Scroll down, to my last post, have some new questions

I need some help with building a box. Here's what crutchfield says for the recommended volume:

Recommended Vented Box Volume: The vented box sizes recommended by Alpine range from 0.75 cu/ft to 2.0 cu/ft. Within this range, the ideal size recommended by Alpine is 1.7 cu/ft, so this is the enclosure recommended by Crutchfield. A slot port with the following dimensions should be used with the 1.7 cu/ft enclosure: W=12", H=1.25", L=21". If you cannot use a slot port in your enclosure, you will need a port tube with the following dimensions: Diameter=3", L=9.9".

I have an Alpine SWR-1242" (Alpine Type R 4-ohm DVC), I'll be giving it 350RMS.

If you already know what I need to do, please reply, where I could get a diagram or dimensions or something please.

Here I'll just ramble on trying to understand this. Now I'm gonna need to figure out the dimensions for the box volume and how how do I incorporate the port into that? The box will have to be at least 21" deep. So to fit this kind of port the box has to be on the outside 22" deep and Width (measuring along the bottom) lets say 14" and height (bottom to top) 13" . Now I would have to cut a rectangle that's 12"x1.25" in that, and then put wood pieces that extend it 21" deep into the box. Would this work? Am I getting this right?

All these measurements are just confusing the crap out of me. I looked on google and searched on forums but I'm still not sure if I'm thinking right.

Basically the port measurement is confusing me the most, since I don't know how to incorporate it into a box. And also some measurements for a 1.7^3 box would help too.

Big thanks in advance,
Mike

 

im a little lost but those dimensions seem to make it much larger than 1.7cuft. check otu bcae1.com and click on #110 link for box dimensions.

 

these will help:

http://www.carstereo.com/help2/Articles.cfm?id=31

http://www.the12volt.com/caraudio/boxcalcs.asp#por

 

The port can bend, so the box doesn't have to be 21" deep. It can be 13" deep, and then bend the port [no more than 90 degrees] around the extra 8" (actually, only another 7.5" due to effective length if you are planning on putting the port up against the wall of the enclosure). If, after reading up on it, it seems too difficult, buy a flexible aeroport, 3" in diameter, 9.9" long, and put it into a box approx. 2.0 cubes [plus sub displacement] and it'll give you the same 30Hz tuning that the slot port is made for. By the way, you'll need a 2.2 cube box if you use the slot port [plus sub displacement].

Sorry for all the numbers, but I put an excel spreadsheet together yesterday to do all the figuring for me, and you gave me the first opportunity to test it out.

dh

 

Thanks for the links, played around with it and made me realise some stuff. Yeah it would be really hard to put a 1.5x12 that is 21" slot port into a 1.7cubic foot box. So now I understand, I'll need to make a box then that is 1.7cubic feet and stick a round port in there that is 3" in diameter and 9.9 in length.

Now what dimensions would you guys suggest for the box? Or it doesn't matter as long as it adds up to 1.7? Also where can I buy the round port?

Thanks a lot everyone, I'm finally getting it. What confused me was that the slot port size was so big for a 1.7 cubic foot box.

 

Also does it matter where I place the port. Or would something like this be fine?

 

you would want the port and the speaker facing the same direction.

 

What you have realize is that the port will take up inturnal volume aswell so, what you have to do is find out the volume of the port itself then add that to the inturnal volume of you enclosre (ie. 1.7^3 Xwhatever the volume of the port) that would give you an indication on how big your box is gonna be. Also go to http://www.mtx.com/caraudio/educatio...nstruction.cfm there is a lot if info here! If your good at math you can probally figure out everything you need by using the formulas there, also if you want, e-mail me i have a program that calculates box volume according to the subwofer type.

iron_rhino@hotmail.com.
Let me know how it goes!!

