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stuffing your sealed boxes


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casaus19 
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Posted: July 22, 2005 at 8:20 AM / IP Logged  
do you guys stuff your sealed boxes with like pillow stuffing?  what kind of difference does it make for the box, and how much of the stuff do you at in the box.  I have heard of doing this but just have never done it to my boxes and i would like to know if there are any gains to doing so.
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One_Dieu 
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Posted: July 22, 2005 at 10:28 AM / IP Logged  
I might be wrong I don't know?  I read a while back when you stuff the box with fiberfill or pillow stuffing it tricks the sub into thinking its in a bigger bigger box than it is.  I have not built a lot of boxes, but I've read a lot on building boxes.  I hope I was able to help.
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placid warrior 
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Posted: July 22, 2005 at 4:51 PM / IP Logged  
yea...it slows down the soundwaves or something like that.  i posted it in your other topic, but just cut some up and roll it up and staple it in the corners to keep it away from the sub.
Francious70 
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Posted: July 22, 2005 at 5:53 PM / IP Logged  
It actually cools the air inside the box. When aire is pressurised, it's heats up, and the polyfill helps disapate the heat, thereby making the box seem larger.
It does do what it's supposed to, but there is a point of diminishing returns, where you overstuff the box and the polyfill looses it cooling properties.
What I usually do is just line all the sides with 1 layer of high loft batting.
Paul
fugit 
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Posted: July 22, 2005 at 7:36 PM / IP Logged  

If you fill the box with the correct amount of polyfill after you make a box to the manufacturers specs or whatever you came up with, wouldn't that kind of negate the point of having a "right" number of cubic ft.?  I don't know jack about this other than a rule of thumb is 1lb for each cu. ft. of space.  It just seems like you would ruin all your hard earned calculations if you "added" space to the box.

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dwarren 
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Posted: July 22, 2005 at 7:50 PM / IP Logged  
I have had good experiences with going slightly larger than mfr. suggestions. Usually their suggestions are absolute minimal requirements and are used as marketing ploys.
luckydevil 
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placid warrior 
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Posted: July 23, 2005 at 2:47 AM / IP Logged  
thats awesome...thanks for the link  Luckydevil. 
stevdart 
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Posted: July 23, 2005 at 6:20 AM / IP Logged  
fugit wrote:

If you fill the box with the correct amount of polyfill after you make a box to the manufacturers specs or whatever you came up with, wouldn't that kind of negate the point of having a "right" number of cubic ft.?  I don't know jack about this other than a rule of thumb is 1lb for each cu. ft. of space.  It just seems like you would ruin all your hard earned calculations if you "added" space to the box.

The fill is included in your calculations.  When you use a speaker box design program, you tell it how you'll be filling the box and the program takes that into account.  See Unibox, WinISD Pro...  Also, most good speaker manufacturers will give a recommendation of box volume including a fill amount, such as fully filled, loosely filled, walls lined, etc.  If you're not using a design program, follow the manufacturer's advice for volume and fill amount.

stuffing your sealed boxes -- posted image.

This is a snapshot of a part of the Unibox program.  The damping factor shown here can be scrolled from no fill, minimal fill, walls covered, to heavy fill.  Each choice changes the absorption characteristic of the box with a given value for Qa.  The program accounts for this characteristic when plotting the response.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
DYohn 
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Posted: July 23, 2005 at 9:32 AM / IP Logged  
That link has some good information but it is wrong to think of this technique as "fooling" the woofer.  Woofers don't "think," therefor they cannot be "fooled."  It's no trick and it's not magic, it's physics.  Sound is a pressure wave through a medium (in this case air.)  Sound inside an enclosure (or more accurately the pressure wave off the back of the speaker) must move through the air inside the enclosure.  Acoustic fill inside an enclosure means the air must travel through it as well as through the air.  In effect, the fill creates many small passages that the air must travel through rather than simply going straight from the speaker to the back of the enclosure.  It takes longer to go through the many small passages, JUST LIKE it takes longer for the air to bounce off the back wall of a larger enclosure than it does off the back wall of a small one.  No fooling or tricking anything, no magic, by adding fill you actually physicaly increase the effective size of the enclosure.
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