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Thread: SR pros on this forum

  1. #46
    Moderator / Treasurer/Marketplace Czar boputnam's Avatar
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    Quote Originally Posted by Oldmics
    I guess my confusion lies in the intermingling of the term "line array" with trap enclosures.
    I'm suspicious therein lies my confounding, but then again, if it's a part of the first part and not part of the second part then I'm fine.
    bo

    "Indeed, not!!"

  2. #47
    Senior Member JuniorJBL's Avatar
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    Huh

    Quote Originally Posted by boputnam
    I'm suspicious therein lies my confounding, but then again, if it's a part of the first part and not part of the second part then I'm fine.

  3. #48
    Senior Member Akira's Avatar
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    to clear up some confusion

    sorry, i was talking about two separate system designs...

    When I refer to a vertical line array in a trapezoidial design, I am merely referring to a line array of drivers, ie: in this case 3 drivers mounted in a direct line--not a group of speakers mounted vertically.
    This is quite different than the new series of vertical line array systems which do exactly that. These enclosures rely on a wide horizontal splay coupled with a tightly controlled vertical beam; the opposite of a trap. I don't know a lot about these new systems and have had no hands on experience with them. But, in comparing the two systems I like to think of a trap system as identical multiple mini boxes forming a summed image while the new line arrays are almost like a series of wide firing full range horns draped from top to bottom in a tall single row.

    In a trap format the goal is to create a full image box with certain beam characteristics which enable blocks or clusters of identical enclosures to be used together to form a seamless "point source array." Meaning the sound image from multiple boxes grow in size, proportion and SPL in direct ratio to the number of units combined. Walking around the perimeter of the room will reveal a single image point source per cluster group. And yes the combined image can be made spherical and often is with a single large cluster in the front middle of the room. Think of a mirror ball cut in half so there is no ceiling coverage. This was a radical but old idea, which changed the thinking from a previous generation of P.A. systems that where folded horn loaded and used separate bins for bass, mid and highs. Since each enclosure is it's own full range source, the concept makes absolute sense as the number of units need only grow proportionately with the venue. With a folded horn system and even the new line array systems, you can't do that.

    The shape of the box and alignment of the drivers ABSOULTELY CHANGES THROW CHARACTERISTICS.
    I have A/B' trap and rectangular enclosures one on one and in a cluster with the identical driver setup and identical power rack processing, outdoors where it really matters:
    (2) E120 (1) 2445 with 2380 Biradial.
    amp rack: BSS 24db/octave Linkwitz Riley with QSC MX2000 bottom and QSC MX1500 top

    The traps threw way further and the rectangular box with off set drivers sounded way better. The traps had far superior summing characteristics than the rectangular boxes, so yes design shape plays into it. While the rectangles sounded much better standing alone like a very loud studio monitor which does not gain as much from doubling side by side and increases driver interference as a result of firing in the same plane.
    I only tell you this story because I built the above series of rectangular boxes while a competitor built the traps. This design mistake cost me a very large sale...but, that's how we learn, isn't it?

    p.s. I will be posting pics of this and other designs on another post shortly.

  4. #49
    Senior Member Akira's Avatar
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    Quote Originally Posted by Oldmics
    Yeah,I"m with Bo on this one!



    You also make the comment "a trap design will throw further than a rectangular box."

    Are you talking individualy or multiple enclosures?The "throw" charactoristics are defined thru sound pressure levels which are calculated from the use of multiple enclosures,enclosure style (if line array-focusing of the boxs) and hang heigth. There is no difference in "throw" when comparing one rectangular box to one trap enclosure.
    First let me say I am no expert when it comes to building boxes. Rather it became a function of neccessity when I needed to replace my "B" line of P.A. systems from the old horn designs to the then new line of full range boxes.
    Originally, like you I believed that identical drivers in a properly designed bass reflex enclosure would put out the same SPL regardless of, as you say "exterior cut." Physics tell me that is absolutely true.
    This being the case if one design is louder 100' away, then physics also say that the same volume of sound must be more narrowly focused in beam to sound louder at a greater distance.
    In your above example you infer that throw is a function of: "The "throw" charactoristics are defined thru sound pressure levels which are calculated from the use of multiple enclosures,enclosure style (if line array-focusing of the boxs) and hang heigth. This being the case, if one style of box throws no better than another style of box, then there would be no advantage between either system when combining multiple enclosures.

    p.s. I was not aware of the deficencies in my own design (below) until I was up for bid with another builder. The potential customer was a medium sized touring company who heard my excellent sounding boxes in a club. (their main application) We set up different combinations with the competing designs set on a loading dock firing into an empty field. The difference was night and day...a lesson in design I will never forget. BTW, my design sounds like a big studio monitor and when using the rig with 4 tops and 4 subs a side, you can clearly hear the entire image 150' at the back of a room. It was only in an out door application where I was taken to school.
    Attached Images Attached Images  

  5. #50
    RIP 2011 Zilch's Avatar
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    I doubt that the shape of the box "focuses" the sound field.

