Presonus StudioLive 24.4.2 and DBX Drive Rack PA- Some RTA Questions

Photovor

New Member
I currently have another thread going about how we're temporarily relocating our sound booth soon, but it's caused me to look back at some other things that I'd like to tidy up and get taken care of.

We have a StudioLive 24.4.2 that has it's main out connected to a DBX Drive Rack PA. Before the StudioLive soundboard showed up on the scene, we had a old Mackie that was connected to the DBX. We had used the DBX to pink the room and get an EQ that somewhat worked to prevent feedback. So the EQ and Feedback modes are enabled on it. We haven't done any other changes or tuning to the DBX.

When we got the StudioLive, it was connected to the DBX, with no changes. Firmware updates came along for the StudioLive that then added the RTA and Smaart Wizards. We've made some small adjustments to the Global EQ on the main mix in the UC software, but those adjustments are still on top of whatever the DBX is also doing.

I was wondering if we should take the DBX out of the mix and properly run the Smaart Wizards to pink the room and allow the board to do all the work. I feel like whatever we're trying to do on the board, the DBX is probably just getting in the way, as we basically have 2 EQs in the chain. Our sound lacks a lot of depth because of this, and we have a hard time adding more volume without feedback.

Just looking for some feedback (no pun intended) or recommendations on some corrections that we should make.
 

TimMc

Well-Known Member
Premium Member
In general, one does not re-optimize the sound system unless loudspeakers have been moved, added, or removed.

The dbx unit is a "system controller".... Once set, it should not be necessary to make changes.

I'd trust dbx long before I'd trust Personus. Also using "wizards" and "auto eq" are generally ways to achieve suckiness, or mediocrity (at best but).

Probably not what you wanted to hear.
 

Photovor

New Member
In general, one does not re-optimize the sound system unless loudspeakers have been moved, added, or removed.

The dbx unit is a "system controller".... Once set, it should not be necessary to make changes.

I'd trust dbx long before I'd trust Personus. Also using "wizards" and "auto eq" are generally ways to achieve suckiness, or mediocrity (at best but).

Probably not what you wanted to hear.
I'm completely open to any feedback, snarky (yours wasn't) or otherwise. The wizards on the presonus are the same as doing a pinking with the DBX RTA, but it (being the presonus) allows for a more granular adjustment, from my understanding. On the presonus, we have individual channel EQs, and a global EQ, then that's all being patched over to the DBX which is applying another EQ on top of everything. Just seems to be too much. When I flatten the global EQ on the presonus board, we're more likely to have feedback issues in the higher ranges. I would think the DBX should be taking care of that with its EQ and feedback eliminator, but it's not. So just trying to figure out what I need to do in this case. Seems funny to have 2 full EQs in the line. The DBX is designed specifically for this type of thing, so I'd want to trust that over the Presonus, but...)
 

Aaron Becker

Well-Known Member
I've always been a fan of an independent, standalone, locked down, access controlled, system master controller/DSP. aka - your DBX. For me, it offers a level of system protection (limiters and compression) as well as crossover control. I don't like end-users (volunteers, untrained staff, staff from other departments, etc) monkeying with system global settings, because, well, they shouldn't be.

While the advances of digital systems are great, I still like having an independent system for the system control - EQ, crossovers, tunings, limiters, etc. Obviously, this doesn't idiot-proof the system, and doesn't stop all feedback, but it prevents someone from being "helpful" by changing global settings that were likely programmed by someone who knew what they were doing and had the tools to do it correctly. No matter how high the end-user pushes up the mains, or how loud they turn up the low freqs on the master EQ, the DSP will protect the speakers and amps from clipping (if they were set up correctly).

If someone wants to use the global master output EQ on the console for coloring specifically to a specific show, or further tune for a show-specific sound, I'm not opposed to that, but generally speaking, house control systems (DSPs) are designed to be left alone, providing the heart of the "even" sound throughout the room. It also provides a benchmark if the console is swapped out, someone wants additional line-level inputs directly to the mains (a road show wants to go direct into the system DSP), etc.

