Understanding the Driverack PA - dbx

Understanding the Driverack 260
First, let’s look at the main Program screen.
This picture shows the Preset # and name for the currently selected preset. If “Not
Loaded!” is displayed at the bottom of the diplay, the ENCODER must be pressed in to
load the currently selected program.
This screenshot shows the inputs and outputs of the program screen.

Here is a breakdown of the components in the Driverack 260.
If at anytime you want to come back to this main program screen just press the
PROGRAM button. Think of it as a kind of “Panic” button.
The below screenshot is a typo in the manual. This is actually a screenshot from the
Driverack PA and will never be displayed in the Driverack 260.

Configuration Mode
The Driverack 260 has a CONFIGURATION mode that enables you to go in and
change the internal routing of the signal, link/unlink processors and select different
processing blocks. This gives you much more control and many more configuration
options over the Driverack PA.
In order to perform the below procedures, it is recommended that you familiarize
yourself with the navigation of the Driverack 260. Please see the owners manual for more
information on navigation.
When setting up your system the procedure order is as follows:
1. Set the x-over points, slopes, driver alignment delays and post x-over PEQs
(optimizes your speakers, but doesn't take the room into account). These are usually
available from the speaker manufacturer. If your speakers were selected in the WIZARD
these settings will be set for you automatically (do not go back into the x-over and change
these settings if you are unsure of what you are doing). If you use passive (full range)
speaker cabinets you shouldn’t have to worry about any PEQ settings, but you may want
to set a high pass and possibly a low pass filter if needed (look at the frequency response
of the speakers).
2. Set the gain structure (optimizes your signal to noise ratio and helps prevent
clipping). This includes setting the gain of each device (in this case the Driverack and
amps) and the output limiters. If you selected your amps in the WIZARD, the x-over
(output) gains and limiters will automatically be set. Do not go back into the X-over or
Limiter and change the settings if you are unsure of what you are doing.
3. EQ the system (tune your system to the room). Use the Auto EQ function to tune the
system to the room. Some fine tuning will likely be needed. Fine tune gain structure to
take the EQ gain into account.
4. Ring out the system using the AFS (feedback suppression) to eliminate feedback.
5. Add extras to desired taste. This includes the Subharmonic Synth, compression, etc.
1. X-OVER & PEQs
If you selected your speakers in the Setup Wizard, the Driverack will
automatically set your x-over parameters, driver alignment delays and PEQs. If your
speakers are not in the Wizard, you should select “Custom”. You will need to obtain the
recommended x-over settings (and other speaker tuning info, if available) from the
speaker manufacturer. There are some tuning programs available for download. Please
check the dbxpro website to see if your tunings are available for download. You will have
to use the provided Driveware software to load these programs into the 260. If you use
passive (full range) speaker cabinets you shouldn’t have to worry about any PEQ settings.
If the subs are not lined up with the mains, driver alignment delay may be needed.

