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Thread: DBX Driverack PA

  1. #31
    Moderator / Treasurer/Marketplace Czar boputnam's Avatar
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    Quote Originally Posted by Steve71 View Post
    Sure you can, but since it's done in the digital domain, it's unless for setting up correct gain structure (unless you already happen to be in the ball park). IE it does nothing to reduce the noise the DRPA adds to the chain.
    Obviously it's in the digital domain. And, there is nothing you can do about the unit "noise" - if you're using that unit, you accept it's offerings.

    Dood - I don't have the manual in front of me, but memory serves there is +/-12 dB on each band pass, allowing a 24 dB relative gain differential between band passes. That should be plenty? I sincerely doubt few systems are so far "out of the ball park" that this would not be enough. dbx aren't dummies in this. I was merely pointing out that your comment was limited in it's scope - it did not acknowledge there is ample gain accommodation, by band pass, available on-board.

    Quote Originally Posted by Steve71 View Post
    And while the auto EQ function is far from perfect, it's not a bad starting point.
    Bad starting point, and bad idea. If one is embarking into this arena, you are accepting the responsibility of needing a greater understanding of what is going on, and should learn how to work with the acoustic animal you are facing. Get some proper measurement equipment and knowledge - neither is too expensive nor arduous. You can get a LOT more out of this unit by limiting it's auto-functions. That said, I merely know how to run them - I run into them frequently, but own zero of these.

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    Quote Originally Posted by boputnam View Post
    Obviously it's in the digital domain. And, there is nothing you can do about the unit "noise" - if you're using that unit, you accept it's offerings.

    Dood - I don't have the manual in front of me, but memory serves there is +/-12 dB on each band pass, allowing a 24 dB relative gain differential between band passes. That should be plenty? I sincerely doubt few systems are so far "out of the ball park" that this would not be enough. dbx aren't dummies in this. I was merely pointing out that your comment was limited in it's scope - it did not acknowledge there is ample gain accommodation, by band pass, available on-board.
    jerry_rig said he was using an amp without gain controls, which I assumed to be a consumer amp. If it was a pro amp, then my comments don't apply. However assuming JR was using a consumer amp, we have a potential problem which could well account for the sub par sound quality.

    So in the context of JR setup, I'm talking about global gain, not relative gain between individual band passes. The outputs on the dbx (+4dbu) will overdrive the inputs on a consumer amp (-10dbu). To overcome this your only option, sans gain controls on the AMPS, is to use the dbx's digital gain controls. Now you've just reduced your s/n ratio by 14db. Not to mention the reduction in resolution on the d/a conversion. Another option would be to turn down your pre amp 14db, but that isn't going to change the s/n ratio as it's fixed in the case of the dbx. And now you've just messed up the a/d and the d/a conversion.

    Quote Originally Posted by boputnam View Post
    Bad starting point, and bad idea. If one is embarking into this arena, you are accepting the responsibility of needing a greater understanding of what is going on, and should learn how to work with the acoustic animal you are facing. Get some proper measurement equipment and knowledge - neither is too expensive nor arduous. You can get a LOT more out of this unit by limiting it's auto-functions. That said, I merely know how to run them - I run into them frequently, but own zero of these.
    This is just a hobby for me, but I do have an Electrical Engineering Degree so I'm not exactly in the dark here. And I agree the auto eq is no free pass, you still have measure if you want to get the most out of the unit. However you can get good results with the auto eq and a little tweaking. Just don't do a single pink and expect it to be right. Don't forget you can also use the RTA monitor function with a PC as a white noise generator and move the mic around the room to get an idea of what's what.

  3. #33
    Moderator / Treasurer/Marketplace Czar boputnam's Avatar
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    Quote Originally Posted by Steve71 View Post
    jerry_rig said he was using an amp without gain controls, which I assumed to be a consumer amp. If it was a pro amp, then my comments don't apply. However assuming JR was using a consumer amp, we have a potential problem which could well account for the sub par sound quality.

