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House limiters -- EQ, driverack, something else?

Discussion in 'Sound, Music, and Intercom' started by jkowtko, Dec 10, 2007.

  1. jkowtko

    jkowtko Active Member

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    In our theater I am at the point where the FOH is fairly well EQ'd for the current show we're running, feedback problems are pretty much behind us, and I'm well into the process of balancing the house volume scross all seating areas.

    Some of the seating areas run a little hot, and in general when we run loud shows, without limiters in the system equipment there is no easy way for me to prevent the board operator from pushing the volume a little too high for the (elderly) audience.

    So I would like to install limiters of some sort, and I would like to put it on the "system" equipment so I don't have to worry about what people do on the board. What should I use?

    Current equipment:

    - two DBX 231s and one 131, to cover the 5 full range speakers.

    - I also have two subs that I'm not using right now, but for shows when I use them I need to handle EQ, crossover and limiting. If I followed my current path I would simply purchase another DBX 231 (or increase the existing 131 to a 231) to handle the subs.


    Options I know of:

    - up the EQs to the 2231, something that has limiting built in

    - swap out the EQs for Driverack PA ... gives me EQ, limiting, and also crossover when I run the subs against a pair of FOH speakers. The Driverack also fits nicely within 1U (vs the 2231 which is 4U).

    Any opinions on the above two options? Any other equipment I should be considering instead?

    Thanks. John
     
  2. fosstech

    fosstech Active Member

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    Putting a limiter in to keep the mixer from pushing the levels too high is not such a good idea. He or she will just keep bringing up the level to try to make it louder to the point of clipping (of not necessarily the amplifiers) which will toast your speakers. Limiters should only be placed in the output chain to prevent amplifier clipping.

    I think this problem is best solved by a little talk with the mixer in question.

    As for the equipment, why a separate EQ for the subs? Unless you're running them off an aux there really is no reason not to have a single EQ before the crossover.

    Considering you have five speakers in the house, the Driverack PA won't be enough. It only has the capability of processing two channels with a 3-way or 2-way with sub crossover. We use a Driverack 260 here for our LCR system with delays. It would probably work for you as well, although it is significantly more expensive as the DRPA. Your five speakers could be fed from five of the outputs, while the subs could be fed by the sixth. The 260 also has a very nice feedback supression feature that identifies feedback frequencies during a pre-show test and applies up to I think 12 very narrow notch filters to eliminate it.
     
  3. Eboy87

    Eboy87 Well-Known Member

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    If you're deadset on EQing the subs, then I suggest you pick up a parametric EQ just for them. They're a little more precise than the GEQ for that purpose. and as fosstech already said, the DRPA doesn't have enough outs for what you want to do. Your best bet is to have a sit-down with the board-op(s).

    How do you have your system configured now? I apologize if that's been discussed in detail in one of your other threads, but I don't recall. Are you still using the Mackie active cabs? And when you talk about using a 2231 for the subs, you aren't using the GEQ as a cross-over, are you? Once again, I apologize if that's been discussed before, my mind's a bit overloaded by finals.

    This is the way I'd run my system. I'd have a GEQ (231 or 2231) to take care of feedback that might crop up. GEQ signal goes to DSP (DR260 or better) to split it out to zones and EQ each zone. I'd be running Aux fed subs, so that gets it's own crossover before going to the subs, if possible through the DSP, giving it full dynamic processing if needed.

    Once I know your signal chain, I/we can give some better ideas.

    EDIT: I've been mulling over the use of EQ on the subs, and I personally wouldn't use it unless they sound incredibly muddy. The benefits are negligible, in my opinion. On the other hand, I don't know how your space sounds, so I can't in good conscience say you do or don't need the PEQ.
     
    Last edited: Dec 10, 2007
  4. avkid

    avkid Not a New User Fight Leukemia

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    I agree that a DriveRack PA is inadequate for your application.
    You will need at least a DriveRack 260, if not bigger.
    The absolute best thing for under $1K would be a Peavey VSX 48, but unless you know someone with an inside line in Meridian(;)) it will be a 6 month wait at the very least.
     
  5. jkowtko

    jkowtko Active Member

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    After reading your comments, I think the following is probably a good approach for me to take:

    - I'll skip the driverack approach for now ... the PA won't let me split the channels, and I need that for Center and subs. The 260 (much less three or four of them) is just too expensive to invest in right now.

    - Since I just bought a digital board (that's where my money just went) I will have compressors on every channel, so I can set them up wherever I need them and let them do the work. We'll nip the problem at the source ...

