Your AT-12 speaker selector uses high-powered transformers with selectable taps which allow you to obtain maximum
power transfer while maintaining a safe load of 4 Ohms or higher on the driving amplifier, regardless of the number of
speakers in use at the time. A six position rotary switch is provided to allow convenient choice of the appropriate tap. Note
that there is no significant power loss with transformer matching, when optimally set there will be a level drop but the full
amplifier power output will be available, divided equally among the speakers in operation.
This system is capable of transforming a 1/3 Ohm load to appear as a 4 Ohm to the amplifier, which is equivalent to 12-4
Ohm or 24-8 Ohm speakers operating simultaneously. Thus it is apparent that many more speakers can be used than the
number of ON-OFF switchers (12) suggest. Some switches can be used to control individual speaker pairs, while perhaps
others may be used to control "zones" consisting of several pairs on the same switch.
These transformers are rated for continuous operation at 100 Watts RMS (300 Watts audio). They are connected so that
the left and right channels are completely isolated electrically. Wiring to the switchbox is through push-to-connect terminals
on the AT-12 rear panel, which can accommodate wire up to 12 gauge, adequate for most installations.
A built-in self powered, minimum impedance load warning indicator is provided to aid in choosing the best matching
setting of the rotary switch. A red and green indicator on the front panel shows a constant indication of operating status. The
amplifier load is 4 Ohms or higher when the green lamp is lit, below 4 Ohms if the red on. If red, simply rotate the load
switch until the indication turns green, and you are operating within a safe parameters.
This indicator system is useful for maintaining maximum power transfer to the speakers in use. If this is desired, rotate
the matching control clockwise until the red lamp comes on, then back off one position at a time until the green lamp lights.
You will then be matched as closely as safely possible to 4 Ohms at the amplifier output, which is the point of maximum
power transfer for the speakers in operation.
INSTALLATION:
A separate label strip is furnished which has a peel-off adhesive back. It can be affixed to any convenient surface, or kept
loose where it will be a convenient reference during the installation process.
Three connector strips are provided with the AT-12. They are removable, so can be wired while connected to the AT-12,
or disconnected and pre-wired to be plugged in later, when completing the installation. This normally is the preferred method
since it is much more convenient.
Viewing the AT-12 from the front, the connection order is Left to Right in groups of 4, with terminal 48 being the #1
speaker set R+, #47 #1 R-, #46 #1 L+, and #45 #1 L-. This sequence repeats for the entire set of connectors, including the
INPUT FROM AMPLIFIER on which is separate.
Connect the AT-12 terminal strip marked "INPUT" to the amplifier output, observing polarity and proper channel
identification (note that the INPUT connector block is green and the OUTPUT connector blocks are black). Strip about 1/4"
of insulation from the wire ends, twist any loose strands together tightly, insert in the appropriate connector opening and
tighten the associated screw down. Make sure no loose strands are hanging out to be a potential cause of a short circuit.
TECHNOLOGY
INSTALLATION MANUAL
2000 - 6/20/00
AT-12
IN-WALL TWELVE SPEAKER PAIR SELECTOR
Observing the same precautions, connect the speaker wires to the appropriate AT-12 terminals marked "OUTPUT TO
SPEAKERS".
If connecting several pairs of speakers in a "zone" configuration, best results will be obtained with all of them connected
in parallel. Series arrangements can be used, but usually with some sacrifice in sound quality--the evils of each speaker in the
series chain are usually visited on the other.
If the AT-12 is to be installed free-standing or rack mounted, no special precautions are required because no significant
amount of heat is generated in normal operation. Because of this fact, the AT-12 is also safe for in-wall installation.
IN-WALL MOUNTING:
The AT-12 chassis is 3 1/4" deep from the front panel to the chassis rear. This will fit in any standard 2X4 studded wall
with approximately 1/2" clearance for wiring. The in-wall cut-out should be 4 11/16" high by 13 1/2" wide (minimum). The
long cut must be made carefully, there is slightly less than 1/4" overhang at the top and bottom of the panel. The in-wall
panel is designed to fit 16" centered studs. The mounting holes are spaced at 16" and are 5/32" in diameter to clear #6 size
screws.
