dbx DriveRack VENU360 Loudspeaker Management System - Manual (Page 52)

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Manual System Optimization Tips
TIP: You may want to disable the HOME TIME OUT feature located in the Utility menu before performing any of
the following system optimization procedures. This will ensure the VENU360 does not revert back to the home screen
throughout the process. See
‘Home Screen Time Out’ under ‘Utility Menu’ on page 92 for more information on
disabling this feature.
1. Set Crossover Frequency & Filter Settings
The active crossover in the VENU360 is used to allow each speaker or driver in a multi-way loudspeaker systems to operate
within its frequency range limits. If you can’t find any tuning information for a particular speaker/driver, get the specification
sheet for it from the manufacturer. It can give you a good idea where to set crossover frequency settings by providing the
speaker or driver’s frequency response, which is the range of frequencies each speaker or driver is capable of reproducing.
If you’re bi-amping or tri-amping main speaker cabinets, the speaker manufacturer should be able to provide you with the
recommended crossover frequency settings, and oftentimes, filter types and slope rates. If you’re using subs and can’t find
recommended crossover frequency settings, you can dial it in by ear. Typically, subs and mains will be crossed over at around
80-100 Hz, so somewhere in this range is a good place to start. You can then fine-tune the settings from there by ear using
full-bandwidth reference material that you are familiar with. When auditioning these crossover settings, it helps to first balance
the amp levels for all drivers or cabinets to achieve a frequency response that suits your taste. When auditioning the sound
system, don’t turn it up too loud until you’ve calibrated the gain structure – more about this later.
If you’re configuring a simple full-range system then you don’t necessarily need to enter any crossover parameters. However,
it is a good idea to take note of the speaker’s frequency response spec and set a high-pass filter at the lower frequency limit
specified (45 Hz, for example). This will prevent excessive driver excursion caused by subsonic frequencies and allow for more
headroom in your amp. You’ll then want to choose a filter type and slope rate that will effectively roll-off the low end without
dramatically compromising the low-end response of the sound system (try auditioning BW 24-BW 48 filter types). Note that
the VENU360 may automatically set a high-pass filter after configuration. This is a precautionary measure and these settings
can easily be adjusted as just described. See
‘Crossover Module’ on page 84 for information on editing the crossover.
Once the crossover frequencies have been set, it’s time to set the filter types and slope rates. Determining which settings to
use here can be a bit difficult. These settings are dependent on the natural frequency response and roll-off characteristics
of each speaker cabinet or driver. The goal is to achieve a flat frequency response throughout the loudspeaker system
with seamless transitions throughout the crossover overlap regions. For example, a midrange driver in a 3-way system may
inherently exhibit a fairly gradual roll-off up into the high end, whereas the tweeter may require a steep roll-off to protect it
from over-excursion. In this case, the midrange driver can be set with a more gradual roll-off to fill in the “gap” created from
the steep roll-off of the tweeter. You can use a combination of the RTA and your ears to dial in these settings. Just make sure
you don’t exceed the frequency range limitations of the drivers. The difference between the LR and BW filter type options is
in the way they sum together. You want to select the filter types that provide the flattest frequency response throughout the
crossover overlap regions. Note that it’s okay to mix and match these filter types if that’s what it takes to achieve a flatter
system response. Also note that you may not be able to achieve a flat response at this stage of the process due to driver
alignment, polarity, and/or phase issues. Therefore, just get it as close as you can for now. For more information on LR and BW
filters, see “LP TYPE” and “HP TYPE” under the section,
‘Crossover Module’ on page 84 .
2. Set Driver Alignment Delays, Polarity, & Phase
Once the crossover frequencies, filter types, and slope rates have been set, you’re ready to optimize the system’s phase
response. All drivers in the system need to work in unison in order for the sound system to sound its best. This is accomplished
by setting driver alignment delays to make up for any physical driver offsets, matching the polarity for all drivers, and adjusting
the inter-band phase relationship (if applicable).