User`s manual

B-Chain Alignment Procedures
Notes
5-21
Slowly advance the fader to position 7.
The subwoofer and center channel response should be observed on the RTA.
Adjust the subwoofer output level control on the Cat. No. 511 to match the
level of the midrange frequencies.
While observing the RTA, note the change in the average level of the bands
from 20 Hz to 100 Hz when the subwoofer is turned on and off via the norm/
test connector on the EQ board. There should be a level increase when the
subwoofer is on norm. The subwoofer is out of phase with the center channel
if you do not see this level increase. Reverse the subwoofer(s) speaker
connections if necessary.
5.4 Subwoofer Alignment