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Murphy Corner Line Array

fluid

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The best results I have achieved have been based off in room measurements at the listening position. I have tried as many other methods as I can to look for a universal solution and failed. I now have the speakers dead on axis to the listening position instead of 10 degrees off axis. What I found was when the speakers were positioned off axis to the listening position, tuning the listening position to be correct caused the off axis sound to be brighter due to the true on axis direction pointing somewhere else. I did not like the effect this produced. It seems natural to me for the sound to get duller off axis, but odd when it gets brighter.

This is caused by the narrowing of directivity as frequency rises and would be the same in any design with a similar directivity. The more constant the directivity the less of an issue this would be.
 

Newman

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If you had a 2-way you would have had more freedom in that regard. But then a huge challenge to get a side-by-side 2-way to have a good horizontal polar.

And hence another inherent negative to the layout: you can’t do a vertically-aligned 2-way in a vertical line source. (One of the points I made in post #10)

cheers
 

ppataki

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This is how my room looks like (not very ideal I guess - I have 5 corners)

The blue triangle represents the current location of my setup. The green triangle shows how it would look like if I went for the corner placement with the default 45 degree cabinet design. The orange triangle shows corner placement again but this time with a modified 30 degree design.
1628397183571.png

45 degree original design viewed from the top:
1628397363016.png


30 degree modified design:
1628397378199.png


I am just not sure if this would work the same way as the original design
I found a thread where John L Murphy himself says that it should not invalidate the design

1628397551423.png


I definitely want the sweet spot to be in my listening position; I have a lot of experience with fullrange drivers and they sound best in an equilateral triangle facing the listening position

I am not too much worried about the cabinet volume; I have designed a cabinet in BassBox Pro that is big enough (88 liters) for the ND91-8 drivers with Qtc=0.5

1628397987614.png


The -20dB point would be 27Hz in free air according to the simulation so I believe when placed in the corner + using DSP it should nullify the need for a sub

Any comments would be appreciated :)
 

fluid

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Any comments would be appreciated :)

That arrangement will create some strong early reflections from the baffle edge to the wall. I can't see how it is the best compromise.
Is there a reason why you are attracted to the corner mounted option rather than freestanding?
 

ppataki

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I was thinking about putting absorbers on the wall next to the speakers to mitigate the early reflections (in fact I am planning to add some more absorbers on the front wall anyway)

There are a few reasons for my attraction:
- WAF (she is complaining about the huge speakers currently eating up the space in the room)
- corner placement would give me a "huge" sound stage (just compare the blue triangle with the orange)
- I could go real fullrange = I might be able to remove my subs (hence I was asking the question about feeling the power of the bass)

But of course I have some concerns too:
- about sound stage depth
- about the modified design
- about how focused the phantom center image will be

Overall I am very tempted to try this....
 
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fluid

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The absorbers need to be at least 6" thick to be broadband but they will still be at a low incidence angle making them less effective.

This arrangement might provide some inspiration as well as the thread to go with it.

new panel.jpg


https://www.diyaudio.com/forums/full-range/337956-range-line-array-wall-corner-placement.html

My speakers image well outside the physical distance when that information is encoded on the recording. Adding early diffraction is unlikely to help with depth perception. In general you need to close your eyes to avoid seeing where the speakers are overriding what you hear.
 

ppataki

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In the meantime I have decided to move forward with this. I will use 24pcs of ND91-8 drivers per channel in a box with Qtc=0.5 and will use the 30 degree design instead of the original 45 degree one in order to be able to maintain the equilateral triangle listening setup (the size of the triangle will be approx. 350cm)
Build will start as soon as the drivers arrive in approx. 2 months' time
 

bigjacko

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In the meantime I have decided to move forward with this. I will use 24pcs of ND91-8 drivers per channel in a box with Qtc=0.5 and will use the 30 degree design instead of the original 45 degree one in order to be able to maintain the equilateral triangle listening setup (the size of the triangle will be approx. 350cm)
Build will start as soon as the drivers arrive in approx. 2 months' time
Those are really nice drivers, the klippel measurements really nailed it. It is crazy how Dayton can achieve it with that sale price. How much discount you got from that 48 drivers?
 

ppataki

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I ordered 54 pcs just to be on the safe side + potentially I might replace my rear speakers with a smaller line array too
I got 25% discount
 
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Ericglo

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Ppataki has his MCLA up and running.
 
