10-2
Banks 11-12: the Random Halls and Spaces Program
About the parameters
Page One
RTM (Mid-Frequency Reverb Time)
RTM sets the reverb time for mid-frequency signals
when the signal stops. Because low-frequency reverb
time (BASS MULT) is a multiplier of RTM, RTM acts as
a master control for the stopped reverb time. When
DECAY OPT is set to Reverb mode, the actual value
set for RTM varies with the setting of SIZE. SIZE should
be adjusted before RTM. This interaction is deacti-
vated when DECAY OPT is set to EFFECTS mode.
When RTM is moved to full scale, infinite reverb is
switched on, and is displayed on the LARC. Program
material fed to the inputs of the machine running RHall
prior to enabling infinite mode will reverberate infinitely!
Moving the RTM slider until the LARC displays Reverb
time disables infinite mode. The RTM slider will fade
the infinite loop if no other input signal is present.
SHAPE
SHAPE and SPREAD work together to control the
overall ambience of the reverberation created by the
480L. SHAPE determines the contour of the reverbera-
tion envelope. With SHAPE all the way down, rever-
beration builds explosively, and decays quickly.
As SHAPE is advanced, reverberation builds up more
slowly and sustains for the time set by SPREAD. With
SHAPE in the middle, the buildup and sustain of the
reverberation envelope emulates a large concert hall
(assuming that SPREAD is at least halfway up, and
that SIZE is suitably large—30 meters or larger.)
The Random Halls and Spaces Program
RHALL is similar to the standard Hall program in the
480L, with the addition of random delay elements.
These elements have several effects. First, there is a
reduction of long-lived modes in the reverberant de-
cay, which makes the decay less metallic and reduces
the apparent reverb time. The apparent reverb time of
RHALL is much closer to the value indicated by the
display than the standard Hall. For this reason, decay
optimization is not needed in this program. However,
the controller has been left in place to enable switching
between the REVERB and EFFECTS modes of opera-
tion. The random elements also improve the steady-
state timbre of the program.
The amount of coloration has been substantially re-
duced from that in the standard Reverb programs —
especially at small settings of the spread control. In
addition, the steepness of the filter in the TREBLE
DECAY control has been increased. — Don’t be sur-
prised if you need to set this control higher in this
program than in the standard Reverb programs.
The Random Hall and Ambience programs are particu-
larly useful in sound reinforcement where it can im-
prove the existing acoustics of a hall by adding lateral
reflections (and possibly also delayed dry signal) from
speakers hidden around the listening space. The fact
that many of the reflections are time-varying is impor-
tant to increasing gain before feedback in such a
situation. Ambience incorporates both a PRE-DELAY
and an INPUT DELAY that can be set to further
enhance this application.
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