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Find a central place in the audience where the center cluster is 6 to 8 dB louder than the direct sound
from the performer. Delay them so that their sound arrives 5 to 8 milliseconds after the direct sound
from the performer. Experiment by bypassing the GRAPHI-Q in and out to hear how the source of the
sound seems to move from the loudspeakers to the performer and back. Now your ears have the same
directional information as your eyes, so the performance will sound more natural and exciting. The
best seats in the house just got better.
What about the front fills? Their purpose is to add intelligibility and listening comfort to the first few rows
nearest the stage by filling in the areas missed by the center clusters. Add about 8 msec. to the front
fills to take advantage of the Precedence Effect.
The 8 msec. setting presumes the performer is standing on the front few feet of the stage. But some
stages are well over 30 feet deep. What if there is a second performer standing 25 feet behind the first?
The direct sound from his or her voice will reach the first few rows about 25 msec. after the first
performer's. The audience will perceive the first performer directly and the second performer through
the loudspeakers.
We can add the advantage of the Precedence Effect to the second performer by placing the GRAPHI-
Q in the mixer's channel insert point and adding a 25 msec. delay.
Certainly taking advantage of the Precedence Effect is not as obvious to the audience as eliminating
feedback, but it is nice to know you did all that is possible to make the performance enjoyable.
9.4.4.3. Application III: Synchronizing the signals of a far-throw and short-throw loudspeaker.
In order to reach the proper coverage in larger venues, we often stack two full range speakers - a short-
throw center cluster for the audience below and a far-throw speaker for the back of the auditorium. It
is almost impossible to perfectly align the stacked speakers mechanically, so comb filter distortion
becomes a problem in the area where the levels from both speakers are equal. The same thing
happens with speakers mounted on the right and left sides.
It is impossible to remove comb filters with equalization, but the GRAPHI-Q eliminates them in short
order without affecting the spectral balance for the rest of the audience. Find the axis where the levels
from the two speakers are equal. This is where the comb filters are most severe. Carefully adjust the
GRAPHI-Q so that the signal from both speakers arrives at precisely the same time. The GRAPHI-
Q provides 20 microsecond resolution for this purpose.
Use the same procedure to align speakers within a cluster when necessary.
Delay Figure 7: Aligning far-
and short-throw speakers.
(The level from both
speakers is equal.)
Section Nine: Suggestions for Optimal Use of the GRAPHI-Q
