Murphy Corner Line Array (MCLA)

[bekeys88]

Re: Thanks John

Thanks John.....

Yes, it would be portable and yes... some of the rooms aren't even close to 90 degree corners (and ceilings seem to be an afterthought in some of the clubs!)....
But I'm still intrigued with the multiple drivers. I'm ancient enough to remember the "sweet 16" project back in the (60's?)... I've got a pretty good set of 12" JBL woofers.... I'm thinking of maybe using 4 of the drivers (or 8?) in a column, (maybe giving them a bit of offset from a 0 degree front) as mid-range & highs.
While I've got your ear..... If I have the theory correct... I know it would be a waste of power to not cross over if the speaker falls off rapidly at 3.5k, but... it wouldn't hurt anything correct?. And if I just passed over 3K or so through a capacitor to the array... It would at least be simple (power for a musician is no problem... we all seem to have amps with knobs that go to 11).
I run full stereo (because of the Leslie).. and I'm getting to dang old to haul around the heavy mains anymore. I know there will be a trade-off in sound quality... I'd just like to minimize it as much as possible. Any other thoughts/ideas would be appreciated
Thanks Again....... cl

[axes4less]

Re: Murphy Corner Line Array (MCLA)

Just wanted to share.....

I am a full believer, and "user" of DIY line arrays in live band performance. My classic rock cover band in Austin, TX has used this system for more than 5 years now both in large/small indoor clubs and in outdoor venues. A friend also built a pair, and his band does the same. What's also funny...is that someone hijacked a similar posting I put on the Carvin Forum a few years ago, and pasted it over onto the BOSE PA1 Forum, where the thread got plenty of interest, and finally got shut down by Ken Jacob Director and Chief Engineer @ BOSE.

http://bose.infopop.cc/eve/forums/a/tpc/f/6806048934/m/1971052103/p/2

Believe everything you read about the benefits of these Full Range driver arrays. I did not rely on corner loading (because as several mention, placement is often not possible like this on many stages), and do run subs with them. Many thanks to John Murphy for sharing his projects and insights. Certainly makes me interested in how much better my solution might be, if I was to invest a few hundred more dollars and try a Version2 using the new Dayton drivers.

Here also is a small system I built for my daughter and wife, who are teachers. They use it in their classrooms. The kids love using it. It also uses the Full Range NSBs, and would greatly benefit I'm sure with the new Dayton drivers. http://techtalk.parts-express.com/sh...d.php?t=215460

[axes4less]

Re: Murphy Corner Line Array (MCLA)

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/showthread.php?p=1679922#post1679922

[John L. Murphy]

Re: Murphy Corner Line Array (MCLA)

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

[John L. Murphy]

Re: Murphy Corner Line Array (MCLA)

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

[oodesigns]

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

[John L. Murphy]

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

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

[Adam Bernau]

Re: Murphy Corner Line Array (MCLA)

Dear John,
I am an architect, living in Prague and DIY audio in general is my hobby.
I was very inspired by your MCLA design and i have decided to build one pair, but i will be happy if you can answer my possibly entertaining and also maybe a bit stupid questions.
First of all, i want to ask : Can i build the speakers like normaly positioned " towers " ? I have issues with the corner placement because my corners are too far away and i do believe that the stereo-base will be destroyed. I also do like to have realistic bass response, can i still have reasonable spl when i will compensate the bass drop with the eq ?
I was also thinking about trying something smaller with the Daytons ND-90 like a smaller " towers " with maybe only 10 or 16 speakers per side and desktop/PC monitors for my work table with maybe two or three. In the last two cases, the compensation of the frequency response via the Behringer that you have used for the big speakers seems inadequate, so i wanted to ask what do you think about the posibilities of compensating them passively. I am unfortunately not much educated in electronic circuits and i dont know if it will be better to use the mini DSP or try to go the crossover way.
I have read through the great article of the man who designed Mcintosh speakers and he says that he was equalizating the response to be flat between 30 Hz-18 kHz, that was done with passive filtering i take it ? He is selling some equalizing box with his last project but i don´t know what is inside.
I was also thinking about putting the speakers in their separate sub-enclosures , would you see that like an improvement ?

Thank you very much for going through my questions !

[oodesigns]

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

[bjohng]

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?

[cfelliot]

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.

[Chris Roemer]

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.

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

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

[cfelliot]

Re: Murphy Corner Line Array (MCLA)

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!

[PET-240]

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.

[PET-240]

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!