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Thread: SR pros on this forum

  1. #61
    RIP 2011 Zilch's Avatar
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    You said the centers were running mono. Do we correctly presume the two sides are stereo, L & R?

    Are you proposing to split the feed to the separated centers, then, or continue in mono?

  2. #62
    Senior Member JuniorJBL's Avatar
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    Mono

    Quote Originally Posted by Zilch
    You said the centers were running mono. Do we correctly presume the two sides are stereo, L & R?

    Are you proposing to split the feed to the separated centers, then, or continue in mono?
    Everything is mono. I would like to have a L/R stereo only as I think this would be a better approach to this type of room/setup.

    The other problem is this is a church and people do not want to see ANYTHING!

    So we do this "behind the sceen"
    Shane

  3. #63
    Senior Moment Member Oldmics's Avatar
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    If you guys don"t mind,I"m gonna continue my chat with Akira.

    I wanted to keep it in this thread for those following (although it should go to its own place so that we may concentrate on JuniorJBLs situation)

    Akira-the pictured enclosures are your workmanship? I say-Nice Job

    So when you compared those boxes to trap enclosures-You lost out in the SPL war?

    The first thing to consider is the reason for the enclosure.



    The enclosure keeps the front wave from meeting the rear (inside the enclosure) wave.



    Rear cavity volume can be calculated on any enclosure shape whatsoever be it square,rectangular,trapezoid,etc.



    The shape of the enclosure does not matter to the speaker driver (yeah,yeah,I know cubes are bad due to standing waves-I’m trying to keep it short).The only thing that matters to the speaker driver is the enclosure volume.



    Again I submit that as long as the volume of two given boxes (be it rectangular or trapezoidal) are identical and that ALL of the components used are identical and loaded in the same fashion along with the porting being identical ,the two boxes will produce the same sound pressure level (or throw).



    This is only a singe box comparison. This also precludes that both enclosures are built of similar materials and no standing wave issues are encountered due to construction techniques or inappropriate materials used.



    When multiple enclosures are utilized trap boxes have a slight advantage because of there ability of mutual coupling. Rectangular enclosures also can do this (piles of Clair S4s) but a trap box will have a wider frequency range of beneficial mutual coupling. This is due to tighter component spacing.



    In my opinion,the biggest deficency of trap enclosures or rectangular boxes in a vertical array is comb filtering (regardless of how incrementally narrow the horns horizontal pattern exhibits).



    This is where the line array systems are superior.Checkout this link for line array information



    http://www.prosoundweb.com/lsi/tech/la/la.php



    The information is a few years old but still applicable



    Point source arrays don”t exist (except in the minds of the marketing departments) .

    Again the comb filtering issue.


    The closest thing I have heard to point source is a mono Tannoy system.

    There has to be another reason why your boxes lost in the shootout.It would take a pile "o" test gear and lotsa time to find out why-But it was not because of the shape of the enclosure.

    Oldmics-still learning that I"ll never know it all

  4. #64
    Senior Member chad'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.


    1) I personally configure, hookup, eq, troubleshoot and mix live sound nearly every weekend of the year. The venues range from 50 to 500 occupants, the room acoustics range from gorgeous to absolutely horrid. Primarily my SR work is for my own personal band, but hey - I've dealt with pro audio for 20 some years and also get hired by local club bands to mix their FOH.

    2) Would you please give your definition of "SR Pro"??

    3) I think this forum needs an SR section, as the majority of discussion is related to home audio and studio monitors.


  5. #65
    Senior Member Akira's Avatar
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    Apologies to JuniorJBL

    i seem to have inadvertently hi-jacked your thread.
    i would like to start a new thread as there is an interesting topic i would like to learn more about: box design in general

    NOW BACK TO WHAT'S IMPORTANT...let's keep on topic and help shane out.

    as for your diagrams:
    i can see two problems with diagram #1. all speakers should be vertically aligned which you are correcting. and, the mouth of the front enclosures is out of alignment with the sides. this combined with the system problems you have mentioned now totally makes sense.
    diagram #2 is an improvement and depending on the buttress (pic) that hides the speakers maybe your only practical layout. the ideal configuration is a true half spiral splay with all cabinets tightly together, but that doesn't seem possible.
    i try to avoid placing speakers in close proximity firing in the same plane like a wall. (your two fronts) but, if it works that's all that matters. i would try playing the two front's only in your new configuration and see how they sound on their own. this may also be a good time to try EQ and finer placement adjustments--you want it to sound good and cover it's intended area. for now pretend the sides don't matter. you say the sides sound good. again play them on their own. do the same for the opposite side and in all three listening tests, also walk around the room and notice spill off and anomalies as the sound becomes increasingly off axis. that will give you a clue if the room still sounds bad when the full system is on. if all three sides sound good individually, then you would think combining them all should work out.
    where the corners meet in the buttress which is also the same plane as your L/R speaker pairs, is a potential problem for the audience in direct line of them. this would be the acoustic boundry between front and side....but, there's only one way to find out.
    i have worked in rooms with a similar layout and while not ideal are not a problem. i think that your end result should yield a decent sound. please follow through on your updates and we will promise not to interfere.
    p.s. not sure why you would prefer stereo; i'd keep the system mono.

