the headroom can be accomplished by
moving down the Target Level and/or raising
the Limit Threshold. The headroom in BS.1770-
based standards is typically 22 dB – significantly
more than broadcast ever had before.