    - the subs are on an aux out and are a bit muddy right now. There is some mid-bass reverb in the room that I haven't been able to deal with yet (not enough time to build and install a zillion bass traps) so I would like to leave it on the EQ to tame it some. I think through EQ and sub placement on stage I'll be able to tame this beast reasonably well for now. The digital board has a 4-band parametric on each aux out so I will likely just EQ it there where I have more control.

    Another thing I forgot to mention is the cause of this concern ... our venue is small and when we run a production with a live band, the band is too loud to be miced, so we have to set a manual mix by sound-checking the band and then running the vocals on the board "over" the band volume. In order for the band to even hear themselves they are already close to max house volume ... so everything is running pretty hot. I just wanted to keep from bumping over that volume threshold since we're so close to it. Channel compressors should work here, and over time improving the acoustics of the room (primarily bass traps) will help as well.
     
  6. museav

    museav CBMod CB Mods Departed Member

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    I agree that limiting should be used for system protection more than for volume control. In many cases where it is used to limit the volume, all general compression or limiting on the system ends up doing is squashing the peaks and dynamics while the operator keeps turning it up until there are no dynamics. If you really need to limit volume, then the place to do that is at the amplifiers, or in the case the powered speakers.

    On the aux fed subs, you still want to low pass them and not feed them a full range signal. Also keep in mind that while you may be able to reduce the severity of these issues, EQ will not be able to correct for room modes or interactions between speakers and the room or between multiple speakers.

    I am curious as to your system configuration. You apparently have five powered Mackies each on their own EQ channel as well as two aux fed subs. What is the speaker arrangement and are you running mono, stereo or some form of LCR?
     
  7. jkowtko

    jkowtko Active Member

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    I'm replacing this post with updated information --

    The "house system" I have in place now consists of:

    * 5.1 speaker system
    - LRC are SRM450s
    - LR/RR are SRM350s
    - sub channel is a pair of SRS1500s daisy-chained off each other.
    - I rehung the front speakers for better audience coverage -- every seat in this flex- theater now has decent sound :)

    * EQ
    - 3 DBX231s feeding the six channels above
    - I have no crossover, limiter, or delays on the house system. The board outs plug directly into the EQs and then off to the speakers
    - my sub "crossover" is one of the EQ channels right now.

    Since the system is pretty high powered for the house I would still like to implement a limiter in the "house system", so I don't have to worry about what sound designers might try to feed it from whatever equipment they bring in. If it's not too much trouble I'd prefer to upgrade to an EQ that has a built-in limiter ... sounds like a simple adjustment that will provide the needed protection (against ears as well as equipment).

    And even though feedback has been reduced quite a bit with the EQ'ing, the natural room reverb and speaker placement (flex-theater with floor-level stage and no orchestra pit) still puts us on the edge. I like the concept of the Behringer EQs that the fader light will indicate a frequency that is feeding back ... has anyone used these and do they actually work?

    Keep in mind -- this theater has no budget, so anything I get has to be in <$200 increments. That pretty much limits me to used DBX, Behringer, and the like.

    Thanks. John
     
    Last edited: May 29, 2008
  8. jkowtko

    jkowtko Active Member

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    (updated the previous post ... bumping the datestamp on this thread)
     
  9. Eboy87

    Eboy87 Well-Known Member

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    You're using an 01V, correct? Like you said in your previous post, use the board's PEQ for the subs on its aux. I think the 01V has graphics built-in, but it's been a while since I used one. Anyway, are you still using the graphic EQ for your crossover? If so, I suggest picking up a used dbx 223 (I'd spring for the XL model, it gives you XLR). It's a two way crossover that'll let you properly split the signal to the subs. Ebay has a few used between $50-150. That should help clean up the subs a little bit.

    As for the Behringer EQ, I have one and I'd say pass on it. Mine's more trouble than it's worth.
     
  10. jkowtko

    jkowtko Active Member

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    I personally have an 01v, but the theater has an analog board -- a small Mackie CFX-20 that I'm planning to upgrade to an A&H Zed, GL2400, or Soundcraft equivalent in the near future. So the house system really should be set up to run on it's own.

    I'll check out the DBX223 crossover -- they seem inexpensive enough -- however the subs seem to be doing fine with one of the DBX231 channels.

    I am still in search of something which can act as a limiter for the house system, short of running each channel through a compressor/limiter (which may end up being the only cost-effective option?). That was why the question on the Behringers ... they always seem to be feature-packed for the price.

