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Loudspeakers How to rig SRX725 speakers

Discussion in 'Sound, Music, and Intercom' started by OTO1702, Feb 26, 2009.

  1. OTO1702

    OTO1702 Member

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    Hello,

    We are making some major changes in our club, We had the idea of rigging our main PA, wich are JBL SRX725. The heigth of the seilling is about 24 foot. I would like to know if this is a good idea and what could be the average heigth when rigged. is it better to put them as much high as possible and tilt them or else ?

    The stage is 26 foot long and the room is 120'x30' and the height is about 24

    Presently, the speakers are on top of the subs (SRX728s).

    Is there any tools I can use to measure the best possible height ?

    Thank you !:)
     
  2. DaveySimps

    DaveySimps CBMod CB Mods Premium Member

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    You are encroaching on a bit of a forbidden topic here on CB. For all rigging issues, I highly recommend consulting a rigging professional to be sure it is done safely.

    ~Dave
     
    Last edited: Feb 26, 2009
  3. len

    len Well-Known Member

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    SRX725 are NOT fly-able. The 725F is, but should only be done by qualified technicians. DO NOT EVER hang a cabinet by the handles, or by drilling/mounting additional components onto the box.

    If I were you, I'd sell them or trade them in on VRX cabinets, which are line array and fly-able. And you'll get a bit more fullness in the midrange, but that's my opinion.
     
  4. avkid

    avkid Not a New User Fight Leukemia

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    Do you have a structural engineer, a rigger and a certified welder available?
    If not, don't try it.
     
  5. OTO1702

    OTO1702 Member

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    I am 100% in the same thinking. Its too dangerous.

    1. These units are flyable,
    2. The club is owned by an engenering school
    3. Its done by our the technical department of the school, these engineers and technician are working full time by the school. (ETSMTL.CA)

    I am not going to do anything, they are asking me advices on the preferable height and this was my question.

    My regards,

    OTO
     
  6. proaudionet

    proaudionet Member

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    Dear Junior Techie,

    I would not recommend flying or rigging a regular set of SRX's, unless they came in the F version, which is correctly internally reinforced to handle the stresses that come with flying. You might be able to check with ATM flyware, and I believe they have a kit already made for your SRX speakers. Once again, do not fly speakers that do not have a fly kit installed, you're taking someone else's life in your hands.

    That being said, you should take a look at the dispersion pattern of the horn. I believe the horn has something like a 50 degree vertical pattern, so if you have a fly kit installed, you should tilt them back until you have adequate coverage over the listening area. At a height of 25 ft, I'm going to guess at a tilt of about 30 degrees off axis to cover the floor.

    In addition to the first paragraph, I would suggest getting a professsional rigging company to fly them.... if you have an issue later on, and a cabinet falls, then you can refer back to them. Always setup a suspension rig that has a load capacity approximately 5 times the load of your cabinets, and always use dropforged steel hardware, not the kind of bolts found at your typical hardware store.

    If you need more information, send me an email at [email protected] or visit my website at ProAudioNet.

    Good Luck!
     
  7. Sony

    Sony Active Member

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    IF you have the flyable versions (I.E. SRX725F's ONLY) and IF you have Qualified Engineers (NOT STUDENTS!!) to do the rigging. THEN and ONLY THEN I would recommend putting the speakers around 12 feet. This puts them high enough that that are out of reach of drunk hands...which love to bang, hang onto and grab stuff but also will keep your output from diminishing from being too far from the floor and still allowing easy maintenance with a ladder or lift.

    You're on very touchy ground here...CB has strict rules about NOT telling people how to rig things...because you can very easily kill someone. Also take [user]proaudionet[/user]'s advice and tilt them down so that the dispersion field fills the floor.
     
  8. museav

    museav CBMod CB Mods Departed Member

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    I definitely agree with all the warnings on flying but have to disagree with the 12' height and 30 degree down angles suggested.

    The idea is to try to to use the speaker height to keep the sound going where you want it and to improve the front-to-back coverage. You need to consider the relationship of the speaker pattern and listener area as well as the room acoustics, so the preferred method to determine the optimum height and aiming would be by modeling. But in general, with a 24' ceiling you would typically benefit the most from having the speakers as high as possible.

