Box facing direction in a hatch, aero help

[SomeGuyDude 10+ year member]

Hey all. Me again.

After some cursory research I noticed that a lot of places are suggesting up-firing for hatchback builds, which frankly would make my life a lot easier in a number of ways. Since the hatch has slanted back seats, I could more effectively use trunk space by building the box flatter but longer. For rear-firing I can do, at most, 17x16 for the height and depth to give it room for breathing in the back, but I can do at least 13x22 if I fire upwards.

Now if I do that, I get a secondary boost in that it'd be easier to use aero ports than a slot because a 22" wide slot would be gigantic. So my quick question is just this: can I get a basic rundown of mounting/construction on these things? I'd probably be using 4x12 ports, two of 'em, to get my ideal tuning of ~33Hz at 4.2cu.

Click to read more...

 

[dappa5 10+ year member]

what subs?? for that fit??

depending on subs hell go downfiring and port up rough but you get the idea

 

[SomeGuyDude 10+ year member]

Single 15, whatever'll take 1200-1300 RMS the cleanest (to match my amp). I've been told a DD2515 could work if the box is made made right, I still like the Soundstream T5, or possibly a Mach5 IXL, or hell I could get a CVX. Who knows. I'm not sure what sub yet, just the space to work with.

That box looks pretty intense. I'd have to get some extra help with the construction of that, what with the angles and all. Also, why downfiring? Wouldn't that waste potential box internal space with the struts holding the thing up off the floor?

 

[dappa5 10+ year member]

well you said hatch and cargo space iu got the wrong idea if you need any help w a design utilizing angles and such just hit me up ill walk you thru them g/l with this one

 

[superbang 10+ year member]

most effective setups i've seen for hatch style cars are sub up and ports back. Most suv, wagon, and hatch backs run it that way.

 

[SomeGuyDude 10+ year member]

Really. As in ports toward the rear? I always thought ports should face the same way as the driver. Doable, but still require some fiddling.

 

[NJTStang11 10+ year member]

Really. As in ports toward the rear? I always thought ports should face the same way as the driver. Doable, but still require some fiddling.

IMO I agree with Subs Up/Port Back

I've had an Explorer and it was the loudest way.

I also am getting an enclosure for my Integra hatch the same way.

 

[SomeGuyDude 10+ year member]

Actually upon further review, that's super easy. Given the seat angles, making a shorter box means it can be deeper, but still have enough room to give the port about 3" of clearance from the rear of the vehicle. I'd do this and put the sub on the top instead of the front.

Now that's just a random config, there's a lot of wiggle room.

 

[mazdakid 5,000+ posts]

Sub up port rear or side works good in my hatch, id have to have it on the meter to know what's louder for sure.

 

[Xprime4 10+ year member]

double poast

 

[SomeGuyDude 10+ year member]

I've also heard some suggesting that it helps reduce rattling since the air is shooting up at the ceiling instead of back into the lid. Makes sense to me.

Now that I've kinda had time to think, I'd really like to do both up, but if I can't find a way to make that work, sub up and port rear will be the method. Sub up no matter what.

The nice thing is that if I go from plastic to plastic, my top external dimensions are around 38x18x19, which is 6cu before port/sub displacement. If I wanted to make the thing up to the headrests on the back seat it could be a lot more. But again, that only works with UPFIRING ports because that setup involves having the thing pressed to the side and rear walls. Which is another reason I'm thinking aero ports. Would require less port displacement.

 

[ironchef b 10+ year member]

If you do decide to go sub up, port back you should have atleast 4" of space between the port and the rear. Well thats what I read as I was doing research before building my enclosure.

 

[SomeGuyDude 10+ year member]

If you do decide to go sub up, port back you should have atleast 4" of space between the port and the rear. Well thats what I read as I was doing research before building my enclosure.

Yeah, that's proving a huge limiter thanks to the angled seats. To move the box away from the door, I have to also make it shorter. A 17" tall box can't slide as far back as a 15" tall box.

Doing some math with a pair of 4" aeros I'd only need a box about 33x17x17. Now that's fuzzy math since I calculated the port volume just by their internal volume minus the .75" for the baffle (PVC being fairly thin). Interesting indeed. If I do aeros I can probably still rear-fire without any issues just by virtue of less volume taken up by them.

So, yet another Q: how far from the wall does the end of an aero need to be? I'm thinking 4" should be fine, yeah? I can do this pretty easily now. Make the box 33x16x19 (that's 16 tall and 19 deep) with a pair of 4x12 aeros and that's juuuuust about 4.5cu tuned to 31-32Hz, which should be perfect for any driver I want to throw in there, yeah?

 

[mazdakid 5,000+ posts]

Id go with more than 2 4" aeros if your box is 4.5 cubes. And i dont know if youre thinking a stock aero is 12" long, but its 12" plus 5" from the 2 flares.

 

[SomeGuyDude 10+ year member]

Hm. More to think about.

Problem with more is that the more you add, the longer they have to be to get the right tuning. I hit a point where it can't be a single straight aero any more.

A possible mix solution could be a 4cu box with a single 6" aero, which would need to be ~14" long. Would that be adequate?