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U T I N G
• Isolated left- and right-channel grounds ensure safety with
any amplifier.
• May be used with 4-, 6-, or 8-ohm speaker systems.
• Ideal for home and commercial sound installations.
• UL-rated to comply with all local building codes.
• Installation requires only a screwdriver and wire stripper.
• Power handling: 100W/channel RMS.
• Frequency response: 20Hz to 20kHz ±1.5dB.
• WMVC 100: Available colors: Bone and White.
• 10 years parts and labor warranty.
INSTALLATION CONSIDERATIONS
Calculating the Impedance Magnification Setting
Use the following instructions and the accompanying charts to
select the correct switch setting for the number and type of
speakers in your system.
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CAUTION! Every speaker pair in
TOOLS REQUIRED
the system must be connected
to
an
impedance-magnifying
• 1/8" Standard
volume control and set to the
same magnification.
Slotted Screwdriver
1. Count the number of pairs of
• 1/4" Standard
4-ohm speakers and the number
Slotted Screwdriver
of pairs of 8-ohm speakers you
are connecting. Count pairs of
• Wire Stripper
6-ohm speakers as 4-ohm pairs.
2. Determine whether the amplifier should see a 4-ohm load or
an 8-ohm load. You should find this information in the
owner's manual of the amplifier.
3. Read the correct switch position from the charts on the next
page. See Figure 3 if your amplifier can drive a 4-ohm
load. See Figure 4 if your amplifier must have an 8-ohm
speaker load.
4. Set the switches on all of the controls to the same position
(1x, 2x, 4x, or 8x).
Limitations in Volume with High Magnification Settings
Using an 8x setting limits the power to each speaker pair to
one-eighth of the amplifier's output.
W
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E A T H E R P R O O F
U T I N G
In a typical application of
IM volume controls, a
12 AWG
system has eight pairs of
8-ohm speakers through-
14 AWG
out the house. Each pair of
speakers is connected to
TECH TIP
an IM volume control with
Wire size is expressed by its
its switches set for 8x.
AWG (American Wire Gauge)
number. The lower the AWG
number, the larger the wire.
With eight pairs of speak-
Thus, 12 AWG wire is physically
ers, one-eighth of the
larger than 14 AWG.
amplifier's power is avail-
able to any pair. Therefore, an amplifier rated at 100W per
channel RMS into 8 ohms will deliver up to 12.5W to each of
the eight pairs – whether you play all eight pairs or just one pair.
This translates into a drop in the maximum volume capability
of about 9dB at the 8x setting.
USING SPEAKER SELECTORS WITH IM VOLUME
CONTROLS
Although IM controls provide volume and on/off at the volume-
control location, they do not give you central control of speak-
ers playing throughout the house.
Speaker-selection systems give you central control, but some
speaker selectors have non-defeatable impedance-protection
circuits. Combining IM controls with such a selector will
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reduce your maximum volume substantially. To solve this prob-
lem, specify a speaker selector with a defeatable protection
circuit (Niles models HDL-4, HDL-6, SPS-4, or SPS-6). Then
keep the protection circuit off at all times.
JUNCTION BOXES
WMVC 100: The mounting depth of the MVC 100 is 2-9/16".
When installed, the unit extends 2-1/16" behind the sheetrock
wall (assuming 1/2" sheetrock). For installation, use a standard
18-cubic-inch (or larger) junction box. Suitable junction
boxes are available from your Niles dealer or local electrical-
supply company.
WMVC 100E: Use the PVC junction box (supplied), mounted
atop a PVC conduit through which the wires will run.
TYPE OF SPEAKER WIRE
We recommend 16-gauge stranded copper speaker wire for
most connections, and 14-gauge wire for runs longer than 80
feet. Don't use speaker wire larger than 14 gauge, because larg-
er wire may not fit into the connectors. Never use solid-core,
aluminum, or Romex wire with an IM volume control. For
speaker-wire runs within walls, most U.S. states and munici-
palities require a special type of speaker wire with a specific CL
fire rating, such as CL-2 or CL-3. Consult your Niles dealer,
building contractor, or local building-inspection department if
you aren't sure what kind of wire is best for your application.
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