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 Post subject: The Driverack, Gain structure, and system setup information
PostPosted: Mon Oct 08, 2007 11:43 am 
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Joined: Fri Feb 17, 2006 6:01 pm
Posts: 4821
Location: Northern Minnesota
Greetings! and thanks for visiting the Driverack support forum where we delve into all things Driverack and often beyond. There is a wealth of information here at your fingertips and online so please look through the Driverack training modules(available via the link in the upper right hand corner of this site under \"Driverack Training Modules\") which will answer a lot of your frequently asked questions. You will also find some more training modules at the \"FORMER FORUM\" under \"User submitted white papers\". That is the location of the DRPA training as well as some 4000 series modules.

Please also note the link to the \"FORMER FORUM\". There you will find a search able database of items from the old forum that are not available in the search on this site. Keyword searches work best and some of the data pulled up may seem irrelevant so add keywords for better results.

OUR PURPOSE HERE IS TO EDUCATE AS WELL AS ANSWER QUESTIONS! So if your looking for us to do all the work... move on.. you won't find us willing to do all the work for you.

If your wondering what the differences between the DRPA and 260 are go here:
http://www.driverack.com/drug/attachmen ... rackPA.pdf

For broader topic support, say you need to find out what a parametric EQ is or does you might take advantage of the links I have provided below.

The first link will give you a very good idea what a crossover is, what it is supposed to do, how we accomplish this goal to tune our systems, as well as provide a host of other audio knowledge posted in a logical and informative manner


http://webphysics.davidson.edu/Applets/ ... fault.html

These links have so much information it will most likely seem overwhelming at first but if your in the sound reinforcement business it's all relevant. As you go through this stuff you will find that the more you learn the less you know.

We, the people that answer your questions are all volunteers (unless the post carries a DBX moniker) who give freely of our time but you must understand that DBX neither endorses what we provide or can be held liable for it's content. We do make every effort to insure the accuracy of what we provide, but your mileage may vary...We do not stick to a very strict protocol here and you may even notice a degree of levity, this is perfectly acceptable, and we even answer non Driverack questions from time to time. :mrgreen:

So enjoy, read and learn, and welcome. Below I will be providing some information that was put together by a team of Driverack users and designed to help answer some of the questions we get often. If your looking to have us \"do it all for you\" so you don't need to do anything you have come to the wrong place. This new technology carries with it a steep learning curve and can really make a huge difference in your systems... BUT, you need to understand what is in the unit, and what it does. The manual was NOT written to be understandable by a novice, and if you don't understand what a compressor, limiter, crossover, GEQ or PEQ are you need to go to the first two links provided and read up. Further the Block diagrams provided in the manual are good for understanding signal flow, and what the Driverack does.

Please take the Driverack (especially the DRPA) and play with all the buttons and familiarize yourself with the routing and how to navigate the unit. you cannot screw anything up so go for it! find out what EVERYTHING does! With the GUI (graphical user interface 260/240 400 series)you will be much more productive, but you NEED to be able to use the front panel buttons in case of emergency... and you can only get into the AUTO EQ function via the front panel..

NOTE: if you are using the 200 - 400 series use of the GUI for setting up the unit will greatly increase the visual representation of what you are doing, and simplify matters greatly...even if your using the DRPA/PA+ or even PX download the GUI and play with the modules.. the graphics will help you understand what is going on inside the Driverack...

Those with the 4800 series will want to download and use "System Architect" either way they are available for free download here:

Getting started....

Fist thing you will need to to do is (you can select a preset but it's good practice to set it up yourself) set up your system in the Wizard. It's simply a matter of answering some questions and telling the unit what equipment configuration you have... If your specific equipment isn't listed "DON"T PANIC" simply enter "CUSTOM" for those pieces not listed...As for the much ballyhooed amp "sensitivity" setting... don't worry about it! We will end up setting that in the Gain Structure anyway...

If you have the new PA+ after you set up the system the next thing it's going to want to do is set the system balance...STOP :!:
first you need to verify that the crossover is properly set up... So, you will want to exit the system balance and return later once we are sure that the xover is properly set up, or the balance will be useless if you do it later... Press the [preset] button... use this as a "home" key when ever you want to go to the system screen... Next press the [xover] button. This will take you to the xover pages. Here you will want to verify that the HPF (lowest frequency you want the crossover to pass to the selected speaker) is set high enough to protect your speakers (passive) and low enough to allow the the speakers to set their own HPF for most active speakers....

