Trying To Fit 2 Lbs Of Stuff In A 1 Lb Box

[rusty959]

Alright, so ive got 94 ford probe. I also have a dat 2500.1 and a DC 18" lvl4 and soon to be another on the way. Im planning on doing a wall starting right at where the back of rear seats ended, though they will likely be removed to gain a couple cubes. Im wanting low tuning, around 32 or so hz, though im not too particular on any number obviously. I have right around 17-18 cubes total in the rear hatch to work with. Ive been spending some time designing some boxes, but would like some further opinions before I decide on the final design and start building. Im following dc recommended specs at 5.75 ft^3 a sub, and about 180 inches^2 of port. the calculator ive been using has been putting me in the low 30 inches for port, assuming 11 cubic feet of net space (anyone know the displacement of a lvl4 18 so I don't have to pm rusty to get the number?)

At any rate, here is the first and more simple design I had. The exact measurements arent 100% on this one, mainly port length/height and the overall width of the box.

Now my main concern with this box is the port is getting pretty close to the back wall, and its not even the full 30+ inches I am needing. This may not be too big of a deal in itself, but it seems to me like the effective port might would wrap around nicely with the board above it, especially when I lower it a few inches so I have room to install my amp, possibly giving me an efective port of 40+ inches and lowering the net box size. Any opinions?

Here is the second box i designed. The main thing I like around this one is it gets the mass of the subs lower in the car to keep from destroying my CG quite so badly. After quite some time trying to figure out how to get the port right I realized how simple it actually was to make the akward curve. (I think I have it right....) The actual box dimentions are closer on this one to what they will actually be, and the circles are the cutout diameter for the subs.

Also, as I briefly mentioned earlier, I do need to take the back portion behind the slope down a bit if at all possibly to put my amp(s). There is otherwise very little space in the cabin etc to put them, but it could be done if it had to be.

In both of the boxes, I am at approx 12-13 cubic feet after displacements. This will give me some room to play around with braces etc, besides the amp placement.

Just for the heck of it, here is a pic of a side view of what im taking about. This is my older probe, not the one it will be going in, but they are the same otherwise.

I appreciate any suggestions anyone can give me

[Colin - STAPUFT]

I am a fan of number 2 personally- subs on bottom with port up top. I would put the subs close to the port or at the least in the center- not all the way at the bottom. IDK, but it seems that it would load better with the subs higher or in the center (may make no difference at all).

Also, if you need more length in the port, couldn't you get it the distance of the size of your port from the back of the box and use that space as functional port? Follow me? It would help you lower your tune a bit. You could always 45 the corner or cut quartered pvc to help round the corner to facilitate in air flow around the end of port in the box corner.

[doug118]

hooray for modifying a sketch up rendering with MS paint! lol sorry about butchering your design but what about just rounding the back of the box and cutting away the black area? it will give you space to mount the amps underneath and possibly some extra batteries.. plus it would give the air a perfect flow from the subs to the port

[Colin - STAPUFT]

Even better! Boosh!

[rusty959]

hmm.... well port length shouldnt be a problem with the second drawing. i believe what ive got should be getting me to the low 30 hz range so i should be good in that respect. unfortunatly i dont remember exactly what i had shown and i cant really see it well since im on my cell.... but the ideas given do address my wonderings of the flow of air at the back of the box... but im not sure if it would warrent the time to do a curved back... although if i were to do it id probably just do a big kerf and glass it in... i wonder if i were to just extend the slanted piece ald the way down would do the trick? then i could even do a bigger than normal 45 at the rear bottom to give a similar effect to your curved piece... i think extending the slant down will give me enough room to mount the amps and i have room on the sides of the box to put my d925's. i forgot to measure today before i got to school but i got the idea of glassing a spot for each amp on the sides of the seats partially over the rear side windows.... that might would work.

well enough of my ramblings... i cant really proofread of see how much ive written on my phone so i better stop here. anyone have experience with a slanted port as such?

[rusty959]

here's a rough sketch before I go to work what I was meaning in my last post. Kind of a simpler twist on the curve back idea. I just checked my port length and it is enough.

[brewer_brewer]

subs on bottom port on top.

that box will have great airflow which equals efficient.

[rusty959]

subs on bottom port on top.

that box will have great airflow which equals efficient.

Thanks for the reply.

Im guessing by your post the "45's" would be a good idea for the back side atleast?

I guess now im in the stage of doing the final calculations of all pieces/braces etc to see where im at, and if I can get that done ill start building this week depending on my work schedule if im lucky.