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Murphy Corner Line Array

fluid

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Great. I wonder if using something more elliptical would better for a vertical array of drivers.
It might but I haven't tried it know. Further in the thread linked @Wesayso had idea of lips between the drivers but it was never pursued very far.
Also, wouldn't a roundover be better than a chamfer?
Not really, in this circumstance they are pretty much equivalent.

Here is a comparison of the simulated effects of a chamfer, round over, 13mm step and flush connection of a woofer to a baffle. The outer edge of the baffle had a 36mm round over in all cases so this is a fair comparison. 1m on axis and 45 deg off axis traces.

1m.gif
 

ppataki

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@Ericglo @fluid Can you guys please enlighten me about the difference between chamfer and round over?
I mean from a carpentry perspective - maybe if you could please post some pictures
Many thanks
 
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fluid

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So basically it does not really matter which one to use; if I understood correctly
Not from a diffraction reducing standpoint no. As long as the radius and the chamfer are an equivalent size as they are in my drawing there is no meaningful difference.

A round over can be used to better effect on a 3 way corner if a rolling ball is used, but it is splitting hairs really.

Rolling Ball Corner.png
 

thewas

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ppataki

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One more question if I may @fluid
Is there a recommended roundover or chamfer size for any given cutout size?
For example if I have a 150mm cutout what shall be the roundover size? Or if I have a 120mm cutout, 100mm, etc...
Or maybe it is a 'one size fits all'? :)
Many thanks
 

hollis

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So, from my 4-driver ND90 prototype, I have some realworld off-axis free air and corner loaded measurements at varying distances. Drivers are internally mounted in 3/4" ply. Free air match the simulation, while corner loaded... goes nuts. All degree amounts are to be taken with a grain of salt, this is just me physically moving the mic and eyeballing it.

If needed I will pull the full array out and retest in a corner. I dont think free air benefits us much at this point.
 

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hollis

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Not apples to apples, but after that I discovered the moving mic method, and measured a combination of nearfield (as close as I can) + MLP. Full scale 25 driver line array indoors measured as follows.

These are without eq, except a single Linkwitz transform for the low end.
 

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hollis

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My next step is using the 8c as my source of truth, and matching the MCLA target curve to that. Right now, I have boosted highs a bit too much and equalized "too flat".
 

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Ericglo

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It might but I haven't tried it know. Further in the thread linked @Wesayso had idea of lips between the drivers but it was never pursued very far.

Not really, in this circumstance they are pretty much equivalent.

Here is a comparison of the simulated effects of a chamfer, round over, 13mm step and flush connection of a woofer to a baffle. The outer edge of the baffle had a 36mm round over in all cases so this is a fair comparison. 1m on axis and 45 deg off axis traces.

View attachment 189443

I read through more of the thread last night. I forgot that DIYSG gets the SEOS guides from somewhere else.

Instead of the lips guide, wouldn't a horn with a more narrow vertical dispersion like this one be a better fit?
270-041_HR_0.default.jpg



I saw Wesayso was looking at an adapter to put between each driver. Wouldn't it be easier to cut some Neoprene and put it between the drivers? It wouldn't cost much and should be easy to test how effective it is.
 
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Ericglo

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So, from my 4-driver ND90 prototype, I have some realworld off-axis free air and corner loaded measurements at varying distances. Drivers are internally mounted in 3/4" ply. Free air match the simulation, while corner loaded... goes nuts. All degree amounts are to be taken with a grain of salt, this is just me physically moving the mic and eyeballing it.

If needed I will pull the full array out and retest in a corner. I dont think free air benefits us much at this point.

If I am seeing this correctly, then the sensitivity goes way up when corner loaded at the expense of an uneven frequency response.

Is that D&D 8Cs in your setup? If so, how does the MCLA compare to them?
 

hollis

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Is that D&D 8Cs in your setup? If so, how does the MCLA compare to them?
Yes, those are 8c. I have done a couple of shootouts and have able to tune my MCLA to the point where they win on some tracks and 8c win on others. Myself an others thought the MCLA has the best and most even bass. 8c had better "air" or extreme hf response. Imaging could go either way, 8c can create a pinpoint phantom center, which MCLA cannot, the center is a bit more spread out vertically.

If you have a room with multiple rows, or want good sound while doing yoga on the floor. MCLA totally win, hands down.
 

fluid

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One more question if I may @fluid
Is there a recommended roundover or chamfer size for any given cutout size?
For example if I have a 150mm cutout what shall be the roundover size? Or if I have a 120mm cutout, 100mm, etc...
Or maybe it is a 'one size fits all'? :)
Many thanks
The size of any round over or chamfer for rear mounting a driver would depend on the baffle material thickness, available bit size and how much material neds to be left for the driver to fix into.

The deeper the chamfer or round over the lower in frequency it will have an effect but it also creates a cavity type of effect from the depth and that may not produce a desirable characteristic.

There really is no simple rule of thumb to follow and be certain of the outcome. Test or simulation is advised.
 

fluid

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Instead of the lips guide, wouldn't a horn with a more narrow vertical dispersion like this one be a better fit?

I saw Wesayso was looking at an adapter to put between each driver. Wouldn't it be easier to cut some Neoprene and put it between the drivers? It wouldn't cost much and should be easy to test how effective it is.
The length of the line creates a narrow directivity vertically over a wide frequency range, a horn will not do that due to the limited vertical height, but an array of them would gain it back.

Some form of divider between the elements can have a positive effect but it needs some consideration or testing, I don't understand what the neoprene would be for?
 
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Ericglo

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I think I have that link correct.

Wesayso was thinking of making an adapter to put between the drivers. It seems like cutting a 1/4" piece of Neoprene as a divider would be easier to test.
 

hollis

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Subs array on front wall and absorbing as possible back wall :cool:
That would be a SBA, single bass array. If you are willing to consider an active solution you could run line array on the rear wall, highpassed around 100hz, polarity flipped, and delayed according to room distance. That would be a DBA, double bass array. Doing that with line array would be a bit of overkill, but it would definitely work.

As for bass in room corners, that is a common audio myth. Its mostly correct. But not a rule by any means.
 
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