AVProAlliance AViMUX4 User guide

iMUX4
PROFESSIONAL MICROPHONE
MULTIPLEXER
Operation and Application Manual
MIC 1 MIC 2 MIC 3 MIC 4
MICROPHONE MULTIPLEXER
iMUX4
MICROPHONE
SELECTION
1
2
3
4
1-4
AVProAlliance.com
PO Box 90703, Sioux Falls, SD 57109

1
iMUX4
PROFESSIONAL MICROPHONE
MULTIPLEXER
Operation and Application Manual
MIC 1 MIC 2 MIC 3 MIC 4
MICROPHONE MULTIPLEXER
iMUX4
MICROPHONE
SELECTION
1
2
3
4
1-4
AVProAlliance.com
PO Box 90703, Sioux Falls, SD 57109

2
TABLE OF CONTENTS
SAFETY PRECAUTIONS............................................................................................................3
DESCRIPTION
Introduction..........................................................................................................................4
Features................................................................................................................................4
Specifications.......................................................................................................................5
Controls................................................................................................................................6
Supplied Accessories...........................................................................................................7
Kit Accessories ....................................................................................................................8
OPERATION
Introduction..........................................................................................................................9
Power On/Off Switching......................................................................................................9
Battery Installation/Replacement.........................................................................................9
Microphone Selection Switching…...................................................................................10
Microphone Input Calibration Controls.............................................................................11
iAI2 Microphone Calibration.............................................................................................11
APPLICATIONS
Introduction........................................................................................................................12
Measurement Setup............................................................................................................12
Microphone Room Placement............................................................................................13
Real Time Analyzing –Multiplexing Microphones for Spatial Averaging ......................13
SERVICE AND WARRANTY INFORMATION ....................................................................14

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Every precaution has been taken in the design of the iMUX4 to
insure that it is as safe as possible. However, safe operation
depends on you, the operator.
1. Never exceed the limits of the iMUX4 as given in the
specification section or other special warnings in this manual.
2. Always be sure that your equipment is in good working order.
Broken or frayed test leads or cables can be dangerous exposing
you to circuit voltages.
3. Remove test leads immediately following measurements to reduce
the possibility of shock.
4. Do not work alone when working under hazardous conditions.
Always have another person available in case of an accident.
5. Never assume that a cable shield is at earth ground potential.
Both static and electrical voltages can be present on a cable’s
sheath.
6. Always follow standard safety procedures.
When in doubt, be careful.
WARNING
Please observe these Safety Precautions
There is always a danger present when using electronic test equipment.
Unexpected voltages can be present at unusual locations in defective
equipment and distribution systems. Become familiar with the
equipment with which you are working, and observe
the following safety precautions.

5
DESCRIPTION
Introduction
The iMUX4 Microphone Multiplexer is the perfect instrument to expedite the testing,
adjustment, and documentation of the acoustically averaged frequency response of cinema
theaters, home theaters, churches, halls, banquet rooms, meeting rooms, clubs, or any other
venue in which great sound in the least amount of time is a requirement. The iMUX4 features
common XLR input and output microphone connections.
Because room resonance modes cause
different low frequency response in different
parts of any small room, equalizing the
response for multiple listening positions can
be a long process of repeated measurements at
multiple locations and change-and-check
equalization adjustments. Adjusting for
smooth response in just one or two listening
positions may leave other positions with
uneven, boomy, or wimpy bass response.
Averaging multiple measurements manually
is time-consuming and doesn't give you a
real-time display to immediately indicate
results of room adjustments.
The iMUX4 Microphone Multiplexer, with a
high resolution RTA, provides measurements
of the average response of a listening room or
multiple listening positions. This allows you
to position subwoofers or adjust equalizers as
you immediately see the measured results of
your adjustments. When you complete your
adjustments, you can store one RTA
measurement to document the average
response of the room.
Features
Provides a single, spatially-averaged acoustic input from up to four microphone positions
for Real Time Analyzer measurements.
Provides a continuously updated average measurement of the overall response of the
listening area to allow easy equalization adjustments and average response documentation.
Avoids the problem of making room adjustments based on the acoustic response of just a
single point in a room or of manually averaging measurements to determine needed
adjustments.
Performs four microphone multiplexed sampling, as used by all major cinema/home
theater organizations, for a good average of overall room response.
Measure the averaged output of two, three, or four attached microphones, or monitor
individual microphones for gain equalization.
Internal microphone supply voltages and preamps eliminate the need for extra boxes and
simplify setup.
Portable, battery-operated design eliminates the need for AC power connections.
Unit power is controlled by phantom voltage from the connected RTA.