Now here is where amp power available becomes a determining factor for where we cross the subs and tops...(2 way systems) If we are limited by the amount of power available for the tops ( this is typically 2-4 times the "program" rating of the speaker for live sound and NO more than program rating for DJ/Disco applications...this is because most pre recorded music is HEAVILY compressed...and if you put too much power to the speakers you will let the smoke out). If you don't have the power you would be advised to raise the crossover point between the subs and the tops because lower frequencies draw more power.

This is where I think the PA+ setup wizard should go instead of directly to the system balance screen.

So, lets take a quick look at what a typical setup should look like... this presumes a standard 15" woofer and horn , and a set of subs capable of at least 45 hz (typical 18" single except for the cheapest crap out there) Set the HPF for the sub at 45hz BW 18, set the LPf @ 100 hz LR24 if you are ok power wise, or 118hz if your short on power, or if you have a 12" woofer in the tops...

It's a good idea to ALWAYS use the same crossover type on adjacent crossover points, and for simplicities sake lets also set the same frequency.. so then the HPF for the tops will be either 100hz LR 24 or 118hz LR 24 depending on what you set the subs LPF at.
(this will be reiterated below.. as this was added for the PA+)

Once you have set up what you have for equipment you need to store it as a preset...his is accomplished by three presses of the [store] button, where you identify the preset, select a location for it (usually a preset you will NEVER use.. or a convenient location will work.. remember, you cannot destroy the factory presets anyway.. a Hard Reset will restore these to factory default) (you WILL however loose all user modified presets, so always keep a hard copy of your settings on the DRPA and PX for re-inputting should you have a failure) And finally do you want to replace_____ preset (this is referring to the one you are modifying right now) ... answer the prompts and store the preset...now your ready for a basic rough-in. press the program button on the DRPA to select the program you have just set up, or the preset on the 260...also on the 260 back up your presets to a computer by exporting them. (for this procedure see the manual or one of the tutorials)

Now, if you are not comfortable with your knowledge of crossover theory, what a crossover is, what it does what a slope is and what differing crossover topologies do, you may not need to go here :


The first link I provided above. If however you could stand a refresher, or want to learn more about what we are doing I highly recommend you visit this site and learn all you can. It will really help you understand the crossover setup process. There is also a wealth of other info there about comb filtering in live sound, mixing techniques and so much more. As I have said this technology you have gotten into (driverack) comes with a steep learning curve, and an obligation to avail yourselves of the knowledge to understand the technologies at work so you can make the most of the tools provided.

The lower the point the tops are allowed to go the more power is required,(same for the subs..low frequencies take way more power than upper frequencies) and the less clarity they will exhibit in the lo mid frequencies... The higher the frequency of crossover of the sub the more honky it will sound.. a general rule of thumb is that subs should NOT have anything intelligible in them...like vocals you can understand...This is why we refer to this as a series of trade offs or compromises, Generally if your under powered, select a frequency around 100-120 hz for crossover... this usually applies to tops with 12\" speakers and under as they generally fall off quickly below that point...I generally recommend a Linkwitz Reily 24 DB / octave slope for sub to top crossover... your mileage may vary and it's very easy to experiment.. and I highly recommend you do so IF you have the time. What sounds best often IS BEST! I also generally suggest a BW 18 slope for the Hi-pass (this is the lowest point we want the subs to go) on the subs... this is the one that protects the subs from blowing up so if your under powered, or are a novice I would suggest no lower than 45 hz and 50 hz outdoors...This is the "hipass" or the LOWEST point we want the speakers to go...(This is NOT a hard and fast rule but a STARTING POINT...different speakers react differently to different crossover slopes, and they should be tuned AT the volume they will typically run...and NO the speakers sound isn't linear from soft to very loud) The subs should end and the tops should begin in the 70-120 hz point, again depending on the size of the drivers in the tops, and the power you have..the crossover region is problematic in that the area that both speakers are producing the same frequencies can cause cancellations... so overlapping the crossover point is generally a bad thing. The point where the subwoofer crosses to the tops is the lopass (highest point you want the speaker to go) Generally try and start out with the crossover gains at about 0db... Now that you have set up the crossover points...

