# custom sub box.



## XtremeRevolution (Jan 19, 2012)

How much airspace are you looking at, and how well does that sub work in the airspace you plan on using it in?


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## thormxkid (Nov 19, 2012)

sub calls for 1.25ft 
as far as what i'll have i don't knoe yet, i'll figure that out when then mold is pulled.
whatever air space im sort. if i'm, i will fill with polyfill.


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## XtremeRevolution (Jan 19, 2012)

thormxkid said:


> sub calls for 1.25ft
> as far as what i'll have i don't knoe yet, i'll figure that out when then mold is pulled.
> whatever air space im sort. if i'm, i will fill with polyfill.


I didn't quite catch that. 

Don't go by what the manufacturer recommends. You always need to model it for yourself and see what it looks like. I have a thread here (a sticky in the electronics section) where I would be more than happy to model it for you. 

Polyfill is by far the least effective box stuffing/wall treatment material out of your options. Look into Roxul fire batts/mineral wool. You can get it in 2.5" thickness and add layers until you have the amount of fill you need. Take it from a speaker designer who has extensively used both, in addition to acoustic foam and fiberglass rigid board.


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## thormxkid (Nov 19, 2012)

i currently run 12w3's in my other car in 1.25 cubic foot boxes. they sound and perform great. i'll be sticking close to these specs. 

also had good results with polyfill in other boxes i've built. 

never really heard of using roxul before. 
is there a set amount to use or do you just take wild guesses? at how much is need to make up for being sort on airspace needed


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## XtremeRevolution (Jan 19, 2012)

thormxkid said:


> i currently run 12w3's in my other car in 1.25 cubic foot boxes. they sound and perform great. i'll be sticking close to these specs.
> 
> also had good results with polyfill in other boxes i've built.
> 
> ...


Does sounding good to you mean it can't sound any better?

You always add as much as you need to get the desired effect. There is no pre-set amount.

Ats acoustics sells scrap mineral wool for $28 shipped for a large, 4 foot long box. 

Sent from my SGH-T999 using AutoGuide App


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## thormxkid (Nov 19, 2012)

XtremeRevolution said:


> Does sounding good to you mean it can't sound any better?
> 
> You always add as much as you need to get the desired effect. There is no pre-set amount.
> 
> ...


jl put alot of time into r+d of the products. I will be sticking close to their specs.
i really don't see any reason to vary from their numbers when im currently running their product and it sounds good. smooth clean and loud.

what else should i be expecting from a sub?


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## iCruze2 (Dec 16, 2011)

Xtreme builds boxes, he knows his s-h-I-t bro


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## Wyre (Jul 23, 2011)

Have used Polyfill myself. It works pretty well... mineral wool is better bro. Just sayin


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## XtremeRevolution (Jan 19, 2012)

thormxkid said:


> jl put alot of time into r+d of the products. I will be sticking close to their specs.
> i really don't see any reason to vary from their numbers when im currently running their product and it sounds good. smooth clean and loud.
> 
> what else should i be expecting from a sub?


Don't buy into the marketing BS JL has plastered all over their site about all the patents they own and all the R&D they've done. I can't tell you how many times I've heard it from JL fans and I don't really care for it. They're nothing special. Frankly, I've discovered that companies who don't flaunt and brag about all the patents they own tend to sound quite nice. Companies like Arc Audio, Image Dynamics, Aurasound, and Dayton Audio come to mind. The W6 cannot compete with the IDQ V3, and the W7 cannot compete with the IDMax, but Image Dynamics keeps it simple.

Box recommendations from manufacturers are always full of compromises. They will not design you a box for all-out sound quality or all-out SPL. Simply put, they will design you a box that sounds acceptable and meets the constraints of a size most people are willing to work with. If you are an audiophile, you always model your own box to see how you can make it sound in a given alignment. The majority of the time, you will want something different than what the manufacturer recommends. 

I've designed hundreds of boxes; so many that I stopped counting. I'm not telling you this to waste your time or my own. I'm telling you this because you need to be aware of what you're doing. 

1.25 cubic feet in a JL 12W3 will result in a box Qtc of 0.93. That is extremely high. The highest Qtc I've ever designed a box around was 0.80. A Qtc that high results in a boomy, uncontrolled sub that lacks a solid bottom end and features a lot of "boom" around 50-60hz. Output at 30hz is choked down. For a bass head, it will sound ok, but I wouldn't ever use it in that alignment for anything other than "bass fill." To me, it might as well be a bazooka tube. 

