Well I just tried to fit my 6.5 cuft box in the car but it wouldnt even go in the backseat (it was designed for my old car)..so i suppose im forced to make a sealed box. however, i still want it to be in the actual car. Does anyone know what the best way would be to make a design for a JBL W15 GTi sealed enclosure that would take up only the middle seat of a car? If I have to take up two back seats its ok..im mainly looking for some good sound, but i also want it to be as loud as possible.

from the JBL web site an SPL box at 65 Hz is 5.5 cf, 70 Hz is 4.7cf
and SQ vented box is 4 cf, sealed is 1.5 cf

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MECA SQ

www.cardomain.com/memberpage/769882

I don't know what your problem is, but I'll bet it's hard to pronounce.

ok i made a design for it..im definitely not experienced with enclosure designing but here's what i came up with and it seems to fit into the middle back seat.

the box will be 21" high, 18" wide and 18.75" deep with a double baffle. thats about 3.07 ft^3 of airspace. would this sound good or would i need more air?

The JBL website has drawings of optimum box designs I would recommend them... but they may not fit where you want it to (their sealed box may be perfect though)

-the external measurements are important to make the box fit where you want it to.
-the internal measurements are important since they determine the subs performance.
-the internal volume does not include the port volume nor the volume taken up by the sub itself.

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MECA SQ

www.cardomain.com/memberpage/769882

I don't know what your problem is, but I'll bet it's hard to pronounce.

well yeah but the box is sealed so port volume isnt a concern and on their website didnt they inclue the displacement? it would be really hard to fit 4 cuft in the middle back seat so i found a perfect one that came up to 3 cuft which is the one above that i wrote the dimensions for..will it stil sound good if its 1 cuft below the optimal one?

The optimal size for that driver is approximately 2 cf. This will allow for volume displacement caused by bracing and the driver itself. Once fully stuffed with dacron or similar stuffing material you can anticipate an anechoic F3 of ~42 Hz. Taking into account the naturally occuring bass boost of a car interior its response should be pretty much flat to as low as your amp can drive it. Given that this driver is a little more efficient than most car subwoofer drivers that should be pretty gut wrenching.

aww crap i guess i was looking at the recommendations for a vented box... and i already have all my plans drawn out. will 3 cuft sound bad or should i redesign it to make it 2 cu ft

do a ported box then

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EVERY FAMILY HAS A RETARD IN IT. IF YOU THINK THAT YOURS DOESNT HAVE ONE, THEN ITS PROBABLY YOU.

ok i made another design that was about 2.1 cuft sealed. tried to upload the image but wouldnt work

With sealed enclosures there is an optimum performance vs box size that once exceeded is not necessarily detrimental to the sound quality but wasteful of materials and effort.
For example your 15" driver in a 2.0cf sealed enclosure should have an F3 of approximately 42.77Hz. The same driver in a 20cf sealed enclosure should have an F3 of approximately 42.40Hz.