The single MOST IMPORTANT thing you can do is set up your GAIN STRUCTURE so we will deal with that as one of our first orders of business. The Gain Structure gets all the equipment \"talking the same language\" and in the process offers the benefit of giving you a visual picture of where the system is at with regard to headroom. If you are running your system in the red all the time you are heading for disaster! Below is a general gain structure setup to give you an idea where to begin...there is MUCH more on this subject in the study hall @ the PSW (the third link provided) and the below example is a starting point for those that have never done a Gain Structure before..
Gain Structure...

note: the below was written PRE PA+ which is covered above... but the principles work well with the PA+ as well (I generally skip the auto balance step and use this method...

1. Turn amplifier(s) attenuators all of the way down to zero (fully counter clockwise), disable amplifier(s) clip limiters (if used), and disconnect the speaker cables.

2. Make sure all DriveRack dynamic processors like GEQ, Compressor, limiters, PEQ, AFS, SubSynth, etc., are disabled. We will set those things after we are roughed in...

3. Play pink noise through one of input channels of the mixer because it's consistent dynamically...(equal energy to all frequencies with a crest factor that is consistent across the full spectrum)

Note: The Binkster CD is no longer online but here is a cool tool you can download for free and play on your computer, you should be able to record a cd from this as well, they have provided a burner as well...
Click on the [Download] link it's free..

4. Set the mixer input channel fader (with pink noise) at \"unity\" (0dB). Also zero the EQ.

5. Disable the AFL(s) (after fader listen) on the mixers master output channel(s) and enable the PFL (pre fader listen) on the mixer input channel (with pink noise). If your mixer does not have these features just make sure you have no clipping and sufficient signal to not run into signal to noise problems.

6. Turn up the mixer input channel gain trim pot (with pink noise) until the meter bounces in the yellow at least 6dB below clipping. MAKE SURE THERE IS NO CLIPPING! (actually anything over 0 VU will be fine)

Note: If your mixer doesn't have PFL simply set the input gain just below the point where the channel \"clip light\" barely (occasionally) bounces on.

7. Disable the PFL on the mixer input channel and enable the AFL(s) on the mixer master output channel(s). Again if you don't have these features just make sure that your output meters are just at the clip point.

8. Slide your mixer's master fader(s) up until meter is just barely (occasionally) bounces in the red at clipping.

9. With the DriveWare GUI open (DR260) the DriveRack panel meter and then one of the mixer input dialogs (click on the \"M\"). Put the master fader at “unity” (0dB). Watch the DriveRack’s panel meter and pull the input fader up or down until the output meters are bouncing in the yellow about 3dB just below clipping. Absolutely no clipping (red) on the DriveRack’s input or output panel meters!
If you are using a DRPA you have a button on the back that sets the input sensitivity to +4db (pro level) or -10 (consumer level) if the meters on the mixer are at just clipping and your using +4 and the meters on the Driverack are anywhere above the 0vu but below the clip light your fine... there is no input mixer to adjust... If the signal is low try the -10 setting and see if that gets you to a more appropriate setting.

10. Click on the other channel’s mixer input dialog (click on the “M”), set the master fader at “unity” and put the input fader at the very same location as the previous channel.

In the DRPA, output levels are controlled by the crossover gain... this means that if your at 0db as we discussed earlier the output meters will be showing the output gain... as long as they show a decent signal this is fine... remember this is all in the digital domain so signal to noise is not as big a problem as in analog circuits... try adjusting the amps before you change the gain of the crossovers, if you cannot get the amps to clip, or your amp sensitivity is perceived to be too high... then adjust the crossover gains...

11. Make sure all speakers are DISCONNECTED FROM THE AMPS..(unplug speakers as proscribed in step #1).. modern amps have open circuit protection) Turn up the amplifier gain trim pot (clockwise) until the amplifiers red clip light barely bounces on.

12. Turn back the amplifier gain trim pot (counter clockwise) about 3dB to 4dB from the clip position. Mark this position. This position provides approximately 3 to 4dB of headroom before clipping. This is the highest the pots should ever be turned...More headroom can be achieved here by turning DOWN the control but it is NEVER to be turned up past this point!

