Orban OPTIMOD-FM 8700, Operating Manual

Page: 223 / 390

OPTIMOD-FM DIGITAL OPERATION
3-53
8700i MX Technology Peak Limiter Controls
The MX peak limiter is designed to make FM analog broadcasts more competitive
with the cleanliness, punch, and open high frequencies of the digital media against
which FM analog transmissions now battle. To achieve this, it offers decreased audi-
ble distortion, more transient punch and a crisper, more open high frequency tex-
ture. Compared to the 8500-style peak limiter, the MX peak limiter typically provides
2.5 to 3 dB more power at high frequencies, which minimizes audible HF loss caused
by preemphasis limiting. Drums and percussion cut through the mix. Highs are airy.
See
Measuring the Improvements in Optimod-FM 8700i’s FM Peak Limiting Technol-
ogy starting on page 3-100 for a more detailed discussion.
The MX technology peak limiter consists of two main stages—first, a pre-limiter
stage to control low frequency and high frequency peaks ahead of the main peak
limiter and then the main peak limiter, which uses various proprietary techniques to
control distortion, minimize transient loss, and minimize high frequency loss.
The controls affecting this section allow you to trade off loudness, distortion, and
bass energy. Because the laws of physics apply to MX technology, increasing bass in-
creases the likelihood that audible IM distortion between bass and other program
elements will occur. Depending on your station’s format, you may prefer to have a
cleaner sound (with less bass) or a sound with more distortion but punchier bass. We
offer controls, explained below, that allow you to make this tradeoff.
Peak Limiter Drive determines the level applied to the MX peak limiter and thus how
much peak reduction the peak limiter must do. The MX peak limiter uses a variety of
tactics to adapt its operation intelligently to the program material applied to it.
Compared to the 8500-style peak limiter, the MX peak limiter produces a different
set of artifacts when overdriven. Depending on how you set the other controls,
these artifacts may include loss of bass punch, harsh clipping distortion, “soft” IM
distortion, and/or excessive density that can cause fatigue. If you intend to make ad-
justments at the intermediate or advanced levels, it is wise to familiarize yourself
with these artifacts by purposely overdriving the peak limiter via the
P
EAK
L
IMITER
DRIVE
CONTROL
and listening to what happens with different types of program ma-
terial.
MX Peak limiter Controls
Intermediate Name Advanced Name Range
Peak Limiter Drive Limiter Dr
–6.0…+6.0 dB
Bass Pre-Limiting BassPreLimit
0 … 1
Bass Pre-Limit Mode BassPreLimMode Soft, Medium, Hard
Bass Clip Threshold BassClpThre
–6…+6 dB
Bass Limiting Bass Limiting
0…–6 dB
Distortion Control Dist Cntrl
0 … 1
—
Multiband Clipping
–4.0…+5.0 dB
—
Speech BPLim
0 … 1
Table 3-8: MX Technology Peak Limiter Controls