importance of pin hole pressure equalization and how to make one safely - Page 4 - diyAudio
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Old 15th December 2005, 06:35 AM   #31
diyAudio Member
Join Date: Aug 2003
Location: Santa Cruz, California
Originally posted by dscline
Unless my math and wild guesses in the posts above are way off, I think pressures in excess of 25lbs can EASILY be realized on a driver under the temperatures that could easily be reached, IF the box were absolutely air tight. That would certainly be enough to push the driver more than 1mm. It'd be enough to push it to the end of its ecursion. Obviously though, this is not typically an issue with most sub construction. The biggest unknown here is how leaky a "tight" box really is.
I'll be a son of a gun. PV=nRT never crossed my mind for sealed cabinets. Thanks!

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Old 15th December 2005, 07:10 AM   #32
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Join Date: May 2002
Location: Switzerland
I assume that most "airtight" boxes are leaky enough that pressure changes aren't a problem.

But I just had an idea how one could make a really tiny hole of exact diameter:

1.) Drill a suitable hole into the cabinet (preferably at a hidden place).
2.) Glue a piece of insulated wire into the hole and make sure that everything is airtight.
3. Pull the conductor out of the wire and clip bot ends of the remaining tube close to the cabinet walls.

If you want to get a tube that is longer than the wall thickness then you could simply leave the inner part of the wire longer.


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Old 15th December 2005, 08:18 PM   #33
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Join Date: Jul 2004
Location: Mountain View, CA
"While the hole will relieve the spring effect... the driver will not see it."

Yes and no. The driver will not see it at operating freq. It will see it statically.

This says it very well:

"The idea is to create a hole that's resistive enough that the pressure differentials during operation inside the enclosure won't create any serious air movement through the hole, but air can very slowly pass through it to do the pressure equalization thing."

"But I just had an idea how one could make a really tiny hole of exact diameter:"

There is no reason whatsoever to make an exact diameter.

The felt over a hole idea was good.

Tiny holes can be surprisingly noisy. I had a ticking noise coming from around a hole with a tight woodscrew in it.
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Old 15th December 2005, 08:42 PM   #34
poobah is offline poobah  United States
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Thanks Noah!
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