    Just curious, what was the specific issue with the Behringer EQ? I know a couple of experienced sound people with Behringer EQ and compressors and they are happy with them (and their productions sound pretty good, too).

    Thanks. John
     
  11. Eboy87

    Eboy87 Well-Known Member

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    My issues are mostly mechanical ones. The 6/12dB range button on one channel bought the farm, so I can only cut frequencies up to 6 dB, which isn't always enough. There's also a pseudo ribbon-cable that connects the front PCB with the one on the inputs, and it keeps coming loose, or even unconnected completely, so it's constantly on the bench.

    I personally use mine for monitors, and I've run into problems with the filters themselves before, they often aren't very accurate or precise.

    In my professional opinion, I still think that putting limiters to limit overall volume is a bad idea. I agree with their use to protect drivers, but that generally means the cabs can still get loud. If they limit to a softer volume, the engineer tends to push the system harder, causing the limiter to work harder. Eventually, the signal gets compressed to the point where it can look like DC, which gets sent to the amps, and can fry the voice coils of your speakers. If you're still dead-set on the limiters, take a look at used dbx, or, if you can find one, an old (keyword) Behringer comp.

    BTW, I suggest Soundcraft over the A&H Zed. I've always thought the Soundcraft was far superior to the A&H, and I like the way its EQ behaves.
     
  12. howlingwolf487

    howlingwolf487 Active Member

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    If you're looking for a way to control the overall output level (dB/SPL) of the system, you might consider this gizmo:

    Goldline SLC-1
     
  13. cutlunch

    cutlunch Active Member

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    Although it probably is to pricey you might look at something like a Matrix mixer.
    A school I was at had a Peavey X-88 one. It had been set up with the EQ for the room stored in it. It also took the Mixer output and split off a signal to feed the active powerd subs. It has a limiter compressor etc bultin.

    You land up with control panels and just by pushing different buttons you get the different settings instantly.
    So you could set an EQ for when you had the subs or you don't although our system the subs signal was there regardless if we used it or not.

    It let us decide at the push of a button if we wanted the foyer and hearing aid loop to be taken from the output of the PA or a suspended room mike.

    The peavey one is good and you can get the software it is a bit harder to program then some other matrix mixers.
    You can still EQ at the mixer but you also could set the controls flat and know the rom will sound OK. It is a good idea if you have a lot of outside hires.
     
  14. silvrwolf

    silvrwolf Member

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    If your really crazy about how much the sound op. is pushing the system. You could install The Electronic Orange. Here is a description I found from dream4sweet.blogspot.com "Castle GA904 Electronic Orange: The Castletech Electronic Orange Noise Controller is connected to the main power supply for the amplification equipment, the Electronic Orange flashes a warning when the pre-set sound levels are exceeded. If the operator doesn't turn down the sound within a pre-set time, an automatic cut off activates. The music never has to stop, because a warning light flashes if the limit is exceeded, and only when this is ignored does the power supply cut off to prevent further abuse."
    So basically if you exceed a set dBSPL level then the "Orange" cuts power to FOH for a preset time limit ex:5 min.
    Here is the spec sheet for the Orange.

    I cant even imagine how pissed off an engineer would be after a show if one of these "orange boxes" were set too low. Someone even told me that they are required by law in some areas of the UK. Not sure if its true but still what a PITA.

    Obviously this isn't intended to be a dynamic limiter for protection of speakers and amps
     
    Last edited: May 29, 2008
  15. jkowtko

    jkowtko Active Member

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    Thanks for the other info on your experience with Behringer EQs ... I may pick one up cheap and try it out. The HPF/LPF would be handy. And the "feedback detection", if it works, will really come in handy in our theater.

    I do have some questions on sound board options. I'll start another thread, or look for an old one to dig up, to continue that discussion.

    Thanks. John
     
  16. jkowtko

    jkowtko Active Member

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    Yes, a noise limiter, or at least a sound level monitor and alarm, would be great. Making the sound op aware of the issue would likely solve the bulk of the problem, especially if there's a bright orange light flashing in their face :)

    This particular unit looks good but not cheap. There seem to be at least a couple others out there ... I'll start looking ...

    Thanks. John
     
  17. museav

    museav CBMod CB Mods Departed Member

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    Behringer has the reputation it does for several reasons. Some people like it because they get a lot of bells and whistles and capabilities for the dollar. Some people refuse to use their products because of Behringer's business practices (won't get into all that). Others just don't trust the reliability and durability.

