Actually i built the box within specs for that particular sub these are the sealed box dimensions reccomended from that sub

"Min Rec Sealed Box Volume (CU. FT., Liters) 2.25, 63.7
Max Rec Sealed Box Volume (CU. FT., Liters) 5.0, 141.6"

Built close to 3 cu. feet so maybe do some research before you say my system is ghetto it's the best one ive ever seen or heard of in an 84 pickup.

Edit: it's wide but only 9" at the top and 11" at the bottom

 

Check your math - judging from 10's on the top, a 12 on the front and ~48" wide, you're closer to 4 cuft (admittedly, within JBL's barn door size specs)

I had 2 10's in the same space - only difference was mine was an '89 (pix in post 23)

 

Maybe it was more than 3 i dont remember but it definitely wasnt's over 5

btw, ported are generally a lot smaller if i put square ports on the sides it would be sufficient for two 12's but i like the deep sound the large sealed box gives you and dont need two subs.. i'm not into pumpin massive bass or anything

 

Since when are ported boxes smaller?

 

Im rockin' the stock tape deck with some old GnR. oh ya.

 

but nobody wants to steal it now.

 

x2 - you have to subtract out any volume the port displaces if it's inside the box

 

1 15" fi btl sub woofer
3000 watts RMS
67 lbs.
Dual 2 ohm voice coils
Magnet is around eleven and a half inches in diameter.
Cost around $450 Smackaroos

And 0/1 Gauge wiring.

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i was reading that the max size for a sealed box is a lot bigger than for a ported box

 

I dont think so Tim...

This is a direct quote from the User Manual for your JBL Sub (if its the GT5-12)...

"An optimum vented enclosure is always larger than the optimum sealed box for the same woofer and will require more space inside the vehicle."

Here is the link to the manual it is on page 2.

The specs JBL recommends for the GT5-12 are...
Sealed: 1 ft^3
Vented: 1.75 ft^3
Bandpass: 2.25 ft^3 (all together)

 

I thought your enclosure looked a little big for the sub. You might want to check it. If it is to big you can damage the sub. Not enough pressure and it will move to far.

 

i got a rockford t1500 amp and 4, yes 4 15" sony xplod subs in a custom non ported box. double-dynamat throughout. i dont think i can have babies anymore though...