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Adjusting Phase Alignment

Adjusting Phase Alignment between the Main Speakers and Subwoofers

When adding a subwoofer to a home theater system or two-channel audio system, adjustments of the subwoofer’s level and phase settings are critical to achieving optimum performance. When performed properly, perceptible improvements in frequency response, imaging, dynamic range, and impulse response can be achieved, with distinctly audible results.

Initial Setup

Set the desired low pass crossover frequency to be used on only ONE of the following:

  • The bass management controls on the receiver or preamplifier/processor
  • The crossover settings on an outboard active subwoofer crossover (CR-1)
  • The on-board low pass filter of a powered subwoofer
  • The on-board 2-way crossover of a powered subwoofer (E-Sub)

Adjust the settings for the subwoofer:

  • Set the Level Mode to the Variable position, if equipped. Turn the master level all the way down.
  • If using the bass management crossover in a receiver, preamplifier/processor, or outboard crossover, set the LP Filter to Off.
  • For home theater systems, temporarily set the receiver or preamplifier/processor to Stereo mode.
  • Set the ELF to 0, if equipped.
  • Turn the Phase knob fully counterclockwise to 0.
  • Set the Polarity switch to the 0 position.
  • If using the onboard low pass filter or E-Sub crossover, set the LP Filter to 24 dB and the LP Frequency to the desired filter frequency.

Adjustments

Perform the following procedures in order, one channel at a time:

Level match the volume of the main speakers and subwoofer

  1. Disconnect the main speaker that is furthest from the subwoofer. For a system with two subwoofers, disconnect one main speaker and turn off the subwoofer on the same side.
  2. Play a test tone of the selected crossover frequency or low pass filter setting at a medium volume level.
  3. Sit at a center position in front of the main speaker and subwoofer. With your head placed equidistant from each, slowly adjust the subwoofer's level control and notice the tone level transition from the speaker to the subwoofer, and back.
  4. Set the subwoofer level control at the position where the speaker and subwoofer appear to have the same amplitude.

Align the phase of the main speakers and subwoofer

  1. Reverse the polarity of the speaker by connecting the positive speaker wire to the negative terminal and the negative speaker wire to the positive terminal.
  2. Return to the center seating position in front of the main speaker and subwoofer. With your head placed equidistant from each, slowly rotate the subwoofer's phase control knob clockwise and notice the bass drop off significantly, then begin to rise. With the speaker and subwoofer playing the test tone at the same level, but 180 degrees out of phase, a null point is created, and the bass cancellation should be easily discernible.
  3. Set the subwoofer's phase control at the position where the bass appears to have the least amplitude.
  4. Reverse the polarity of the speaker again by connecting the positive speaker wire to the positive speaker terminal and the negative speaker wire to the negative speaker terminal.

Repeat the process for the opposite side.

Ideally, if you have a friend available to assist with this procedure, you can improve the outcome by listening from your favorite listening chair while the volume and phase adjustments are made, as the results might be slightly different between the two locations.

Upon completion of the phase alignment procedure, the subwoofer's level control can be adjusted to the desired position.

 

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