An "ideal" Qtc is 0.707. I strive to get my boxes between 0.60 and 0.75. I would never put a box in my car with a Qtc of 0.93. Since the numbers do the talking, I modeled it for you in 1.25 cubic feet, also accounting for subwoofer displacement, and here's what it looks like. Keep in mind, this is an in-cab simulation.










I would personally use this sub in *no less than 2 cubic feet gross*, with all walls except the baffle lined with 2.5" of mineral wool or rigid fiberglass board (owens corning 703/705 or equivalent). The reason why it doesn't work well in such a small box is because the moving mass is too high for such a weak motor, and the motor isn't strong enough to overcome the suspension of the air inside a sealed box with frequencies below 50hz. 

Ask yourself the following questions:

1. Who did JL Audio market this sub toward?
2. What compromises were made in the specification of the box size?
3. What else can you buy with the same money that isn't sold in a retail store that would actually work well in 1.25 cubic feet?

At the end of the day, it's your sub and your box you're building, and it will probably sound "ok" to you if you haven't heard a sub in a properly designed box, but I wouldn't ever recommend it in that box size. If you haven't already purchased the sub, there are a few subwoofers I would be more than happy to recommend you that will work well in the size you're looking at using.


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## thormxkid (Nov 19, 2012)

XtremeRevolution said:


> Don't buy into the marketing BS JL has plastered all over their site about all the patents they own and all the R&D they've done. I can't tell you how many times I've heard it from JL fans and I don't really care for it. They're nothing special. Frankly, I've discovered that companies who don't flaunt and brag about all the patents they own tend to sound quite nice. Companies like Arc Audio, Image Dynamics, Aurasound, and Dayton Audio come to mind. The W6 cannot compete with the IDQ V3, and the W7 cannot compete with the IDMax, but Image Dynamics keeps it simple.
> 
> Box recommendations from manufacturers are always full of compromises. They will not design you a box for all-out sound quality or all-out SPL. Simply put, they will design you a box that sounds acceptable and meets the constraints of a size most people are willing to work with. If you are an audiophile, you always model your own box to see how you can make it sound in a given alignment. The majority of the time, you will want something different than what the manufacturer recommends.
> 
> ...


so what ur telling me is ditch the fiberglass box (which i want so i don't lose trunk space). for a huge box that will take up trunk space.

and what do you mean model the sub?


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## tecollins1 (Nov 6, 2011)

thormxkid said:


> so what ur telling me is ditch the fiberglass box (which i want so i don't lose trunk space). for a huge box that will take up trunk space.
> 
> and what do you mean model the sub?


He's saying to make the sub sound "good" and not sound boomy. 
You will need a much bigger enclosure if you are to use the same sub.

you should get another sub that requires less space. Or yes ditch the fiber glass.

Modeling like the graph above shows how a particular sub will sound in a particular box and the car space it will be in.


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## XtremeRevolution (Jan 19, 2012)

thormxkid said:


> so what ur telling me is ditch the fiberglass box (which i want so i don't lose trunk space). for a huge box that will take up trunk space.
> 
> and what do you mean model the sub?


No, I'm not telling you to ditch the fiberglass box for a "huge" box (frankly, 2 cubic feet custom at 18" tall won't take up that much room in width and depth); I'm telling you to get a different sub. That is, if you want it to actually sound great. There are a few 12" subs out there that will sound great in 1.25 cubic feet, but that JL 12W3 is not one of them. 

When I say model a sub, I'm referring to simulating. There are various applications out there that you can use to plug in the sub's T/S parameters and determine what it might sound like. Granted, you have to know what you're looking at when you do that, but they give you a better idea of what it will sound like. For example, the software I use consists of an Excel spreadsheet that allows me to model the subwoofer's in-cab frequency response, which is how I got the image I showed you above. If you gave me a subwoofer, I would be able to tell you how big the box would need to be in order for it to sound good, and I'll be able to show you by way of a frequency response simulation what it will sound like in that box.

Edit: looks like Terry beat me to it while I was typing out my response.


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## bakerboy908 (Feb 12, 2013)

Im looking to mount a sub in the exact same location, was wondering how your install went?


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## Dolladog (Jun 25, 2014)

Here is my Custom 2014 Cruze Sub Box built by Ntense Auto Werks for $235 on Ebay in case anyone is interested.


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## YIN (Dec 6, 2014)

What size sub? How much air space?


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## billseast (Feb 5, 2013)

Dolladog said:


> Here is my Custom 2014 Cruze Sub Box built by Ntense Auto Werks for $235 on Ebay in case anyone is interested.


Thanks for showing off my box builds! I do sell on ebay and amazon but prefer for people to get them from my website. Intense auto werks


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