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EQ stage monitors vs. loudspeakers

Discussion in 'Sound, Music, and Intercom' started by Gohanto, Feb 3, 2009.

  1. Gohanto

    Gohanto Member

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    I'm doing system EQ for my old high school and I've got a decent amount of experience, but have a couple questions since a lot of my knowledge is from books and not working (though I've mixed a few shows).

    They have 2 stereo 31 band graphic equalizers, and a stereo digital PEQ. They're running 3 JBL horns with compression drivers and dual subs in a single box for the audience, and JBL stage monitors.

    I'm looking at using a program I was suggested by a friend, WaveCapture, as a decent way of looking at the direct sound of the system to eq it. Then of course walking through it with program material to fine tune it.

    My question comes in about how to best use the digital PEQ. I can use it on the monitors ring them out and increase gain before feedback, or on the main speakers or the sub. Naturally I'd use the graphic eq on whatever I wasn't using the PEQ on.

    Any suggestions?

    Thanks,
     
  2. gpforet

    gpforet Active Member

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    Is there a system processor controlling the FOH rig? What about a crossover?

    With 2 stereo 31 bands, that's 4 channels of 31 band eq. I'm guessing their running FOH in stereo so I'd put a channel of 31 band on the left and a channel of 31 band on the right FOH.

    If there is more than one monitor send/mix, you could put a channel of 31 band on each of the monitor sends.

    Regarding the PEQ:

    I'd use that as the main FOH tuning eq.

    Once I had everything patched, I'd fire up SMAART and start tuning the rig.
     
  3. museav

    museav CBMod CB Mods Departed Member

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    I am not familiar with their software (WaveCapture is the company, they offer several different programs and it is not clear which one you are referencing) but that is not the type of software you typically plan on just buying and using. There is usually a pretty steep learning curve and a need to have a good basic understanding of how things work in order to use it effectively. For example, I noted that some of their programs allow you to use windowing which can be very useful but only if you understand the general concepts and how to apply it, otherwise it can be used improperly and lead to erroneous results.

    Also, tuning for direct sound is just part of the process, interactions with the room and other devices are also relevant and areas where analysis programs like the WaveCapture programs (or Smaart, SysTune, etc.) can be very helpful. What they can let you see is what is direct sound that can be equalized and what is interactions that can at best be mitigated by EQ but may require other treatments.

    There was a discussion in another forum regarding a similar software and hardware that attempted to measure the direct sound and automatically apply equalization and the general consensus is that this might be a good start for live sound but that you still had to address the effect of the environment and having multiple devices that interact. It is good to have the desired response from the individual speakers but that is not all that affects what the listeners hear.

    Also, be careful with spatial averaging, both research and practical experience have shown that this can often be a less than optimal approach. For example, if you measured ten points and nine of them were 100dB at a certain frequency and one was 80dB, spatial averaging would simply shown an average of 98dB at that frequency and not take into account that nine of the ten points were 100dB. If you were trying to get 100dB at that frequency this could lead to your negatively impacting nine of the locations in order to slightly help one of them. The point is that sometimes you have to apply logic beyond simple averaging. I much prefer measurement platforms that let you capture and overlay multiple measurements so that you can more readily see trends and make better informed decisions.


    There are pros and cons both ways and it would really help to know the system configuration, for example is it a center mono cluster or stereo or LCR mains? How many monitor sends are there? How is the subwoofer signal derived, is it an aux send or off a crossover? It would also help to know the actual products, details such as whether the graphic EQs include adjustable high and low pass filters could make a difference.
     
  4. Gohanto

    Gohanto Member

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    Thanks for the help. I finally was able to get to my high school and get a closer look at the system for a better understanding. The system is mono running 3 JBL 2445H Compression drivers with 2365A horns (~18" between horn edges), and a 4648A low frequency box using a JBL crossover set to 500 Hz (which is correct oddly, based on the frequency responses of the components, although the bass sounds like junk, possibly blown). Everything in a center cluster in a high proscenium. One dual channel JBL amp powers all three HF drivers, and another powers the LF box (then there are two amps not connected to anything)

    The monitors are run mono, and there's two of them on either side of the stage.

