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2 questions regarding sealed enclosures


akuma4u

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as title states, i have 2 questions regarding sealed enclosures

1) I know that lining the enclosure with polyfil helps with sound and makes the subs think they are in a bigger enclosure than they really are BUT, if you have ample enough room to build an enclosure that gives the subs their optimal net space required for a sealed box, is the polyfil still necessary or does it serve no purpose at that point? i think i did read once somewhere that even if there is enough space in the box that polyfil should still be added as it helps with the sound in some way.. can someone elaborate on this?

2) when using 2 or more subs, i know using a divider for each sub will be safer because if one blows the other will be safe vs if they are in the shared space if one blows then the other will prob blow as well as the single sub would now be in a too big of airspace and will bottom out. But again, I did read somewhere that using NO divider has another benefit.. i forgot what it was.. can someone elaborate on this as well?

Thanks

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1) I have heard that if the box is built to spec for the specific sub, then polyfil is not needed. That being said, I have always used polyfil in my sealed enclosures, which I build as close to spec as I can. In my opinion, the polyfil will make the bass tighter and sound better. It usually takes me weeks to get the amount just right as I will start with none, and add little by little until it sounds right to me. I listen to nothing but metal so I want that bass drum sounding perfect. This has been my experience with polyfil. I am sure others will have other advice.

2) I have always used a divider in my sealed enclosures. Each sub should be in its own chamber. Again, this is how I have always done it. What you say about one sub blowing causing the other to blow does make sense to me. I have just always divided them. 

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The following applies to car audio sub boxes:

Damping can be modeled, take a look:

1) SA-12 1 cube net, with and without heavy damping:

image.jpg

 

2) SA-12 0.3 cube net, with and without heavy damping:

0.3.jpg

 

As you can see on the small box damping helps a bit to reduce peaking and increase low end extension, in the 1 cube proper box you see very little difference.

 

On the divider, some manufacturers recommend using it due to driver tolerances, so that if the drivers operate a little different in a common chamber this could lead to distortion due to interaction between them, as long as drivers are the same and have been broken in together you usually should not expect any significant effects, the divider can act as heavy bracing as well so in some cases that can be a difference. Separate chamber boxes produce bigger boxes for the same net volume. 

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thanks guys..

with my max dimensions im able to JUST perfectly give the subs what they need. They require 2.75 net after all displacements.. and i come up at 2.74 but this is WITHOUT a divider in the middle.. so if i were to add a divider in the middle , that would be another displacement but i dont know how to calculate that displacement.. maybe you can give me a rough estimate? my box is 32 wide x 13.5 high x 16.5 deep, 2 subs each .14 displacement. each sub needs 1.375 net

entering in these dimensions into torres and using a double baffle i get 2.74net but i dont know how to calculate the divider displacement..

 

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