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Need Advice for Lousy Theatre Sound Reinforcement

Discussion in 'Sound, Music, and Intercom' started by kjones9999, Apr 16, 2019.

  1. kjones9999

    kjones9999 Member

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    Hi all.

    So I work in a school system that has two identically horrible theatre spaces. Basically an 800 seat house with concrete walls and little if any sound absorption.

    I typically use two large cabinets on the sides of the stage, and EQing so that the wireless mics are intelligible makes them very tinny. Any low end gives a bad echo. So I just pick an area in between. I do have a Sabine GraphQ that helps me isolate some of the frequencies, but its still hit and miss.

    I am trying out powered 15" JBLs this year, and the plan is to put them in a horizontal array at stage level facing the audience (3 speakers). The hope here is so that the main part of the house (we typically only use the center 400 seats) the audience will be guaranteed to hear sound directly from the speakers and not from a secondary reflection.

    Am I thinking correctly? How do others deal with really "echoey" spaces?

    On another note -- we have sennheisers and I usually run the sensitivity low -- -45db or so and compensate with the mix. What do you do?

    Thanks all, as always, for the input...
     
  2. jkowtko

    jkowtko Active Member

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    How about ... more speakers, closer to the audience, evenly spaced, lower volume.

    If possible I would suggest to try to cover or break up the reflective surfaces by hanging tarps, placing tall floor standing items in front of flat walls, etc ... but if that isn't practical then it seems the only foolproof way to minimize the reflective sound is to put your destination much closer to the source than the reflective surfaces so the direct sound will be much louder than the reflective sound.

    Ever been to Disneyland? Their landscape speakers are around 30 feet apart and at low volume you can hear the audio tracks playing pretty clearly no matter where you are walking and what other noise is in the background.
     
  3. MNicolai

    MNicolai Well-Known Member Fight Leukemia

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    There are many concert halls that do not have significant absorption (absorption is wasted energy -- it has its purposes but it's not the be-all-end-all).

    You need to get your main speakers in the air and point them down. When you put them at ground level in a generally flat room, your strongest reflections are all going to ping around the room at ear level with strong reflections off of the rear wall. Get them up and pitch them down. The excess energy gets diffused by your seats and the reflections onto the walls will bounce to the floor/seats and then back up toward the roof. You won't hear such a strong accumulation of persistent sound energy hanging around down at your listening plane.

    There's a lot more I can say about sound system design but unfortunately I don't have time today and others will need to chime in. Try a solution with the speakers suspended (by a competent person using rated hardware and speakers with integral rigging points) above the lip of the stage.
     
  4. Rod Reilly

    Rod Reilly Member

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    Why 15" .. now your vocal is split between 2 drivers that both do awful thinks to the vocal - the 15 rarely reproduces the fundamentals accurately and the crossover point to the horn means it is handling almost all the harmonics that make a voice sound "right". I am a great fan of vertical line arrays - what we used to call column speakers - for vocals, and if you need bass add a sub or two.

    For your space try a pair of JBL Eon One systems or Turbosound iP2000 or LD Maui - self powered, subwoofer included plus a column on top. The VLA also controls dispersion down to 300 better than a 15, so less reflections from those hard surfaces.
     
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  5. mbrown3039

    mbrown3039 Active Member

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    Currently working on a similar problem here in Vegas -- ~40-year-old church, longer than wide, with concrete walls and no appetite for sound treatments. So, instead of a L/R system, we're using a single center cluster and focusing that energy pretty tightly on the congregation (luckily, the floor is carpeted and the pews are upholstered). There's a delayed speaker mid-way down the room for the back rows. Are you able to fly a rig or is it ground stack only?
     
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  6. JD

    JD Well-Known Member

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    I'm a big fan of breaking the system up into a series of smaller speakers along the walls, each set on a delay line. We use this system at my church and despite the horrible acoustics, vocals are clear and crisp. When you are designing sound for basically a cement tank, power is your enemy as there is just that much more sound bouncing around. Best tactic is getting smaller speakers closer to your audience and running them at a much lower level. Since low end does not produce a sound image, Subs can still be located near the stage. That being said, low frequencies are the most likely ones to wallow in the tank.
     