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Specifications
Frequency Response: 20Hz-20kHz +/- 2 dB
Dynamic Range: 30 dB to + 120 dB (SPL) input
Inputs
Microphone Inputs: Four
Type: Balanced
Connector: XLR Female
Input Impedance: 40 kohms nominal
Freqeuncy Response: 20Hz –20kHz +/-2 dB
Dynamic Range: 25dB to = 120dB SPL
Maximum Input Level: 135 dB SPL
Gain Adjustment: ±4 dB
Phantom Mic Power: 48 volts
Output
Output: One
Type: Balanced
Connector: XLR Male (Pins 2 & 3 signal, pin 1 ground)
Output Impedance: 110 ohms +/- 20%
Microphone Selection: Manual selection of Mic 1, Mic 2, Mic3, or Mic 4.
Automatic alternating switched selection of attached
microphones.
Microphone Switching: Approximately one second dwell time per microphone
Mic. Dwell Time Range: 0.5 sec to 1.5 sec. (Factory adjusted to approx. 1 sec.)
Power
Power: Internal 9 V battery Pack (6 AA cells)
Power Switching: Controlled from RTA (Phantom voltage on/off)
General
Case: Metal
Size: (3.25" x 7.5” x 4.25") HWD
Weight: 1 lb. 5 oz. w/supplied battery installed

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Controls
MIC 1 MIC 2 MIC 3 MIC 4
MICROPHONE
MULTIPLEXER
iMUX4
MICROPHONE
SELECTION
1
23
4
1-4
6.
Multiplex
Rate
MIC 1 IN
MIC 2 INMIC 3 IN
MIC 4 IN
CAL 1
CAL 2
CAL 3
CAL 4
OUTPUT
2.
4.
1.
7. 5. 1.
3.
6.
Figure 1. iMUX4 Controls
1. MIC OUTPUT CONNECTOR: Connects output of iMUX4 to the MIC INPUT jack of the
RTA for sound measurements.
2. MICROPHONE SELECTION SWITCH: Switches the microphone inputs (5) to the MIC
INPUT Connector (1).
3. BATTERY COMPARTMENT: Contains AA batteries used to power the iMUX4 and
provide phantom power to microphones.
4. CAL 1, 2, 3, 4 MIC LEVEL CALIBRATE ADJUSTMENTS: Variable gain controls to
adjust the microphone input levels for proper calibration of the individual microphones.
5. MIC 1, MIC 2, MIC 3, MIC 4 INPUT CONNECTORS: Connects the external individual
microphones to the inputs of the iMUX4.

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6. LED(s) TEST CONDITION INDICATORS: A LED indicates the RTA is connected and
turned on to activate the iMUX4. Constant LED illumination indicates that microphone input
is selected and a microphone is connected and powered. Flashing LEDs indicate low
batteries which can produce erroneous measurements.
7. MULTIPLEX RATE CONTROL: Adjusts dwell time or the time each microphone is
sampled.
Supplied Accessories
1.
2.
3. AA AA AA AA AA AA
Figure 2. Accessories
1. (4) color coded 20 foot microphone extension cables, XLR male to XLR female (13G122):
Connects the individual microphones to the MIC INPUTS of the iMUX4. Five cables are
supplied with the iMUX4 including the jumper to the RTA
2. Microphone (39G1156): Meets or exceeds ANSI S1.4 Type 2 specifications. Measurement
microphones that connect to the MIC Inputs of the iMUX4. Four microphones are supplied
with the iMUX4.
3. AA Batteries: Comprise nine volt battery pack to power the iMUX4. Six batteries are
supplied with the iMUX4 to be installed into the battery compartment.
4. Case (not shown): Your iMUX4 is installed in an intuitively designed case designed for
rapid deployment and secure storage of cables, microphones, and accessories ready for use.

