10/29/2019
Tech Works CI-Series Systems Planning & Installation Manual Page
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The setup strategy is also often a matter of convenience. Access to Audio Source Level trim pots
is usually easy. Access to Rack mounted Amplifiers is usually easy, but not as convenient as the
Source. Access to a Speaker, especially ceiling mounted Speaker, usually is very difficult!
It is recommended, when two (or more) level controls are in tandem, all Controls but the one,
used to set the listening level, are at full level (Clock Wise (CW)).
Feedback prevention
,
cautionary measures
:
Many Intercom systems require "full duplex" operation; simultaneous communications in all
directions
When many microphones, and speakers, are in operation together, many feedback paths exist
The most important feedback prevention technique is speaker Microphone Placement
The sound level at the microphone from the user, must be much higher than the level from the
speakers
Microphones should be directional, aimed at the user
Speakers should be placed away from the microphones, and out of the pattern of the Microphone
The next most important feedback prevention technique is
“Minimum Gain”
Minimum Microphone Gain; place the microphone in close proximity to the User(s)
Users need to 'Speak up' so the gain settings can be reduced
Minimum Speaker levels to accomplish reliable communications
The number of 'Open Microphones' should be kept to a minimum
When possible Microphones should be keyed;
Foot
Switches
And only enabled when the user needs to talk
This also reduces the background noise; making it easier for the listener to hear the talker
Wireless
headsets are preferable to individual microphones.
This reduces the number of Microphones & Speakers required in 'large' systems.
This also reduces background noise in the system.
Tech Works CI-Buss Products provide additional Feedback Prevention techniques:
Selective Gain Reduction, “Ducking”, can be very effective.
When a Microphone is keyed, the associated speaker can have its level automatically
reduced.
Usually when the User is speaking, the listener is not talking, and only would need to
interrupt.
The speaker level can be much lowered because the user is paying attention to
communications.
Jumper Options on the Products allow the "Ducking Level" to be optimally set.
Notch Filtering the Microphone reduces acoustic room resonance peaking.
Rooms without acoustic treatment have significant resonances. This 'peaking' has the effect of
greatly increasing gain at these resonance frequencies.
This is significant with directional hanging microphones; floor to ceiling resonances are magnified.
A notch filter can be used to reduce this peaking, without adversely affecting communications.