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  7. mbrown3039

    mbrown3039 Active Member

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    Major consideration as it regards low-end: is your stage a wooden deck (that is hollow beneath) or a solid concrete slab? If hollow wooden deck, you may be better off getting that bass away from the stage somehow....m
     
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  8. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    @JD Were 'pewback' speakers ever a thing on your side of Donald's walls? We had an installation in a nearby Catholic Basilica with approximately 100 pew back cabinets installed in the backs of every second row of pews. Each cabinet contained two extremely shallow cones with each cone measuring approximately 3.5" < 4.0"; from memory, there were approximately 9 cabinets across the width of the cathedral per row and 22 rows for an approximate total of (9 x 11) 99 cabinets.
    Amplifiers were a barrage of BGW 250B's each operating as 2 mono channels per amp driving into transformers stepping them up to 70V with the necessary step down transformers included within the cabinets of each pair of cones. Delays were analogue 'bucket brigades' by IRP, Industrial Research Products, which passed for full bore broadcast quality in their day. (The installation would have occurred in the early 1970's as part of the restoration post a devastating fire closed the Cathedral Basilica for several years [Lot of that going around.]) The installation was impeccably delayed but sounded less than optimum, possibly due to the economy TEAC model 3 console a local Catholic music store donated and added in line with its pair of top quality, phantom equipped, modular mic pre-amp inputs when the music store's owner, no doubt a parishioner, decided several SM58 clones were exactly what the cathedral needed along with a smattering of nasty Nady wireless lavs (which left something to be desired when hastily pinned to a robe then hidden beneath a colorful, THICK decorative scarf. The originally supplied microphones were a pair of condensers from a modular small diaphragm line which included tasteful VR1 and VR2 curved extension tubes; the VR1 on a pulpit and the VR2 on a floor stand located for Priests standing DSC, or whatever passes for Down Stage Centre in a Catholic Basilica.
    EDIT: The originally installed microphone capsules were both AKG CK-5's on VR1 and / VR2 rigid, curved, extensions with AKG C451EB electronics modules and their integral low end roll-offs set appropriately for the (vocal) reinforcement application. Within the equipment rack the microphone inputs were additional IRP modules which also provided appropriate phantom powering. Purportedly the music store owner / member of the congregation was confident his SM58 clones on economical (Cheap 'n cheerful) glistening chrome stands equipped with multiple (mechanically NOISY) Atlas GN series chrome plated CLONES would doubtless out-perform the tasteful matte black CK5's and VR extensions and then he installed a TEAC model 3 in place of the IRP modules and added his nasty NADY wireless lav's. Yesiree Bob! Definitely an improvement in his mind. Presumably the Basilica paid their music store-owning (self proclaimed) architectural and electro-acoustic expert handsomely for his time and expertise. @MNicolai I'm sure you've never encountered such expertise / improvements! (Where's those cackling Smilies when I need them?:wall::liar::clap::D [Found a few.]
    Toodleoo!
    Ron Hebbard:eek:
     
    Last edited: Apr 17, 2019
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  9. macsound

    macsound Well-Known Member

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    Definitely echo others about using smaller speakers, flown, LCR, C+Delay, whatever you can muster.

    I think another issue is how you are applying your EQ.
    Graphic EQs are great when making soft sweeping adjustments, but rooms typically have resonant tones that are fairly slim and harmonics.
    For example, might cut 300Hz, 600Hz, 1.2k. and 2.4k. All of a sudden it sounds horrible because you've also cut every frequency in between (by a lesser amount).

    You might have better luck with a parametric EQ because of the ability to pinpoint the couple problem frequencies and be conservative in your cuts.
    Also, cutting a varying amount of low end, depending on the performer will allow you to get rid of unnecessary lows on men who tend to be boomy and cut less on women who might need some of that low end for warmth.
     
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  10. kjones9999

    kjones9999 Member

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    Thanks for the responses everyone.

    Flying the speakers wont work in this space for a few reasons. Some physical and some political.

    I do have a parametric EQ (an old sabine graphiq that we use for feedback elimination). It allows me to also delay. But one big issue with delay and with feedback elimination is how is recorded music handled? Thats what concerns me about many speakers -- is the need to delay.

    I did move one speaker as a test closer to the audience, and indeed a lower volume helps. I also have enough drapery to cover one wall-- so how stupid is this idea?

    https://www.autodraw.com/share/51H8GEQ1RAMF

    Our house is about 80 feet deep. I know this would just be on one side, but I think it may be better than two sided echo chamber. I am worried about the need for delay however, Please keep the suggestions coming, and thank you!
     
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  11. jkowtko

    jkowtko Active Member

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    It sounds like there are other proponents of more, smaller speakers spread out. As examples here are a couple of configurations that I use:

    * Instrumental music concert for the local middle school, in the gym, stage/bleachers ~120 feet across and bleachers ~30 feet deep:
    - 2 SRM450s on stands at the front corners of the "stage", and an Anchor AN-1000x as center fill (mono) next to the conductor podium ... L-M-R ... the center as tiny as it is really fills in the sound and evens it out across the audience, especially for the emcee mic.

