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Dual 10" coupling

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moyano View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote moyano Quote  Post ReplyReply Direct Link To This Post Topic: Dual 10" coupling
    Posted: 14 October 2021 at 12:11pm
I’d love to know how the new nexo ID 84 works. 

I thought that multiple dome tweeters would cause issues. 




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Augusts View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Augusts Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2021 at 3:16pm
There is so much to learn in the field of acoustics, it gets easier if you read heavy books I guess but I learn by doing, so there are some conclusions I have came about but they also change over time as they where wrong. So I'm no genius, merely a student. But an enthusiastic one :)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2021 at 2:19pm
Not quite right. Summation occurs in the ‘coupling zone’ of the 'phase wheel'. Where that can get confusing is that the cycle isn't really in a 2D plane, but along a cylinder that represents 'laps' behind or ahead of the current frame of reference to relative phase.

This a good place to start:

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Post Options Post Options   Thanks (0) Thanks(0)   Quote fatfreddiescat Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2021 at 2:10pm
One method to get a better picture of what happens is to measure the response at various degrees off axis and import it into a program such as Vituixcad. You can then add copies of the measured response, adjust spacings and angles and then scroll through the frequencies whilst viewing the 'Polars' etc graphs.
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moyano View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote moyano Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2021 at 11:05am
Yes, destructive interference can start at 1/2 lambda. The idea is to keep all drivers between 1/4 and 1/2 lambda. 

I was wondering what else happens between 1/2 and 1 for example. But if interference starts at 1/2 then surely nothing good can come of it. 

Xx 



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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2021 at 10:17am
Originally posted by moyano moyano wrote:

I’m also interested to know exactly what happens once you’ve been forced outside of the 1/2 wave coupling distance even though the drivers are still touching / very close together ? 

What are the negative effects after this point ? 

Xx 


It’s not 1/2 lambda for coupling. At 1/2 lambda you’re in full cancellation.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote fatfreddiescat Quote  Post ReplyReply Direct Link To This Post Posted: 11 October 2021 at 6:18pm
Here's something for you to play with:









Edited by fatfreddiescat - 11 October 2021 at 6:50pm
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moyano View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote moyano Quote  Post ReplyReply Direct Link To This Post Posted: 11 October 2021 at 5:27pm
I was hoping that you were the genius here ! Lol 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Augusts Quote  Post ReplyReply Direct Link To This Post Posted: 11 October 2021 at 5:25pm
Phase issues and therefore distortion in the range over the point of 1/2 wavelength. Is that corrrect?
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moyano View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote moyano Quote  Post ReplyReply Direct Link To This Post Posted: 11 October 2021 at 4:47pm
I’m also interested to know exactly what happens once you’ve been forced outside of the 1/2 wave coupling distance even though the drivers are still touching / very close together ? 

What are the negative effects after this point ? 

Xx 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote John Boom Quote  Post ReplyReply Direct Link To This Post Posted: 28 August 2021 at 12:52pm
Your mid spacing will lead to lobes in the vertical coverage pattern. The main lobe will get smaller as you go up in frequency. The size of that lobe at your crossover freq is a limit on the vertical coverage angle of the system. So, the narrower your design vertical coverage, the higher the crossover frequency can be. Using this method you can space the drivers more than a quarter-wave.

What you have to trade against this is, can your compression driver/horn combo really go that low and not start to distort at power? Manufacturer's specs can be misleading - you often have to double the specified usable lower limit. And compression drivers have a harder time driving smaller horns. Generally, beefy comps and carefully chosen horns with the lowest possible horn cutoff freq are the way to go.



Edited by John Boom - 28 August 2021 at 2:58pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JonB67 Quote  Post ReplyReply Direct Link To This Post Posted: 27 August 2021 at 6:43pm
Im aware its a specific thing, but it was in discussions and info on the d'appolito arrangement that I found out about the pros and cons of mtm

I didn't suggest he used the d'appolito arrangement, just that googling it was a source of some info.


Edited by JonB67 - 27 August 2021 at 8:19pm
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