    I've always viewed the tapered sides as merely facilitating clustering the cabinets at the proper angle.

    BUT, the same models offered in different dispersion angles don't have different side angles.

    See also the concept of "Exploded cluster," I linked to above, which seems more like the presently troublesome installation.

    They gotta be really close to sum at higher frequencies.

    Apparently, I know nothing....

    Is there a JBL clustering/rigging manual that describes this?

  6. #51
    Senior Member Ian Mackenzie's Avatar
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    Quote Originally Posted by Zilch
    I doubt that the shape of the box "focuses" the sound field.

    I've always viewed the tapered sides as merely facilitating clustering the cabinets at the proper angle.

    BUT, the same models offered in different dispersion angles don't have different side angles.

    See also the concept of "Exploded cluster," I linked to above, which seems more like the presently troublesome installation.

    They gotta be really close to sum at higher frequencies.

    Apparently, I know nothing....

    Is there a JBL clustering/rigging manual that describes this?
    Try the tech library at jbppro.com or the better Pa bibles..its not something you can pick up in 5 minutes and come up on here comment fluently on! You might have to go back to school depending on your level of education...was that Cal tech?

    I recall Bo's engineer was into all this stuff.

  7. #52
    Senior Member Akira's Avatar
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    Quote Originally Posted by Ian Mackenzie
    Try the tech library at jbppro.com or the better Pa bibles..its not something you can pick up in 5 minutes and come up on here comment fluently on! You might have to go back to school depending on your level of education...was that Cal tech?
    ...maybe I'll have to go back to school.
    if you look at the pic above there is something about it's design that made it sound fabulous close up front, dispersing immediately. I designed the box on it's smallest possible baffel space and size with the horn, thinking shape and alignment would make very little difference.

  8. #53
    RIP 2011 Zilch's Avatar
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    O.K., called "Planar" arrays, you set the included splay angle as desired. The angle of the cabinet sides defines a nominal (not necessarily optimal) splay:

    http://www.jblpro.com/ae/pdf/BRACKET1.pdf

    Exploding the cluster creates increasingly overlapping sound fields at greater distances where path length differences become proportionately smaller....

  9. #54
    Crash
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    Why are non-SR Pros even posting in this thread?
    I was hoping to learn something.

  10. #55
    Senior Member Ian Mackenzie's Avatar
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    Quote Originally Posted by Crash
    Why are non-SR Pros even posting in this thread?
    I was hoping to learn something.
    Good point but perhap being on the Off Topic Forum say it allll ,

    Hey , we need a spell checker.....the thread title ain't too good either

    SR pros on this fourm

  11. #56
    Crash
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    Oh

  12. #57
    Senior Member JuniorJBL's Avatar
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    Sometimes.....

    Quote Originally Posted by Ian Mackenzie
    Hey , we need a spell checker.....the thread title ain't too good either

    SR pros on this fourm

  13. #58
    Senior Member Ian Mackenzie's Avatar
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    Apparently, I know nothing....

    1st quote of the week
    Affirmative Will Robinson


    BTW, my design sounds like a big studio monitor and when using the rig with 4 tops and 4 subs a side, you can clearly hear the entire image 150' at the back of a room. It was only in an out door application where I was taken to school.

    2nd quote of the week.

    Well mine sounds like a big studio monitor because it is...but I know what you mean. By the way you are giving you age away.

    My best recollection of a PA box sounding like a studio monitor was the Clair Bros S4 cabinet...2 2240's 4 K110's, 2 2441, 2 2405's per box. The Roadies JBL 4350...nothin even comes close.

    Get 20 or so of those per side of the stage and you got something worth listening to..sheer brute force.....

  14. #59
    Senior Member JuniorJBL's Avatar
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    Here is a simple drawing.

    First this is what we have
    Attached Images Attached Images  

  15. #60
    Senior Member JuniorJBL's Avatar
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    Another

    This is what I think we need. And yes there is tilt as well but I did not draw it.

    BTW This is top view just in case there is
    Attached Images Attached Images  

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