SIGNAL
PATH
There
are signals coming from the stage, (signals carrying
the instrument levels of guitars, keyboards, etc.
or microphone levels) which have to reach the mixing
desk and then get amplified. The instruments/mics
on stage are input directly into the side stage panels
(the pic to your left) through a Direct Injection
box (an impedance matching device) and the stage panels
are hooked to the FOH point by a snake (a big fat
cable consisting of smaller cables inside).
The diagram below represents
the signal path from the stage to FOH and vice versa
(the picture below is a representation of the diagram
in the recital hall). Study the diagram carefully
and follow the legend.
Snake
layout - Recital hall
Snake-
the charmer!
You are reinforcing
the acoustic/electric event i.e. a performing band
on stage to a larger audience, which means that
their respective instrument outputs should in a
way reach the mixing desk where they all will blend
and come out of the main speakers. For this, well,
you certainly would need a large number of cables
to connect all the instruments from the stage to
the FOH desk or Front of House mixing desk. Practically,
you could just patch all the cables one by one from
the stage to the mixing desk, but this would mean
running long mic cables from the stage, but there
definitely is an easier way and that is, the incorporation
of a snake. Ah, now that word or rather the pest,
what is it doing here?
It can be
seen as one long, thick cable, which comprises of
smaller cables called multipairs or cores which
is insulated by polypropylene. You can visualize
a snake as a long (sometimes ugly cable) which carries
all the smaller XLR cables from stage to the FOH.
But the snake is also the lifeline of a live sound
setup.
So,
in the snake layout diagram above, you can see a
thick, black line pointing from the stage to the
FOH mixer, this is the snake, which is carrying
all the stage signals (instrument/mic outputs).
The snake end on stage can terminate into a stage
box or a fixed wall panel like at the recital hall.
The snake end terminating at the FOH console is
called 'fan out'. Why? Because this is the end where
all the multipairs are terminated 'separately' into
an XLR connector to be input into the mixing console.
A snake's configuration goes something like this:
28 channel (24 in, 4out) 100 ft. What does this
tell you? The snake carries 28 signals altogether
inside, but 24 are 'ins' or the signals coming from
the stage to the mixer 'input'. The 4 outs are the
return signals carrying the mixer's output to the
stage. Why is this done? Read on...
Refer to
the diagram's legend; the green cable (returns from
the FOH). So far, we have seen the signals arriving
from the stage to the FOH mixing point via the snake,
but as we have seen earlier, the objective is to
reinforce the band on stage for the audience and
we know this is done with the help of loudspeakers,
which are connected to the mixing board output usually
called the 'main stereo out' either directly or
via power amplifiers. Practically, you could run
two long cables separately from the mixing board
to the speaker, but professionalism is the key word
in audio production. With a snake, facilitation
of signal passage is much more convenient and 'concealed'.
Therefore, with the same snake you also send the
mixer's outputs back to the stage panel, where the
power amps are normally located. Again, if you're
wondering, what are we sending from the mixer? We
know a mixer is used to blend different signals
and output them from the board, therefore we mix
the instruments coming from the stage via the snake
and send them out to through the snake back to the
stage panel or the stagebox.
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