Pics of my fiberglass box- suggestions?

[bumpin96monte!]

Hi all, I put this box together last summer, because I wanted something a little more 'custom' looking, and seeing that I never used my backseat- a fiberglass box in its place seemed the best bet. I posted this over on the termpro forums for some help too, and haven't had a whole lot of responses, so I figured I'd post on here since there seems to be a lot more fiberglass specific threads.

Here are some pics of its construction (I set them up as links to make it better for the 56k people):

My old box:

http://i5.photobucket.com/albums/y183/bumpin96monte/100_1824.jpg

Stock:

http://i35.photobucket.com/albums/d167/cfrederi/100_2142.jpg

Basic Platform:

http://i35.photobucket.com/albums/d167/cfrederi/100_2144.jpg

Mostly with the framework:

http://i35.photobucket.com/albums/d167/cfrederi/100_2147.jpg

Framework done, ready for fabric:

With just the one layer of fleece:

http://i35.photobucket.com/albums/d167/cfrederi/100_2163.jpg

Resin drying:

http://i35.photobucket.com/albums/d167/cfrederi/100_2168.jpg

After that, I added 2 more full layers of the chop matte fiberglass from the inside; and 1 more layer of chop matte on the outside to try and keep it from flexing. To me it seems pretty solid.

Then I wrapped it in my finishing cloth:

http://i5.photobucket.com/albums/y183/bumpin96monte/MyboxCovered.jpg

Finally a pic of it installed in the car:

Now to my questions; when I switched to this box, I lost about 3-4 dB on an older, portable Audiocontrol meter (the two readings were done almost a week apart, so I know there will be some variation anyway). Plus now it does seem overall just a tad less powerful (I also went from 2 batteries to just 1 between the two runs).

Obviously I made the port easily removable, and made a gasket for it to seal perfectly when screwed in, so I can vary port length. My actual questions:

1.) Is this box too big for these 12" Atomic ELE's?

2.) About what length port should I be running?

3.) Is my port too big? (I can pretty easily make a smaller cross sectional area port)

4.) Any suggestions or changes I should make to make it louder (I don't intend to compete in any organized events like dbdrag, but I do sometimes go to small local competitions)?

BTW- here are the sub's specs (well this is for the dual 2 ohm, I've got a dual 4; but the rest is the same):

---------UNITS ELE12D2

Revc (ohms ) 1.80

Fo (Hz) 50.7

Sd (sqM) 0.055

Bl ™ 20.06

SPLo (dB) 92.43

Xmax (mm) 10

Dvc (mm) 75

Qms (m.q.) 5.38

Qes (e.q.) 0.37

Qts (totQ) 0.35

Vas (liter) 32.4

Cms (uM-N) 75

Mms (gram) 130

General size for the box (since I have no way to calculate volume at all)- these are all outside measurements:

The box itself is about 48" wide, 24" deep, and 26" tall. The port is currently 6" wide and 13.5" tall; and can be a maximum of 13.75" deep before it hits the back wall.

I know if it were triangular (instead of the curvy front) it would be ~8 cu ft considering the port, but not taking into account the internal bracing or subs; but the box slopes back so much on the top sides, that it should be a good bit less than that, but I don't know for sure.

Any help is appreciated!

Click to read more...

 

[bumpin96monte!]

Oh, and one thing I already know is that I am leaking air into the trunk. I didn't fully bolt it into the car yet(hence why stuff doesn't quite line up in the installed pic, its sitting a little forward and rotated). I know I still need to fully seal the trunk off to make it louder- it is just a very very small bit louder with the trunk open.

Also, I thought of another question- is there any possibility of this setup ever being louder than my old setup?

 

[AcidicDreams 10+ year member]

nice box.... unfortunately I'm not the one who can answer your questions... my guess is the box is too big and the port needs tuned but I've never built a ported box and I know nothing of those subs...

 

[Volenti 10+ year member]

Assuming those driver specs are accurate (Bassbox had a spaz over the BL, 20 is very high, the re-calculated 14 was more reasonable) your enclosure is way too big.

About 3 cubes is all you need, if you square your port off, 6'' x 6'', and make it 7.5'' long you'll have a nicer response.

I'm sorry to say after all your work but I think that these subs were far better off in the old box loaded in the boot, the high Fs and low Vas make the driver rely heavily on that type of loading. It's possible they may prove usefull in a TL or horn loaded design but that would require far more accurate specs.

 

[blue93corsica 10+ year member]

not really sure on this but, it looks like you just cut a hole in the box for the port and didn't actually add in a port, and thats uaually the difference between mdf boxes and glass boxes, mdf can be built to specific specs and accurate tuning can be achieved but it is much harder with glass boxes

never the less, the project came out real nice, good job

 

[negativezeroz 5,000+ posts]

**** thats good man

 

[bumpin96monte!]

Volenti- do you think its impossible for these subs to work well in a forward firing application at all? So you say about 3 cubes huh... I think I'm probably closer to 6 right now. I think I may be able to partition off some of the internal volume of the box to bring that down, but I doubt I could knock a full 3 cubes off. Also, would putting a larger sub in there (say 15"s instead) help any?

blue93corsica- I know I didn't post a good shot of my port, but its not just a hole in the box like in that framework pic. I added wood to the backside of it to make it into a port, all sealed and everything. You can kinda tell in the finished pic if you look hard (its spray painted black so its hard to see).

 

[Volenti 10+ year member]

Well they'll "work" where they are, they are there now, making bass, just not at the kind of level they were when loaded in the boot by your own results. The subs are designed around a specific application, (small vented enclosures, they would also probably work very nicely in a front horn), and when you load a sub in a boot correctly you can get a "poor mans" horn, with increased output.

Move the sub up to the center of the car and the horn loading effect is gone (though cabin gain remains)

15''s or even 12''s with a higher Vas (that require a larger box volume) would give you better results that you are getting now.