Section 9: Auto Room EQ
25
9.4. REFERENCE MIC PLACEMENT
It is an unfortunate reality of room acoustics that acoustic analysis may
vary quite a bit with differing reference microphone positions, depending on the size, shape and surface
reflections of the environment. For example, in very small rooms, or in the reverberant field of larger
spaces, the number of paths for sound reflection may produce less than optimal results due to the phase
interference patterns created by direct and reflected sound arriving at the reference microphone at differ-
ent times. There are several rules of thumb you may follow to achieve the best, most accurate results of
room analysis:
·
Position your reference mic where you think the audience will tend to congregate most, thus insuring
the best sound for the largest number of people.
·
Keep the mic away from reflective surfaces (e.g., walls, corners, or large structures in the middle of a
room).
·
Keep the mic relatively close to the front-of-house speakers (the direct sound field, where reflected
sounds are lower in magnitude relative to the sound coming directly from the speakers). The larger
the component of reflected sound in the sound heard by the reference mic, the greater the phase
cancellation and comb filtering.
·
Bass frequency analysis is more prone to measurement anomalies than higher frequencies. The
smaller the room, the greater the problem. Use your ears and listen to bass response at different
room locations, in addition to considering the information and analysis of the POWER-Q.
·
When running a mono sound source through two or more speaker stacks or enclosures, run Auto-
matic Room EQ using only one speaker cabinet or stack, since sound arriving from multiple point
sources will arrive at the microphone at different times. When running a stereo source through a
stereo sound system, the POWER-Q will automatically analyze one channel at a time in sequence.
But again, multiple speakers in the sound path of either channel should be selectively disconnected so
only one speaker plays sound during the analysis.
NOTE: Make sure you plug only a microphone level signal into the POWER-Q reference microphone
input. Do not plug a microphone preamp into the reference input. This may cause the reference mic
board to overheat and damage the POWER-Q and will not be covered by the warranty.
9.5. POWER-Q CONTROLS FOR AUTOMATIC ROOM EQ
. Select “AUTOMATIC ROOM EQ” from the display
window by pushing soft key #1 from the MAIN MENU.
Because pink noise is played at audible levels, do not run this procedure during a performance, or even
during rehearsal. You should run the Automatic Room EQ procedure BEFORE the performers or audi-
ence arrive. To prevent accidental injection of pink noise through your sound system, the Automatic Room
EQ function requires you to deliberately choose the procedure by hitting the “ENTER” button when
prompted.
You may run the Automatic Room EQ analysis for either the A channel alone, the B channel alone, or both
channels in sequence depending on your application of the POWER-Q. Select “INIT A,” “INIT B,” or “INIT
A&B” using the left/right arrow keys before hitting the “ENTER” button to begin the analysis. NOTE: Any
time you run the Automatic Room EQ for a given channel, it will erase and replace the previous analysis
for the channel(s) chosen. In addition, the current program shaping curve will be erased from active
memory (though you may save the program curve and reload it from memory). For more information
about program shaping curves and memory options, see sections 10.2 and 16.0.
Fig. 26: Automatic Room EQ, page 1.