    So in the context of JR setup, I'm talking about global gain, not relative gain between individual band passes. The outputs on the dbx (+4dbu) will overdrive the inputs on a consumer amp (-10dbu). To overcome this your only option, sans gain controls on the AMPS, is to use the dbx's digital gain controls. Now you've just reduced your s/n ratio by 14db. Not to mention the reduction in resolution on the d/a conversion. Another option would be to turn down your pre amp 14db, but that isn't going to change the s/n ratio as it's fixed in the case of the dbx. And now you've just messed up the a/d and the d/a conversion.
    There is nothing in jerry_rig's post to suggest he was using "consumer" stuff - in fact he stated he was using a pre-amp, and he did not mention any issues of overdriving his amps. He seems plenty savvy, and made a good decision based on his sonic preferences.

    Quote Originally Posted by Steve71 View Post
    This is just a hobby for me, but I do have an Electrical Engineering Degree so I'm not exactly in the dark here. And I agree the auto eq is no free pass, you still have measure if you want to get the most out of the unit. However you can get good results with the auto eq and a little tweaking. Just don't do a single pink and expect it to be right. Don't forget you can also use the RTA monitor function with a PC as a white noise generator and move the mic around the room to get an idea of what's what.
    Good for you. I have an MS in other stuff, but I haven't hung it on the wall in some time... Anyway, I stand by my experiences with this unit and reiterate what I said: Do not use the auto EQ, especially if you have no means to measure what it is doing and what it has done. Without those tools, you really shouldn't be using this level of gear anyway. If one is going to this level, get the requisite gear to measure what is happening in the acoustic (and time) domains, and how much, and how little, you can do about it. It's fun!



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    Quote Originally Posted by boputnam View Post
    There is nothing in jerry_rig's post to suggest he was using "consumer" stuff - in fact he stated he was using a pre-amp, and he did not mention any issues of overdriving his amps. He seems plenty savvy, and made a good decision based on his sonic preferences.
    The issue is not over driving the power amp. This quote below from JR tells us all we need to know. IE gain structure was not set up correctly - end of story. Now without more details I can't if that's 100% to blame for the SQ issues JR was experiencing. Maybe it really does sound sub par compared to the other crossover, but until we setup both crossovesr correctly, we'll never know.

    Quote Originally Posted by jerry_rig View Post
    All lights on the dbx indicated very low operating levels. As I recall only the first level was lit up. Note that the crossover is being used to match a pair of 2235s to my other speakers. All are driven from the same pre-amp and the low-end power amp does not have attenuation, so I don't have much flexibility to push (or limit) signal strength at the crossover. It is what it is...


    Quote Originally Posted by boputnam View Post
    Good for you. I have an MS in other stuff, but I haven't hung it on the wall in some time...
    No need to be patronizing. I mearly mention my degree since (1) it's very relavent to the subject at hand and (2) unlike you I don't have a career in the industry.

    You work in the industry, that's enough for me to know where you're coming from. MS in 'other stuff' isn't relevant to the discussion.

    Quote Originally Posted by boputnam View Post
    Anyway, I stand by my experiences with this unit and reiterate what I said: Do not use the auto EQ, especially if you have no means to measure what it is doing and what it has done.
    The auto EQ / RTA should be no better or worse than any other auto eq/rta. It's just a tool and is subject to the limitations of that tool. IE room modes and mic calibration. If there is some inherent fault in the dbx's RTA function, I'm all ears.

    Quote Originally Posted by boputnam View Post
    Without those tools, you really shouldn't be using this level of gear anyway. If one is going to this level, get the requisite gear to measure what is happening in the acoustic (and time) domains, and how much, and how little, you can do about it. It's fun!
    No argument there and obviously there is much more to speaker design than slapping a bunch of drivers together and pushing the RTA button.

