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Murphy Corner Line Array (MCLA)

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  • Chromedome2000
    replied
    Re: Murphy Corner Line Array (MCLA)

    One other thing. I noticed in the MCLA design the drivers are rear mounted with a flare routed into the front of the baffle. It seems the ND90 has a thin mounting flange and I was wondering what the effect of surface mounting the drivers would be. Surface mounting would greatly simplify the construction of the baffles, though at the same time would make a grill harder to fabricate. I realize the rear of the baffles would need to be chamfered to allow the driver "breath". I guess what I'm trying to ask is, would surface mounting cause any real problems with diffraction effects or something else I haven't considered?

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  • D, Rose
    replied
    Re: Murphy Corner Line Array (MCLA)

    Hey John! Interesting design. I was thinking about using a line array at my church. Its a long room with a high peaked ceiling, walls go up about 10' before going up to that classic "cathedral" design. I could put two of these in the front corners. We have a praise band for the contemporary service, and a choir for the traditional service. Think this would work? Thanks for your time on this thread.

    Leave a comment:


  • Chromedome2000
    replied
    Re: Murphy Corner Line Array (MCLA)

    The shape of my listening room precludes corner mounting. I would like to make an array of 25 of these drivers which would have to be located some distance from any side walls. I'm wondering what volume the cabinet should ideally be and if a Mini DSP system could be used for EQ? What should I expect as far as bass performance? Modeling the system I come up with about 39L for the internal volume, does this sound about right? I like the efficiency provided by a line array and would really like to experiment with the ND90 driver in this application. Thoughts, ideas?

    Leave a comment:


  • PET-240
    replied
    Re: Murphy Corner Line Array (MCLA)

    One other thing John,

    Does your equip rack interfere with the reflected sounds or are they Placed elsewhere? Can you show a photo of your room/setup please?

    Many Thanks!

    Leave a comment:


  • PET-240
    replied
    Re: Murphy Corner Line Array (MCLA)

    G'day All,

    Still on the learning curve regarding arrays, I have 64 of the Audience A3 drivers in the 16ohm coil config, John I am wondering if you could advise on the freq response from the Audience site and let me know your thoughts in this config as opposed to a bi/dipole config as the Audience does please? Am still in a large learning curve regarding arrays and all the advice you can give would be great.
    http://http://www.audience-av.com/pa...StatsGraph.pdf

    http://http://www.audience-av.com/loudspeakers/

    They do have alot of xmax so that may change the bottom end response in the corner loading, they were also designed for use in arrays so I believe they have a rising freq response in the upper freq to combat combing. Having read your site regarding the corner loading, I would like to avoid using eq if I can as it affects my current setup in regards to musicality, which is part of the reason I also want to use arrays. I want to use these as mains for a 2 channel setup, not too stressed regarding movies, I look forwards to your assistance, hope all had a great Christmas/New Years break!
    Many Thanks!

    Drew.

    Leave a comment:


  • cfelliot
    replied
    Re: Murphy Corner Line Array (MCLA)

    Originally posted by Chris Roemer View Post
    I believe the MCLA uses full EQ, so . . .

    Also, surround speakers don't really need to be that elaborate to be effective.
    I know the MLCA has EQ, but if the speaker performs better raw in a larger enclosure why not do it if size doesn't matter. It is probably a moot point as my subs handle 100Hz down in my system.

    As far as use as surrounds(7.1), I am looking to make the sound field more diffuse in my surrounds and rear. If built as a rectangular box, they also could be made to take up very little room on the walls to the left/right/rear of the main listening position. Or, even built into the wall!

    Leave a comment:


  • Chris Roemer
    replied
    Re: Murphy Corner Line Array (MCLA)

    Originally posted by cfelliot View Post
    Just a 2 quick questions:

    Running WinSpeakers for a single driver and a Q of .707, the cabinet volume is much larger than what is used in the array. Is there an advantage in using this larger volume?

    Thoughts on using the array as surrounds in a home theater? I would think that the larger sound source would be excellent in this regard.

    I believe the MCLA uses full EQ, so . . .

    Also, surround speakers don't really need to be that elaborate to be effective.

    Leave a comment:


  • cfelliot
    replied
    Re: Murphy Corner Line Array (MCLA)

    Just a 2 quick questions:

    Running WinSpeakers for a single driver and a Q of .707, the cabinet volume is much larger than what is used in the array. Is there an advantage in using this larger volume?

    Thoughts on using the array as surrounds in a home theater? I would think that the larger sound source would be excellent in this regard.

    Leave a comment:


  • bjohng
    replied
    Re: Murphy Corner Line Array (MCLA)

    There has been a lot of discussion concerning different room widths. However, unless I have missed it, there has been no consideration given to changing the face angle from 45degrees to aligning crossing/sweet spot with listening position.

    Does the resulting asymetry invalidate the design?

    Leave a comment:


  • oodesigns
    replied
    Re: Murphy Corner Line Array (MCLA)

    Thanks for the information.

    Just to get something clear about the speaker cabinet placement

    1) Would it be ok to add a packer to fill the gap between the speaker cabinet and the wall ie a strip of wood around the edge of the cabinet with it removed at the bottom to allow for the skirting board?