    * At home in the backyard, ~70x20, I have 8 speakers arranged in rectangular array around the perimeter of the yard, :
    L-R-L-R
    R-L-R-L
    so no matter where you are standing you tend to pick up stereo reasonably well.
     
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  12. FMEng

    FMEng Well-Known Member Fight Leukemia

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    If the room is severe enough, different portable speakers will just vary the degree of badness. Your problem is the same as what is experienced in many churches. Some churches have had barely intelligible amplified speech despite carefully designed and installed central clusters, also known as point source arrays. The acoustics required more than the speaker technology could cope with. In just the last few years, a number of new solutions for highly reverberant spaces have emerged, ranging from steerable column speakers to DML speakers, and some of the worst spaces are being tamed.

    If you want a good, long term solution, hire an acoustical engineer to look at both the room and the sound system together. It might be cheaper and easier to fix the room along with a properly designed sound system rather than just throw money at sound equipment.
     
  13. TimMc

    TimMc Well-Known Member

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    How smart do you want to be? The "gold standard" is Bob McCarthy's "Sound Systems: Design and Optimization". Runner up is "Sound System Engineering" by Davis & Patronis.

    A central cluster is the preferred way to cover this kind of space and with proper component selection it's possible to significantly reduce the amount of sound hitting reflective surfaces. Also, because there is only 1 source of acoustic excitation it's much easier to time-align and optimize with any small zone mixes (front fill, under-balcony, etc).

    A distributed system of any flavor actually makes intelligible sound more difficult unless loudspeaker coverage is *very* tightly controlled or loudspeakers covering other areas, near or far, are significantly lower in level at the location under test. If a listener can hear the desired loudspeaker and multiple other loudspeakers you've built a significant impediment to understanding words, which IINM, is the exact problem you are having now: Multiple unsynchronized arrivals of identical signals.
     
  14. macsound

    macsound Well-Known Member

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    Is the delay you are talking about echo from the room or the need to delay the signal to the speakers if you have more speakers like in your drawing?
    In reply to your drawing, it wouldn't be very balanced to only have speakers on one side of the audience. If you were to hang drapery for acoustic purposes, it would make more sense to cover the back wall and keep the speakers flanking the stage.

    I think initially you need to analyze if your issues are stemming MORE from the PA or the room (of course both may be contributing but if you can solve the 60%, you can deal with the 40%). Then you can make more definitive decisions.
    Even in an apartment, garage or outside, you can play some music that you know sounds good and try a vocal mic and see if it sounds natural. This surprisingly easily can identify issues like a blown HF driver or messed up crossover that you previously didn't notice in the rush of setup in the space.
     
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  15. JD

    JD Well-Known Member

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    Delay or Delay line?
    In our church, the first set of speakers, near the altar area are in real time. The second set are at 15ms behind RT, the third set are 28ms, and the 4th set are at 48ms. These were based on calculating the speed of sound at 70 degrees temp. No matter where you stand, the sound is clear and it is a very reverbarant room. The catch is, you have to do the math or the results will be bad. In this case you are measuring from the center pew area diagonally to the speakers, which are at 25 feet elevation. We have had performance groups come in and use their own stage-side gear with speakers in the front and the result is atrocious.
     
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  16. Jay Ashworth

    Jay Ashworth Well-Known Member

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    It sounds like your major problem is an unecessarily reverberant room, and while I saw one person mention damping it, everyone seems mostly to be concentrating on EQ and speakers/positioning.

    Damp the room.

    If you can put in permanent damping (once you've tested), that's best; if all you can do is get pretty comforters and hang them on the back wall, start there. :)
     
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  17. TimMc

    TimMc Well-Known Member

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    In post #10 he links a quick sketch of possible speaker and drapery placement. I have a couple of ideas, see what you think, Jay...

    I'd rather not put speakers on 1 side only, nor would I want them too close to the audience. In general, though, moving the speakers closer reduces the amount of output SPL needed for EAG and that's less energy exciting the space. The down side is that coverage still needs to reach the furthest listener - I can see a potential problem with blasting the patrons on the speaker-side while the folks over house right are 12dB down... and I suspect the eye/ear link would be massively messed with, seeing action forward or to the right while hearing most of the audio from the left would make for a fatiguing experience.