    In your line of work, getting uniform response for the entire room is important so I'd imagine the RTA to be less than useful. But for the 'audiophile' sitting in the sweet spot I've found it to be very useful as a starting point. As I'm sure you know getting a good result for a single spot is a hell of a lot easier than for a whole room.

    I've purchased an emu 0404 and will be getting my mic calibrated soon. So at some point in the future I'll be doing a bunch of measurements to fine tune the setup. I've also purchased a Beginner dcx (for use in a IB sub setup) so might even get the chance to compare the two.

  5. #35
    Senior Member jerry_rig's Avatar
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    Again, please do not take my comments as a serious review of the DriveRack PA. Just FYI, my "consumer amp" for bass duty is a Krell KSA 300s (recently refurbished at the Krell factory) and I seriously doubt it -- or an incorrect gain structure -- had anything to do with my experience. The system and front end are extremely revealing and I would certainly be aware of anything amiss, gain-wise.

    Look, the DR could well be an excellent unit for many users. And in some ways I wish that I had its flexibility in an analogue x-over. Peace.

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    Quote Originally Posted by jerry_rig View Post
    Again, please do not take my comments as a serious review of the DriveRack PA. Just FYI, my "consumer amp" for bass duty is a Krell KSA 300s (recently refurbished at the Krell factory) and I seriously doubt it -- or an incorrect gain structure -- had anything to do with my experience. The system and front end are extremely revealing and I would certainly be aware of anything amiss, gain-wise.

    Look, the DR could well be an excellent unit for many users. And in some ways I wish that I had its flexibility in an analogue x-over. Peace.
    Hey JR, thanks for chiming in with a bit of more info.

    As for doubting the gain structure wasn't contributing to the degradation in sound quality... well all I can say is that the lights on the front of the dbx DR PA range from -30 to +20dbu. If you were only hitting the -30dbu light on peaks, then there was (potentially) 50db of signal range you weren't using.

    So even if we were to ignore the potential degradation of quantization in the D/A process, you've just reduced the drive racks s/n ratio by 50db! That is significant especially since the the DR only has a s/n ratio of 95db to begin with.

    In other words the DRPA you tested had a S/N ratio of 45db due to the way it was setup. I do understand that you're not touting your experience with the DRPA as all encompassing. However you can't say, in the same breath, that the krell and/or an incorrect gain structure had nothing to do with your experience. To say that is to not understand gain structure.

    There is nothing wrong with the Krell amp I'm sure, but it's simply the wrong tool for the job (at least the way it was being used). The amp quality is really of no significance when it's fed a by a crossover with a s/n ratio of 45db.

    Please don't take this as argumentative, or criticism of your equipment. It's simply just matter of fact. Get those lights dancing (without clipping) and then, and only then, we can make a fair comparison.

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    Moderator / Treasurer/Marketplace Czar boputnam's Avatar
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    From Rane's web site on setting sound system level controls.

    Correctly setting a sound system's gain structure is one of the most important contributors to creating an excellent sounding system. Conversely, an improperly set gain structure is one of the leading contributors to bad sounding systems. The cost of the system is secondary to proper setup. The most expensive system set wrong never performs up to the level of a correctly set inexpensive system. Setting all the various level controls is not difficult; however, it remains a very misunderstood topic.
    http://www.rane.com/note135.html

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    Rane....!? you've dragged this piece of crap Driverack out to ad nauseum, and now you are quoting techspertise from RANE!!!? The poor man's Behringer?! There are very few "pro" devices of any sort than can corrupt the signal chain merely by pushing the "in" button without actually using the device's features...Rane makes most of them....

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    Quote Originally Posted by Tim Rinkerman View Post
    Rane....!? you've dragged this piece of crap Driverack out to ad nauseum, and now you are quoting techspertise from RANE!!!? The poor man's Behringer?! There are very few "pro" devices of any sort than can corrupt the signal chain merely by pushing the "in" button without actually using the device's features...Rane makes most of them....
    Are you suggesting that the quote from Rane is incorrect? If so please enlighten me. Lets avoid the straw-man argument please - correct what was said, don't just discredit who said it.

