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[Lukasz Lison]

Hi,
im new here, hope its the right subforum:).

Im predicting some sub arrays for my university degree, mainly using MAPP XT (former MAPP Online).

I designed a physical subwoofer arc, consisting of ten 1100LFC speakers. Than I wanted to design an alike array using the same amount of speakers but with implementation of proper delays set in the output configuration.

Delays, which I used, correspond with the distances in the physical arc, but.... simulation results between those two arrays differ A LOT!!!

Can you tell me why? Where is my mistake?

Below i attatch mapp xt project files for the arcs that cause that problem:
https://www.dropbox.com/s/7mxg1bb54r4r8bx/SZW%20luk%20cyfrowy.zip?dl=0

https://www.dropbox.com/s/7t948gu9uoufnlx/SZW%20luk%20fizyczny.zip?dl=0

[David Sturzenbecher]

Hi,
im new here, hope its the right subforum:).

Im predicting some sub arrays for my university degree, mainly using MAPP XT (former MAPP Online).

I designed a physical subwoofer arc, consisting of ten 1100LFC speakers. Than I wanted to design an alike array using the same amount of speakers but with implementation of proper delays set in the output configuration.

Delays, which I used, correspond with the distances in the physical arc, but.... simulation results between those two arrays differ A LOT!!!

Can you tell me why? Where is my mistake?

Below i attatch mapp xt project files for the arcs that cause that problem:
https://www.dropbox.com/s/7mxg1bb54r4r8bx/SZW%20luk%20cyfrowy.zip?dl=0

https://www.dropbox.com/s/7t948gu9uoufnlx/SZW%20luk%20fizyczny.zip?dl=0

Lukasz,
You may have better luck if you post screenshots.  Also have you checked out the S.A.D. calculator? Written by one of our own.  https://www.merlijnvanveen.nl/index.php/en/calculators/28-sad-subwoofer-array-designer-en

[Lukasz Lison]

Lukasz,
You may have better luck if you post screenshots.  Also have you checked out the S.A.D. calculator? Written by one of our own.  https://www.merlijnvanveen.nl/index.php/en/calculators/28-sad-subwoofer-array-designer-en

I didnt use the calculator, because I thought that it would be that simple: just expressing the physical distance in the time domain...

Here are the screenshots for the delay arc

[Lukasz Lison]

Here are the screenshots for the physical arc

[Doug Fowler]

Here are the screenshots for the physical arc

And this is the problem with the physical arc.  You murder the stage with LF.

[Rob Spence]

And this is the problem with the physical arc.  You murder the stage with LF.

I did a gig several years ago with 6 subs across the front. We pushed the middle pair forward about 18" if I remember and the next pair about half that. I would have used delay but only had 2 amp channels to work with.

The result was nice bass out front and little on the stage.


Sent from my iPad using Tapatalk HD

[Lukasz Lison]

And this is the problem with the physical arc.  You murder the stage with LF.

true, but your reply still not answers my problem: why the differencies between physical and digital arc are THAT big?

[Stephen Kirby]

Looking at the curved plots, at least you don't need a sub for the drummer.  ;-)

[Tom Danley]

Hi,
im new here, hope its the right subforum:).

Im predicting some sub arrays for my university degree, mainly using MAPP XT (former MAPP Online).

I designed a physical subwoofer arc, consisting of ten 1100LFC speakers. Than I wanted to design an alike array using the same amount of speakers but with implementation of proper delays set in the output configuration.

Delays, which I used, correspond with the distances in the physical arc, but.... simulation results between those two arrays differ A LOT!!!

Can you tell me why? Where is my mistake?

Below i attatch mapp xt project files for the arcs that cause that problem:
https://www.dropbox.com/s/7mxg1bb54r4r8bx/SZW%20luk%20cyfrowy.zip?dl=0

https://www.dropbox.com/s/7t948gu9uoufnlx/SZW%20luk%20fizyczny.zip?dl=0

Hi Lukaz

While it’s hard to imagine and this factor is usually ignored, Subwoofers  (all loudspeakers)  actually radiate in 3 dimensions in space, up and down, side to side, front and back.  This is why there is big a difference between what seems logical based on a simple view and what really happens.

Time delay allows one to change the point in time the radiation emerges from each source (something like the front to back location in time) BUT that (DSP) has no effect on the other two dimensions or where the radiation happens in 3 dimensional / physical space.    If you model an curved array and also look perpendicular (in this layout up and down) one sees also that this configuration forces a great deal of energy to be radiated in that plane.

If one were to construct the array in 3 dimensions, stacking the boxes to be half the height as it is wide (sitting on the ground) and treated the center bottom speaker as 0 time and progressively delay the boxes moving away to the sides and up, this will work as envisioned.   Then you are dealing with the other spatial dimensions and are creating the “pulsating sphere” in 3D which is a point source, using the boundary mirror to create the bottom half.    Doing so will also make the on stage SPL even more intense as the desired dispersion on the front side is the same effect as focusing to a point on the back side.

That is why the time delay and location produce very different results with this configuration.   What you might try (if you have space) is an end fire array (usually less efficient is a cardioid array), at least then what you have up/down and side to side is symmetric and what you see in the prediction will also be what happens in the up/down dimension.
Hope that helps
Tom Danley

Fwiw, we have a free program which models sound in 3d if desired and one can select idealized point sources which makes the acoustical physics clearer.

Pick windows or mac here
http://www.danleysoundlabs.com/support/ddt-files/

How to video’s here
http://www.danleysoundlabs.com/danley-u/training-videos/

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