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View Full Version : Dual Alpine SWR-1242D Ported Box Help



Mardos
01-22-2008, 03:47 PM
Hi,
for those of you that didnt see my other post im working on putting together a sub box for 2 Alpine SWR-1242Di've played around with the numbersand i have come up with what i believe will work but im not sure. it is 4ft^3 tunned at 32hz and here are all the dimensions (just once you open it maximize the window then zoom in and you should be able to see all the numbers. all the numbers include the MDF width so the first numbers are NET width/depth/height)

http://img47.imageshack.us/img47/9633/boxplansgm1.jpg

again im looking for all your comments/suggestions this is my first time putting together a system never mind putting the box together so any suggestions you guys could give would be much appreciated

Also i always planned on putting carpeting on the sub box but i just thought of something, what the heck does the carpeting do? i guess it must dampen the sound but other than that does it do anything else and should i or shouldnt i get is based on my setup? what would you do? adn what type of carpet should i use?

~Thanks

littledude
01-22-2008, 04:13 PM
the box looks good but i wouldn't use re, you have to look at the total port length, not port length 1 and 2 they only add to 18.75 which would tune your box way higher than 32, im not on my computer to go on winisd to check if its accurate, but i would make sure the total port lenght is 24 when you make that box so you keep that 32hz, i use to own those subs, and i had a box around that size it was 4.4ft^3 at 32 but take away sub displacement and it was around 4cubes.
it sounded pretty good too.

carpeting does nothing more than make the box look better it doesn't change the sound or anything.

Mardos
01-22-2008, 06:11 PM
correct me if im worng but i think the total port lenght is the Port L1 which is 13 + the port width because thats the length between the Port L1 and the back wall so 3 which = 16 then the Port L2 which is 5 + 3 again (same reason) which gives you 8. then do 16 + 8 =24 which is the total port length..... i could be totaly wrong but i mean playing around with the numbers and dimensions thats the only way i can see RE is coming up with that number....

also what is the difference between a square slot port and just a normal square port?

05F150SuperCrew
01-23-2008, 12:15 AM
also what is the difference between a square slot port and just a normal square port?

+1??? although i think a slot port uses a wall of the enclosure as a side...

Mardos
01-23-2008, 01:21 AM
+1??? although i think a slot port uses a wall of the enclosure as a side...

what do you mean +1??? , i asked what the difference is because i have another port lenght calculator that says when the port is square and slotted it should be like 22.5 inches but when it is square and NOT slotted it should be 24 inches :confused:

this is seriously starting to confuse me bad because i keep going to sites people tell me are good for creating boxes and then i post the box i created from that and everyone tells me that it wont work or somethings wrong and im back to square 1 again :crying:

inapontiac
01-23-2008, 02:49 AM
what do you mean +1??? , i asked what the difference is because i have another port lenght calculator that says when the port is square and slotted it should be like 22.5 inches but when it is square and NOT slotted it should be 24 inches :confused:

this is seriously starting to confuse me bad because i keep going to sites people tell me are good for creating boxes and then i post the box i created from that and everyone tells me that it wont work or somethings wrong and im back to square 1 again :crying:

That is EXACTLY what you get for being Canadian.










jk??

Mardos
01-23-2008, 08:46 AM
:wow: thanks for the suggestion???

jk??

im actually looking for someone to look at my first post and A. tell me if it works and B if it doesnt where is it being thrown off and what do i need to do to fix it?

or

If my plans that i made with RE are totaly off what is another way i can start from scratch and make my own ported sub box and not have people tell me after that the website *****

~thanks

Mr Cabinetry
01-23-2008, 12:51 PM
Rather than getting totally confused by what you see based on what the calculator is providing as information of the design shown, consider applying alittle math to the problem to resolve the confusion.

Ok, this deals with the port issue only, don't confuse it with all the other stuff:

Port is 3" wide
Box Depth - 17 1/2"
Subtract 1 1/2" for the front and back = 16" ID depth
Subtract 1/2 of the 3" width, add that to 16" = 17 1/2"
now add back 3/4" for the front baffle = 18 1/4"
18 1/4" is the center line length for P1, NOT the length of the port wall ( 13" )

OK, next leg of the port, if the calculator came up with a total length of the port at 24" - 18 1/4" = 5 3/4" is the centerline length of P2.

So, this would effectively make Port wall P2 = 3 1/2", NOT 5"

Now, it we take the math according to the calculator and added 5" for Port Wall 2 + 1 1/2" ( half the port width ) + 3/4" ( Port Wall #1 thickness ), this would effectively make P2 centerline length 7 1/4", thus, the total centerline length of the port - 25 1/2", NOT 24"

WTF is going on you ask???? Simple - the calculator is automatically accounting for and adding to the ports length for the - END PORT CORRECTION FACTOR - which is half the width of the port adding to the actual calculated length of the port.

In reality, the true length of the port vs the end correction factor added to the port length as to the difference the port tuning is and will change is so fr!ggin minor that is not worth being **** retentive about it.

So, either build the port to the Calculator or do the math and build the port walls to their true lengths without the end correction factor, either way, you are not going to notice the difference if this is for everyday listening.


Phil
Woodlawn Cabinetry

Mardos
01-23-2008, 09:26 PM
allright thanks a ton that really did help i had no idea about this end port correction factor and juss figured that i mighte have been adding things wrong or sumthjing because i've tried to do the math believe but every time i got something new just trying to get my numbers to add up to 24 but finaly you have made sense of this all.

Thanks a Ton