Dual 10" coupling |
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moyano
Young Croc Joined: 12 May 2008 Location: Bedfordshire Status: Offline Points: 1219 |
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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
Registered User Joined: 07 January 2017 Status: Offline Points: 180 |
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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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toastyghost
The 10,000 Points Club Joined: 09 January 2007 Location: Manchester Status: Offline Points: 10919 |
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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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fatfreddiescat
Young Croc Joined: 15 October 2010 Location: N.E.Wales Status: Offline Points: 1083 |
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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
Young Croc Joined: 12 May 2008 Location: Bedfordshire Status: Offline Points: 1219 |
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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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toastyghost
The 10,000 Points Club Joined: 09 January 2007 Location: Manchester Status: Offline Points: 10919 |
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It’s not 1/2 lambda for coupling. At 1/2 lambda you’re in full cancellation. |
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fatfreddiescat
Young Croc Joined: 15 October 2010 Location: N.E.Wales Status: Offline Points: 1083 |
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Here's something for you to play with:
Edited by fatfreddiescat - 11 October 2021 at 6:50pm |
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moyano
Young Croc Joined: 12 May 2008 Location: Bedfordshire Status: Offline Points: 1219 |
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I was hoping that you were the genius here ! Lol
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Augusts
Registered User Joined: 07 January 2017 Status: Offline Points: 180 |
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Phase issues and therefore distortion in the range over the point of 1/2 wavelength. Is that corrrect?
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moyano
Young Croc Joined: 12 May 2008 Location: Bedfordshire Status: Offline Points: 1219 |
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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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John Boom
New Member Joined: 19 July 2021 Location: Cambridge Status: Offline Points: 9 |
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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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JonB67
Young Croc Joined: 22 April 2016 Location: UK Status: Offline Points: 1376 |
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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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