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View Full Version : Help needed with enclosure design



sweety
12-16-2009, 12:23 PM
Hi all:) I'm about to build my first box as the box I bought i've found out is a bit to small at 28L. The sub I've got is a JBL GT3-12 which i've found on the net should have either a 40L sealed or 50L ported but thought I would ask you guy's the spec's for the sub are as follows
JBL GT3-12 12"
RMS Power Handling:225W
Peak Power:1800W
Voice-Coil Diameter:50mm
Mounting Depth:155mm
Qes:0.6
Qms:5.53
Qts:0.54
Vas:100.45 ltr
Fs:28Hz
Pe:225watt rms
Frequency Response:35Hz - 3kHz
Sensitivity:89dB
Impedance:4 Ohms

At the minute I have a wedge shaped box which fits perfectly against the back seat so would like the new box to be of the same shape. The room I have for the box to take up is 41" wide, 16.5" high & 12-13.3" depth can put up the size of the box I have at the minute if it helps:rolleyes: Ideally I would like a ported box if it's possible but have know idea on size of port(s) to use. I listen mainly to dance music & rock if that helps.
I would be most grateful with any help & possible design with measurement if you can
Many thank

sweety
12-16-2009, 04:48 PM
Just had play with an online enclosure calculator & have worked out a enclosure measuring 30" wide, 14" high, 12" deep at the bottom & 8.5" at the top will give me a volume of 1.804ft3 or 51.082litres but this is not including the displacement of the sub or port which I didn't add as unsure how to work it out. Does this sound about the right size box I need ? Still have no idea on what size/length of port that would be needed:confused:

robertoyoung08
12-16-2009, 05:33 PM
you would need to know what you want the box tuned to in order to find out the port length

zierbox
12-16-2009, 06:29 PM
With that size box the port is going to be long, so you will loose even more volume for the port
Its going to be close, not impossible but I think do-able

sweety
12-17-2009, 08:39 AM
Thanks for the input guy's, had a chat with a lad on this side of the pond & he thinks for the set up i've got that a sealed box would probably would be the best option for my sub but said build a 50L box & see how that sounds then poss partly fill the box with polystyrene & see how that sounds:confused:wondering if I should go for a 40L box & if needed fibre fill it:confused:

sweety
12-28-2009, 12:37 PM
Well after a bit more thought & playing about with these online calculators I've come up with a box size of about 50L as mentioned above & from what I can gather a port 2.5" x 4.75" should tune the box to 34Hz:rolleyes: As I listen to mainly dance music would the be about the right frequency to tune the box to ? & would it be possible to fit 2 ports 1 either end of the box on the top & just 1/2 the length of them