    Also, I found out that the Rane graphic EQs are actually 2/3 Octave and they have a feedback destroyer in the system as well.

    From the tests we did, the most obvious thing we noticed was the slap echo when you clap in the room, and giant phasing issues walking around the room with pink noise. The room plays mainly amplified musicals and plays, but also some unamplified orchestra performances. Since the walls are plaster and the back wall has very thing carpeting, we're looking at adding absorption to the walls at all of the first reflection points. (Trying to only target the first reflection points so that it doesn't deaden the room to much for unamplified bands and orchestras)

    We're also considering moving the HF drivers closer together so that the horn edges are within a 0.5" (vs. 18" separation currently) to help out with the phasing issues as well.

    Any other suggestions?

    Thanks,
     
    Last edited: Mar 24, 2009
  5. jkowtko

    jkowtko Active Member

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    In the area of other suggestions -- get a new FOH speaker system!

    I don't know why, but the high schools in our area with their new performing arts centers, also have the JBL speakers hung high with messy center cluster, making the sound system sounding poor for anything but lecture.

    I did a dance show last year, and for that I brought in my own pair of speakers and set them up on stands on either side of the stage, with subs on the floor next to them. I also added side fills about 30 feet into the audience area. I ended up turning down the center cluster quite a bit as it only sounded muddled when compared with the stereo speakers I added.

    I didn't even have delays in the side fills, and it still sounded pretty good with the dance music.

    For theater/musical I would still recommend having stereo FOH speakers on stage left and right, not too high up off the stage, to bring your sound field down to stage/actor level and allow you to play stereo reverb and music/FX through them. It will sound much better than those sky-high house systems ;)
     
  6. hsaunier

    hsaunier Active Member

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    [QUOTE=Gohanto;125910 From the tests we did, the most obvious thing we noticed was the slap echo when you clap in the room, and giant phasing issues walking around the room with pink noise. The room plays mainly amplified musicals and plays, but also some unamplified orchestra performances. Since the walls are plaster and the back wall has very thing carpeting, we're looking at adding absorption to the walls at all of the first reflection points. (Trying to only target the first reflection points so that it doesn't deaden the room to much for unamplified bands and orchestras)

    [/QUOTE]

    For the side wall absorbtion treatment, you might consider some type of drapery which can be deployed to deaden the room for amplified programs, or stored for acoustic programs. We have a system to "tune" our room which consists of 11 sets of drapes placed in strategic locations. I can change the room verb from 1.9 sec to 1.1 sec.
     
  7. Gohanto

    Gohanto Member

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    Thanks, however having a stereo ground speakers in a high school setting, they'd likely go missing quickly. Plus the crews are never really large enough to accommodate moving the ground stacks every night.

    I am considering locking some front fills into the front of the stage though to help image the sound down a bit.
     
  8. museav

    museav CBMod CB Mods Departed Member

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    To each their own, but that is typically the last configuration I would consider. There are reasons for flown systems and while stereo effects can be nice for some uses, factors such as coverage and intelligibility typically have a much higher priority in most applications and facilities and these are almost always negatively impacted by a stereo system at stage level.

    The most critical issue is normally that stereo can work great - at one listening position. But it is very difficult to get stereo to work effectively over large audience areas. Add in interactions from multiple speakers with mono sources (like mics), losses due to distance from the speakers, gain before feedback, the effects of speaker patterns and so on and you typically end up with many people having a lesser experience for the benefit of a few. So unless you can do stereo right, which takes a lot more than simply having a left and right speaker, then at least in my opinion it is rarely the best approach.

    The speaker height is also not as much of an issue as you probably think, having the speakers lower would likely only benefit a few people up front and they are often better served by front fills anyways, especially given the amount of natural stage sound they receive compared to most of the audience. On the other hand, having the speakers mounted higher is typically a huge benefit in regards to coverage and in helping get the speaker output directed at the audience and not the walls, ceiling, etc.
     

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