Crown IQSMX-6, IQAMB-5 cable, shielded, Twin-lead, 6.1.2 IQ–AMB-5Ambient Sensing Input, Output

AMB-5 /SMX-6IQ Mixer/Multiplexer

Balanced sources should be wired as shown in Figure

6.3.Notice that the shield is not connected to the chassis ground of the source if the source is also connected to the AC ground (that is, it has a grounded AC plug). This prevents unwanted ground loops.

Floating	Shield connected
source	to ground terminal
Output +				cable
	2-wire line cord	INPUT
(or battery power)		+	–	shielded
Grounded	Shield not connected
source	at this end
Output +				Twin-lead
	3-wire grounded line cord	INPUT
(or other ground connection)		+	–
Floating	Shield connected to both negative
source	(–) and ground input terminals
Output +
	2-wire line cord	INPUT	–	Single-conductor coax ortwisted pair
(or battery power)		+
Grounded	3-wire grounded line cord	INPUT
		Input ground
source		terminal not used
Output +
(or other ground connection)		+	–

Figure 6.4 Unbalanced Audio Input Wiring

Unbalanced sources should be wired as shown in Figure 6.4. The examples in Figure 6.4 are grouped according to whether twin-lead shielded wire or single- conductor coax (and twisted pair) wire is used.

6.1.2 IQ–AMB-5 Ambient Sensing Input

In addition to its automatic mixing capabilities, the IQ– AMB-5 also has the ability to adjust the output level of Channel 1 to the ambient sound level. (Remember, Channel 2 functions manually only). It does this with its sensing input (input 6). For instance, with an IQ–AMB-

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5 the paging level at a train station can be automati- cally adjusted so pages can be heard over the roar of an incoming train and yet quieted to an appropriate level during periods of softer ambient sound levels.

The sensing input section of the back panel is shown in Figure 6.5 below. It has the same features as the other mic/line inputs: input gain control and input level switch.

SENSE		ADD 25
IN	0	5 FOR MIC
	-5	10
	-10	15
	-12	21

M L P

+ –

Figure 6.5 Sensing Input Section

The most common use of the sensing input is to con- nect a microphone (such as a Crown PZM®) and lo- cate the microphone so that it can accurately receive the ambient sound level. Great care must be taken in the placement of the ambient sensing microphone so that it is not too close to the loudspeakers being driven by the system.

It is also possible to connect more than one ambient sensing microphone to the sense input. This can be accomplished by taking advantage of the manual mix- ing function of Channel 2. Simply connect each ambi- ent sensing microphone to one of the five regular inputs of the IQ–AMB-5 and use the IQ software to assign each of them to Channel 2 only. Switch the sense input to the line-level position (L) and connect the main audio output of Channel 2 to it. Use the IQ software to control the level of the ambient sensing microphones. The microphones which are located in more critical areas can be set to a higher level so they will trigger the level controller first.

Be sure the microphone has adequate sensitivity for the spectral content of the ambient sound. For ex- ample, a microphone with a bandwidth designed solely for speech reinforcement may not have ad- equate low-frequency sensitivity to pick up the low- frequency noise of machinery in a factory.

6.1.3 Output

Three-terminal removable barrier block connectors are provided for audio output (Figure 3.15). Both “main” and “bus” outputs are provided for each of the two mixer channels. They are balanced and can drive 1200 ohms or more to +26 dBu or 600 ohms to +20 dBu.

IQ–AMB-5 / IQ–SMX-6 Reference Manual