Rane AC 22B (2003 version) - Manual (Page 11)

Manual-
5. Now release the MID MUTE switch so that the tone is emit-
ted from both the high and mid drivers. Check the reading on
the SPL meter:
i. If the meter reads +3 dB, then the drivers are properly phase
aligned and no Delay is necessary; leave the MID DELAY
control at full minimum.
ii. If the meter reads less than +3 dB, slowly turn up the MID
DELAY control until the meter just reads +3 dB. Now the
drivers are electronically phase aligned and the DELAY
control should be left in this position at all times, unless the
speaker system is physically altered.
iii. If you have turned the MID DELAY control all the way
up and still do not obtain a +3 dB reading, you will have
to physically move the high driver farther forward until the
SPL meter reads +3 dB. The amount of displacement correc-
tions available from the Delay depends on the actual cross-
over frequency: the higher the frequency the less amount
of correction capability. If the drivers are built into a single
cabinet and/or it is impossible to change relative positions,
then you will have to obtain additional delay to achieve
proper phase alignment such as the Rane AD 22B.
iv. If turning the MID DELAY control up makes the SPL
reading decrease instead of increase, this means that the high
driver is actually in front of the mid driver; adding delay to
the mid driver then only worsens the situation. There are a
couple of ways to deal with this:
a. Try to move the high driver back as far as possible without
losing stability in balancing the speaker stack. You may
want to raise it up as well to restore dispersion close to
the stack. If you cannot move the high driver, then you
will have to obtain an additional external delay source to
align the high and mid drivers. The built-in Delay system
in the AC 22B is designed to accommodate the majority
of common speaker configurations; if you encounter con-
fusion or difficulty with your particular system, it is best
to consult your dealer or the Rane factory for assistance.
b. If this decrease in the display due to the LOW DELAY
control occurs at a low frequency crossover point below
about 150 Hz, set the LOW DELAY control to mini-
mum and leave it there. Frequencies below 150 Hz are
actually omnidirectional, so that phase misalignment is
virtually inaudible below this point. Subwoofers will of-
ten possess long folded or straight horns, resulting in the
diaphragm being well behind the rest of the stack. Most
authorities agree that phase alignment of subwoofers is
unnecessary. Otherwise you will have to obtain additional
delay equipment to align these to the rest of the system.
6. Tune the tone generator to the next lower crossover frequency
and then repeat steps 2 through 5, using the appropriate Level
and Delay controls. Once the Delay control is set, you may
re-adjust any of the crossover Level controls at the beginning
of each alignment procedure. Once all of the crossover Delay
controls are set, then re-adjust the output Level controls as
outlined in Setting the Output Level Controls on page
Manual-11.