    Can you honestly say that Jerry Rig had his gain structure set correctly? Did I make a mistake with my 45db s/n calculation?

    I'm more than willing to eat my words, but I'll need some facts please, not just a 'because I said so'.

    And once again, in case you missed it the first time, I'm not suggesting that the dbx is the be all, end all. I'm just pointing out that the comparison was invalid due to the incorrect implementation.

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    Quote Originally Posted by Tim Rinkerman View Post
    Rane....!? you've dragged this piece of crap Driverack out to ad nauseum, and now you are quoting techspertise from RANE!!!? The poor man's Behringer?! There are very few "pro" devices of any sort than can corrupt the signal chain merely by pushing the "in" button without actually using the device's features...Rane makes most of them....

    I would never consider Rane "the poor man's Behringer" Maybe not my first pick but still way better than Behringer.

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    Senior Member SMKSoundPro's Avatar
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    I have read this thread, and although I have a dbx 260, software and serial cable for my laptop, I have not installed it anywhere. The more I read online from people that work in the pro audio world, the less I want to use it.

    That being said, I am currently doing some service work for one the mom/pop pro sound and lighting companies here and have received a sound rig that they send out on raves and other dj gigs that uses a dbx 260 and two qsc mx1500 amps to power four EVSx500s atop four EV eliminator single "subs."

    I viewed the settings programmed by the architect of this setup and while running pink noise through it and using the dbx condenser mic for it, have realized that the this unit is fine for its use, but not for me. My bar manager boss was looking over my shoulder and saw my laptop plugged into the rig and thought "ooooohhh coool!" then I reminded him that we come from the record groove analog world and this dbx device apparently is not "exactly" garbage in = garbage out. He asked why "we" don't have them installed on all of our sound systems to keep the dj's from chewing up gear, and I explained that with all of the different stuff we have going on, its easier to reach over and grab a knob and twist it like our fathers did. He instantly understood and left me alone to figure these settings out.

    Bottom line.
    Thank you to dbx and all of the designers of DSP products, but using these seems to go against my signature line posted below.

    Merry Christmas and Happy Holidays to all!

    Scotty.
    One step above: "Two Tin Cans and a String!"
    Longtime Alaskan Low-Fi Guy - E=MC▓ ▒3db

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    Senior Member 1audiohack's Avatar
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    I have four of the DBX 260's and for the money I think they rock. The more capability you load into something the more chances you give someone to make a disaster. There is a lot you can do wrong with them, and a lot you can do right. To make a blanket statement like "they suck, are noisy, kill all the dynamics" and so on indicate to me that something in the setup/ configuration / system is wrong and the owner / operator does not have the knowledge or patience to figure it out. It's pretty amazing what a knowledgable person with some real measurment gear can do in a hurry with one of these. With out the above mentioned assets it's almost gauranteed to be trouble.

    The statement that Rane is the poor mans Berhinger is just bullshit.
    If we knew what the hell we were doing, we wouldn't call it research would we.

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    Quote Originally Posted by 1audiohack View Post
    The statement that Rane is the poor mans Berhinger is just bullshit.
    You said it in fewer words than I did and a more to the point!

    As for the DBX 260, good units, a huge step up from the Drive Rack PA. The only thing I would not use on them is the auto eq.

  15. #45
    Senior Member 1audiohack's Avatar
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    Quote Originally Posted by Mike Caldwell View Post
    As for the DBX 260, good units, a huge step up from the Drive Rack PA. The only thing I would not use on them is the auto eq.
    Yup! Auto EQ, trouble for the unknowing with the push of a button.
    If we knew what the hell we were doing, we wouldn't call it research would we.

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