2. GAIN STRUCTURE & LIMITER
By properly setting the gain structure, your signal to noise ratio will be optimized
(your system will be as quiet as possible) and you can minimize the possibility of
clipping any components in your system. Make sure that your amplifiers are properly
rated for your speakers before proceeding. If you are unsure, contact the speaker
manufacturer. If you selected your amps in the Wizard this has already been set for you.
If not, please proceed. Make sure to select “Custom” for your amps when you run the
SETUP WIZARD. Make sure that all the dynamics processors (limiters and compressors)
and the graphic EQ are off before proceeding. Unplug your speakers from your amps.
Most solid state amplifiers will not be damaged when operated without a load connected.
If you are unsure, contact the amplifier manufacturer. Keep in mind that the amp may
clip slightly sooner when the load is connected, so make sure to leave a “cushion” of
headroom. If possible you can use a dummy load to get a more accurate reading. Make
sure that your output limiters are off before proceeding. Run pink noise through your
mixer (from a cd or generator). Set your CD (pink noise source) channel to unity gain.
Bring up the master faders on the mixer until you barely clip the mixer. If you can’t clip
it, bring up the channel fader. If you still can’t clip the master section, try raising the gain
or trim pot slightly. Now adjust your mixer to just under the clip point. Now adjust the
inputs of the next device (for the sake of this document, this will be the 260) until you are
just below the clip point. If your amplifiers have a voltage sensitivity switch, set them to
around 1.4 Volts. Now, select one of your amps to start with and set the attenuator so that
it just clips, then back it off so that the clip indicator just goes out. Now lower it slightly
to provide a little extra room to compensate for there being no load connected. Mark this
setting with a piece of tape or something that will not permanently mark the amp. Now
turn the amp attenuator up until the clip indicator just lights again. Go into the Limiter,
for the outputs that you are currently working with, and turn it on. Set the Overeasy
setting to “off”. Set the limiter Threshold so that you no longer clip the inputs of the amp.
Now set the attenuator back to the mark that you made earlier. Repeat this process for all
other amp channels in the system. Turn your mixer down and your amps off. Reconnect
your speakers, turn your amps back on and try running some music through your
speakers. You should not be continually hitting the limiter when you are running your
system at performance level, which should be unity gain (0 VU on your mixer). If you
do, go back and redo the gain structure process. The limiters should only be triggered by
the peaks. You will want to then adjust the attenuators to achieve as flat of a frequency
response as possible before you run the Auto EQ. Make sure that you turn down
attenuators (you don't want to set the attenuators past the mark that you made earlier). So
for example: If you don't have enough low end, turn down your mid and or high amps. If
you are using powered speakers you will need to know what the maximum input of the
powered speaker is. The maximum output of the Driverack PA is 20 dBu (about 7.75
Volts).You would have to find out how much attenuation is needed on the amp/speaker
so that an input of about 7.75 Volts (20 dBu) would be just under the clip point of the
amp.

3. GRAPHIC EQ
If you have the optional RTA microphone, you can use it to tune the system to the
venue. If you have set the gain structure properly, when your system is at unity gain
throughout, you will also be at the desired performance level. So, this means when you
run the AutoEQ, you should reach the desired performance level when the Driverack
260s output levels are around 0 to +5 dBu (they may be slightly below this due to x-over
and speaker tuning settings). Just make sure that the outputs aren’t really high before
running the AutoEQ function. You need to leave some headroom available for the EQ to
make it’s adjustments.
Microphone placement can be a big issue. If running both sides at once, place the
mic out approximately the same distance as the speakers are apart. Place it so the distance
between the mic and either speaker is the same. You don’t want there to be a time delay
(one speaker being further from the mic than the other). You could also try placing the
reference mic directly on the floor. This can have a big effect on frequencies near 250Hz.
You may want to try running the pink noise out of only one side, so that you are not
trying to compensate for the comb filtering effects of the two speakers combined.
There are a few different response curves in the Auto EQ. Usually, response 0
(flat) is a good place to start, but may require some fine tuning. If you plan on running
your system at loud levels, you will want the response to be more flat. If you are running
the system at lower levels, you may want to use one of the other response curves that
contain a low and high boost. You may want to set the lower frequencies (from about 100
Hz down) closer to flat after the Auto EQ completes. This is usually a better choice
because EQing these lower frequencies are going to affect other listening positions in the
room anyway. Unfortunately, you cannot make every listening position in the venue have
the same low frequency response. Since you cannot EQ non minimum phase problems,
any bands that are boosted or cut more than 6 dB should be brought back closer to 0 dB.
You may want to fine tune the higher frequencies by ear. There is a natural high
frequency roll-off that occurs as the distance from the source (speaker) increases. If you
boost the high frequency bands too much, you run the risk of distorting your high
frequency drivers (running out of headroom) and/or deafening the people in the front
row. You may want to experiment with the other response curves to see what sounds best
with your style of music and at different system levels. However, typically you want your
speaker system to not introduce its own color on the sound, so a response setting of “0” is
usually a better choice for live sound. You will need to experiment to find what works
best for your application.
A precision setting of “LOW” will finish the fastest, but will not be as accurate as
a “HIGH” setting. Sometimes a setting of “MEDIUM” or “HIGH” may take a long time
or never finish because the acoustic environment may be too complex or ambient noise
may be impeding the process. The “LOW” setting should be acceptable for most
applications and will get you up and running the fastest. The LOW setting also has
convergence criterion that allows more bands to be off. Use this settings if the Auto EQ
does not finish or you want a first cut of the EQ. You can always "freshen up" the eq
settings with a subsequent Auto EQ procedure - it will pick up where it left off.
There can be many circumstances where the AutoEQ will not work. AutoEQ can
only fix the problems that EQ can fix - if there are speaker placement, gain structure,
xover, speaker presets, time alignment issues etc, AutoEQ will not be able to tune the

