Rockford Fosgate FA15.0 - Manual (Page 14)

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Phase Control
The Phase Control switches allow the Fosgate Audionics subwoofer to be acoustically aligned with
other speakers in your system. 0˚, -90˚, -180˚, or -270˚ degrees of phase shift at 80Hz can be selected
using DIP switches 2, 3, and 4. For 0˚ degrees of phase shift, leave all three switches in the OFF (up)
position. –270˚ degrees of phase shift occurs when switch 2 is selected in the ON (down) position.
–180˚ degrees can be achieved by selecting both switches 2 and 3 in the ON (down) position. Finally,
selecting all switches 2, 3, and 4 in the ON (down) position produces –90˚ degrees of phase shift.
Set-up Procedure
1) Place all your speakers and any acoustically significant components in their working location in the
listening environment.
2) Insert a sine wave signal into the audio path. Be careful to turn down the level before turning on
the amplifiers.
3) Choose a frequency that corresponds to the crossover frequency between the Fosgate Audionics
subwoofer and the reference monitors.
4) From the listening position, alternate between the Fosgate Audionics subwoofer and the full range
speakers and adjust the levels until they have the same acoustic output. Use an SPL meter, a micro-
phone on a VU meter, or your ears to accomplish this.
5) With all speakers on, try the 0˚, -270˚, -180˚, and –90˚ degree phase settings. The setting with the
highest SPL reading from your listening position will produce the most effective acoustic alignment.
6) Set the FA10.0/FA12.0/FA15.0 gain control according to your preference. This will not affect the
acoustic alignment of your system.
Here is a list of some items that can affect acoustic alignment: Relocating speakers, changing the
Fosgate Audionics subwoofer Low Pass frequency, changing the acoustic environment (i.e., traps, dif-
fusers, etc.), changing the listening position.
Although this procedure produces the maximum achievable acoustic gain for your system, listening
tests may still lead you to prefer another setup.
Example of how phase misalignment between high frequency speakers and a subwoofer can cause
cancellation
Operation