DBX Driverack PA

[Steve71]

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.

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.

[boputnam]

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.

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!

[Steve71]

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.

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...

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.

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.

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.