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Old 2nd April 2010, 22:16   #1
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Default Ideal Enclosure for the JBL W12 GTi MKii?

Hi everyone! After a long hiatus, I am back with a query!
My fibre glass enclosure is not giving me good enough results for the W12 GTi in my boot, and I am now running of a makeshift enclosure that measures roughly around .7 cu ft. I am making a new MDF enclosure for the sub.
NOW, the JBL sub documentation says that the enclosure must be 1 cu ft. in size. They haven't given the exact dimensions, and I am stumped as to how to go ahead. I am enclosing the PDF. Please advise me as to how to go ahead with this.
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File Type: pdf W12GTi_rev_f.pdf (82.3 KB, 1280 views)
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Old 2nd April 2010, 22:29   #2
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I'm sure you knew this site Speaker Enclosure Volume Calculator, is it about anything else other than what's on this site
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Old 2nd April 2010, 22:55   #3
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You can also check it here: Subwoofer Enclosure Calculators, Fraction to Decimal, Parallel, Series, Port Length and Volume Calculators
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Old 2nd April 2010, 23:13   #4
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Considering the sub displacement ( if you plan to put it normally) , make a non cubic enclosure of around 1.08-1.1 cu ft.

the exact dimensions are never as such required.
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Old 2nd April 2010, 23:33   #5
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Why not a ported box with a tuning freq of 25-30 hz range ?
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Old 2nd April 2010, 23:34   #6
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How does one tune a port??? I am confused. Never had a ported box professionally made!
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Old 2nd April 2010, 23:39   #7
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Simple question: What results you expect from the sub and what do you think the sub is not playing well in the said enclosure ?
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Old 2nd April 2010, 23:45   #8
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I don't expect the sub to do anything extraordinary. But even my Luccents outperformed it in terms of sheer quantity of bass. I gave the luccents 250 Genesis watts.
I am giving the GTi 1200(!) RMS watts of power. It's just not singing the way I want it. Either too much bass or too less. And when the volume is pumped up, it sounds like a ONE NOTE sub. Did an RTA but to no avail. The enclosure change (presently a leaky one) made a world of difference. But I am still unhappy. The BASS package costed me a cool 40K and it's definitely not showing it's worth here.
Could it be the sub (which is HALLOWED and spoken about as 'the Holy one' all over the world?)
Cannot be the amp. It's working perfectly.
The FG enclosure was surely at fault.
Can someone suggest a solution? I am getting the sub to gel with the fronts well (with the help of TA), but am unhappy with quality and quantity (considering 1200 W are going to it) of bass. Have been unhappy since weeks. Losing sleep over it now.
Can someone help me design a 'ported' enclosure (PURELY FOR SQ) please?
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Old 2nd April 2010, 23:58   #9
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Frank not to play spoil sport here but I would suggest you to go for a sealed enclosure as I have made a enclosure for the GTi and really like the way it sounds.Anyways you've got plenty of power for your sub so Im sure it will sound amazing in a sealed enclosure.
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Old 3rd April 2010, 00:00   #10
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I ran on 2 sealed enclosures with not so convincing results. Maybe it's cabin gain? Maybe it's the acoustics of the car playing spoilsport?
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Old 3rd April 2010, 00:10   #11
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Yes I certainly agree that the acoustics of the fiesta do play spoilsport till a certain extent and the results are not as expected(mohitd had the same reaction) but i have always felt that after listening to a ported enclosure for a period of time the bass kind of gets monotonous.
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Old 3rd April 2010, 00:12   #12
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ported enclosures can sometimes give better results than sealed ones. it's a known fact. one just needs to strive that much harder to get it right with a ported enclosure. it's not just about 'boom-boom'
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Old 3rd April 2010, 00:25   #13
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Well you should try ported enclosure and do try to play with Gain settings at amp end on the current enclosure and see if that helps.

I think none of us will be able to tell you what enclosure size will suit you other than the ones specified in the manual. People who have already auditioned your setup will be more helpful in that way. If i am not mistaken Invinsible has auditioned your setup and he might be able to give you a better input on the enclosure size according to your taste and needs.
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Old 3rd April 2010, 10:46   #14
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Size I can help you design the enclosure but what thing you are missing. How is the sub performing now ? It there two much low end or to much of high end (I mean in term of bass low means sub bass...30-40 hz and high end in terms of midbass 60-80 hz) ?
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Old 3rd April 2010, 11:19   #15
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Frank, my friend you are running an enclosure size which is half of what is required. I suppose I had given the design earlier to you.
Your sub requires around 1.25cu.ft net internal volume or 1.4cu.ft with the displacement to perform optimally in a sealed enclosure. However with the kinda power you are running and the amount of excursion you will face with that power you will need to limit your sub to net internal volume of 1.25cu.ft
I had discussed with Andy long back regarding this sub, here's what he had to say "Hi Abhi,
Connect the coils in parallel. That'll give you 3 ohms and yes, 400-600 watts will be great. Inside the box, there's an enclosure design sheet that indicates the appropriate enclosure size. I suggest building the vented box. Here's a link to the design sheet on the web:"

Reg the sealed enclosure this is what he had to say, "It'll go just as low and sound great. Vented would really be better, though. If that's impossible, then sealed will be fine too."
A well tuned ported design can sound at times even better than the sealed enclosure. More than the port tuning is the design and build and how you place it in the boot place more imp role. The idea is to keep the port tuning above the Fs value of the sub. The sub values suggest that it could be used both for ported and sealed. Anyways if you decide an ported can workout the design or else you have the above sealed enclosure

Last edited by Invinsible : 3rd April 2010 at 11:33.
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