Lowpass Crossover Control, Phase | Boston Acoustics GT-28, GT-24

Setup Tuning—Subwoofers (cont.)

2) Head Unit

The head unit should have all controls such as bass, treble, balance, and fader set to the ﬂat or centered position. The volume control should be at the minimum setting. If the head unit has any equalization or bass management features such as boost, they should be deactivated at this time. Turn head unit on, and verify that the GREEN status LED is lit on the ampliﬁer.

3) Volume

With the chosen musical track playing, turn the head unit volume control up until the maximum level of undistorted signal is heard from the speakers. For most head units, this will be at the end of the volume control range.

WARNING! A distorted signal from the head unit sent to the ampliﬁer can cause loudspeaker failure at higher listening levels!

4) Input Sensitivity Control

Turn control all the way counterclockwise (minimum position). In this position, the ampliﬁer will be less sen- sitive to the input signal from the head unit. Slowly rotate this control clockwise until maximum undistorted playing level is heard from the subwoofer(s). Listen closely for faults such as bottoming from the subwoofer(s). If fault is detected, rotate INPUT SENSITIVITY control counterclockwise until fault is eliminated. At this point, the maximum undistorted subwoofer playing level has been deﬁned.

5) Lowpass Crossover Control

Move the selector switch to “ON.” In this setting, lowpass signal is sent to the speaker outputs. Experiment with the crossover point setings while the subwoofer is active. A higher setting will increase the perceived output, and a lower setting will make the bass response more omnidirectional. 12 or 24dB crossover slopes are available. Depending on your installation and listening preferences, one will work more effectively.

LOWPASS SLOPE

12dB12dB 24dB

ST MONO

6) Phase

Subwoofer phase is relative to the front loudspeakers. Correct electrical phase does not always mean correct acoustic phase. Swap positive (+) and negative (-) connections at the speaker outputs where the subwoofer is connected to the ampliﬁer. It is beneﬁcial to listen to the subwoofer connected in both phase conditions. The subwoofer should be left in the condition in which the strongest bass response is noted.