# 12W7 Need box advice



## bradinar (Jul 20, 2009)

Hello everyone, 

I'm sure that this has been covered before. I did run a search for this but there are literally hundreds of threads on the W7 and I didn't see exactly what I was looking for. I'd bet some members have a lot of experience with this sub and maybe you can help me out. 
I need to build a box for my W7 but want to make sure to get it right. My main goals are a nice flat and smooth response. I don't want the sub to be "boomy" or "peaky". I listen to primary electronic/techno some rap and rock occasionally. 
1. Should I go ported or sealed? I'm not overly worried about SPL. I think it will be enough output either way. Mainly concerned about smooth response. 
2. What airspace will I need? I've been building my box to specs but I'm usually disappointed with them. I think they are to small for a smooth response. Should I trust JL's box recommendations? If not can someone give me a good airspace size for the box? 
3. They recommend 1" MDF. I've never seen 1" mdf and its not available in my area. Is 3/4" good enough. Should I double face the front? 
4. To further my previous question, how is the best way to brace the box? 

basically I want to be sure the box is strong enough and big enough for the driver to sound its best. Any help greatly appreciated!!


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## sienna1 (Sep 4, 2009)

WinISD shows a 2.294ft3 for sealed and 5ft3 for a vented enclosure tuned to 21.87hz.


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## czechm8 (Oct 15, 2008)

Those boxes seem way too big. JL suggests a 1.375 cf sealed box and a 1.7 cf ported box.
Why would you want to tune down to 21 Hz in a car anyway?

It sounds like a sealed box would fit your requirements better.

Check with a local lumber yard. They can probably get 1" MDF if you feel you need it. I picked up a sheet of 1" a while back, and it was pretty expensive compared to 3/4".
You can just double up the baffle to support the driver, Internal bracing on a box that size probably isn't necessary, but it wouldn't hurt either.


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## cubdenno (Nov 10, 2007)

As heavy as that woof is, I would double up on the baffle. Use threaded inserts or tnuts to mount. No screws for mounting!! As for output, Sealed boxes fall off fairly early. Thanks to cabin gain you get a large amount of low bass. Personally I would go ported. I also now sucribe to Andy W.'s method for low frequency reproduction. get as much output out of your box/woofer system. Eq out the peaks for flatness.

As far as box volume specs from manufacturers are concerned, that is really more for power handling. The smaller the box, the greater the power handling.


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## bradinar (Jul 20, 2009)

Wow 2.3 cubic feet for a single 12"! Sienna 1: Wouldn't 22hz be a pretty low tuning frequency?


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## cubdenno (Nov 10, 2007)

bradinar said:


> Wow 2.3 cubic feet for a single 12"! Sienna 1: Wouldn't 22hz be a pretty low tuning frequency?


Now to me, that sounds about right for maximum SQ and efficiency. Tuned that low and that volume probably gives a flat frequency response. I haven't modeled it but that is usually how WinISD does it.


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## sienna1 (Sep 4, 2009)

I had the same question when I was building an enclosure for my JL 10W1's. The specs given from JL will produce a sub/enclosure Qtc with a range in the high .8's. The ideal Qtc of .7 (produces the flattest response from the sub) which equates to better SQ than SPL. The smaller the box from a Qtc of .7 will produce greater SPL but with an earlier roll-off of the bottom end (lower freq). This increase in SPL also comes with more boom vs smooth tight bass. I went with .88ft3 in a sealed box as apposed to JL's recommended .65ft3 (the ideal size would have been 1.6ft3). I didn't want to loose too much trunk space so I made a compromise at .88ft3 (had to low-pass the sub at approx 70hz to attenuate some of the boom). As for the MDF, JL only calls for 1" on the front panel therefore doubling up on .75" MDF would solve your problem.


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## bradinar (Jul 20, 2009)

Well I can't really pull off a 5 cu ft enclosure in my trunk. I could do about a 2.2 cu ft sealed. Other than output is there any other advantage to going ported?


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## sienna1 (Sep 4, 2009)

bradinar said:


> Wow 2.3 cubic feet for a single 12"! Sienna 1: Wouldn't 22hz be a pretty low tuning frequency?


A sealed enclosure will have a natural roll-off at the bottom end. The tuned frequency would be for a ported enclosure.


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## sienna1 (Sep 4, 2009)

bradinar said:


> Well I can't really pull off a 5 cu ft enclosure in my trunk. I could do about a 2.2 cu ft sealed. Other than output is there any other advantage to going ported?


A ported enclosure will usually be more efficient (more SPL with lower bottom end) and a sealed will usually have a smoother response with less SPL for a given input. I personally like the sound of sealed boxes. I find them to have a tighter, smoother response.


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## bradinar (Jul 20, 2009)

I'm leaning more toward sealed myself. I've only heard ported subs in prefab boxes which are always a compromise but they always sound boomy and "one notey" to me. Do you think about 2.0 Ft^3 sealed would be enough space for it?


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## sienna1 (Sep 4, 2009)

bradinar said:


> I'm leaning more toward sealed myself. I've only heard ported subs in prefab boxes which are always a compromise but they always sound boomy and "one notey" to me. Do you think about 2.0 Ft^3 sealed would be enough space for it?


I think 2ft3 should be OK. You can download WinISD and see for yourself what different parameters will produce.


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