  6. #66
    Senior Member JuniorJBL's Avatar
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    Thanks Guys

    As far as others talking about whatever that is fine with me I am just glad that when I do post you guys answer.

    The reason for stereo is there is a LOT of video in the room w/ four projectors lots of stuff. This would be my primary reason. It does look like we are trying to plan a day within the next two weeks to move the speakers and to have enough time to maybe move them to a different location if what we have talked about does not work. This would probably be the saturday after thanksgiving.

    I will also try to get better pics of all the room so people can see everything in the works.

    There are other issues w/this room as well that I would like to address but as we all know it is better to tackle one problem at a time.


    Thanks again to all who have put there 2c in to get to this point.

    Shane

  7. #67
    RIP 2011 Zilch's Avatar
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    Before you move anything, try disconnecting (turning off) one of the centers first. I'm betting everything will improve substantially, even though the aiming of the remaining active speaker is not optimal.

    My analysis: They've packed 240° of controlled dispersion into 150°. There's major overlap of the sound fields with concomitant phase interference. That's why they disconnected one of the tweeters. They shoulda killed the mid, as well, which is also giving you excessive midrange emphasis.

    When you connected them out of phase, you nulled out the overlap at the center and one of the sides, which you perceived as an improvement, a clue as to how to fix it.

    The "spinning" you hear walking down the center is the two centers overlapping in the middle. In mono, it's the entire frequency range creating phase issues. Turning one of them off reduces the total dispersion (horizontal, of the complete system,) to 180°, a better match to the space. Separating the centers as you propose would reduce the problem at the center, but increases the interference with the sides.

    If disabling one of the centers works, remove one of them and fly the remaining one upright after rotating the M/H assembly back to vertical and re-aiming it straight out. Keep the present downward tilt angle, which increases the splay in the direction of the listeners, reducing the remaining overlap.

    As I read the JBL tunings, they're only provided for passive and triamp modes. You'll have to work out what's appropriate for your biamp setup, not shown. Schematic tells me the full mid/high filters remain in play in the biamp mode, simplifying the task.

    I suspect the four units could be made to work very nicely with more precise aiming and downward tilt adjustments, but perhaps not within the constraints of the existing screened platform. That's a task requiring 3-D modeling of elliptical cone sections, well beyond my capabilities. There are likely resources available at JBL for that, but I don't have access to them.

    As you know, stereo would create it's own new set of difficulties....

  8. #68
    Senior Member JuniorJBL's Avatar
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    So...

    What you are saying is it may be better to have 3 instead of 4?

  9. #69
    Senior Señor boputnam's Avatar
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    Quote Originally Posted by JuniorJBL
    What you are saying is it may be better to have 3 instead of 4?
    Thanks, Shane... I'm gettin' lost too.

    But, I also wanna congratulate and thank-you for being so open about this problem, and for seeking ideas / advice here. We have ALL learned a great deal from the varied posts and suggestions on this, whether we are posting or just reading.

    Too often we muddle along, without understanding what or why. The ideas here seem to be getting you closer to some substantial improvements. That is pretty darn cool...
    bo

    "Indeed, not!!"

  10. #70
    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by JuniorJBL
    What you are saying is it may be better to have 3 instead of 4?
    'Zactly. And you can easily try it to see, though without repositioning the center speaker that is running, it will not be as good as after you do.

    Draw 60° angles coming out of the speakers in the present and proposed postionings and see how quickly they overlap to interfere with each other. Spec sheet says they're actually 70° wide at -6 dB from 500 Hz up, average, i.e., worse.

    Look at the horizontal polar plots in the spec sheet. At -6 dB, they're 60° wide all the way out through 16 kHz. That's why I say draw with 60°.

    The downward tilt increases the splay of the boxes, and works in your favor to further minimize the overlap while covering more of the audience area and reducing reflections off the walls and ceiling....

  11. #71
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    - Zilches instincts are correct . HiFi & the basic principals behind a "Good Install " aren't mutually exclusive.
    - ( ie ; as in Home HiFi , the fewer sources the ear has to contend with , the better ) .
    - "Sources" can easily include reflected sound , like the many focussed reflections offered up by glass, brick and stone .

    - For the most coherent sound you want each geographical location ( anywhere ) to be "acoustically serviced" by only a single source. Think about that for a moment. Any more than that and anything can and will happen . You've previously discovered the down side of the "anything" syndrome.

    What you are saying is it may be better to have 3 instead of 4?
    Sort of but ,,,,
    - it's unfortunately never that simple . A single 1.75" diaphragm isn't going to come anywhere close to providing the necessary resolution ( necessary for live music ) within the typically "acoustically-challenged" environment found in a church . It can easily be overwhelmed when just voice is the playback source .