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Ericglo

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Quite right, but as Roger Russell would have said, paraphrased, “nothing to see here, I see line source speakers that break all the rules and sound juuuuust fannnnnntastic.” Which takes me right back to the first line of my first comment: we get ‘mind blown’ subjective reviews for every type of loudspeaker.

Either you stick to the ideals, and go for it, or start clattering your way down tin can alley with compromises that ‘sound fine’. I’ve seen all the same claims about horn speakers, how they can be compromised every which way and still be the best thing since sliced bread. Eventually, you realise you are dealing with fans.

cheers

I meant to reply to this when I read it last year. While I definitely agree with the N=1, I can review the reviewer. Based on ppataki's review and measurements, the MCLA seems to be a nice speaker.

To the more general line array, every year Wisdom has their all out system at Cedia it is usually best of show. That isn't just me, but a general consensus from multiple attendees.

In this thread, Fluid chose his arrays over the his highly touted Linkwitz speakers. Wesayso has gotten excellent feedback on his arrays. Again review the reviewer, but it is better than nothing.
 
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Ericglo

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I was thinking that maybe using a horn/waveguide with the drivers might mitigate the issues with the walls. Has anyone tried something like this?
 

Abelard

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The major issue with line arrays is that you have to keep the distance between the driver centers as small as possible and this isn`t going to be changed just by puting it in a corner. So with the speed of sound and the distance you can calculate when side lobes arise. The spacing with the Dayton ND90 is at least 90mm, so at 4kHz. If you take some usual tweeters the distance is around 40mm -> 8,5kHz.
Remember that driver to driver distance must be taken into context with listening distance.
 

ppataki

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I was thinking that maybe using a horn/waveguide with the drivers might mitigate the issues with the walls. Has anyone tried something like this?
Would a chamfer on the outside of the cutout function as a waveguide? (when drivers are rear-mounted)

@fluid has mentioned that in my MCLA project thread here:

Actually I am going to give this a try with my next projects:

I am just not entirely sure how to measure the impact.....
 
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Ericglo

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Would a chamfer on the outside of the cutout function as a waveguide? (when drivers are rear-mounted)

@fluid has mentioned that in my MCLA project thread here:

Actually I am going to give this a try with my next projects:

I am just not entirely sure how to measure the impact.....


When I originally saw your original post, I thought that it wouldn't make a difference. Then reading this post I reconsidered. A 3/4" or 19mm baffle is in waveguide territory. I believe Augerpro's 5" waveguide is that deep. People like @augerpro or @Joecarrow who have tested waveguides/horns would have a better idea than me. Maybe @René - Acculution.com has simulated this.
 

fluid

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When I originally saw your original post, I thought that it wouldn't make a difference. Then reading this post I reconsidered. A 3/4" or 19mm baffle is in waveguide territory. I believe Augerpro's 5" waveguide is that deep. People like @augerpro or @Joecarrow who have tested waveguides/horns would have a better idea than me. Maybe @René - Acculution.com has simulated this.
I'm not sure if you saw the simulations posted at diyaudio but certainly the small 6mm chamfer had a positive effect on the directivity.

Here is flat
Test Enclosure Polar Curves.png


6mm chamfer

Test Box 6mm Chamfer H Polar Curves.png

A fairly obvious improvement. Acoustics and intuition do not go together so it is always advisable to test or simulate. Imagining something will work because it is similar to something else often leads to disappointment.
 
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Ericglo

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Thanks for that.

If I saw this, I probably forgot.

Do you have the link? Is that one driver?
 
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Ericglo

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