Orban OPTIMOD-FM 8700, Operating Manual

Page: 219 / 390

OPTIMOD-FM DIGITAL OPERATION
3-49

H
ARD
operates the clipper like the clipper in the 8200. It produces the most har-
monic distortion.
This can be useful if you want maximum bass punch, because this setting
allows bass transients (like kick drums) to make square waves. The peak
level of the fundamental component of a square wave is 2.1 dB
higher
than the peak level of the flat top in the square wave. Therefore, this al-
lows you to get low bass that is actually higher than 100% modulation—
the harmonics produced by the clipping work to hold down the peak lev-
el.
The square waves produced by this clipper are filtered through a 6
dB/octave lowpass filter that is down 3 dB at 400 Hz. This greatly reduces
the audibility of the higher clipper-generated harmonics. Nevertheless,
the downside is that material with sustained bass (including speech) will
sound substantially less clean than it will with the Medium or Soft set-
tings.
Note that the
H
ARD
C
LIP
S
HAPE
control determines how squared-off the
clipped bass waveforms become. (See Hard Clip Shape on page 3-52.)

LLH
ARD
differs in two ways from the normal H
ARD
mode of the bass clipper:

LLH
ARD
automatically defeats the compressor look-ahead. This action
is functionally equivalent to setting the
L
OOK
-
AHEAD
control to
O
UT
,
except that it reduces input/output delay by 5 ms).

LLH
ARD
prevents the bass clipper from switching to M
EDIUM
mode
whenever speech is detected. By constraining the system in these
ways, it ensures that the delay is always 13 ms.
To minimize speech distortion, the speech/music detector automatically
switches the bass clipper to
M
EDIUM
when speech is detected, provided
that the Five-Band structure is active, L
ATENCY
is H
IGH
, and the B
ASS
C
LIP
M
ODE
is set to H
ARD
. (See “Look-ahead” on page 3-73 for more about the
speech/music detector.) If the bass clipper is set to LLH
ARD
, the
speech/music detector will reset the clipper threshold to the setting speci-
fied by the
S
PEECH
BCT
HR
control. The default setting is “0 dB,” which re-
sults in very little bass clipper action during speech. This prevents audible
speech distortion that this clipper might otherwise introduce.
8500-Style Peak limiter Controls
Intermediate Name Advanced Name Range
—
OSComp Dr
–2.0 … +2.0 dB
Bass Clip Thresh BassClpThre
–6.0 … 0.00 dB
—
SpeechBCTh
–6.0 … 0.00 dB
Bass Clip Mode BassClpMode Soft, Medium, Hard, LLHard
—
Hard Clip Shap
0 … 10
HF Clip Thr HF Clipping 0 ... 6.0 dB
Table 3-7: 8500-Style Peak Limiter Controls