To ease final installation, it is suggested that the wires be pre-connected to the removable connectors, and dressed in the
order of connection to avoid crossovers as much as possible because of the limited rear space. An additional suggestion is to
form the wires as close as possible to the way they will be when the installation is complete. The large number of wires
involved may make the assembly rather stiff and performing will reduce strain on the connectors during final installation.
Complete the installation by mating the connectors to the AT-12 chassis and gently moving into position in the cut-out.
Secure with whatever fasteners you will be using into the 2X4 studs.
USING YOUR AT-12:
The rotary IMPEDANCE MATCH-ATTENUATION switch is used to make connection to the appropriate impedance
matching tap on the AT-12 transformers. The front panel markings show the attenuation of level for each position. As the
attenuation is increased (CCW), the number of speakers that can be operated simultaneously also increases.
Matching impedance for each switch setting follow: (for a 4 Ohm load to appear on the amplifier output). The first
number indicates the level drop in decibels, as marked on the front panel.
0 No transfer, 1-4 or 2-8 Ohm speakers.
-3 Load X2, 2-4 or 4-8 Ohm speakers.
-6 Load X4, 4-4 or 8-8 Ohm speakers.
-8 Load X6, 6-4 or 12-8 Ohm speakers.
-10 Load X9, 9-4 or 18-8 Ohm speakers.
-11 Load X12, 12-4 or 24-8 Ohm speakers.
Combinations of speaker impedances can be mixed, the resulting load will fall somewhere in between those shown on the
chart.
Good practice would be to set the matching control for the worst case (maximum number of speakers) and leave it there.
However, if maximum power transfer is important when a specific number of speakers are in simultaneous operation, the
above chart will enable you to choose the optimum setting.
NOTE: The red-green light indicating system is self-powered and may flicker somewhat, especially if the driving
amplifier is operating at very low power. It requires approximately 1 Watt input minimum to light up the system. When
closely matched, the green indication may occasionally change to brief red flashes. This is due to the non-linear
characteristics of most speakers and need not be cause for concern. If the duration of red is longer than the green, the
Omnimatch (tm) control should be backed off one position or more until the green indication predominates.
AMPLIFIER
OUT
+ R -
+ L -
CONTINUE THE SAME PROCEDURE FOR SPEAKER PAIRS 3 THROUGH 12.
AT-12 TOP VIEW
SPKR. PAIR 1
+ R -
+ L -
SPKR. PAIR 2
+ R -
+ L -
WIRING DIAGRAM
#1
R+
R-
L-
L+
#2
R+
R-
L-
L+
#3
R+
R-
L-
L+
#4
R+
R-
L-
L+
#5
R+
R-
L-
L+
#6
R+
R-
L-
L+
#7
R+
R-
L-
L+
#8
R+
R-
L-
L+
#9
R+
R-
L-
L+
#10
R+
R-
L-
L+
#11
R+
R-
L-
L+
#12
R+
R-
L-
L+
AMP.
R+
R-
L-
L+
WARRANTY:
Your AUDIOPLEX TECHNOLOGY AT-12 Sound Distribution Center is covered by a LIFETIME
warranty against any defects in workmanship and materials. Any defects will be remedied without charge
for labor or parts.
Damage incurred by shipping or accident is not considered to be a defect, and not covered by this
warranty. AUDIOPLEX TECHNOLOGY, is not responsible for defective operation caused by abuse or by
modification or service by any unauthorized person or agency.
The unit must be properly installed and operated according to instructions for the warranty to apply.
Any necessary servicing must be done by AUDIOPLEX TECHNOLOGY. The product must be returned
expenses prepaid, with written authorization from the company. The product must be shipped with the
proof of purchase and in the original carton and packing material to aviod damage.
This warranty gives you specific legal rights. You may have other rights which vary from state to state.
AUDIOPLEX TECHNOLOGY
404 GWH, P.O. BOX 440
MELVIN VILLAGE, N.H. 03850
1-800-257-2077 IN N.H. 1-603-544-8601
FAX: 1-603-544-8901
E-mail: [email protected]
2000 - 6/20/00
Note: INPUT connector block is green
OUTPUT connector blocks are black
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2
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