OEM Systems TT-IMP100WV — Impedance Matching Volume Control Instructions

Instructions for the OEM Systems TT-IMP100WV Impedance Matching Volume Control. This device compensates for the decreasing impedance that occurs when connecting multiple pairs of speakers to a single audio amplifier, by multiplying the effective speaker impedance seen by the amp — while also providing 12-position volume control.

Specifications

• 100 Watts RMS power handling per channel
• 1X, 2X, 4X, 8X, and 16X impedance multiplier settings
• 12 volume positions, including one Off position
• Removable input/output terminal strip
• Stereo control (can also be used in mono applications)
• Suitable for residential and commercial applications

Features

• Protects the amplifier by maintaining a safe impedance
• 1X position for use in ordinary applications (single pair of speakers)
• Easy installation with clear instructions
• Limited Lifetime Warranty

Installation

1. Set the position of the impedance multiplier jumpers (see Jumper Selection below) before wiring.
2. Connect the left & right channel outputs of the amplifier/receiver to the input of the volume control.
3. Connect the left & right channel outputs of the control to the speaker inputs.
4. Test the system initially at low volume settings on both the amplifier and the volume control.

To change the multiplier, remove the access panel on the bottom of the unit, slip the jumpers off the pins, and reinstall them on the pins for the desired multiplier (1X, 2X, 4X, 8X, 16X). All jumpers on all volume controls within a system must be set to the same position, and both jumpers on each individual control must also match each other.

A "system," for purposes of this manual, is any combination of volume controls and speakers connected to a single receiver or amplifier.

Jumper Selection — Two Methods

There are two ways to determine the correct jumper position: the Chart Method (simple) or the Calculated Method (more accurate, more work).

Chart Method

Select the chart matching your speakers' impedance (8, 6, or 4 Ohm — most residential installs use 8 Ohm speakers). Find the row matching your amplifier's minimum safe impedance rating (check your amplifier's owner's manual), then move across to the column matching the number of speaker pairs you want to use. The value shown is the multiplier to set on every volume control in the system. Gray-area combinations (from the source charts) are slightly below the amp's minimum impedance but will likely work.

If your system has a mix of speaker impedances, calculate the multiplier directly, or use the "worst case" — select the 4 Ohm chart if speakers are mostly 4 Ohm, or the 6 Ohm chart if mostly 6 Ohm.

Jumper Position — 8 Ohm Speakers

Full detailed multiplier charts for 6 Ohm and 4 Ohm speaker systems, and per-pair-count granularity from 1 to 16 pairs, are included in the downloadable PDF.

Calculated Method

1. Calculate the net impedance for all your speaker pairs.
2. Determine the minimum safe operating impedance for your amplifier (see amplifier's owner's manual).
3. Divide the amplifier's minimum impedance by the calculated net speaker impedance — the result is the minimum necessary multiplier.
4. Round up to the next highest available multiplier (1X, 2X, 4X, 8X, 16X), unless your calculated value is within approximately 10% of a multiplier value, in which case rounding down is acceptable.

(Formulas and a worked example using 8, 6, and 4 Ohm speakers on one system are provided in the full PDF.)

Note: OEM assumes no responsibility for damage to audio equipment due to operation at an impedance below that recommended by the manufacturer.

Manufacturer

OEM Systems Company, Inc., Sparks, NV — www.oemsystems.com