Subs firing upwards, trunk sealed off from cabin?

[ancorp 10+ year member]

I was thinking of putting four 12"s into a Mazda 3 trunk, and firing them into the cabin with the trunk sealed off.

Is it possible to have them fire upwards, and then have more MDF around it as the poorly drawn picture shows? There is not enough room on the face of the box to have more then 2 (maybe 3) firing directly into the cabin, so firing up and then against another MDF chamber is the only way I can see it fit.

I was thinking sealed box as I don't have enough volume to go ported, nor enough for bandpass either.

How tall should the opening be? Just a tad more then the subs maximum excursion so the woofers don't hit it, or does it need to be much more?

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[BrownVanMan 10+ year member]

why have the piece on top? i would think somehow that would act as a port of sorts?

 

[RangerDangerV2 5,000+ posts]

no

 

[ancorp 10+ year member]

Has anyone actually tried this? What are the downfalls?

 

[CAT MAN 5,000+ posts]

if its a dedicated 4th order it would work fine. ive done some in crown vics like this

 

[ancorp 10+ year member]

Well it's not so much a 4th order. It's basically a sealed box with a wood "trunk lid" replacement. Something to stop trunk and rear deck rattle basically. That's why I sealed off the current setup in the first place.

 

[CAT MAN 5,000+ posts]

Well it's not so much a 4th order. It's basically a sealed box with a wood "trunk lid" replacement. Something to stop trunk and rear deck rattle basically. That's why I sealed off the current setup in the first place.

it is a 4th order....

 

[ancorp 10+ year member]

Fair enough. Any tips as to where to start for measurements? I'm not sure how to calculate it as a 4th order, since the ported section has no separate port, it's just a 3 walled chamber.

My apologies I don't know that much about 4th orders. Please enlighten me.

 

[CAT MAN 5,000+ posts]

Fair enough. Any tips as to where to start for measurements? I'm not sure how to calculate it as a 4th order, since the ported section has no separate port, it's just a 3 walled chamber.

it would just be a 4th order without a loading wall(or with) . take all the measurements for length width and depth then we can figure out the amount of space your subs/port will need.

 

[mazdakid 5,000+ posts]

Id try to make the sealed side smaller and the top bigger.

 

[ancorp 10+ year member]

The biggest box that I can fit through the trunk opening is 31" wide, 26" deep, 14.25" in height. Tight space for four 12"s, I know.

If I insert the box from the inside (removing the rear seats first) I could squeeze an inch more in width and height, more if I have rounded top corners (see photo):

http://www.jbcarpages.com/mazda/3/2004/pictures/images/2004_mazda_3_picture%20%2835%29.jpg

Subs are Clarion PXW1252.

 

[CAT MAN 5,000+ posts]

The biggest box that I can fit through the trunk opening is 31" wide, 26" deep, 14.25" in height. Tight space for four 12"s, I know.
If I insert the box from the inside (removing the rear seats first) I could squeeze an inch more in width and height, more if I have rounded top corners (see photo):

http://www.jbcarpages.com/mazda/3/2004/pictures/images/2004_mazda_3_picture%20%2835%29.jpg

Subs are Clarion PXW1252.

hmmm cant fit a fourth but you could do subs up port back

 

[mazdakid 5,000+ posts]

Build inside the trunk or just take the box in your pic and seal the ported part and port the bottom sealed part.

 

[ancorp 10+ year member]

Subs up and port back would mean firing into the trunk lid. Unfortunately it would defeat the purpose.

Mazdakid, to what specs em I building? What port area, tuning, and volume of top and bottom?

 

[akheathen Premium Member]

hoping someone can step in with better ratios. i would shoot for a 1:1, meaning there is as much sealed as ported. take the displacement of the subs into account. i have not built many of these, but i have done well. it's just been years...