AVProAlliance AViMUX4 Manuel d'utilisation et d'application - Page 15

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Microphone Room Placement

The microphones should be randomly

placed in the room in the listening area.

Avoid placing the microphones too close to

any speaker, so as to avoid direct sound

energy from the speaker. Also avoid the

center and quarter axes of the room, as

strong room mode peaks and nulls at these

positions can unduly influence the

measurement. Microphones should be

mounted on microphone stands near the

Real Time Analyzing – Multiplexing Microphones for Spatial Average

Multiplexing microphones placed throughout the listening position provides a single continuous

measurement of the overall response of the listening area. This permits more accurate

equalization adjustments, as you can see an average of the entire listening area. Sequentially

switching to each microphone briefly with the iMUX4 and accumulating a running active

average on the Real Time Analyzer provides an average room response. This has the added

benefit of revealing the most audible response anomalies while minimizing less audible ones.

To perform a spatially averaged RTA

measurement, connect the iAI2, to the iPad,

and deploy microphones from the iMUX4

case. Connect the toslink cable (from the

iAI2) to the desired input on the pre-amp in

use. Place the microphones in the room as

described above. Set the iMUX4 Microphone

Selection Switch to the "1-4" position. This

position cycles through the microphone

inputs, switching the sound from each mic to

the RTA at approximately one second

intervals. Choose a full-range pink noise

signal. Access the iAI2 signal generator

control by touching the "sine-wave" icon on

the RTA or FFT screen.

The AudioTools RTA or FFT function

averages the alternately selected microphone

measurements over a period of time, creating

a spatially averaged display. In most case

setting the decay time in AudioTools to

"Average" provides to best results. At the

listeners' ear height. Point the microphones

straight up for the best omni-directional

pickup. Use a staggered parallelogram or

diagonal microphone placement formation

with Mic 1 located at the central listening

location or sweet spot at ear height. Each

microphone should be a different distance

from the side walls and a different distance

from the end walls. In addition, try to avoid

placing any microphones at the same height.

This will provide a more uniform sampling

of the sound field in the room.

onset of each measurement be sure to touch

the "Reset" control to clear any previous data.

The measurement is complete once the plot

has stabilized. This indicates that all

acoustical effects have been measured. When

using a shorter decay time make sure it is at

least 4 seconds long so all microphones have

contributed. Any ambient noise extraneous to

the test tone spoils the measurement requiring

a redo.

To multiplex microphones for a spatial

average RTA/FFT measurement:

1. Set up as shown in figure above.

2. Set iMUX4 Microphone Selection Switch

to position "1-4".

3. Select & perform the RTA/FFT test.

4. Set decay to averaging mode.

5. Reset averaging.

6. Adjust speaker placement, equalization,

treatments for best overall room response.