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B-Chain Alignment Procedures
Action
Indication
Step
No.
5-16
18
19
20
a. Setting Room Equalization
Paul
B-Chain Alignment Procedures
Notes
5-17
a. Setting Room Equalization
When equalization is completed, the average of the 27 third-octave band controls should
be approximately 12 o’clock (not mostly up or down). If you find the controls are set
differently, repeat the equalization procedure until you obtain the proper equalization;
settings that diverge from this average may result in unpleasant sound.
Although the equalization may be set correctly for the chosen microphone position, it still
may not be correct for providing the best sound to the greatest number of seats in the
theater. You should therefore check the sound quality at several locations (three or more)
in the auditorium with the calibrated microphone and RTA system. If time does not permit
this procedure, walk around the theater with pink noise playing. If necessary, adjust the
equalizer for a compromise at several seat positions so that all of them sound acceptable.
Mark the settings for each control on the white card provided inside the Cat. No. 64
module.
If the sound quality varies significantly as you walk around, the equalization has not been
adequate:
• You may have over equalized. Check the positions of the controls; all should be
as close to 12 o’clock as possible.
• There may be phase shift present if the adjacent controls are pointed in opposite
directions, especially if you did so to eliminate a sharp dip that resulted from
physical problems in the auditorium (horn location, speaker orientation).
• The size of the room may be a multiple of a given wavelength, wall surfaces are
parallel, or there may be a severe balcony overhang.There may be reflection off
the walls behind the screen or crosstalk from adjacent theatres.
• The seat and seat materials may be too reflective.
• The microphone may have been placed in an untypical position.
Repeat the procedure with the microphone in other average locations in the auditorium.
Adjust the controls for the best compromise to fit all of the locations of the microphone.