 

Thanks, figured out I'll need to make the box 22.5(w)x14(h)x13(d) using 3/4 MDF. And I'll put the port in the upper corner of the front(same side as the sub). Since it says it's best to have the port be 6" away from the cone of the speaker and 3" away from a wall. Now all I need to do is get the materials and hope I don't screw up. I have a circular saw so I have to try to be careful and make really straight cuts. Now I just need to get the materials and I'll be getting to work.

 

go to home depot and have them cut it for you, thats what im going to do!
Im building a pretty complicated box this weekend, altogeter there is 9 pieces of wood that need to be glued and screwed together. Anyways im not sure how the American Home Depot's eork but here in Canada you can have them cut the wood for you, they will make 3 cuts for free but after that its like 50 cents here for every cut after that.

 

Awesome, that will make it so much easier.

 

It looks like your box will come out to 1.75 cubes before sub/port displacement [close to 1.5 cubes assuming .1 displacement for sub]. To get your 30 Hz tuning freq, you'll need a 10" long 3" diameter port. As for the 6" away from the cone, it's just the internal end of the port they are talking about [I think], not where the port is in comparison to the sub on the face of the enclosure.

If you want the box to be 1.7 after displacement, add an inch to either dimension [assumes .1 displacement], and take off a tenth of an inch on the port. Personally, I doubt you'd notice much difference, but I thought I'd throw it out to you, anyways.

dh

 

Thanks, I'm trying to go along with this.
From the MTX website that was posted: "Vent placement is not that critical, however a good rule of thumb is to keep the vent openings at least the diameter of the vent away from any wall, and two times the diameter away from the speaker cone itself."


Oh yeah anyone know a good site to get a speaker terminal cup and a 3" port? The only site I have so far is crutchfield and it would be a total of $26 shipped for the terminal and port.

 

try www.partsexpress.com they seem to have alot of stuff for a pretty good price.

 

You could use regular PVC pipe, but try to sand down the ends to 'flare' the ports.

dh

 

You should do a slot port, a lil more difficult but looks alot better and reduces the risk or port noise. BTW: According to Bassbox Pro that sub is better suited for a sealed box. For the speaker terminals, just drill a hole and run the wires through it, sealing it with sealant after. Many of the terminals you buy nowadays will cause small air leaks. For the ports you can simply use PVC pipe and save a buncha money.

 

terminals are ok as long you seal them up properly. but yeah, my speaker wires to my sub goes through a small hole in my box, sealed up nicely with some silicon.

 

D'oh, already ordered the terminals. I know the old Type R (SWR-1241D) was pretty much for sealed boxes. The one I'm ordering (SWR-1242D) had recommendations for both sealed and ported, so I decided to go with the more efficient one. I couldn't all the specs to input in one of those box programs for the 1242. Alpine's site has them for the old 1241

 

Don't worry about it, use the terminals if you want, most have a foam gasket to help keep a decent seal. If you're that worried about it, use some silicone to seal it as well. Either way, I guarantee you will not be able to hear a difference.

dh

 

quick question, what gauge speaker wire should I use for the subs?

 

i have 12 gauge going to mine.

 

i used to have 1/0 gauge but i use 12 now...

 

i would love to see a pic of that.

I'll have 16 gauge from the amp wiring kit, but I'm guessing that's too small if I'm giving the sub 350W RMS, 700W peak. I'll go ahead and pick some 12 gauge wire up.

 

haha i was joking...16 gauge is fine but 12 is always nice.

 

don't worry, i'll smack slick if he used 0 gauge for his subs

 

nah im way too cheap (ask kevin)...maybe i would have had a higher spl score.

 

run some 12 or 10 gauge and call it a day

 

lol alright I'll get some 12 gauge to be safe, don't want to be short changing myself by running wire that's too small.
Now I'm gonna mount the amp onto the back of the backseat. If I screw it in with some drywall screws, will it hold up?

Thanks to everyone helping me out with millions of my questions.

 

yep it should be fine...

 

yeah, drywall screws are fine. i'm using them to secure my amp.