need help with subs...

[1991 e30 bmw 318is]

I bought some really cheep 12" subs and amp i have a 10gauge wiring kit. all i need to know is how big to make the box. i think its going to be a sealed box. and should i use 5/8" or 3/4" mdf? do i divide the box in between the subs? and i will probably just paint the box with rocker guard. was thinking about height 15" depth 15" width 35". is it too big or small? it will fir right between my shock towers and the amp i will mount on something on the side or make the box a little lower and it might just fit on top of it. (its about 5cubic feet) and suggestions will be a help. and the subs are... http://www.bestbuy.ca/catalog/prodde...gon=&langid=EN
and i know there cheep but its all i need in this car.

[Jean]

Looks like it states the size on that page - Sealed Box Volume 1.48 FT/3

[StereoInstaller1]

1. Use 3/4" MDF
2. Don't bother dividing the box
3. Use only one of those woofers, 2 is going to be less loud, believe it or not.
4. 13.5 X 13.5 X 33.5 is 6105 cubic inches / 1728 = 3.53 cubic feet, nowhere near 5 cubic feet.

If you build your box with an angle on the front, you can fire the woofer through the ski hole. You will gain as much as 6db by doing so, as long as you COMPLETELY seal the woofer against the trunk wall, like so:


The box should look something like this:


Good luck!
Luke

[Jean]

That box is just sick!

[StereoInstaller1]

Thanks, Jean.

[1991 e30 bmw 318is]

well i don't have a opening in my seats so its staying in the back i will be using the 2 subs. ok so my box should be much smaller then what i was thinking. whats the difference if i divide the box or not?

[StereoInstaller1]

Yes, you do have an opening in the back. You just haven't seen it yet!

Pull the trunk liner. It is there. Smack dat hoe with a hamma, it'll pop right out.

If you want to run 2, go for it, but you will have either half as much power or overheat the shit out of that amp.

Dividing the box is pointless. You cannot divide the output of the box, so dividing the inside will make the box stronger, but aside from that is a waste of time/wood/weight.

Luke

[1991 e30 bmw 318is]

i thought you meant to like open seat where there is the thing that opens. my back seat is one big piece it wont open up. any way there staying in the back and I'm using the 2 subs because thats what that amp is made for too run the 2 subs are 200rms each. the box i am trying too find out how big to make it now. the front will be 14.5X28 so there will be about 1 inch between the subs now i just need too find out how deep to go too get the right cubic volume.

[Jean]

Since 12x12x12 = 1728 = 1 cu.ft and you need about 1.5 , that's 2592 / (14.5X28 ) = 6.8 ". You can go slightly bigger or smaller, it would be nice if we had more specs on the woofers though...

Now I don't know if they listed 1.5 cu.ft total for both, or for each sub.

[Skoobeesnak]

Luke, so what do you use to seal the box to the ski hole opening? I have a decent sub but I just can't seem to get any sound from the trunk. I am using an image dynamix 12" driven by a planet audio 4 channel amp with 2 channels bridged driving the sub which should be delivering around 150watts. But compared to the same set up in my old hatchback it is seriously "dead" in my 325.

[twistednut]

http://s233.photobucket.com/albums/ee215/Stan141/91%20Car%20stereo/?action=view&current=91carstereo011.jpg
Or maybe something like this would work for you.

[StereoInstaller1]

i thought you meant to like open seat where there is the thing that opens. my back seat is one big piece it wont open up. any way there staying in the back and I'm using the 2 subs because thats what that amp is made for too run the 2 subs are 200rms each. the box i am trying too find out how big to make it now. the front will be 14.5X28 so there will be about 1 inch between the subs now i just need too find out how deep to go too get the right cubic volume.

No, that amp is made to operate best on a 4 ohm mono load, or 2 ohms per channel.

That amp will perform best on one of those subs, they are 4 ohms each.

Repeat after me...wattage is meaningless.

If you want to ignore the advice of a guy who has been professionally building high performance Car Audio since 1980, go ahead. Bwaaahahahaa!



As far as your box, measure your space, multiply INSIDE measurements: (H)X(W)X(D) to give you your cubic inches, then divide by 1728 to get your cubic footage.


Luke

[StereoInstaller1]

Luke, so what do you use to seal the box to the ski hole opening? I have a decent sub but I just can't seem to get any sound from the trunk. I am using an image dynamix 12" driven by a planet audio 4 channel amp with 2 channels bridged driving the sub which should be delivering around 150watts. But compared to the same set up in my old hatchback it is seriously "dead" in my 325.

E30s are about the toughest cars to get decent bass in, and hatches the easiest.

One of the many reasons I do ported boxes, generally.

Look a few posts above this to see how I build E30 boxes...angled front that fits perfectly to the angle of the trunk. Then, I cover the section of the box that actually meets the trunk wall with 1/2" closed cell foam as a gasket. You can see the foam in the picture.

Good Luck!
Luke

[1991 e30 bmw 318is]

I'm not saying you don't know your stuff I'm sure you do. its just that its a set i bought and i thought that thats what its made for. any way it works just fine as it is set up in this box in the store. http://www.bestbuy.ca/catalog/prodde...on=&langid=EN#
so i would say the cubic size is for each sub. what exactly will be the difference if the box is smaller or bigger? thinking about 14.5x28x15.5 but it might be too small. gives me 2.79cubic feet.

[DrMcDave]

why not drop the extra weight and do what luke is suggesting. It doesn't make sense to add an extra sub that is doing essentially nothing.