    2) How important is the distance of the drive unit away from the walls ie if the cabinet was slightly bigger.

    thanks

    Mike

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  • Adam Bernau
    replied

    Leave a comment:


  • John L. Murphy
    replied
    Re: Murphy Corner Line Array (MCLA)

    Originally posted by oodesigns View Post
    Hi

    Looking at making your speaker design and I have some questions:

    Design considerations:

    When coping with skirting boards what is the best option.

    1) Just leave a gap between the wall and speaker cabinet and try to round the edges?

    2) Add a packer to fill the gap between the speaker cabinet and the wall?

    3) Adjust the cabinet to fit the wall by making the bottom part of the cabinet indent to allow for the skirting board. ie How important is the distance of the drive unit away from the walls.

    Generally when placing the speaker cabinet against the wall should it touch the wall or not.

    All the best

    Mike
    Mike,

    In an ideal situation the cabinet would be rigidly integrated into the wall and would meet the wall at 90 degrees. I would not round the corner where it meets the wall (think of the top view with reflected images). If you place the cabinet against the wall it would almost certainly buzz at some frequencies. Rubber bumpers at the top and bottom of each side will allow the enclosure to fit against each wall while maintaining a small spacing from the wall to prevent buzzing. Try to keep the enclosure within about 0.5 inches of the wall.

    I place mine on a short shelf made of 1x2 material that is hidden once the enclosure is in place. A strip of velcro keeps the enclosure in place and maintains a small offset from the wall. I just live with the gap. I guess I'm not too fussy about the trim details.

    Regards,

    John

    Leave a comment:


  • oodesigns
    replied
    Re: Murphy Corner Line Array (MCLA)

    Hi

    Looking at making your speaker design and I have some questions:

    Design considerations:

    When coping with skirting boards what is the best option.

    1) Just leave a gap between the wall and speaker cabinet and try to round the edges?

    2) Add a packer to fill the gap between the speaker cabinet and the wall?

    3) Adjust the cabinet to fit the wall by making the bottom part of the cabinet indent to allow for the skirting board. ie How important is the distance of the drive unit away from the walls.

    Generally when placing the speaker cabinet against the wall should it touch the wall or not.

    All the best

    Mike

    Leave a comment:


  • John L. Murphy
    replied
    Re: Murphy Corner Line Array (MCLA)

    Originally posted by axes4less View Post
    Hi John, I wonder if you could share your experiences/opinions about the 3.5" ND90's off-axis performance in the ranges above 8Khz? I know your project was designed for corner loading, and therefore this wasn't really an issue. But I have a need to improve on my current line array "PA" solutions which are sometimes forced to be used on wide/narrow stages. On another thread I started, I've been discussing this...it began with "what-if" discussions about having side-by-side 2" drivers on convex baffles, and has now evolved to discussing how I might alternate the baffle angles on a single driver array. If however the ND90's off axis performance in the high end is very good, maybe all of that isn't needed. Please share...either by responding here, or on my post. Thanks - Brian
    http://techtalk.parts-express.com/sh...22#post1679922
    Brian,

    The response of the array is essentially constant from floor to ceiling so directivity in the vertical plane is not an issue. In the horizontal plane the directivity is equal to that of a single driver. In other words, the horizontal directivity will be that of a 2.5" diameter piston. A good first approximation of the horizontal dispersion is probably Beranek's "piston in an infinite baffle" model even though the array is corner loaded. The "ka" factor and corresponding beam width (at -10 dB points) for a 2.5" piston at various frequencies is as follows:


    ka - frequency - beam width (-10 dB)
    4 - 6.9 kHz - 86 degrees (or +/-43 deg)
    5 - 8.6 kHz - 66 degrees (or +/- 33 deg)
    10 - 17.2 kHz - 32 degrees (or +/- 16 deg)


    (See the classic acoustics text book: Acoustics, by Leo Beranek, figure 4.10)

    Note that for a speaker placed in the corner the furthest you can get off axis is just 45 degrees. Corner placement definitely reduces the horizontal dispersion requirement for a speaker system.

    Bringing an array of ND90's out of the corner to cover a wider horizontal pattern would probably still give very good results for live sound applications. I would bet that such a full range line array system would still be a stunning improvement over many of the best house PA systems.

    My intention is to eventually document the off axis response of the MCLA but I do not have those results yet. In a listening test where I walk along the center line of the room from the listening area to the front wall I can just notice the high end dropping in the last for or two as I approach the front wall. How's that for a subjective assessment! In any event I do not really notice the high end change as I move about the room.

    Regards,

    John

    Leave a comment:


  • John L. Murphy
    replied
    Re: Murphy Corner Line Array (MCLA)

    Originally posted by Ron_E View Post
    Can I assume a MCLA would work as a sub-woofer? I'm thinking about putting eight 8" woofers in the front corners of my listening room.

    Ron
    Ron,

    Yes! The SPL increase due to corner loading is greatest in the bass range. So corner loaded sub-woofer arrays would make sense to me...unless they are competing for the location with a full range line array. Then I would let the full range array have the corner location.

    Regards,

    John

    Leave a comment:

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