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Kit Accessories (Kit Only)
Figure 3. Studio Six Digital iAudioInterface2 (iAI2) (available from AVProAlliance.com)
Figure 4. Reed SC-05 microphone calibrator (available from AVProAlliance.com)
Figure 5. Microphone with 9/32” grommet sound seal used to seal microphone
inlet while using Reed SC-05 calibrator
Figure 6. AVPro 2.0 Software; Home Theater acoustical analysis, design and
calibration wizard (available from AVProAlliance.com)

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OPERATION
Introduction
The iMUX4 Microphone Multiplexer connects to a variety of XLR based RTA’s to provide
acoustic analysis of rooms using multiple microphones. Be aware that the microphones use
inverse polarity and a 48v phantom voltage when setting up your RTA. The iMUX4 provides
accurate sound speaker equalization by enabling the simultaneous use of up to four microphones
placed throughout the room. Due to the inherent signal to noise ratio of Type 2 microphones and
the switching circuit of the iMUX4, it is recommend to drive your test tone to a level of at least
70 dB SPL for best results. Care should be taken to periodically calibrate your iMUX4 with your
RTA. This includes alignment of microphone #1 with the RTA and then each remaining
microphone with the first. AVProAlliance.com recommends the Reed SC-05 for this function.
Power –On/Off Switching
The iMUX4 contains no on/off switch. The
iMUX4 circuitry is powered by a 9 volt
battery pack consisting of 6 AA batteries
mounted inside the battery compartment of
the iMUX4. Phantom microphone voltage
supplied to the unit from the RTA switches on
the iMUX4. The phantom microphone
voltage is supplied from the RTA ANALOG
INPUT jack to the "OUTPUT" jack on the
iMUX4.
The RTA (or iAI2) must be connected,
powered on, and the phantom voltage of 48V
selected in the top tool bar before microphone
voltage is output to the iMUX4 and its
internal circuits are powered on.
LEDs on the iMUX4 provide an indication
when the unit is powered on and ready for
operation. When any LED is blinking or
illuminated, the iMUX4 is powered on and
ready for use. Erratic LED blinking indicates
new batteries are required.
Battery Installation/Replacement
AA
AAAA AA
AA AA
Figure. 7 The iMUX4 battery compartment
The AVPro iMUX4 requires six AA batteries
for proper operation. The iMUX4 draws very
little current from the batteries, so the battery
lifetime will be close to 24 hours. The
batteries are replaceable.
To install or replace the AA batteries:
1. Remove the battery compartment on the
iMUX4 by gently releasing the tab
holding the battery compartment door.
2. The battery compartment door releases
and may be lifted away. Lift gently and
remove the cover.
3. Pull each of the batteries out of the battery
compartment.
4. Install AA batteries into the battery
compartment observing proper polarity.
5. Reinstall the battery compartment door.