system. If AutoEQ is not consistently converging, look at the rest of the system - there
may be issues with the setup that Auto EQ can not address. AutoEQ does best when it
only has to compensate for room resonance. Tuning your speakers is best done with the
x-over/PEQ/alignment delay. If the display reads "not done", take a look at the EQ
settings after you have run the Auto EQ. It will tell you which frequency region you are
having problems with. If it's around the x-over point, then you have most likely
improperly set the x-over settings. If the problems are in the lower frequencies, it could
be caused from room modes or lack of low frequency response in your system. If it is the
high frequencies it could be that the mic is placed too far away and trying to boost the
extreme high frequencies (the Driverack PA cannot take a systems natural high frequency
roll-off into account).
If you do not have the optional RTA microphone, you will have to go into the
GEQ and fine tune the system manually by ear using a music CD that reproduces all
frequencies that your system is capable of reproducing. You will most likely need to fine
tune the gain structure to compensate for any EQ adjustments. Keep in mind that you do
not want to alter the overall balance between the low, mid and high drivers.

4. AFS FEEDBACK SUPRESSOR
Run the AFS Wizard to ring out the system and achieve more gain before
feedback. There are two modes or types of filters in the AFS. These filter types are
FIXED and LIVE. Keep in mind that it is very important for the systems gain structure to
be properly set for the AFS to function properly.
The FIXED filters are used as permanent notch filters and the LIVE filters will be lifted if
one of the below conditions are met:
1. Expiration of a period of time that is pre determined by the user (LIVE filter lift
setting).
2. All filters are used and begin to round robin (lifts the first LIVE filter set to use it at
another frequency location). Chances are if this problem persists and begins to loop, then
you need to turn down the gain at your mixer.
3. The unit is power cycled.
You will want to do a quick sound check on the microphones first. Get them as
close to the desired performance level as possible before feedback occurs. Make sure to
use proper gain structure techniques for adjusting the individual mixer channels. You can
start with 6 FIXED and 6 LIVE filters. Select the desired notch filter size. The selections
range from SPEECH, which have the broadest Q factor to MUSIC HIGH, which have the
narrowest Q factor. Speech will be the most audible and may not use as many filters to
eliminate the feedback. Music High is the most inaudible, but may use the filters up
faster. You will have to find a happy medium when selecting the width of the filters. Now
with no signal going to the mics, but with the mics active, slowly bring up the master
fader(s) on your mixer until you reach the desired performance level (probably around
0dB on your mixer’s master fader, assuming your gain structure is set properly). You
may want to push the master fader(s) slightly above 0 VU so that you are not right on the
verge of feedback when set to unity gain. If you run out of FIXED filters, go back and
allocate more filters as FIXED and repeat the process. If you still can’t eliminate the
feedback and don’t have many more FIXED filters to set, try setting the filters to a
broader Q (such as Music Low). If you don’t use all of the FIXED filters, you can go
back and designate more of the filters for LIVE and repeat the process. Once you are
done the unit will automatically enter LIVE mode.