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Chip73
Dodge Dakota
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12/25/2003
08:55:45
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 Subject: Sealed Box Test
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Message:
I have been reading the below post about testing a sealed sub box. I am a bit confused. It is stated that if a box is 100% sealed then it will take several seconds for the woofer to return to its resting position. This doesnt sound right to me. If the box is 100% sealed then would the air not act as suspension? When you push the woofer in it will compress the air in the box, the air should then force the woofer back to its original position. If it takes time then it would seem to me that when you pushed the woofer, air was forced out and the woofer takes time to return as air returns to the box equalizing pressure. If I am wrong please tell me why. Thanks
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DSW
Dodge Dakota
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12/26/2003
21:12:21
|  RE: Sealed Box Test
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Yeah, if the box and speaker were 100% sealed and didn't leak any air AT ALL the cone would pop up immediately to it's resting position, but I have never seen this with the 30+ sealed boxes and different sub combinations that I have done.
If the sub has a small, minute amount of air leakage through the suspension, cone or dust cap which is the norm from my experience, try this. Push down on the cone for 1-2 minutes to push air out of the microscopic pores in the sub. Next, release the cone quickly and it will pop up immediately part way and than slooooowly return to it's resting position. It can be hard to see the cone rise slowly since it is sucking in air through the misroscopic pores. It can be easier to feel it then see it. Place a finger between the surround and edge of sub, you'll feel it press against your finger as it slowly rises.
The main thing is, you don't want to see the cone rising from the compressed to resting position in several (1-2) seconds as it sucks in air. This indicates that the sub is pushing air out and sucking air back in again from somewhere at a high rate.
If you see the sub "pop" back up, that's good! Your able to pressurize the inside of the enclosure without any significant air leakage. But, normally there is a small amount of air leakage and the sub cone will slooooly rise to it's resting position, however so slightly.
My Dak sub enclosures with RF XLC 10's take about 30 seconds for the sub cone to return to the resting position. After compressing the sub cone for 1-2 minutes the cone pops back up part way and then it takes about 30 seconds for the cone to travel the rest of the way to the resting position,,, maybe 1/8-1/4" of travel in 30 seconds or so.
Hope this helps,
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Chip73
Dodge Dakota
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12/26/2003
22:03:44
| RE: Sealed Box Test
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Message:
Makes sense. It just sounded to me that if it takes time to return that it was good.
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Jim Z
GenI
12/26/2003
23:31:10
| RE: Sealed Box Test
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Message:
DSW is pretty much right on. I have, however, seen/made a few *almost* perfectly sealed enclosures... but what it takes is a good gasket on the woofer mounting flange, and a woofer with a rubber surround and non-paper cone. Almost all foam surrounds out there are lossy and will pass air through.
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