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Does the shape of the enclosure matter ?


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#1 of 8 OFFLINE   Andrew-_-_P

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Posted July 18 2004 - 04:33 PM

Does the shape of the enclosure matter if the volume stays the same and the distance between the driver and panel are the same also? This would be for a sealed enclosure.

#2 of 8 OFFLINE   Patrick Sun

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Posted July 19 2004 - 01:25 AM

For a subwoofer? Not really.

For a conventional speaker, possibly, due to need to factor in baffle diffraction effects (placement of the drivers on the front baffle).

I'm confused about "driver and panel".
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#3 of 8 OFFLINE   MikeN

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Posted July 19 2004 - 09:51 AM

Actually... I'd say for a subwoofer, it matters more (technically).

Standing waves are your enemy, and parallel surfaces (walls of your enclosure) help to create standing waves. The perfect enclosure would have 0 parallel lines.

Is this getting extreme? Yes somewhat... but I've definately noticed differences in my testing over the years.
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#4 of 8 OFFLINE   RoyceDB

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Posted July 20 2004 - 02:06 AM

I agree with Mike. My experience with car audio tells me that the less like a cube an enclosure is, the better it is.

#5 of 8 OFFLINE   Mike Keith

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Posted July 20 2004 - 05:14 AM

For true sub reproducing 80Hz and below the wavelength is so large that the enclosure shape will not have any effect, a cube is fine. Now for car subs, that's a different story most go up well above 80Hz. The enclosure shape is most effective in the midrange area, and not just the outside but the inside is equally important as any acoustic energy reflected back to the cone with enough amplitude will distort the drivers movements. Standing waves are easily delt with with batting/polyfill or similer wall lining.

#6 of 8 OFFLINE   Michael_UK

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Posted July 23 2004 - 10:20 PM

The reason square boxes have been rejected in the past is because in *higher* frequnecies you can get standing waves forming.

For bass this is *not* an really issue at all due to the small boxes we use and the extremely long wavelength of bass frequencies

You see the size of the distance between parrallel boundarys dictates the refelection of the wavelength.

To reflect a low frequency the wave this distance has to have be of significant size to do so.

A standing wave is only created buy the two parallel sizes being at least *half* the length of the wavelength.


So...


Basic sound maths.

Length of sound wave = Speed of sound/Frequency.

The length of an 80 hz sound wave is 332 meters a second divided by 80 hz = 4.15 meters.

For a 20 hz sound wave you take 332 divided it by 20 hz = 16.6 meters

So unless the subwoofer enclosure is really large (over 2 meters) in width, height or depth you are safe at 80 hz.

As bass frequnecies are so long in wavelength you will see it is difficult for a standing wave to occur in our small enclosures.

#7 of 8 OFFLINE   RodN

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Posted July 24 2004 - 12:06 AM

Ok so it's determined that standing waves are not an issue for subs - so why then does more stuffing in a sealed sub effectively increase an enclosures Q? I thought it was because they broke up standing waves?

#8 of 8 OFFLINE   Ryan Schnacke

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Posted July 24 2004 - 12:27 AM

No, it dissapates some of the energy. As the pressure waves inside the box moves the stuffing strands around it generates some heat, hence energy is dissapated. This reduces the higher frequency output and results in a lower Q alignment.