What do you think?
 

Ok I want to attempt my first ported box for 2 10" alpine type R's (300rms) I think I have it figured out but just need some one to clarify this first.

The dimensions are 28x11.5x14 which gives me a volume of 1.917cu'

I am tuning the box to 36hz. The port will be 10x2x17 giving me a port volume of .197cu'

The port volume plus the volume of the interior brace (forming port wall) is .243cu'

So inturn, I should end up with an overall box volume of 1.674cu' and frequency of 36hz.

The only thing that I am unsure of is if I have to take the woofer displacement into account, and I dont know if the port length is correct to give me the frequency that I want. I am unsure because I figured out the port volume using the 1.917cu' and I dont know if the ports displacement changing the internal volume has any effect on overall frequency. I think that its right, im just not positive.

Any input is GREATLY appreciated.

Quick responses would be great so I could get on this today.

where did you get the specs for the box? did it specify gross or net internal volume? if it's net, then you must calculate all volume displacement, eg. driver displacement, braces, port walls and port volume. If it's gross then they already calculated those things for you as long as you use their dimensions. Keep in mind that some manufacturers specify a volume with polyfill added.

Thats my prob. I had a sweet site with a bunch of free plans that I lost lol. So I am trying to make my own box plans. I just started throwing out some dimensions to see what kind of volume id get and then found out how big my port needed to be. So the gross volume is the 1.917 and the net would be 1.674. That is thaking the ports and port wall into consideration.

What would the displacement of the subs be? The manual has:

displacement front mount:.092ft^3
displacement rear mount: .115ft^3
added volume reverse mount: .047^3

So Im assuming that the displacement would be the second one there. So since im using 2 subs I would have to take .230ft^3 away from the internal volume.

What is confusing me here is this. If I figure out the port volume using the gross internal volume, then the volume to box takes up changes the internal volume, so does this throw everything off? By figuring out the port length using a 1.917^3 box, then subtracting the port volume to get 1.674ft^3, the volume has changed and thrown off the tuning frequency so everything is ****ed.

Here's a link to the Crutchfield page for those subs. it recommends a 1 cube enclosure with a 3" x10" port for each sub. by the way you would use the front mount displacement in most cases, unless you're bolting the sub from behind.

http://www.crutchfield.com/S-7FKlWlbLQhB/cgi-bin/ProdView.asp?g=520&tab=detailed_info&i=500SWR1021# Tab

How could I figure out what that would be if I am using a slot port? That is kind of the way i would like to go.

Ok so I have to figure out the port volume (0.041ft^3) Then the woofer displacement (0.092ft^3) add that to the 1ft^3 (1.133ft^3) So I need to make a box with 1.133ft^3 to get the recommended 1ft^3?

The problem with Alpine is their slot port volume specs are different than their tube port volume specs by quite a bit, at least for the new type R's. Normally, you just have to take the radius of the tube port, in this case 1.5", square it and multiply by Pi( 3.1415). This yields, 7.068 square inches of port face x the length= 70.68 cubic inches of port volume. You then divide that by your slot port dimensions. eg. 70.68/11(port height)=6.42/1(port width)=6.42 which equals your port length. This will give you the same mass of air to move in your port and should give you the same tuning as the round tube port. Unfortunatly, Alpine has not specified a slot port for these subs, but they do for the new models, and the slot and round volumes are very different.

I goofed on the first port volume. It should be .049ft^3. So if I made a port that was 10"x2"x4.25" it would give me a port volume of .0492ft^3, which is pretty damn close to the recommended.

So then it would be the woofer displacement (0.092ft^3) + the port volume (0.0492ft^3) + the port wall (.0015ft^3)

So if I aimed for a box that was 1.1427ft^3 I would end up with 1ft^3 after everything has been taken into account? And I would have the recommended port specs (even though its now a slot, same volume though)

Why is there a difference in the recommended cylinder volume and the slot volume when over all the volume still remains the same?