Before designing a multi-room sound distribution system, we must fully understand impedance and why it is important to match the impedance of a speaker load to an amplifier output. Impedance is the opposition of current flow in an AC circuit which is measured by the total resistance, capacitance and inductance in the circuit.

Measuring AC impedance is not the same as measuring DC resistance. You must use an AC impedance meter for a true measurement. Using a DC ohm meter will only allow you to check for shorts and opens in a circuit.

Resistor-based Impedance Matching Products:

• Advantage - Usually considerably less expensive than transformer-based products

• Disadvantage - Usually much less efficient than transformer-based products. Large resistors in the circuitry can rob 1/3 to 2/3 of the power in your system.

Transformer-based Impedance Matching Products:

• Advantage - Usually much more efficient than resistor-based products. Insertion loss through an autoformer is considerably less than a voltage drop over a resistor.

• Disadvantage - Usually more expensive than resistor-based products. Some loss in frequency response at low and top end depending on frequency response of autoformers used.

WIRING STEREO SPEAKERS

• Wiring your system properly can be as important as selecting the right components.

• Always select the correct gauge wire according to the total length of wire in a run.

• Always make sure to run speaker lines away from AC lines and

any other noisy circuits .

• Cross AC lines at 90° angles .

• Run speaker lines at least 1 stud spacing away from 120V lines when running parallel.

• Stay away from lighting dimmer products.

• Always use twisted construction wiring in the walls. This will help provide noise immunity from AC 60Hz hum.

• Parallel zip type wire can be used anywhere outside the walls. Many clear zip cables have a nicer appearance for exposed wiring.

• For 8 ohm runs under 100’, use 16 gauge

• For 8 ohm runs under 200’, use 14 gauge

• For 8 ohm runs under 300’, use 12 gauge

• Distances will be half for any 4 ohm runs

INFRARED REPEATER SYSTEMS

Just what is an infrared repeater? Simply stated, there is a device which is designed to receive an infrared signal at one location, convert it to an electrical signal for re-transmission by wire to a second location where the signal is then converted back to infrared.

From a practical sense, the infrared receiver in the remote location receives a signal from a hand-held remote and re-transmits that signal directly to the equipment being controlled. The equipment has no way of knowing it hasn’t received a direct command from the remote.

INFRARED RECEIVERS

The infrared receiver picks up the signal and converts it to a pulsed DC control signal. This signal is sent down a wire and then terminates a connecting block which distributes the signal to the attached LED emitters. This emitter will flash in front of the IR window of the equipment to be controlled.

The majority of infrared remote controllers used today work on the same principles. They modulate the infrared signal at a frequency from 30 to 100kHz. This modulated carrier contains the digital code assigned to a specific function of the equipment bring controlled, such as Play , Fast Forward, etc.

Wiring:

• All of the IR receivers from Xantech or Russound are designed for 3-wire home run mode of connection. They can be configured for a 2-wire phantom power mode using a specific power module .

• Use 22 gauge for runs up to 600’.

• Use 24 gauge for runs up to 200’.

PROGRAMMABLE KEYPADS

If a keypad control is desired instead of an IR receiver , a Smart Pad from Xantech or Russound can be used. Follow the same wiring instructions as an IR receiver . A Smart Pad and an IR receiver in the same room can share the same wiring.

INFRARED EMITTERS

An infrared LED assembly is necessary to re-transmit the infrared control signals to the equipment. Most commonly used are Mini-Emitters. These units are an ultra-small LED housed in a miniature, dark red plastic assembly that is adhered to the IR window.

Outdoor Use: Direct sunlight & infrared energy radiating from all heated objects such as large rocks and swimming pools can pose problems to IR receivers. Place them in as much shade as possible. Some newer IR receivers on the market from Xantech are rated for outdoor use .