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Microphone Selection Switching
The iMUX4 has four separate microphone inputs. These inputs are switched to the RTA or iAI2
ANALOG INPUT jack by the five-position MICROPHONE SELECTION switch on the
iMUX4. The first four positions are labeled 1, 2, 3, and 4. These positions switch only the
respective single microphone input to the RTA. These positions are used to calibrate the
individual mic inputs or to monitor the response of only one location in a multiple microphone
setup.
MIC 1 MIC 2 MIC 3 MIC 4
MICROPHONE
MULTIPLEXER
iMUX4
MICROPHONE
SELECTION
1
23
4
1-4
Figure 8. Microphones are selected or multiplexed
to the RTA with the MICROPHONE SELECTION
switch. LEDs indicate which microphone(s) are
selected or active.
The fifth position of the MICROPHONE
SELECTION switch is labeled “1-4.” This
position electronically selects each of the
iMUX4’s MIC IN jacks momentarily. The
iMUX4 alternately switches to each of the
active microphone inputs, providing a path
from these inputs to the OUTPUT jack.
The multiplex switching action is done only
between active MIC Inputs. An iMUX4 MIC
Input jack is active if a microphone is
connected to the jack. MIC IN jacks that do
not have a microphone connected to them will
be omitted from the multiplex switching
sequence.
Each active microphone input is selected for
approximately one second. The MIC input
selected is indicated by an illuminated LED.
As different inputs are alternately selected,
the different LEDs light, indicating multiplex
switching.
NOTE: MIC Inputs are active only when a
microphone is connected and drawing current
from the iMUX4. If a microphone is not
connected to a particular input, the iMUX4
will not switch to that MIC In jack. This
permits the iMUX4 to multiplex switch to only
the active inputs. In this manner, the iMUX4
can multiplex switch between 2, 3 or 4 active
microphones.
To multiplex between microphones to analyze with the iAI2 connected to AudioTools iPad App:
1. Connect a cable from the iAI2 Microphone jack to the iMUX4’s OUTPUT jack. Power up
the iAI2 and open AudioTools. Once the iAI2 is connected to the iPad there should be an
indication that the audio interface is connected. In AudioTools select Settings then
Microphone Setup. Select the iAI2 microphone input and confirm calibration. Select
position “1-4” on the iMUX4 MICROPHONE SELECTION switch.
2. Connect desired microphones to iMUX4 MIC IN jacks.
3. LED indicators indicate the MIC Inputs that are being alternately selected by the iMUX4.
The dwell time, or time each MIC Input is selected, is factory set by the iMUX4 internal circuits
to about one second. This time has been optimized for Real Time Analyzing (RTA) when using
AudioTools. This time can be made longer or shorter for special applications by changing the
Multiplex Rate control located near the OUTPUT jack of the iMUX4.

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Microphone Input Calibration Controls
The calibration control for each microphone input is located beside each of the MIC IN jacks.
The CAL controls are multi-turn pots, adjustable with a miniature screw driver (not provided).
Multiplex
Rate
MIC 1 IN
MIC 2 INMIC 3 IN
MIC 4 IN
CAL 1
CAL 2
CAL 3
CAL 4
OUTPUT
Figure 9. Calibration controls on each microphone
input provides level adjustment for accurate
measurements
The calibration controls are used to adjust
the level from each microphone input to the
iMUX4. Each microphone and its respective
input should be calibrated to a reference
level before using the iMUX4. This insures
that each microphone and its respective
input of the iMUX4 is providing a proper
level to the RTA.
The microphones supplied with the iMUX4
are labeled as MIC 1, MIC 2, MIC 3, and
MIC 4. Your iMUX4 comes pre-connected
to the proper cables and microphones;
observe the color coding when reconnecting;
Mic 1: Red, Mic 2: Blue, Mic 3: Green, and
Mic 4: Yellow. You should periodically
verify proper calibration using the
procedures below. Microphones can change
over time and use so it’s essential to check it
for best accuracy of your measurements.
iAI2 Microphone Calibration
The microphone calibration controls in
Studio Six Digital AudioTools App are
located in the “Settings” menu under
“Microphone Setup”. Once you have your
system properly connected and powered up
you should see the iAI2 microphone
indicated as an input source option. Select it
by touch indicated by the field becoming
yellow. Select the blue arrow on the right
for the calibration menu.
1. Select Mic 1 on the iMUX4.
2. Insert the microphone into the
microphone calibrator with sound seal
grommet ~.75 inch from end (see picture
pg. 7) and select the 94 dB test tone on
the calibrator.
3. In the AudioTools Microphone
Calibration menu:
a. Switch the 48v phantom power to on
and select reverse polarity. Confirm
the LED is lit for Mic 1.
b. Select Low Range and set the Gain
Setting to 35 dB for starters.
c. Now touch the dB level box. This
will reveal the iPad keyboard. Enter
94 dB and touch “Done”. This will
change the trim box to the required
trim.
d. If the trim is between -2 and -7 dB
you’ve got it. If not, try a different
Gain Setting and repeat the
procedure.
4. Now, move the microphone calibrator to
Mic 2 and select Mic 2 on the iMUX4.
5. Adjust the trim screw near the input on
the iMUX4 until this Mic also reads 94
dB in AudioTools. Don’t change the
trim in AudioTools.
6. Repeat for all microphones.
You may find that you’ll need to readjust
Mic 1’s trim control up or down if you do
not have enough adjustment available on the
other trim screws. NOTE: Add a new input
source in AudioTools and calibrate this for
Mic 1 connected directly to the iAI2
(bypassing the iMUX4) for low noise
requirements. This is desired for ambient
noise or ETC measurements.