    - Your initial instincts/thoughts of increasing the size of the hi-frequency horns' diaphragms' are very likely a good avenue to pursue. For Instance : A single 3" diaphragm has twice the surface area compared to a single 1.75" diaphragm . A single 4" diaphragm has four times the surface area. The numbers are; 3.1 sq", 6.3 sq" & 12.5 sq" for the three sizes of diaphragms. Surface area in any pistonic device ( diaphragm ) , when driving through a "point source" device ( like a horn ), does translate into greater resolution / clarity & lower distortion ( with a bunch of other things being equal ) .

    - Since your boxes have rotatable mid/hi horn modules / setup ( orient ) the 4 of the boxes so that those midrange horns never ever overlap .
    - Study the product brochures and memorize the horns 6 db down points in both the vertical & horizontal planes. Line up all 4 of your boxes so that these ( 6 db down ) points ( for the horns ) are parallel to each other. This might mean that you need to choose a "module orientation" that provides the narrowest horizontal coverage. Why ? it's still about coverage and one boxes horn module is not going to be able to provide the @ 120° to 140° horizontal spread needed in the front section. . Obviously , each box ( & it's module ) will need to be rotated away from each other so that their actual horn coverages never overlap .

    (i) Draw the mid-horn coverage patterns ( horizontal & vertical ) out on paper. Hopefully the HiFreq. horn follows the same coverage pattern as the low-mid horn . If they differ much , these boxes are getting close to being a lost cause for proper implementation . I'd suggest making little paper cutouts that represent the enclosure as well as the projected coverage emanating out from the horn walls ( for about a 10' distance ) . This must all be done to scale.

    (ii) Overlay these paper coverage standins onto a ( scale ) drawing of the churches layout . This would represent a " plan view". Play with the four boxes/coverage cones to get the best / seamless coverage that has no overlap.

    (iii) Do the same coverage exercise with a "sectional" ( elevated ) view . I'd suggest "aiming the center of the horns" at the row of pews that are about 1/3 the distance from the back pews ( providing this focus actually gives some horn coverage to the pews closest to the front ) . If you aim the horns too high, you can easily blow too much acoustic energy into the back walls / which exaccerbates the typically "tragic" acoustics found in modern churches / and will return this reflected acoustic energy as echo into the central area .

    (iv) The above "coverage exercises" are, of course, quite simplistic to accomplish if you are handy with the manipulation of CAD files .
    - If you are ; see if you can get the churches original files in DWG or DXF format emailed to you , for use with your progam. If you contact the original architects, you might be pleasantly surprised to discover they have these files available . Getting files like this ( even in paper form ) can sure save a lot of time taking physical measurements.


    - Eventually ( in a couple of days ), I'll post some links to reference books that you need to own . You need these because it seems, you've allowed yourself to be turned into the churches' "resident PA expert" and ( like it or not ) your credibility is now being put to the test .

    Cheers

  12. #72
    Senior Member JuniorJBL's Avatar
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    Thanks Guys

    This info is VERY good stuff .
    I would like thank everyone has contributed.


    Earl k
    Yes I can get the .dwg file anytime I would like. I don't use much CAD myself but The people I work with do. I understand your direction and I wished I had thought of that myself. That is pretty much basic troubleshooting steps if you think about it.

    I do not have to do all this until I just draw it.

    Zilch
    You actually said the same thing in a few posts back basicly saying the same thing.

    This is what I will do in the next few days. I will try and PDF a copy of the print. SWEET

    Shane

  13. #73
    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by JuniorJBL
    Zilch
    You actually said the same thing in a few posts back basicly saying the same thing.
    Heh, heh. That means I thought it through again and came to the same or similar conclusion, making it worthy of reiteration, to my mind.

    [I also forget stuff.... ]

  14. #74
    Senior Member JuniorJBL's Avatar
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    MVF

    (Most valuable forum)

    This is just a great place to be!!

    Thanks Guys

  15. #75
    RIP 2011 Zilch's Avatar
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    Per Earl's suggestion, equilateral triangles effectively model -6 dB 60° horizontal sound field of VS3115. Multiples joined at apex illustrate vertical distribution, as desired:

    1) Three-cabinet proposal.

    2) Front view shows no field overlap at listening height. Significant phase interaction would only occur along the two lines where the triangle bases intersect.

    3) Nested triangles show on-axis at front (left) and ~20° down. Add bigger ones to model the full 40° vertical field.

    Replicate using actual dimensions, heights, and angles to see what you've got going on there.

    Yes, the projections are really conical sections, so it's not fully described by this method.

    Zilch only does "Quick and Dirty."

    O.K., I'll quit now.

    Model's for sale for $1.00 so's I be "SR Pro."

    [Wanna see my elliptical oblate stairway model? ]
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