Theatre Design & Technology - Summer 1983 - 21

taught to move closer to the microphone when audience noise is high (a
necessity in the hands-off dinner theatre
system), this could be a valuable feature.
There are some bad points to this
product. First of all, it would be a very
poor choice for mixing musical instruments or singing voices. Its attenuation
equation would cause it to mix musical
signals completely backwards from the
way a human operator would mix them.
Another feature of the Altec/Dugan system is its complete lack of front-panel
adjustments except for volume controls.
While this would be a real boon to a
non-technical user, for the experienced
operator the lack of adjustments means
a reduction in versatility.
The JBL Automatic Mixer
(James B. Lansing Sound, Northridge,
CA)
This evaluation is based on the JBL
Model 7510. I am impressed at the apparent sophistication of the digital circuitry that makes decisions about turning microphones on and off (it's a lot
more than just a level sensing circuit)
and I like the availability of adjustments
for practically everything. This would
be a good system for an experienced operator: set it and lock or cover the controls. It is my understanding that the
7510 has been upgraded since it introduction and many of these features may
have been improved. It is a welldesigned product with very clever
circuitry.
The IVIE Automatic Mixer
(IVIE Electronics, Orem, Utah)
Although I had an interesting discussion with the design engineer at IVIE, I
did not receive literature prior to this article. Thus, I can only report on my
telephone conversation. The IVIE has
an "automatic level control" system
feature which is apparently similar to the
"Level Matic" option on the IRPI automatic mixer. This feature could be what
you need to use the IVIE (or the IRPI)
product in a musical situation. This type
of "mixing" is much closer to what is
needed for musical instruments or singing voices. It would attempt to keep the
levels of the various microphones more
nearly equal, much like a human operator would do. Again, it is not clear
how thi affects the OM function although the automatic level control feature can be defeated for the more typical
footlight microphone type of mixing.
20

The Rauland Automatic Mixer
(Rauland-Borg, Inc., Chicago, IL)
The Rauland automatic mixer is an
optional expansion of a standard mixer
product. Their "Voice-Entree" module
turns Rauland's 3508 M~'(er-Preamplifier
into a full-fledged automatic mixer with
the on/off, 0 I, and other features.
Another available option is a "Volume
Compressor" which could provide similar operation to the IRPI "Level Iatic."
Thus, the Rauland automatic mixer can
be used as a standard mixer, as a basic
automatic mixer, or as an automatic
mixer with compression, depending on
the options you choose. It should,
therefore, work quite well in most of the
systems discussed.
The Shure Automatic Microphone
System

(Shure Brothers, Evanston, IL)
Shure justifiably calls this new product an automatic microphone SySTem.
That is because it includes not only an
"intelligent" mixer but also specially
designed "smart" microphones. While
this might seem undesirable to those
who already have a favorite microphone, it makes possible a true "system" with capabilities that apparently
could not be achieved with separately
designed microphones and electronics.
It remains to be seen whether or not
Shure's concept will catch on, or how
much real user benefit the system design
philosophy really provides. Yet Shure's
claims are impressive: Each microphone
(there are two types, a flush-mount and
a stand mount), for example, includes
built-in electronics that supposedly allow it to analyze its own individual
acoustic environment and also allow it
to turn on only when it receives a signal
within a 120 degree acceptance pattern.
These features could greatly reduce the
setup time and yet maintain much of the
versatility of other products.
Like several of the other products,
the Shure automatic mixer includes
"logic outputs." Unlike the other product , the Shure logic outputs can be
linked to an optional video switcher interface which would allow automatic
control of video cameras, for example.
Conceivably, this could automate a
video tape recording of a live presentation (although in a very un-creative
manner) by turning on cameras pointing
at "live" microphones. Overall, this
looks like a very advanced product with
good potential in theatre applications.

Theatre Design & Technology/ SITT/Summer 1983

Choosing Microphones
The only special consideration in
choosing microphones to use with an
automatic mixer is, if at all possible, to
use the same model of microphone in all
channels of an automatic mixer to get
the best accuracy out of its functions.
True, many of the automatic mixers
allow threshold adjustment for individual channels, but it still makes sense
to keep all the microphones the same,
especially for a footlight-type application. For those footlights, by the way, I
like the new Crown PZM microphones
or any other mike that sits down practically touching the floor. This minimizes the kind of ragged frequency response problems that can happen with a
single microphone (and the PZM's are
small enough to be unobtrusive). The
Shure tabletop microphones would seem
to be similar in design and operation.
There is no reason why you cannot
use wireless microphones with an automatic mixer, either, and they might be
an excellent way to solve the placement
problem in that hypothetical hands-off
dinner theatre system. However, the
presence of compressors in themselves
seem to "fight" with the automatic level
( OM) feature in the automatic mixer.
I therefore suggest that you try this setup
carefully before committing to purchase.
A Final Thought
It is worth noting again, that none of
the products mentioned were developed
for the theatre. In addition, few of the
manufacturers have actively considered
the applicability of their products to the
theatre. Thus, if you decide to use an
automatic mixer in your theatre system,
remember that you are adapting a product that was probably designed for conference rooms and churches.
Finally, remember that, even as computers go, these products are pretty stupid. While considerably more "intelligent" than manual mixers, they are not
even in the same ballpark with an experienced human operator. Thus, except in
certain cases, the automatic mixer
should be considered as an operator aid.
In that capacity, they may be very useful
in the theatre.
C
Chris Foreman writes frequently on
sound. He has worked for Community
Light and Sound and Allec, among
others.

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