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APPLICATION
Introduction
The AVProAlliance.com iMUX4 allows an analyzer to average sound from multiple
microphones in a room, providing a single RTA or FFT test display. When sound is time
averaged from multiple microphones, measuring different positions in the room, the resulting test
display is called “spatially averaged.” Spatial averaging indicates the average response of the
room across the entire seating or listening area rather than from a single point in the room. This
is ideal for low frequency measurements where point to point variability introduces a high degree
of uncertainty. A spatially averaged measurement is considered the most accurate representation
of the true low frequency response of a room and is essential for accurate calibration.
Measurement Setup
To use the iMUX4 and SSD AudioTools to measure a room's spatially-averaged frequency
response, use the setup illustrated in Figure 5. Run cables from the microphones to the respective
MIC IN jacks of the iMUX4. Connect the cable from the iAI2 to the iMUX4 and connect the
iPad connector from the iAI2 to the iPad as shown below. The iMUX4 case facilities these
connections for maximum efficiency on the jobsite.
The iMUX4 case allows for the deployment and storage of microphones fully connected. This
means that the process of setting up is greatly expedited and simplified. The only connection
necessary will be attaching the iPad to the iAI2 using its connector. Due to the short length of
the iAI2 connector it’s recommended that you place the iPad on top of the iMUX4 case for use.
The long high quality microphone cables allow easy reach of most locations in the room.
MIC 1 MIC
2
MIC
3
MIC
4
MICROPHONE MULTIPLEXER
iMUX4
MICROPHONE
SELECTION
1
234
1-4
Room
Multiple Mics
Figure 10. Typical setup for analyzing a room with the iMUX4 & iPad with iAI2

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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
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.
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
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.

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WARRANTY AND SERVICE INFORMATION
WARRANTY
Your iMUX4 Microphone Multiplexer has been built to the highest quality standards in the industry. Each unit has
been tested, aged under power for at least 24 hours and the every function and range was retested to insure it met all
published specifications. Your instrument is fully protected with a 1-year warranty.
SERVICE
Save the original shipping carton and packing material for reuse should you ever need to ship your iMUX4, or return
it to AVProAlliance.com for repair.
1. If you are returning the unit to AVProAlliance.com for service open a Support ticket on the site and enclose
the following information: owner's address, billing information, purchase order (if applicable), name and
phone number of contact person, description of problem and reason for return. We will contact you and
issue a Return Authorization Number.
2. Completely enclose the unit inside a plastic bag to protect its finish and prevent foreign material from
getting inside.
3. Cushion the unit equally on all sides with a minimum of 3 inches of padding material. Pack the padding
tightly enough to prevent the unit from shifting during shipment.
4. Seal all seams on the container with strapping tape.
5. Send the packed unit to the following address (we recommend shipping via United Parcel Service):
AVPROALLIANCE.COM SERVICE
RA# _____________
Sioux Falls, SD 57109
www.AVProAlliance.com
Most service repairs are completed within 72 hours. If you need to ask about your unit, use the AVProAlliance.com
Support Ticket system.
Fill in for your records:
Purchase date: _________________________
Serial Number (on back of unit) _______________________

16
PO Box 90703
Sioux Falls, SD 57109
www.AVProAlliance.com
Printed in U.S.A.