dbx DriveRack PA2, Owner'S Manual

18

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Manual System Optimization Tips

HiNt: 

You may want to disable the TIME OUT feature located in the Utility menu before performing any of the following 

system optimization procedures. This will ensure the PA2 does not revert back to the Home screen throughout the process. 
See 

‘Utility’ on page 46

 for more information on disabling this feature.

1. Crossover Frequencies

If you can’t find any tuning information for your speakers, get the speaker’s specification sheet – it can give you a good idea 
where to set some of your high pass and low pass filters in the PA2’s crossover by providing the speaker’s or driver’s frequency 
response. This frequency response spec shows you the range of frequencies the speaker or driver is capable of reproducing 
and can help you better determine where to set the crossover frequency settings for your loudspeaker system.

If you’re bi-amping main speakers, the speaker manufacturer should be able to provide you with the recommended crossover 
frequency settings. If you’re using subs and can’t find recommended crossover frequency settings, you will need to dial it in by 
ear. Typically, subs and mains will be crossed over at around 100 Hz – this is a good setting to start with. You can then adjust 
the settings from there to fine-tune the sub/main crossover settings by ear if required.

If you’re configuring a simple full-range system (not requiring any active crossover settings) then you don’t necessarily need 
to enter any speaker tuning parameters. However, it is a good idea to take note of the speaker’s frequency response spec 
and set the high pass filter in the PA2’s crossover at the lower frequency specified (35 Hz, for example). This will prevent the 
subsonic low-end from robbing you of headroom in your amp and prevent the loudspeakers from trying to reproduce extremely 
low frequencies which they are not capable of reproducing.

2. Driver Alignment Delay, Polarity, & Crossover Filter Types

Once the crossover frequencies are dialed in, you’re ready to optimize the loudpeakers’ phase. All loudspeaker drivers in the 
system need to work in unison in order for the sound system to sound its best. This is accomplished by matching the polarity 
for all loudspeaker drivers, adjusting driver alignment delay to time align any physical driver offsets, and selecting the best 
crossover filter type/slope settings for your particular loudspeakers.

The PA2’s output polarity parameter (located in the crossover module) is used to match polarity between drivers. Some 
bi-ampable main speakers require certain drivers to be inverted in polarity when operating in bi-amped mode (bypassing the 
internal passive crossover network). When selecting any bi-ampable main speaker from the PA2’s speaker tuning list, such 
polarity inversion will be performed for you automatically. If you can’t find PA2 tunings for your particular bi-ampable main 
speaker model, check the loudspeaker’s spec sheet or documentation, or contact the speaker manufacturer as they will usually 
be able to provide this information.

If you’re unable to find polarity information for your speakers, or just want to verify your drivers are in phase, you can do some 
investigative work using a tone generator or some sine wave tone samples (which can be downloaded for free online). To 
do so, take note of the crossover frequency setting used between the drivers being tested and play a sine wave tone of that 
frequency through the system. For example, if you’re testing the woofer and high frequency driver in a bi-amped main speaker 
cabinet and the active crossover frequency between the two is set at 2.5 kHz, play a 2.5 kHz sine wave tone through the 
system. Both drivers will reproduce the tone simultaneously as long as the crossover frequency is indeed within the range of 
frequencies both drivers are capable of reproducing. You can then invert the polarity on the PA2’s high outputs and find out 
which setting provides the loudest signal (note that results are most noticeable if sound pressure levels between the drivers 
are matched). The setting which provides the loudest signal is the one which is more “in phase”. Note that if you’re using