- Make sure the head-unit power is off and the GT-BassPro12’s Level control is set to minimum.
- Set the GT-BassPro12’s Low Pass control to its maximum frequency of 120Hz and set the Bass Boost control to the 12 o’clock setting. NOTE: If you are using the Remote Level control, set it to maximum.
- Turn the head unit on and play a selection of your favorite music track that has substantial bass.
- Adjust the Low Pass control counterclockwise until you hear only bass information coming from the GT-BassPro12. For example, you should not hear vocals coming from the subwoofer when you are seated in the normal listening position.
- Adjust the Bass Boost control either clockwise or counterclockwise to suit your taste. Be sure to find a setting that does not create audible distortion in the subwoofer’s sound.
- If you installed the remote level control, set the subwoofer’s Level control to its maximum and set the remote level control’s knob to the maximum level that provides undistorted output from the GT-BassPro12 with the head unit’s volume control at its 3 o’clock setting. Use the remote level control to adjust the subwoofer volume according to your taste while avoiding distortion from the GT-BassPro12.
- If you did not install the remote level control, adjust the subwoofer’s Level control to the maximum level that provides undistorted output from the GT-BassPro12 with the head unit’s volume control at its 3 o’clock setting. After using the subwoofer for a while, if you find that this setting produces too much bass, you can reduce the subwoofer’s Level control setting.
- Phase Switch: This switch will reverse the phase of the GT-BassPro12’s output with respect to its input. When you install the GT-BassPro12 with an existing factory or aftermarket system, changing the Phase switch setting to reverse the subwoofer’s phase may produce a discernable increase or decrease in the amount of upper bass that the system reproduces, depending on the GT-BassPro12’s location in the vehicle and the distance between it and the other speakers in the vehicle.
- With the Phase switch set at 0°, play a music track that has impact drums, and listen for the upper bass content, paying attention to the impact of the drums. Then set the Phase switch to 180°, and listen to the same music again. There may be more upper bass, less upper bass or no change at all. The Phase switch position that provides the most upper bass is technically correct, but you can choose either setting according to your taste. NOTE: In most cases the above steps will provide you with satisfactory results. However, the actual process may require several readjustments of each control, since the settings will interact with one another. If necessary, consult your authorized JBL car audio dealer for help in tuning your system.
SCHEMATICS
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