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A bit overwhelmed... and looking for some setup advise

Discussion in 'Sound, Music, and Intercom' started by banditj13, Mar 16, 2008.

  1. banditj13

    banditj13 Member

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    Ok guys... (warning- long post)
    We covered the stage volume stuff a while back...but I am back with a need for some advice....
    So a basic background
    I have a typical church - rectangle, with lots of parralel walls and faces...
    The stage is a parrelelogram, basically...
    So in attempt to show you what I mean, I attached a picture...
    Obviously, the room is very reverberant... especially with the wonderful support columns that protrude on the sides...
    So right now, our main speaker array consists of 3 cabinets,hung in front of the stage at stage center... they are angled down slightly, so they cover the audience at the center of the room well...
    the center cabinet is aimed dead center, straight back
    The left and right are aimed out, towards the 2 outside walls.
    My question is: if I move the outer left and right cabinets equal distance towards the outer walls and aim inwards towards the center of the church, shouldn't that cut down on the reverberant nature of our sound
    I understand that by the nature of the room we are in, I won't get rid of it, but does what I want to do make sense to at least help the sound?
    I have other questions for our setup, but will ask those in other threads...
    Thanks,
    Aric
     

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    Last edited: Mar 16, 2008
  2. avkid

    avkid Not a New User Fight Leukemia

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    Too many variables are unknown right now.
    What kind of speakers?
    Vertical/horizontal dispersion angles are what?
     
  3. banditj13

    banditj13 Member

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    I guess I did leave alot unknown... sorry...

    not sure on the vertical dispersion angle, but the horizontal is close to 90 degree... each cabinet is identical... not sure of the type of speakers... as the raw drivers have been replaced, I can tell you they are 2 way cabinets, and have hardly any low end...

    we are running around 270 watts at 8 ohms out of each cabinet.

    Thanks,
     
  4. museav

    museav CBMod CB Mods Departed Member

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    First, reverberance is primarily a factor of the room volume and absorption, not the shape, that relates more to issues like room modes, reflections, etc. So the columns do not add to reverberance and actually probably help break up room modes, flutter echo, etc.

    Moving the speakers out and aiming them back towards the center at least seems like it would introduce a number of problems regarding coverage and issues resulting from multiple physically separated sources covering the same listeners. It could actually just make things worse. It would really take looking at the specifics of the room, system and speakers to see what might be done to try to keep sound off the walls while still providing proper coverage, intelligibility, etc. from the sound system. The underlying factor is that the sound system can only work within the constraints of the room, it cannot alter the natural room acoustics. If the sound system works other than some issues regarding the room acoustics then the most effective approach may be addressing the acoustical environment rather than the audio system.
     
  5. banditj13

    banditj13 Member

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    Thanks MuseAV -
    You are right, I cannot use the sound system to cover for the acoustics of the room...

    I am looking to reduce the reflected sound (reflected sound is around 180 degrees out of phase with the original) as well as provide for better coverage, with less dead zones...
    The idea being to reduce the amount of "bounces" to the sound that occur in the room.

    The room we are in is a steel framed, concrete block room, with a 24 foot high tile ceiling... it is my understanding that the ceiling tile is acoustical tile...

    The side walls are 12 foot of concrete block, with the steel frame and drywall above that... the rear wall is aluminum stud and drywall (the church was built with expansion in mind)

    I don't know if that will help or not.....
     
  6. Eboy87

    Eboy87 Well-Known Member

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    I'm with Muse. While yes, it is possible that re-aiming the speakers might reduce some of the reflection, you're still in a very reverberant space from the sound of it, no pun intended. I assume that since it's a church, hanging some treatment on the wall is out of the question?

    I think I may be misunderstanding these two phrases. Are you saying these cabinets are aimed directly at the wall, or are they aimed at the congregation? Even re-aiming doesn't shorten the TR60. Treating the room is the best first step.
     
  7. banditj13

    banditj13 Member

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    Looking back at my original post, I realize I used the term "reverberance" wrongly... I should have said... reflection


    Sorry...
     
  8. Eboy87

    Eboy87 Well-Known Member

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    Wait, are you saying that the room isn't reverberant? I'm confuzzled now.
     
  9. banditj13

    banditj13 Member

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    it is very reverberant.... but that wasn't the issue I was looking to solve...

    Sorry... I meant reflection, said reverberance...
    Wow - what a difference terminology makes :)
    Sound treatment may be in the future... but looking at the cost of good stuff... it is way off in the future...

    right now, I have a $0 budget, and am working on donations only... maybe $20 a week... plus whatever I/The Wife want to spend on this....


    As for the speakers, the center is aimed directly at the back wall, both horizontally and vertically.... (not doing much good for coverage if you ask me)

    The left/right speakers are aimed at the outer edges of the congregation, but mostly look to be hitting the back corners of the room...

    Our congregation is mostly centered in the room, with very few sitting towards the outsides of the room.