    There are all sorts of different ways to process a system. If you are wanting to actually limit how loud someone can get, then limiters just prior to the amps along with proper amp input settings can provide that. The further up the chain you move the limiter, the less useful as a protection device it gets as you then have processing and gain stages occurring after the limiting. However, as fosstech previously noted, using limiters for speaker protection is usually a good idea but using them for volume control is typically not.

    I know you're working with what you have but an octave or 1/3 octave EQ is not a good crossover. You should have a high and low pass filtering on the subs and high pass filtering on the mains. Doing so might help clear the subs up. In fact, some delay might also help with the subs and you could also see if you have any positional issues such as reflections off nearby surfaces cancelling some frequencies or room mode issues, although you may have already looked at that.

    There are very good reasons to have multiple EQs and limiters in a system. For example, in your case you likely want to have different settings for the rear speakers than you do for the mains. When using some DSPs, I actually like to break up the processing, for example I may have a separate EQ and delay specifically to tune the speaker flat, that way that can be set and not changed when someone makes other EQ or processing changes.

    I am curious as to how you are deriving LCR mains plus left and right rears plus an aux fed sub with a CFX-20 and no processing. I didn't know that little board had that many outputs!

    On the level monitoring, why not just a cheap sound level meter and a maximum level noted for each event? The systems that cut power are intended for conforming with the UK Noise in the Workplace regulations which relates to noise exposure of employees and not just event levels. I have worked shows where the house simply had a SLM by the console and told operators that if they saw the level exceeding XdB too much then they were off the console. That also lets you address the situations where a rider or other agreement requires that the 'artist' have complete control including over levels.
     
    Last edited: May 30, 2008
  18. jkowtko

    jkowtko Active Member

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    Brad,

    I actually don't have an issue with EQ on the subs. They sound fine, so IMO using the remaining channel on the DBX231 is okay. The issue with the subs is that they are placed in the wrong place in the theater so I can't get even volume of bass throughout the audience area. So I keep the bass on the mains to help even it out. I know -- terrible compromise ... some day I'll get the subs in a decent location and then I can use LPF/HPF filters on the main outs (and many EQs have LPF/HPF on them)

    That final output limiting though, was just to prevent the ear-hurting volumes, not to enforce a low volume. So I would assume any good sound op would understand when I tell them that if the volume gets to a certain point, house limiters will kick in. Certainly any that I work with will be well prepped on the equipment we have. The problem we had this year with volume was primarily that the resident music director liked it loud, and since he was "resident" AND related to the exec director, nobody else could really do anything about it, short of me having a physical standoff and risk shutting down the production completely. So we suggested and prodded and got our way through the season, and it turns out he is leaving the theater at the end of this production -- and new sound designers, MDs, and the like should not be in a position to create this same situation ... they all can be booted :)

    If I had a choice, I would probably prefer a parametric EQ to tune the speakers ... don't know if there are any inexpensive ones out there (except Behringer, of course).

    For Feedback, I would think either individual parametric channel EQ or group EQ would be great -- which the Yamaha 01v has but the lower end analog boards do not. So for now it's the main out EQs that do the bulk of that job.

    The Mackie CFX boards are 8-bus, with 4-group with 4 aux outs. So I have enough to work with ... barely! That's why I want to upgrade the board :)
     
  19. SHARYNF

    SHARYNF Well-Known Member

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    In all likelyhood the issue with uneven bass throught the hall is the cancellation and interaction with all the speakers you have in the setup. Typically these issues show up first in subs when you are attempting to produce low frequencies for all sorts of overlaping different locations.

    Sharyn
     
  20. jkowtko

    jkowtko Active Member

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    Sharon, I would believe that if I didn't have the subs essentially locked in a closet under the booth. Remember, this is a flex theater with a highly raked 12-row seating area, with the booth behind the last row of seats, about 8 feet off the ground. There's a walk-around corridor around the backside of the bleachers which goes under the booth, and there's a storage area under there. The bleachers are shrouded by plywood around the back, and the outer shell of the theater is cement. So the subs are pretty well cocooned in there. Fortunately they get through the plywood enough to pound the booth and the last few rows of audience. But the effect wears off as you move to the front rows So I'm thinking I have bigger problems than acoustic interference here ... !

    When I first set up for Smokey Joes I had the subs set out on either side of the stage under some platforms that were created for that show, and for the one day I tried them out there, they sounded pretty good and uniform. However we ended up not using them for that show, and the stage platforms came down for the next show .... so the subs went back under the booth :|

    I'm slowly -- very slowly -- getting everyhing I want in this theater ... it's just taking a lot of time ...
     

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