Need help modifying box

[Migz]

Need a bit of help with my box, its a prefab as i haven't got round to building my own yet. It is originally for a 12" but i i've made it slightly larger so it fits my 15", sounds like absolute shite though! I know its going to be because the box is too small for a 15 but i have to make do, as i can't afford to build my own box just yet.

Picture of my box,

As you can see it has a small port on the side and would normally have a larger one on the front but its missing as i took the port out to put in my gf's box. Its definitly too small for the sub but i have to make do with this as really cant afford to build a new box no matter how cheap it is to do

I've put the rough dimensions into the torres box calculater and heres what it comes up with. (If anything is blatently wrong please let me know as i wasn't too sure what to put in a couple of places, i.e the subwoofer displacement as i don't know what mine is, so just had to take a average displacement for a 15" of google.)

If everything is roughly right then my problem seems to be that as the box is so small the tuning is far too high, but i've noticed if i change the port dimensions from what my current aero ports are, to the dimensions of what a slot port would be for my box (13x1x8) then the tuning drops right down to 50hz, still a bit high but much better then 108!!

So i was thinking, ive got about half a metre of spare mdf at home, if i modify the box slightly so instead of having that gap where the old larger aero port used to be and put a slot port there of roughly the dimensions i said above, would it make this box sound a bit better?

I've also been thinking would running a port directly along the back wall of the box be any better? So that the port comes out on the right of the box, because putting the dimensions in that way the tuning comes down to about 40hz, only problem is it would be a bit awkward to build the slot port at an angle.

I just need to know if either of these ideas would work or not, i know that it'd be alot better just building a new box but cant afford it for the next 3 weeks as i have more important things to pay for, and i really don't mind modifying this box as it was given to me for free.

[Loslam]

Imo it's not worth the time, effort, and/or money to fix that box

Just take a day and build your own ported. Easy, cheap, experience

Good luck

$40ish bucks will get it done

Edited May 3, 2012 by Loslam

[Guest]

just make a new box. you'll just be wasting money trying to modify a box that was already too small for a 12, but that now has a 15 in it.

[LZTYBRN]

^^^^ What they said.

And fyi, if you're using circular aero ports, you don't use the height and width, you just use # of ports and the diameter. Where did you even get 7.6? I know that port ain't 7.6"

[Migz]

I'm really not fussed about spending time or effort on it, it gives me something to do.

I know a new box would be much better, but i literelly don't have the money to build one right now, i get about £50 a week, £34 went today on new brake pads, leaving me with £16 for the rest of the week. Need about £20 for the wood and glue. Next week i've got to service my car. Literelly cannot afford it for the next few weeks.

But like i've said ive got just about enough mdf to build a port at home, so ignoring the fact a new box would be better, would this idea work? Won't be spending any money on this and really not fussed on time or effort even though i'll be building a new box in a few weeks.

Edit: @LZTYBRN

Oh right, didn't realise, will change that and see what it says.

One aero port was 12cm in diameter and nothing in depth, the other was 7.5cm in diameter and 11.5cm in depth. So 12 + 7.5 = 19.5, which in inches was 7.6.

I wasn't sure how else to put the dimensions in with 2 different port sizes, also not realising for aero ports i only used the diameter. Thanks for letting me know though.

Edited May 3, 2012 by Migz

[Migz]

Also rather then start a new thread when the time comes, roughly how big should my box for the 15" be when i come to make it? Torres is saying the current cubic foot is either 1.61 or 1.39 not sure which one it is, what should an average 15" be happy with?

[Loslam]

Also rather then start a new thread when the time comes, roughly how big should my box for the 15" be when i come to make it? Torres is saying the current cubic foot is either 1.61 or 1.39 not sure which one it is, what should an average 15" be happy with?

Around 3.5-4.5 cubes net depending on power and the woofer

[LZTYBRN]

I'm really not fussed about spending time or effort on it, it gives me something to do.

I know a new box would be much better, but i literelly don't have the money to build one right now, i get about £50 a week, £34 went today on new brake pads, leaving me with £16 for the rest of the week. Need about £20 for the wood and glue. Next week i've got to service my car. Literelly cannot afford it for the next few weeks.

But like i've said ive got just about enough mdf to build a port at home, so ignoring the fact a new box would be better, would this idea work? Won't be spending any money on this and really not fussed on time or effort even though i'll be building a new box in a few weeks.

Edit: @LZTYBRN

Oh right, didn't realise, will change that and see what it says.

One aero port was 12cm in diameter and nothing in depth, the other was 7.5cm in diameter and 11.5cm in depth. So 12 + 7.5 = 19.5, which in inches was 7.6.

I wasn't sure how else to put the dimensions in with 2 different port sizes, also not realising for aero ports i only used the diameter. Thanks for letting me know though.

You can't just add the diameters together. If anything you'd add the AREAS together, but that'd only really work if the port lengths are the same length. Isn't the other one just a hole in the wood?

If you want a temporary solution until you can build a new box, I'd start with covering up that hole. The woofer displacement is more likely closer to .1. The wood thickness is probably 5/8 (.625") or less. So just by covering the hole, and using the single 3" aero at 4.5" long, you would get a tuning of about 40hz (if my values are correct). You still won't have enough port area or volume, but I'd think it would sound a lot better.

If you wanted to make your own slot port (don't know how you would even do that). I'm not sure, but I'm thinking like 15 sqin of port 17 inches long is the best you can do with that box. And it'd have to be coming out the side, so that it can be long enough. Also, if you can do 2 or more common port walls, that's even better.

Edited May 3, 2012 by LZTYBRN

[Guest]

i'd just use some PVC piping from your local hardware store. something thats the same size as that hole in the front of the box. i'd make it all external too, meaning that the port doesn't go inside the box whatsoever, it all sticks out. just to try to spare some room for that choked to fucking hell sub.

like this

[HatersGonnaHate]

X2 on the external port.

You can also invert the sub to give some extra space inside the box.