13. Repeat steps 11 and 12 for all amplifier(s) channels driven by the DriveRack. Return the master faders on the mixer to -0- . Plug the speakers back in.

Now we have all the equipment talking the same language.. but we haven't balanced the system yet... it's most likely that one set of speakers will be louder than the other so we need to balance them before we move on... it's a good bet that the subs will be the quietest since they require the most power... put some good full range music on your system.. I like Steely Dan, Toto, Dread Zeppelin, ETC and set the input fader on the input channel on the design center( unity gain point) (this gives the best signal to noise in the analog domain) again press the PFL button and view the output meters and verify that the signal is well below clipping but above or about 0vu.. those lucky enough to have channel meters on each strip a yellow indication is acceptable..if only a two light LED is available turn up till red then turn down below clip point.. disable PFL. Turn master fader up till the system comes to life and if the tops are much louder than the subs... turn the tops amp down... get a good balance and turn the system up till near performance volume and assure it still sounds balanced...

If you intend to Do an Auto EQ please follow the \"Former forum\" link above and read the \"Tutorials\" section, and Mikey Kovachs user submitted white paper. Maje sure you have a dead flat omni directional mic for the job, like the RTA \"M\" available from DBX or better yet the TR40 by Audix...

Note: If you're planning on setting-up your DriveRack output limiters follow Mr. Dra's \"Super Duper Limiter Procedure\" (below) before going to step 14.

A. Determine the clip point of all amps by setting the gain structure.
B. After turning down the amp and marking the point where the amp stops clipping, turn the amp up to where it clips again.
C. Press the \"Comp / Limiter\" button 2 times to get to the Limiter section.
D. There is a limiter for each x-over section that it set up. For example: 2-way (Hi and lo) has 2 limiters, 3-way (hi, mid, & lo) has 3 limiters. Select the section that needs to be limited (all need to be limited).
E. For the selected output, select Over Easy as on. This gives a softer, less noticeable limiting effect. Select setting 4 as a starting point.
F. Lower the threshold until the amp stops clipping.
G. Return the amp to the previously marked spot.
H. Repeat steps E - G for all output bands.

Note: It is highly recommended to re-check the DriveRacks output limiters if the X-over gains have been changed, or if any \"enhancements\" have beem made using GEQ, PEQ, or Sub-Synth afterwards

Note: The DRPA, unlike the 260, DOES NOT have a brick wall limiter. For example: With a clip point for the amp at +20db and a limiter threshold at +17db and the limiter, depending on the use and setting of the Over Easy, may successfully reduce an output at the limiter section of a +19db input. But, if the signal spikes to +24 db. The limiter may reduce the output by 2 or 3db, but it WILL let pass the remaining peak output, which is well into, and beyond, the clip point of the amp.

Note: The DR260 can be set with a maximum \"Overshoot\". Regardless of the Over Easy setting, if the Limiter threshold is set to +17 db and the amp will clip at +20, the 260 can have an \"Overshoot\" set as 2db (or more). This feature (along with Attack and Hold time settings) will take a +24db signal that will be limited, starting at +17db, then at +19db the 260 slams the door and lets nothing more pass. The amp will never clip, if proper gain structure and limiter setting techniques are observed.

14. Bring mixer's master fader(s) all the way back down to off, re-enable your DriveRack’s dynamic processors, re-enable amplifier(s) clip limiters (if used), and reconnect the speakers.

Note: It is highly recommended to re-check the gain structure and output limiters if the X-over gains have been changed, or if any \"enhancements\" have been made using GEQ, PEQ, or Sub Synth afterwards. It is also recommended to keep the amplifier's clip limiters disabled If using the DriveRack's output limiters.

More to come folks, thanks to Kevin and Dra for their efforts on this work. If you have any corrections, concerns, additions, or comments please feel free to PM me

Now, go to the FAQ section right below this and find out why all this works the way it does...

Here is a good progression of things to read next:

Be well, and good luck!

We the few, who have done so much for so long with so little now feel we can do anything with nothing!

There is no surer way to ruin a good discussion than to contaminate it with facts

I'm not an everlasting fountain of information but perhaps much more an unstoppable leak

2, BLOWN Galaxy Hotspots, with MCM audio select replacement drivers!

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