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Destructive interferrence

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Augusts View Drop Down
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    Posted: 16 November 2022 at 7:43pm
Does putting two 12" drivers one above the other minimize the destructive interferrence if they are in a horn? If they were in a sealed box with no horn, the interferrence would occur say around 500hz. Two seperate horns for each driver would solve this for sure?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 16 November 2022 at 11:00pm
No. The short answer is it's WAAAY more complicated than that.

Minimizing destructive interference between 2 drivers means getting thier acoustic centers as close together as possible and then restricting thier operating range to frequencies where they only sum constructively. The other option is to horn load them but they have to be loaded into a single horn.... synergy style, separate horns stacked produces even more interference simply because the drivers are further apart. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Augusts Quote  Post ReplyReply Direct Link To This Post Posted: 17 November 2022 at 10:13am
But then how come I see everywhere people stacking horn loaded speakers side by side? Is there a scienece behind this or the interferrence is just being ignored?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 17 November 2022 at 11:45am
Originally posted by Augusts Augusts wrote:

But then how come I see everywhere people stacking horn loaded speakers side by side? Is there a scienece behind this or the interferrence is just being ignored?


There’s plenty of science behind it. The concept of mutual coupling goes back to Rayleigh in the early 1900s.

Most front-loaded horn cabinets are made with a smaller mouth than they’d ideally have, for the sake of being able to transport them more easily.

It can be assumed for the most part that the entire frontal area of a horn radiates sound, but this will typically not be at the same magnitude, phase or wavefront shape at all positions.

When multiple horns are stacked together the larger resulting mouth from the combined array of cabinets decreases the ripple in the acoustic impedance, producing a flatter magnitude response and a smoother roll off at the low corner.

This doesn’t happen by accident, and the horn should be designed appropriately to achieve this effect at the beginning. It’s a common area that people seem to struggle with when moving from axisymmetric straight horn models like Hornresp to actually folding & building the cabinet.

If you want a one-stop shop to learn about this, you need this mighty tome:
https://www.lean-business.co.uk/eshop/high-quality-horn-loudspeaker-systems-by-bj%C3%B8rn-kolbrek-and-thomas-dunker-p-3317.html

It's one of the best things I've ever spent money on.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Augusts Quote  Post ReplyReply Direct Link To This Post Posted: 17 November 2022 at 12:13pm
Thanks for the input. I am familiar with basshorn behaviour, I should have clarified- I am thinking about shorter wavelengths of midrange… the book looks like a good investment, thank you.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote fatfreddiescat Quote  Post ReplyReply Direct Link To This Post Posted: 17 November 2022 at 12:15pm
In some case intereference is just ignored, either by user not being aware or manufacturer design choices, manufacturers on the whole these day's are well aware though and attempt to minimise interference between elements.
Various line array manufacturers explain the concepts, often somewhat sugar coated though.

ProductionPartner have reviews of the Funktion One Evo and L'Acoustics Arcs V2 that may be worth a read.
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