# How Critical are Manufacturer Recommended Subwoofer Enclosure Volumes?



## KP Texan (Oct 26, 2009)

I just ordered a JL Audio 10W0v2 for the small back enclosed storage area in my Jeep Wrangler and JL recommends .65 cubic feet net for the enclosure. Since I still want to use some of the storage area, every additional inch in enclosure size matters to me. I've modeled this subwoofer in WinISD along with another subwoofer I was considering, the Boston Acoustics G110-4. Interestingly enough, the graphs of these two subwoofers are nearly identical and overlap each other, given the same enclosure size and the same input power. Boston recommends .5 cubic feet for their subwoofer, so I would think that the 10W0v2 would perform well in the same size enclosure (and a half pound of polyfill thrown in for good measure). Is this a safe assumption? I suppose that I'm simply trying to ensure that deviating from the manufacturer recommended enclosure volume won't result in a crappy sounding sub. Any thoughts would be appreciated!

Thanks so much,

Wes


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## St. Dark (Mar 19, 2008)

If you have the software, model it and see!

There isn't just ONE sealed enclosure for a given sub, as you probably know. You have a usable range, and the manual will list one within that range based on whatever the manufacturer was thinking at the time they wrote it (what they think is ideal for the most common application for the specific driver; middle of the usable range; etc).

As you go smaller, you get a peakier response and you roll off at a higher frequency and faster rate. You might find it listenable, you might not.


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## Gary S (Dec 11, 2007)

You can go down in size 20 - 30% without a noticeable difference in sound quality. I assume this is a sealed enclosure, not ported or bandpass.... sealed are very forgiving.


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## KP Texan (Oct 26, 2009)

Gary S said:


> You can go down in size 20 - 30% without a noticeable difference in sound quality. I assume this is a sealed enclosure, not ported or bandpass.... sealed are very forgiving.


Yes, it is sealed so I'm hoping I'll be fine. I modeled a .65 cubic foot and a .5 cubic foot enclosure with the 10W0v2 and the same input power. The difference in sound levels when going from a .65 cu. ft. to a .5 cu. ft. enclosure are as follows:

20Hz: -1.6db
30Hz: -1.6db
40Hz: -.9db
50Hz: -.4db
60Hz: 0db
70Hz: +.3db
80Hz: +.5db
90Hz: +.5db
100Hz: +.4db

So basically, I would lose a bit on the bottom end and gain a tad on the top end. Being that my primary preference in music is rock, secondary is country, and a distant third is pop/rap, does it seem like I would not compromise too much in way of "punch"? I also hoping that adding some polyfill to the smaller enclosure will help to make up for some of the difference.

Thanks so much,

Wes


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## Gary S (Dec 11, 2007)

Right, I see the box model program specs you posted... 

Keep some things in mind:

- on the low end, looks like you loose 1.6db... 3db is considered the threshold of audibility.

- the car (it's like corner loading in a room/house) will boost the low end far above that.

- On the top end (low pass), you probably have an adjustable active crossover in the head unit/processor/amp, correct? - you will be able to tame that peak with the crossover.

Like I said, in real life, once you get it tuned, you won't hear a difference.


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## TheDavel (Sep 8, 2006)

KP Texan said:


> Yes, it is sealed so I'm hoping I'll be fine. I modeled a .65 cubic foot and a .5 cubic foot enclosure with the 10W0v2 and the same input power. The difference in sound levels when going from a .65 cu. ft. to a .5 cu. ft. enclosure are as follows:
> 
> 20Hz: -1.6db
> 30Hz: -1.6db
> ...


As opposed to polyfill consider the Focal Black Hole Stuff- it claims provide results simillar to a box that is %35 larger... not sure the best way to explain it but say a box calls for an overall volume of 1.0 cf you can make it .65 cf and fill it with the "Stuff"... If space is your justification for using a smaller enclosure then this may help you out...

Then again the above info may be completely useless to you.


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## nick650 (Feb 7, 2011)

Stuffing is needed in every single box you make for a speaker, period. Just need a little to get rid of back waves and to clear up the sound. How much you need after that is up to you.


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## TheDavel (Sep 8, 2006)

nick650 said:


> Stuffing is needed in every single box you make for a speaker, period. Just need a little to get rid of back waves and to clear up the sound. How much you need after that is up to you.


I never build without some form of internal wave displacement material in a box... sometimes I get a lil crazy and add additional bracing materials, sound deadner, eggcrate foam, pollyfill/blackhole stuff, ect... Ive even been know to put marble slab and concrete in some boxes... seems a lil odd I'm sure but makes for a great sounding, solid enclosure...


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## KP Texan (Oct 26, 2009)

TheDavel said:


> I never build without some form of internal wave displacement material in a box... sometimes I get a lil crazy and add additional bracing materials, sound deadner, eggcrate foam, pollyfill/blackhole stuff, ect... Ive even been know to put marble slab and concrete in some boxes... seems a lil odd I'm sure but makes for a great sounding, solid enclosure...


Or better yet, you should make an entire box out of marble slab! 

Anyway, another frustrating thing about this box design is that it will only fit in my Jeep one way, so I won't be able to rotate it in order to optimize firing direction...I'll post up a few pics to let you guys know what I'm working with here.

Thanks,

Wes


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## TheDavel (Sep 8, 2006)

Looking foward to them... any chance you'd modify the vehicle (cut a hole) to gain extra space and optimize firing direction?


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## KP Texan (Oct 26, 2009)

Here are a few pics of my Jeep and the space I'm putting the sub in:




























As you can see, I'm fairly limited on volume and I still need enough room back there to store my laptop bag and a few other little things that may need to be locked up. Although that "Instatrunk" is made of thin gauge sheet metal, there are a ton of air gaps in it between that and the passenger compartment. From my experiences with subs in the trunks of cars, I'm thinking it should sound okay. I've come up with several plans in AutoCAD (down firing, rear firing, side firing) and it seems like the side firing is my best option since it allows the enclosure to be shorter. The box will go on the passenger side of that area and I'm thinking about firing the sub into the passenger side rear corner, rather than towards the center because it will protect the woofer cone from whatever I'm storing in there. Additionally, the flat side of the enclosure facing inboard will be just right to mount my amplifier on (PPI PC2200.2). I'll also probably put some sound deadener on the trunk in order to prevent rattling. The Wrangler is not great for stereo installs but I still need some bump in my trunk! Let me know what you think! 

Thanks,

Wes


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## TheDavel (Sep 8, 2006)

In nearly every jeep I've done I've always opted to go with the down firing/rear firing route and had great results... normally I'd say down fire it but side firing the sub seems like it would produce basically the same results... hopefully someone here has done this in your particular car and will speak up-


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## KP Texan (Oct 26, 2009)

Here's a more descriptive photo of what I'm doing. There are a couple little steel cargo loops that will prevent the subwoofer from sliding more towards the passenger side. The arrow is the firing direction of the woofer and the ellipse is where my amp will mount on the box. Hopefully this setup will work. If I fire in the opposite direction, I've got subwoofer protection to contend with and will need a grill...I will do that if you think sound quality will be greatly improved. My problem with down firing or rear firing is that I probably need at least a 1.5-2" gap between the bottom or from the back tailgate to give enough room for the woofer to breath. This gap causes the enclosure to become wider in order to achieve the same volume.

-Wes


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