# What is the proper way to stuff a sealed subwoofer box



## coomaster1 (Jul 22, 2010)

Hi, How do I stuff my sealed sub box for the best possible sound of the subwoofer.The subwoofer is the oldschool alpine 6012EX.Alpine gives a few choices for the box.I have decided on a 1.0 cu ft box,what they call neutral sound.It says if you are stuffing the box to stop standing waves,to make the sub box 0.8 since the stuffing will make the subwoofer think it is in a larger box.When stuffing the box I have heard fiberglass is better to use than polyfill.Is this correct?Also I have read that for every cu ft the box is.To use one pound of fill.Is this correct?Also do you tightly pack the sub box balling up a one solid piece,or do you cut it up and place it directly to each inner side of the box.If balled up.How far should it be away from the back of the speaker cone and the speaker port.Then someone threw a monkey wrench in and said that the amount of filling depended on the QTC of the subwoofer.If so, the specs for alpine say beside 1.0 cu ft is: butterworth:,QTC is 0.707:,sound neutral.Alpine also says to offset the woofer to minimize standing waves.I've never saw any subwoofers I ever came across mounted like this.But what do I know,Hence my request for some one that knows for 100% sure.I only have one set of these subs and they are long since continued,and definitely want to get the box built right. Thank you


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## qwertydude (Dec 22, 2008)

If you can avoid it don't stuff a subwoofer box. Standing waves may or may not occur but it makes little difference in such a tiny box. Standing waves generally would be a concern at higher frequencies where the box is bigger than a single wavelength. In a subwoofer this almost doesn't matter.

But a big issue with box stuffing is yes it will simulate a bigger cabinet in terms of getting better lower frequency response but this sacrifices efficiency to do so. On top of that the stuffing also thermally insulates the subwoofer motor more. So the decreased efficiency means you need more power to get as loud and you're also impeding the ventilation of the subwoofer. This means both power handling and efficiency goes down.

If you can build the proper sized box to begin with just do that and forgo the stuffing. You'll get better performance and less thermal issues.


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## Jeepit (Feb 6, 2014)

As for the sealing of the box I have used rope caulk before with sucess. Liquid nails works and will hold it together so you can get your pilot holes drilled also. If it was me Id run the speaker without fill at first to see how it sounded before I stuffed the box.


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## iamstubb (Sep 6, 2013)

Wouldn't you only stuff a box if it was too small to get it to approximate the appropriate size? Otherwise you are overheating the speaker and ruining the response. The main point of a sealed installation is a flatter and more differentiated sound. You need that air to keep the speaker response sharp. 
Or am I wrong?


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## coomaster1 (Jul 22, 2010)

It sounds like everybody is in agreement .That unless I can't fit the desired box size in my vehicle,then,and only then should I put any stuffing in the box whatsoever,since there is no chance of standing waves in a box this small.So is everyone in agreement that for a sealed 1.0 cu ft per side dual sealed box.Absolutely no stuffing is necessary,and in fact detrimental. If so this will be so much easier when making this sub box. What wood would you guys use to get the best sound quality out of the box,and how thick should the wood be. Also why would alpine say to stuff the box,and they are the makers of those subwoofers ,and should know them best.Are they way behind the times,when calling for polyfill to stop standing waves.I tend to trust you guys,since I have never been steered wrong by these forums.


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## qwertydude (Dec 22, 2008)

3/4" MDF works. It is rather heavy so I have used particle board with good results too. But MDF is definitely best.


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## Thoraudio (Aug 9, 2005)

Stuffing is not for standing waves.


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## coomaster1 (Jul 22, 2010)

Hi, Is 3/4 MDF better than birchwood to make it out of. Some people like to use birchwood for their sub boxes.I just wanted to check back with you to make sure. I think most high quality home speakers are made from MDF wood.I've heard that too hard of wood like oak,though it may be quality wood.The sound quality is affected because it is just too hard,and that's why they use MDF wood.Could also be that oak is so darn expensive,and that's why they don't use it.Not really sure though.Also should I put some bracing on the inside to make it more solid.


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## Jepalan (Jun 27, 2013)

Here are a couple of decent discussions of wood, glue, etc...
http://www.diymobileaudio.com/forum/general-car-audio-discussion/124429-best-wood-make-sound-quality-dual-subwoofer-box-2.html
Subwoofer construction tips

Here are a couple of good discussions about the how and why of "stuffing":
How much poly-fill for sealed subwoofer?
http://www.klausaudio.com/subwoofer-box-articles/using-polyfill-in-a-subwoofer-box.phphttp://

Regarding MDF versus Birch Plywood, they have different advantages in different applications, but neither material guarantees a better sounding sub. 

MDF is generally used because it is very stable (if kept dry), is cheap, is very dense, and can be worked easily with a router. BUT - MDF doesn't hold nails and screws well, is prone to chipping, and absorbs water like a sponge. Also, finishing MDF to look 'pretty' is a challenge and you will never fully hide seams unless you cover in vinyl or carpet - some crackle finishes do 'OK'

Birch will hold nails and screws well, tools well, is less toxic, has decent stability and density, and gives more options for finishing. BUT it can cost a lot more. 

BOTH materials can be worked into stellar sounding subs - this has more to do with proper design and construction techniques than the material itself (between these two).


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## nineball76 (Mar 13, 2010)

Birch is better. It's stiffer, lighter, and less prone to moisture damage. 

sent from Tapatalk, via Sony Z1 badassness!


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## coomaster1 (Jul 22, 2010)

I guess since I am in Canada,and we get a lot of moisture here,and it is winter here most of the time. I will opt for the baltic birch.Do you still need it to be 3/4 inch thick or is even thicker better. DO I need internal bracing when I use birch.Do I need anything on the outside of the sub box to stop vibration. These are pretty much the only questions I have left. Thanks for everyones help so far.


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## Jepalan (Jun 27, 2013)

coomaster1 said:


> I guess since I am in Canada,and we get a lot of moisture here,and it is winter here most of the time. I will opt for the baltic birch.Do you still need it to be 3/4 inch thick or is even thicker better. DO I need internal bracing when I use birch.Do I need anything on the outside of the sub box to stop vibration. These are pretty much the only questions I have left. Thanks for everyones help so far.


3/4" Birch should be fine for a 1 cu-ft box. Shouldn't need any extra bracing at 1 cube, but I do like to glue a strip of wood bracing across the face of large rectangular box faces to stiffen things up and keep resonances will out of the sub range. 1/2" or 3/4" lath strip across the biggest face is fine - make it diagonal if you want - but again, probably not necessary on a small 1 cube box. 

There are subwoofer construction guidelines and videos all over the interwebz - start with the links I provided above and feel free to fire up Google.

Cheers


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## coomaster1 (Jul 22, 2010)

Thanks again for your quick response, and for all your great help.


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