    I was not sure if it is a 26' stage and then a 120' listener area or a total of 120' with a 26' stage and then a 94' listener area. I also do not know if the audience is standing or seated. However, assuming that the speakers are at the from edge of the stage and with a 24' ceiling height, to get them aimed with the vertical axis at the furthest listener looks to be about an 8 to 12 degree down angle. You might want a bit more down angle than that, especially if the rear wall is reflective, but 30 degrees is probably a bit too much down angle. It typically does take some tweaking in the field to find the optimum angle.

    If the ceiling is continuous you probably do want the speaker flown either very close to the ceiling or a minimum 8' or so away, between those two conditions you can get some undesired reflections off the ceiling.
     
  9. OTO1702

    OTO1702 Member

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    Hello All,

    Agian, Thank you for your support and great warnings. I have asked what were exactely the models and they are : SRX725F. The school is using industrial eye bolts made for this kind of operations. They have purchased all the hardware from solotech wich is the biggest Pro Audio shop in Montreal. So I guess they have worked the product specialist.

    I have sended an email with these discussions to the maintenance people to warn them !

    Thanks,

    O
     
  10. mixmaster

    mixmaster Active Member

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    Full height flying also improves the consistency of your front to back coverage somewhat. When ground stacking a speaker, the first few rows typically get blasted, while the back rows receive significantly less volume, due mostly to the inverse square law and in part to the number of bodies soaking up the sound. By elevating the speakers, you increase the distance from the speaker to the front row, which makes the volume less offensive, and can smooth out the freq. response. Also by elevating the speakers, you also get a less interrupted path from the speaker to the back row, thus improving the sound to them.
    The main detraction to full height flying is that the pattern of the cabinet is that much wider at the floor level, and it becomes that much harder to keep off the walls. Another consideration should be given to the amount of available power. By elevating the cabinets, you will increase the distance to your audience, which decrease the amount of volume. Inverse Square law again. It may take more power or bigger amps to overcome this.
    Considering all of the above, I still prefer to get my cabinets as high as I possibly can. FWIW, I have a pair of SR4732-X that I routinely fly on lifts (with rated hardware, from the factory flypoints). Set on the apron, on top of the subs, SPL drops about 9 db front row to back row, about 100ft At a trim height of 20 ft, I measure a variation of 3 to 4 db over the same space, with the highest reading about 1/3 of the way back. (measurements taken A weighted slow. I've also noticed that the frequency response of the system is much smoother with the cabs elevated, especially in the 400 to 800 range, although I haven't made any measurements to quantify that perception.
    Matt
     
  11. gafftaper

    gafftaper Senior Team Senior Team Fight Leukemia

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    I want to point out a few things for those reading this thread who may think, "I don't need an engineer and a rigger, I can figure out how to do that myself."

    First, Speakers that are meant to be flown have a strong internal framework making that possible. There may be two variations of the same speaker that look exactly the same to the untrained eye, one is safe to fly one is not. You MUST KNOW FOR SURE you have a safe model to fly. Attempting to hang a speaker that is not meant to fly by the handles or running some bolts of your own into the case puts stress on the speaker in ways it was not designed to handle. The potential for that speaker to literally fall apart under it's own weight and fall to the ground injuring people is high.

    Second key point when hanging speakers you are putting a lot of stress on the structure of the building. You need an engineer to tell you it is safe to put that weight at that point. Plus there are vibrations involved... will the vibrations at that point damage the building? Do you KNOW that for sure?

    Third. A qualified rigging professional will DO THE MATH and KNOW the forces that are acting on the item to be hung. The rigger won't guess, the rigger will KNOW what is needed to make sure the speaker hangs safely. The rigger will also KNOW how to install a backup safety system that insures the speaker will not fall and kill someone. Finally a qualified rigger KNOWS where to get good quality hardware (not the Chinese crap at Home Depot). If you don't KNOW you don't belong hanging anything.

    When hanging things, the smallest mistake in any of these areas can KILL. We want everyone to go home safely when the show is done. Never rig things on your own unless you have had the proper training.
     
  12. museav

    museav CBMod CB Mods Departed Member

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    The issues are also in the application. People say they used a speaker rated for rigging and properly rated hardware not realizing these assume factors such as any load being along the axis of the hang point. It always interesting to see a good speaker flow using the right hardware but to see things like the load being applied at right angle to the axis of the forged shoulder bolts (they aren't rated for that).
     
    OTO1702 and (deleted member) like this.

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