Determine the wall in your room where you want to mount the XLR plate. Keep in mind that in most states, building codes dictate that the wall plate should sit about 12 inches from the floor. Use a laser beam locator to find a beam in the wall. The wall plate should be mounted next to a beam.
Place the wall plate onto the section of the wall where it will be installed. Trace the outline of the wall plate onto the wall with a carpenter's pencil. Drill a hole into one of the corners on the wall's marking. Widen the hole slightly with a utility knife and cut out the hole with a hacksaw. Remove all sheetrock debris from the hole.
Place the wall plate's mounting bracket into the hole. Butt one side of the bracket to the beam in the wall. Attach the bracket to the wall with one or two framing nails. Use a hammer to pound the nails into the beam.
Repeat this procedure to install a wall-mounting bracket into the adjoining room where the audio mixer will be located.
Purchase some XLR audio cable. These are three audio cables, usually with red, black and blue insulation. The black wire is the ground, the red wire is the positive and the blue wire is the negative.
Group the wires together, pull them taut and lay the wires out on a flat surface. Tape one end of the wire group together with electrical tape. Do the same to the opposite end of the wires.
Attach one end of the wire group to a wire-fishing mechanism. Insert one end of the wire into the hole in the back of the mounting bracket situated inside the wall. Use the fishing mechanism to pass the wiring through the wall to the mounting bracket installed into the adjoining room's wall.
Remove the tape from each end of the XLR wire group.
Use a pair of wire strippers to strip each wire's insulation back 1/2 inch. Grasp the XLR wall plate and examine the XLR connector inside the plate. There should be three pins, labeled "1," "2" and "3."
Plug in a soldering iron and let it heat up for about 10 minutes. Touch the black wire to pin 1, while simultaneously touching a fresh piece of solder to where the wire meets the connector. Touch the solder with the heated soldering iron until it melts and connects the wire to the connector pin. Let the solder dry for five minutes. Repeat this to solder the red wire to pin 2, and the blue wire to pin 3.
Place the wall plate over the hole in the wall. Align the screw hole on the plate with the screw hole on the mounting bracket. Fasten the wall plate to the mounting bracket with the Phillips head screw included with the wall plate kit.
Repeat this procedure to install the other wall plate on the adjoining room's wall.