Might be some opinion, but I like having a standalone DSP.
 

TimMc

Well-Known Member
Premium Member
@Photovor - I guess I'm not understanding why it's necessary or desirable to "pink" on a routine basis. The reason you will find different results when you repeat wizard or autoeq is due to changes in placement of the measurement mic or the introduction/removal of other objects that reflect or resonate, within the measurement field.

Think about feedback as a loop (because that's what it is) and that loop has a frequency based on the physical distance between the microphone and speaker. When gain gets high enough to create a self-sustaining loop, changing the distance will change the frequency of the feedback. Note that his has nothing to do with pink noise... ;)

When I mix musicals I use multiple layers of EQ. The system EQ is usually a black box that I can't change so I have a master EQ on the outputs of the console (or each zone mix) that "voices" the system or zone; next up is a "group" or "submaster" EQ, typically I have male & female chorus groups, male & female lead groups, foot/hanging mic groups, orchestra, etc (as needed). Each group's EQ is used to control peaky response and potential feedback with the many open mics, but only 3 or 4 frequencies as much more EQ tends to hurt more than help. That all leaves the channel strip EQs for voicing the actor's mic or whatever the input is - it's your artistic control. Each step in the signal chain has EQ that is used for its own purpose. Trivial on digital mixers, this required lots of outboard gear back in Ye Olde Analogue Dayz. I still own some KT DN410 and DN405 parametric EQs...

A real time RTA can be useful and that is why Behringer, Presonus and other mixer manufacturers are including them in the EQ screen overlay. One should not, however, make ill advised changes based on what one sees; save those changes for basing on what one hears. /nudge, wink
 

Photovor

New Member
I'm not suggesting that we pink the room on a routine basis. It's been at least 7 years since the system has been reviewed, and we've recently moved the power amps to a new location and overall system volumes have changed as well. I also know for a fact that when the last pinking was done, the RTA mic wasn't placed in the best location either. We'd like to increase the overall sound again, and I thought this would be a good opportunity to re-pink the room correctly. I was trying to get a feel if using the Presonus to do it was a better idea (or more capable, since the DBX has been discontinued for many years now), or if we should just stick with the DBX. I also was trying to get a feel for having a global eq on a mixer, then an eq on the DBX, if that was a best practice.

Would anyone recommend flattening the global EQ on the mixer, and just fine tuning or mic or input channels to achieve the same effect? We've also been trying to get more low end out of the system, but looking at the EQ on the DBX, the low end is nearly gone.
 

TimMc

Well-Known Member
Premium Member
Would anyone recommend flattening the global EQ on the mixer, and just fine tuning or mic or input channels to achieve the same effect? We've also been trying to get more low end out of the system, but looking at the EQ on the DBX, the low end is nearly gone.

The lack of LF in the dbx EQ is either the result of bad AutoEq/Wizard stuff or was done manually, probably because of significant LF feedback from actor body mics, or other system uses were killing LF drivers. Fixing the former scenario involves input gain staging, input HPF and group EQ; fixing the latter with EQ was easier than fixing the human problem.

System DSP/controllers are used primarily to help "fit" the system to the room, they can also help address, but do not definitively fix the variety of issues that come up with different uses of the system - that is domain of the operator of the sound mixer.

Teaching system EQ & optimization can't be done in a few forum posts and thus far it sounds like that needs to be addressed before we discuss EQ techniques applied at the console. I'm hoping that an experienced forum member near Altoona will volunteer to help you out; the closest person I know is in Berwick (Jeff @ Cobra Sound, and he doesn't owe me any any favors at the moment).

In short, defeating the dbx EQ is like a carpenter throwing away his hammer although I can see why hitting 'bypass' makes your immediate problem seem more correctable at the mixer. Fix the dbx EQ problem first. Resist the temptation to brute force more LF with the console EQs.

Flattening the mixer's output EQ? If you'd hired me to be your operator I'd start with that by default, especially if it had every band adjusted (and many of them radically so), but I've got 35 years in audio to bring to table... take a look at it and ask yourself "does this look like it was done by random monkeys?" If so starting over may be a better option.