    Next, while I'm a fan of acoustic absorption, I'm also a big fan of diffusion, too. Killing 1 side of the auditorium will help in 1 direction but we need to treat 2 non-parallel surfaces. If his drape/curtains are in 4 panels (or more, legs would be idea), I'd stagger panel - open space - panel - open space along one side, and treat the back wall similarly. If it's possible to have the drape hung away from the walls (say a foot or so), better LF damping will happen. Ideally the opposite side wall could receive the same treatment. It will help if there is time to experiment with placing soft goods and the ratio of exposed wall to drapery to keep from over-damping.

    I like using theatrical drape or exhibit/trade show velour because it has fire code compliance sewn in or has supporting cert docs.
     
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  18. Jay Ashworth

    Jay Ashworth Well-Known Member

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    I'm not sure I wouldn't leave the speakers in their current place, and prioritize damping the back wall first; if the room's a wedge, the mains will be less likely to bounce off the sides, I'd think.
     
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  19. TimMc

    TimMc Well-Known Member

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    I get the impression there are 2 things going on - intelligibility problems and a lot of LF "boom, bloom, and hang time." Treating the back wall will definitely help with any slap-back echos and reflections but doesn't do much for the other reflections or the LF.

    I agree that at least a pair of speakers needs to be up near the stage/proscenium and another pair could be in the house, delayed back to the main PA.
     
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  20. teqniqal

    teqniqal Well-Known Member

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    I'm going to be the dissenter here on several issues.

    Room Acoustics: Many seem to think sucking the life out of the room is desirable. When you add too much absorption to the walls / ceilings it does reduce the reverberation, it also significantly reduces the sense of 'being there' that the performer gets standing on the stage. Dead room = uninspired performer. The most common error acousticians make in trying to tame a room is adding waaaay too much absorption to the back wall of the seating area. If you have distinct echos, then treat them with architectural diffusion shapes and scatter the energy uniformly. AFTER you solve those issues, then you can look at modifying the reverberation time profile of the room. One has to understand that each material you introduce into a room absorbs sound differently at different frequencies (as does diffusive material - its not easy to get a good balance). If you reduce the high, mid, or low frequency reverberation time of the room disproportionately to the other frequencies, then the room can become very odd sounding (rumbly, boomy, tinny, thin, crisp and a zillion other adjectives). Solve your room acoustics issues BEFORE you attempt anything with sound equipment. It doesn't matter how much money you spend on sound equipment, the room's natural acoustics will still suck and there is no knob, fader, or miracle DSP that can change that.

    Sound System: Acoustic challenges require require finesse, not brute force to overcome them. More, bigger, or louder speakers will not help. KISS. Keep It Super Simple. When you chose speakers that have cross-overs in the vocal range (200-4000 Hz) then you start having to EQ them to 'fix' the transitions from one driver set to another. EQ causes phase shifts, phase shifts can affect feedback sensitivities. This can also affect the clarity of the voices because part of the voice is coming from one driver and the other part of the voice is coming from another driver. Speakers that use the same driver(s) (fewer is BETTER) for the speech range and then supplement above and below that with tweeters and woofers will generally sound better (more natural for voices) than boxes with horn(s) and woofer(s) and a crossover in the vocal range.

    That said, consider getting a demo of several different technologies an see what works best in your space (NOT someone else's space!). Since you are constrained to placing the speakers at the sides of the proscenium, I suggest you look at column speakers like the Alcons Audio QR24 series (albeit, they do have a cross-over in the vocal range) and QB363 subwoofer. The phase response of these is fairly linear and introduces minimal feed-back anomalies as long as you don't try to 'EQ the room'. The other speaker that I have had good success with is the Tectonic Audio Labs PL11NR with a modest subwoofer like their LS-212. It has only one cross-over point around 150 Hz (well out of the vocal range), and it's unique DML driver technology interacts less with the room acoustics than conventional cone and/or horn type loudspeakers. (It's difficult to explain, but it works, and that's what matters. People of the 'I can't model it in EASE, therefore it doesn't work' school of thought don't get this. EASE is just a wrench, if the wrench doesn't fit, it doesn't mean that the machine is a bad design, it just means you need a different wrench.) Either of these companies will arrange for you to get a good demonstration in your venue so you can see how they work. Demo the speakers you would likely use, not their big brother or third cousin.

    Bottom Line - GET A GOOD ACOUSTICIAN THAT UNDERSTANDS THEATRE involved with your project (pm me if you are interested). It will be money well spent to fix your room so you don't have to continually fight with it. Then listen to some speakers.
     
    Last edited: Apr 19, 2019
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