Setting Up The SienaSetting Up The Siena
The Siena has been designed with real world sound engineering in mind. With its flexible routing and feature
set, the console is as happy running the front of house (FOH) mix as it is providing monitor mixes for the
artists on stage.
In this section of the manual, we will introduce some of the basic operating principles of the Siena console,
and discuss some typical operating scenarios and the best way to approach them.
Setting the Correct Input Gain
Leaving Enough Headroom
The Siena’s input channel has a mono microphone and line input. Gain is provided on these channels to allow the
operator to obtain the optimal signal for the system.
Microphone Gain +15dB to +60dB (0dB to +45dB with pad switch enabled)
Mono Channel Line Gain 0dB to +45dB (-15dB to 30dB with pad switch enabled)
Each channel of the Siena includes an in-line channel LED meter indicating the channel level (measured after the
channel insert and EQ but before the channel fader). With the insert and EQ disabled, the in-channel meter will
show the level at the input in four stages:-
-18dB - Signal Present
0dB - Normal operating level
+12dB - High Signal Level
+18dB - 3dB before channel overload (clipping)
The input gain of the channel can be used to obtain the best operating level for the console. Too small a signal level
(too little gain) and the best signal to noise ratio will not be achieved; too high a signal level (too much gain) and
there is the chance of overloading the channel causing distortion.
Clearly, the gain should be positioned between these two points, to gain an optimal signal to noise ratio without
overloading the channel. The ideal level for input channels would be around +6dB with occasional illumination of
+12dB.
A channel signal is only permitted to swing high and low by an amount fixed by the power supply. If the maximum
output of the Siena channel strip is +21dBu (0dBu = 0.775 volts RMS) then imagine the following situation:
Headroom is the amount of spare ‘swing’ available to the system. If 6dB headroom was desired at all times, a
maximum level of +15dB is required to retain the headroom.
To prevent overload, the gain must be set to a point that even the highest output from the microphone during
sound check has some headroom left to prevent any surprises during the show!
The consoles Busses (e.g. Left and Right Main buss) are the point where all channel signals are summed together.
In normal operation, it is unlikely that all channels will receive the same signal at the same time so typically when
48 channels are summed together a gain of around 6 to 9dB will be seen. It is important to leave some headroom in
the summing amplifiers so that they do not overload, should the sum exceed the maximum level.
Channel equalisation should be used with care. Boosting or cutting equaliser bands can make monitoring your
actual input level very difficult. Excessive boosting of EQ (+15dB is available on each band)will have the same
effect as applying more gain to the input, taking up valuable headroom. Consider backing off the channel gain
when using large amounts of boost (if you have to use large amounts of boost) to retain a sensible level at the
output.
Excessive EQ cut can have a similarly undesirable effect. If a large amount of signal is cut in the equaliser section,
gain may be used to ‘make up’ the level lost in the equaliser. However, the input pre-amplifier still has the same
amount of available headroom. If gain, added to ‘make up’ the loss in the equaliser, exceeds the maximum level
into the microphone pre-amp then the channel won’t appear to be overloaded but the microphone pre-amp will.
Turning off the equaliser will reveal the true story, whereby the microphone pre-amp may be overloaded. It is
worth considering whether such large amounts of EQ cut is really required, or whether it is being used rather more
as a volume control (in which case the input gain could be set to a normal operating level and the output adjusted
on the channel fader).
TIP: You can monitor the level pre-EQ and post-EQ using the in-channel LED meter by switching the EQ in and out
during sound check.
The Effect of EQ
Operators Manual - Page 28
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