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Hi all, I just built myself a nice 1.25 cu.ft ported box for a JBL GTO804 8" Subwoofer. It sounds awesome, but I'm having trouble to get it sound perfect in the car.

I used WinISD for my design program. It recommended a tuning frequency of 28Hz, which gave a pretty much flat response down to about 25Hz or so.
JBL recommends a tuning frequency of 40Hz for that speaker. This gave the SPL slope almost a +6.6dB increase at about 42Hz, but was already at -3dB at 32Hz.
I chose to tune my box at 30Hz, which gave almost a +3dB gain at 32Hz and -3dB gain at 25Hz.

Now thats all and good, except I didnt factor in that I mostly listen to rock and metal, and that doesnt really do me any good for that. It sounds very smooth, but the car is too small for it to really work right at that tuning frequency. For rap and electronic-type music, which I also listen to, its really awesome and it shakes my head, it really sounds good when playing "Get Low" heh.

I'm probably going to change my ports (my design used 2 2" ports) so that the box is tuned to 38Hz which gives me a +6dB gain at 40.7Hz 0dB at 33Hz, which is 3dB lower than what I have now, and a -3dB gain at 31Hz. I suppose thats not a bad trade off in frequency response considering the music I play.

I just wanted to see what everyone else has their subs tuned to, if using a ported design. I want to see what works the best in our cars.

-phil

I can send the WinISD file to anyone if they want.

PS - this is a badass sub for someone who needs a lot of space in their trunk like I do. There is not a lot of sound outside the car either, even when turned up a lot.

 
Rep Power: 291

you're putting way too much effort into this for a civic! most buy an off the shelf box and throw it in there. that's what i did.

 
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I'm all about effort when it comes to good sound.

 
Rep Power: 237

I'm personally more of a fan of sealed boxes because I don't listen to very much rap. I prefer the quicker "punch" you get from them for rock. When I looked into ported setups, I opted not to go through the process of figuring out what frequency I wanted to tune for.

I'm kinda with electric...just get an off the shelf sealed box. But +1 for you for taking the effort, especially if you go ported.

 
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10 inch in a box is plenty for most types of music in a civic

 
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yea dude, u get all picky and detalied.....enjoy it for about a few weeeks, then wonder why you waste so much effort and realize you dont really giv a crap =]

 
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2 12inch MTX in a sealed box and its punchy for rock and works just fine for rap too. Ive heard a single 10 inch in my friends civic too though and it sound ok. Changing the interior speakers is a must though...im kinda an audio snob.

 
Rep Power: 258

hey phil ill take that file. im sort of an audiophile myself

 
Rep Power: 247

hey phil, i wouldnt mind messing ariund with that program. i just have 2 12" sony's in 2 sealed boxes in the sides of my trunk. sounds great. and its clear with all types of music

 
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you can download the program online. just do a google search for "WinISD"

I'm not sure how to send a file on here without hosting it or using a private email.

so, if you want to mess around with my sub, the parameters of the speaker are:
(tip, click the measurement type to change it from imperial to metric)

Qts - .42
Qms - 6.37
Qes - .45
Vas - 16.4l
Fs - 29.6Hz
Re - 3.49Ohm -- (4 Ohm Driver = Z)
SPL - 91.0dB
Pe - 200W
Le - 1.64
BL - 12.88
Xmax - 11mm
Z - 4Ohm
Diameter - 210mm
Sd - .603ft^2

 
Rep Power: 246

what the hell does that all mean?

can anyone recomend a 12" sub that will handle 1000 watts? i'm thinking about taking my dual 12" box cuting it in half and using a 500watt bridged to a single sub..

EDIT: nevermind i dont want to know

 
Rep Power: 263

MTX Sledge Hammer will handle 1000w/RMS

 
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So I had a round of duct taping, because I can never cut wood good enough (using a circular saw) and that helped the sound quality a lot, because I had a lot of leaks. This is just a temp fix until I have time to take the box out and reseal it from the inside.

Although now it sounds a LOT better, I can hear even more that I need to change the tuning. So thats going to happen too when I reseal it.

 
Rep Power: 256

umm ive heard 32Hz is a little better than 28. Dont exactly know how to explain it or scientifically why it works something about woofers being smaller than 12" lose their effectiveness at below 30hz. This kinda makes sense. I was using winISD when i was building my box. Im running 2 jl 12w0-4. nothing too special but having a box where I know the best frequency helped a lot when i competed in spl. I hit 132.2db and my amp is only like 300w. Either way after around 120db it doesnt matter. As long as the box doesnt have a sloppy sound thats all I care about. Besides you can always tune your stereo to match your setup.

 
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Smaller Drivers = Less ability to move as much air = usable low frequency range

Larger Drivers = Better ability to move more air = More usable low frequency range

I used to have 12" - 15" woofers in my previous vehicles, but for the small amount of space that this takes up, my whole entire car shakes. You should see my windshield mounted GPS shake. haha

 
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just in case anyone else that was wondering about this,

I retuned my subwoofer box to 36Hz which only involved taking out and cutting the ports in there already.

Except the box I made was leaky as hell, so I went around it with a hot glue gun, which is a lot easier to me than using silicone. I've used both before.

Needless to say, it sounds soooo much better. All the lows are still there, except now I can feel most kick drums instead of just hearing them.
I also fixed a problem with my amp overheating with a computer fan and a really big drill bit.

And if anyone else has had a problem with the speaker jacks leaking air (radioshack ones suck), use binding posts instead. I glued a piece of wood to the inside of the box where the rectangular jack used to be, and using a flat bottomed bit, drilled a recessed hole for the binding posts, ring terminals on the inside to banana plugs on the woofer, then on the outside, banana plugs off the box to the screw terminals on the amp.
No air leaks because you only have to make two small holes in the bottom of the recessed area for the posts to stick through and bolt on.