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Time Delay Adjustment
Realtime Analyzer & Pink Noise
This method outlines the use of a realtime analyzer, pink noise generator, and flat response microphone to set the
crossover time delay. The procedure applies to virtually any analyzer system. We recommend using a 1/3 or 2/3-
octave analyzer as either of these is more likely to match your specific crossover points than a one-octave analyzer.
It is important to match the analyzer to the crossover point as closely as possible for proper phase alignment,
otherwise the analyzer readings may be misleading.
STEP BY STEP PROCEDURE
A 3-Way mode consisting of High, Mid, and Low drivers is used here as an example. For other configurations, use
the same procedure starting with the highest crossover point and repeating steps 2 through 5 for each lower
crossover point.
NOTE: If you are running two separate channels on the crossover, tune up only one channel at a time, using the
same procedure for both.
1.
Place the analyzer mic about 15 feet in front of the speaker stack and at a height about midway between the
high and mid drivers. Turn all crossover Level controls fully down.
2.
Connect the pink noise source to the crossover input (or mixer or wherever is convenient). Turn up the
crossover Master Level control and the Mid Out control until noise is heard only from the mid driver at a
comfortable volume.
3.
With a healthy but not uncomfortable volume of noise from the mid driver, set the analyzer level control so the
display corresponding to the high crossover frequency is reading 0 dB.
4.
Press in the Mid Mute switch on the crossover so the tone is removed from the mid driver. Without re-adjusting
either the meter or the crossover input or Mid Level controls, turn up the High Level control until the tone
coming from the high driver reads 0 dB on the analyzer.
5.
Now release the Mid Mute switch on the crossover so pink noise is heard from both the high and mid drivers.
Switch the display sensitivity to ±3 dB (not necessary with full scale analyzers) and observe the display reading
at the crossover frequency:
i.
If the display shows a +3 dB reading, then the drivers are properly phase aligned and no delay is
necessary; leave the Mid Delay control at minimum.
ii.
If the display shows less than +3 dB reading, slowly turn up the Mid Delay control on the crossover
until the display shows +3 dB. Now the drivers are electronically phase aligned. The Delay control
should be left in this position unless the speaker system is physically altered.
iii.
If the Mid Delay control is all the way up and you still do not have a +3 dB (red) reading, you will
have to physically move the high driver farther forward until the display shows +3 dB (red). The
amount of displacement correction available from the Delay depends on the actual crossover
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 external delay to achieve proper phase alignment.
iv.
If turning the Mid Delay control up makes the display 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 only
worsens the situation. There are a couple of ways to deal with this:
6.
Lower the microphone until it is vertically midway between the mid and low drivers. Repeat steps 2 through 5,
using the crossover Level control, Mute switch, and the next Delay control. You may start each series of steps 2
through 5 at a different volume as necessary—but once the levels are set in step 3 do not alter these until step
5 is completed. Once all of the crossover Delay controls are set, then adjust the output Level controls.
12
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 use an additional delay
source to align the high and mid drivers. The built-in delay system in the AC 23S is
designed to accommodate the majority of common speaker configurations.
b.
If this decrease in the display due to the Delay control occurs at a low frequency
crossover point below about 150 Hz, set the Delay control to minimum and leave it
there. Frequencies below 150 Hz are omnidirectional, so that phase misalignment is
virtually inaudible below this point. Subwoofers will often 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.
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