This brings me back to the feedback issue and gain staging. We have this issue where *system* sensitivity is usually fairly high and it gets coupled with a human tendency to turn up stuff until the red lights come on. IOW, often I find input strip gains set far higher than needed (gee, the red light only flashes sometimes!). That results in feedback when fader moves are above, say, 20% from the bottom of travel so the next human tendency is to grab the EQ knobs or sliders and start changing things. Turning down the input trim by -6dB would give a better starting point...

If this is a typical public school installation with some age on it there may well be other issues contributing to the problems you're experiencing and will make it difficult to offer corrective advice in this forum. My suggestions and comments are based on having a system that is reasonable well set up to start with, that is fully functional and maintained.

edit comment - I see in your other post this is a house of worship and that a volunteer member electrician did much of the installation. There may well be some more "interesting" things you've yet to find... but it also goes a long way to explaining why the DriveRack has the LF squeezed out - it was the fastest, easiest guaranteed way to get rid of the LF feedback from the pastor's lavaliere mic.

Good luck, and we'll continue this discussion as you get further into the process of correcting the underlying problems.
 
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Photovor

New Member
@TimMc thanks for the great response. We've had our presonus board since 2012, and we had a close sound guy do the install, do a pink of the room and set the channel EQs, and fix a few other cable termination issues. That was able to fix a tremendous amount of issues that we were initially having with our previous board, a Mackie 32 channel that was second hand and had bus B burned out.

The electrician comments go back to when the church was first built. I don't believe he did any of the actual audio board install, just the speakers and cable runs. Tiny individual holes were drilled for each xlr cable that run under the staging area through joists, and they were mounted in metal single gang electrical boxes that were nailed to the joists, with MC cable connectors acting as the strain relief. Oh yeah, they also used metal staples to hold the wires along the floor joists too. Then they used a surface wall mount place as the cover for the floor box. So you have jacks sticking up, etc. But the metal boxes and wiring kills me. Can't do any new runs and it's impossible to pull any new wires the way things were built. That's just the way an electrician does things, and it's not his fault because you can't blame them for knowing any better. It's just things like this that we've run into over the last 10 years and have slowly tried to correct as funding allows. Buying the new Presonus board was a pretty big deal.

Our primary sound guy knows how to mute/unmute channels and set what channels are going to the different aux feeds. I'm a technical guy so I've learned the board in and out, and when SHTF, I'm the first in and troubleshooting (I run the live stream and projection, so i'm right there). What I haven't gotten to do is get a thorough understanding of all the EQ ins and outs. I can do compressors/limiters, high pass filters, etc, but the EQ for me is more hands off. It's not something that I'm going to be fluent in until I have enough experience with it and learning a little over time. We've kept our input gains down and make sure our output never approaches +-0db. Usually we don't like to go over -10. Sometimes we'll push a DVD a liitle harder, but with choir and that sots, the closer we get to 0, the faster that feedback is going to hit.

Right now we can comfortably run the system with everything set for unity, and there are no feedback issues. Enter some wireless mics moving around and we'll have to do some adjustments. What we really need to do though is bring the entire volume of the system up at the amps, and work backwards through everything. Our pulpit mics mainly need some gain, but then again you're looking at an open mic that is about 2' from the persons mouth. Room dynamics, monitors, reflection all play into the issues we're having and I just need a point to start with.

Plan is to first redo the room pink and get a good autoEQ. Then to look at the feedback settings on the DBX and perhaps lessen the fixed channels and allow more live channels (right now it's 6/6). Then completely flatten the global EQ on the Presonus. From there is a laundry list of things to do, such as dropping choir mics lower, re cabling a few things and just good ol crossing some fingers.
 

Aaron Becker

Well-Known Member
edit comment - I see in your other post this is a house of worship and that a volunteer member electrician did much of the installation. There may well be some more "interesting" things you've yet to find... but it also goes a long way to explaining why the DriveRack has the LF squeezed out - it was the fastest, easiest guaranteed way to get rid of the LF feedback from the pastor's lavaliere mic.