    Thanks,
     
  10. Eboy87

    Eboy87 Well-Known Member

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    Ok, that makes a bit more sense. Find out the coverage patterns of your cabinets. You may be able to cheat on the outer ones and aim them so that their coverage just falls off after the congregation. Re-aim the center one so that it's not the wall's personal monitor. For little budget, the best you can do is re-aim so that they're not firing into the walls. See how that works first.
     
  11. banditj13

    banditj13 Member

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    Thanks Eboy... sorry for the confusion


    That was kind of my thought in moving from a cluster array of speakers to a spaced array... and taking care to aim the speakers correctly...

    I guess my only source of hesitation is that we are running mono bridged signal to the speakers, and the recommendation of a LeftCenterRight spaced array is to move the vocals to the center, since high frequency sounds travel in a straighter line, and then move the instrumentals to the sides...

    does that make sense?

    It would take some work on our setup, but it is doable...

    I would love to be able to put up wall treatments, but the last person that looked at the room said it would take over $25,000 to do it right... OUCH!




    Thanks
     
  12. banditj13

    banditj13 Member

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    Oh, and by the way... here are 2 of the sources I am using for some basic information - besides my limited knowledge of things....


    This one is written by Peavey
    http://www.churchandworship.com/04-07/cwt0407w24.pdf

    and

    This one -
    http://www.sogospellovers.com/forums/showthread.php?t=4544

    The peavey article describes our room pretty well.... side to side its long, a multipurpose room, and the stage is probably 2/3 the length of the main room...


    Eck... wish we had built a real fan shaped sancuary....


    Thanks,
     
  13. Eboy87

    Eboy87 Well-Known Member

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    From the sound of it, your hang is above center stage, pointed out in what amounts to a fan-shaped pattern, correct? If that's the case, using LCR would cause more problems to pop up. Once again, assuming that everything is centered in the middle, and each speaker fires into a different part of the congregation, ie, the house left speaker covers house left congregation, the center one handles the middle of the room, etc, then if you send just vocals to the center channel, only the people sitting in that cab's coverage will hear. Everyone else will get room reflections. I only ever encounter LCR in a theatrical setting, I usually mix everything else in LR stereo when possible.

    Assuming you have one centered cluster, mixing mono would be your best bet. If you do go and split it up, I'd hesitate to do LCR still. It'd depend on coverage patterns and speaker placement. What console are you using? If you split the speakers up, you could use matrix outs on the desk and make zones for each area of seating, each getting its own loudspeaker. That still presents a different set of problems though, once again dealing with different arrival times of the same source.

    For reference books, besides some acoustic texts for class, I use the Yamaha Sound Reinforcement Handbook a lot

    Yamaha SR Handbook at Amazon

    and this other little book I picked up years ago at Borders, Basic Live Sound, written by Paul White

    Basic Live Sound at Amazon

    I'm sure the others will be along to give more solutions. I hope some of what I said makes sense
     
    Last edited by a moderator: May 29, 2014
  14. banditj13

    banditj13 Member

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    yes, currently we are using a cluster centered above the staged, in a fan array... exactly as you are saying...

    Guess I will have to see if I can reaim them, and keep them in a center cluster.....


    we are using a mackie sr32-4 for the mixer, running through a DoD 16 channel EQ, then a Sabine FBX... then to the amps...

    We do have a Alesis MicroVerb FX processor in the mix as well... just for fun...
     
  15. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    $25K to do it right, or maybe $500 to make it much better. Take a look at SoundStop®. You wouldn't have to cover every surface of every wall; in fact, a random placement of 4'x8' or 4'x4' sheets may be desirable.

    Keep the speakers where they are, but re-aim then down toward the seating and NOT at the walls. Enlist the aid of a Qualified Rigger if you have any doubts about your abilities.

    And your "stage" is shaped like a trapezoid, not a parallelogram.
     
  16. soundlight

    soundlight Well-Known Member

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    Some well placed full sheets of acoustic treatment would do your space well. You should listen around the room for the places where the sound reverberates most from, and try putting a few panels in the hottest areas. This should help. You'll notice that many venues and studios who have acoustic treatment don't cover the walls. They just put panels in the important places on the walls.
     
  17. museav

    museav CBMod CB Mods Departed Member

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    You are getting things very confused. The phase relationship of the direct and reflected sound will vary by location and frequency. What is out of phase at one location and frequency can be in phase at a different frequency or location and somewhere in between at otehrs. And not all reflections are inherently bad, concert hall designers go to great lengths to obtain specific types of reflections. Also keep in mind that the phase relationships from the same sound arriving at a listener from more than one speaker that may be the problem with your planned revisions, a listener getting the sound from one speaker and then from another in a different location can be much like their getting a very high level reflection.

    This is probably really more the issue, reducing reflections that are perceived as separate signals or that interact negatively with the direct sound.

    Yes, it tells me that they should have had an acoustician involved! And your Architect should have adressed this as well as your sound system installer recommending that something be done.

    There are many possible acoustical treatments and a qualified acoustical consultant can help you select the type and quantity appropriate for your space, it is often a fine line between having a space that supports sound reproduction and also supports interaction within the congregation. Do be sure that any treatments used are rated for this use, many people try to make DIY panels out of materials that are not rated for this use, including things like flame spread and smoke ratings.

