Low-Delay Monitoring - Orban OPTIMOD-FM 8500S Operating Manual

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INTRODUCTION

Low-Delay Monitoring

•
LLH
ARD
whenever speech is detected. By constraining the system in these
ways, it ensures that the delay is always 13 ms.
Switching the B
five milliseconds of delay from the signal path. If it occurs during pro-
gram material, switching can cause audible clicks, pops, or thumps (due
to waveform discontinuity). If you have some presets with LLH
clipper mode and some without, switching between these presets is likely
to cause clicks unless you do it during silence. However, these clicks will
never cause modulation to exceed 100%.
One of the essential differences between the H
per modes is that switching between H
lay and is therefore less likely to cause audible clicks.
•
Ultra-low latency processing uses a separate, parallel processing structure and is
invoked by recalling any "UL" preset.
The only way to create an ultra-low latency user preset is to start with a
"UL" factory preset and then edit that preset. "UL" user presets cannot
be directly converted to low latency or optimum latency presets because
the preset customization controls are different—UL presets have fewer
available controls because of the difference in processing structure.
UL presets are the closest emulations of Optimod 8200 processing avail-
able in the 8500S. These presets differ from Optimod 8200 processing in
two main ways: (1) the 8500S UL presets still use the 8500S's stereo en-
hancement, equalization section, advanced-technology AGC, composite
limiter, and multiplex power controller, and (2) the 8500S UL presets use
anti-aliased clippers operating at 256 kHz sample rate.
Some talent moving from an analog processing chain will require a learning period
to become accustomed to the voice coloration caused by "bone-conduction" comb
filtering. This is caused by the delayed headphone sound's mixing with the live voice
sound and introducing notches in the spectrum that the talent hears when he or she
talks. All digital processors induce this coloration to a greater or lesser extent. For-
tunately, it does not cause confusion or hesitation in the talent's performance unless
the delay is above the psychoacoustic "echo fusion" (Haas) threshold of approxi-
mately 20 - 25 ms and the talent starts to hear slap echo in addition to frequency re-
sponse colorations.
The 8500S's analog outputs can be switched to provide a low-delay monitoring
feed (see step (B) on page 2-30). This feed has no peak limiting and thus cannot
drive a transmitter, but its 3 to 8 ms delay is likely to be more comfortable to talent
than the 18 ms delay of the full processing chain because of less bone conduction
comb filtering.
If the talent relies principally on headphones to determine whether the station is on
the air, simple loss-of-carrier and loss-of-audio alarms should be added to the sys-
tem. The 8500S can be interfaced to such alarms through any of its eight its GPI re-
mote control inputs, cutting off the low-delay audio to the talent's phones when an
audio or carrier failure occurs.
prevents the bass clipper from switching to Medium mode
C M to LLH
ASS LIP ODE
ORBAN MODEL 8500S
(from any other mode) removes
ARD
and LLH
ARD ARD
and M does not change de-
ARD ED
bass
ARD
bass clip-