+1... and exactly why I made the above comments about locked-down DSPs.
 

RonHebbard

Well-Known Member
Premium Member
@TimMc thanks for the great response. We've had our presonus board since 2012, and we had a close sound guy do the install, do a pink of the room and set the channel EQs, and fix a few other cable termination issues. That was able to fix a tremendous amount of issues that we were initially having with our previous board, a Mackie 32 channel that was second hand and had bus B burned out.

The electrician comments go back to when the church was first built. I don't believe he did any of the actual audio board install, just the speakers and cable runs. Tiny individual holes were drilled for each xlr cable that run under the staging area through joists, and they were mounted in metal single gang electrical boxes that were nailed to the joists, with MC cable connectors acting as the strain relief. Oh yeah, they also used metal staples to hold the wires along the floor joists too. Then they used a surface wall mount place as the cover for the floor box. So you have jacks sticking up, etc. But the metal boxes and wiring kills me. Can't do any new runs and it's impossible to pull any new wires the way things were built. That's just the way an electrician does things, and it's not his fault because you can't blame them for knowing any better. It's just things like this that we've run into over the last 10 years and have slowly tried to correct as funding allows. Buying the new Presonus board was a pretty big deal.

Our primary sound guy knows how to mute/unmute channels and set what channels are going to the different aux feeds. I'm a technical guy so I've learned the board in and out, and when SHTF, I'm the first in and troubleshooting (I run the live stream and projection, so i'm right there). What I haven't gotten to do is get a thorough understanding of all the EQ ins and outs. I can do compressors/limiters, high pass filters, etc, but the EQ for me is more hands off. It's not something that I'm going to be fluent in until I have enough experience with it and learning a little over time. We've kept our input gains down and make sure our output never approaches +-0db. Usually we don't like to go over -10. Sometimes we'll push a DVD a liitle harder, but with choir and that sots, the closer we get to 0, the faster that feedback is going to hit.

Right now we can comfortably run the system with everything set for unity, and there are no feedback issues. Enter some wireless mics moving around and we'll have to do some adjustments. What we really need to do though is bring the entire volume of the system up at the amps, and work backwards through everything. Our pulpit mics mainly need some gain, but then again you're looking at an open mic that is about 2' from the persons mouth. Room dynamics, monitors, reflection all play into the issues we're having and I just need a point to start with.

Plan is to first redo the room pink and get a good autoEQ. Then to look at the feedback settings on the DBX and perhaps lessen the fixed channels and allow more live channels (right now it's 6/6). Then completely flatten the global EQ on the Presonus. From there is a laundry list of things to do, such as dropping choir mics lower, re-cabling a few things and just good ol' crossing some fingers.
@Photovor @TimMc Photovor; When you wrote "That's just the way an electrician does things", you not only raised my ire but my blood pressure too. EXCUSE ME BUT that's not the way all electricians approach "things". If it had been up to me, Rigid metal conduit and liquid tight back boxes for all foreseeable systems plus a few "spares" for future unknowns would have been the first order of business.
Conduit is NEVER faster and cheaper to install than in a poured slab prior to the pour.
Next order of business. Accurate, as built, documentation plus pull strings in every pipe. After that, cover plates, cables and connectors as budgets and needs allow. Last thing, is purchase of equipment. You can ALWAYS beg, borrow or rent equipment. There are no affordable ways to "rent" conduit installed in your slabs beneath the finished floors, installed carpets and seats within your rehearsal and performance spaces. Installing surface mounted conduits is time and labor intensive as it all needs to look straight and pretty in addition to all those straps and touch-ups required by the dry-wallers and painters. Installing conduits under your installed floors and seating after the fact results in lost revenue at the least.
"Grumble bitch!" @Photovor Not ALL electricians "does things" as you suggest. Please be careful with your broad sweeping statements.
Toodleoo!
Ron Hebbard
Retired from IBEW 105 and IATSE locals 129 and 357.
Biased? Moi?? Possibly just a little.
 

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