    Be careful with reaiming the speakers. If they are aimed straight out then aiming them down would likely help but I would avoid randomly making changes, you don't want to start causing other problems. There may also be some other adjustments that could help such as dropping the level on the center speaker that has a shorter distance to throw. You may even have the wrong speaker for the application, three 90 degree horizontal speakers would seem to cause a lot of overlap in your room (although that 90 degree is only nominal and may vary greatly with frequency). Forget LCR with what you have, for that to work at all each array has to evenly cover the entire seating area. There are simply many factors you may want to consider before you start making changes and you may want to get some help on not only determining what would help, but on optimizing the system performance. Please read this, http://www.audiosystemsgroup.com/3Times.pdf, and maybe pass it on to your church leadership as well.

    There are a number of good online forums dedicated to church sound. You might want to look at http://www.churchsoundcheck.com/list.html and http://churchsound.prosoundweb.com/, this very type of thing is discussed all the time on those.
     
  18. museav

    museav CBMod CB Mods Departed Member

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    By definition, sound does not reveberate from anywhere, a reverberant field is defined as being the same everywhere with no changes. In simple terms, adding absorption, such as wall panels, affects reverberation. Where you add it may affect reflections and room modes. And what it is will determine how it affects both of these at different frequencies. Therefore, effectively incorporating absorption requires considering all three aspects; quantity, location and frequency response.

    Where absorption is placed is often critical if it is being used to address room modes, flutter echo, discrete reflections (such as off a back wall and back to the stage), etc. rather than just for overall reverberation time control. Small studios can be a good example as technically many of them cannot support a reverberant field but may have a number of room mode related issues, thus the acoustically absorptive materials are actually being used to address modal rather than reverberant issues. Very large rooms are typically the opposite, the dimensions cause most room modes to be so low in frequency or level that they are not as much an issue but reverberation may be. This is one reason why what is good for studios may not be applicable to large rooms and vice versa and I always worry when I see people applying home studio acoustics information to large spaces.

    And when addressing reflections and room modes, it may be that diffusion or a combination of diffusion and absorption is a better solution. A good example of this is acoustical tile ceilings in churches, they may lower the overall reverberant nature of the space but they also limit congregational interaction by eliminating reflections between members at speech frequencies. In many cases a better solution might be a combination diffusive and absorptive ceiling with some additional wall absorption.

    You also have to consider the material. Putting in a bunch of 1" thick acoustical panels may make a room very dead and/or reduce some reflections at speech frequencies, but won't do much at low frequencies, which can result in a "boomy" room. That's why I try to address the frequency effects and limit my recommendations to products for which octave or one third octave band acoustical data is available.

    The potential for diminishing returns, especially when addressing reverberation, can be seen by a simple example. Say your room has 1,000 sabines (the unit for acoustical absorption) of absorption in it and you add another 1,000 sabines. The reverberation time drops in half. But you now have 2,000 total sabines of absorption and to get that same difference again would require adding another 2,000 sabines. Then it would require 4,000 sabines and so on. The point is that you will usually get the most noticeable difference with the first X amount of absorption introduced and subsequent additions of X amount of absorption will have diminishing returns. That's not saying it shouldn't be done to get to the desired result, but many people concerned about budget do phase installations and decide to stop at some interim point.

    Here's something to consider. To try to get good coverage of a listener area it is common to aim the axis of the speaker at or near the furthest listener since this puts the highest level of the speaker output corresponding to the listener experiencing the highest loss in level due to distance. However, if the speaker axis is aimed at the furthest listener, then only half the speaker's energy is hitting the audience and the other half is hitting the walls and maybe even the ceiling. This is the common dilemma, if you do not acoustically address those surfaces then you have almost half the sound system energy potentially hitting reflective surfaces. If you try to address this by adjusting the speaker aiming to have less sound hitting these surfaces then you typically experience issues with level and intelligibility at the extremes of the seating. This is one reason why the room acoustics are integral with the sound system and the sound system performance may be limited by the room acoustics.

    Sorry for the long and sort of off topic post, but there seemed to be a lot of misconceptions regarding acoustics.
     
  19. banditj13

    banditj13 Member

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    Wow - thx for the information... and i didn't think it was all that off topic!

    certainly cleared up some misinformation I had!

    What was told to me was that the builder didn't care about the acoustics, b/c the room was built as a multipurpose room, and the sound people that they hired worked off of a template designed by the builder...
    I was not in attendance at the church at the time the acoustical guy looked at it, well after the room was built... but from what I was told, he wanted to
    do something to the effect you are mentioning... replacing the cieling with another type of cieling (the majority of the cost) and then absorption at points around the walls, including the back wall and stage...

    Of course this could all vary when we add the 2 subwoofers for the low end...

    I really appreciate the information...
     
  20. banditj13

    banditj13 Member

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    Oh, and as for re-aiming the speakers... we have a nice lift that we can borrow, and the one thing done right was rigging on the speakers... the cabling holding it is adjustable...


    Thanks,
     

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