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airofu

Single American Bass XR 12 box design

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I'm hoping I can get some ideas and help on a box I want to build for a single American Bass XR 12" - looking at pushing about 1500rms and wanting to tune at 28hz as I want it to hit nice and low.

Sounds like pushing the box to 2.5cubes is the way to go (unless smaller is recommended based on tune and power?), sub displacement at 0.15cft, 0.75inch MDF, my maximum outside dimensions are 21" wide (would want to reduce this as much as possible) 17.5" height, and 26" deep which can stay if it works. I am mainly having trouble keeping to 40 squared inches of port area which seems to be the minimum based on the box and power?

The box design software won't give me a U port (colored red, will this work?) and is where I am stuck as the port is too long for just an L:

 

sub.jpg

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I've run some figures, hopefully I am on track. 28hz port at 40 square inches is 2.5" by 16" and 47.24" long with 0.75 MDF would take up 1.91cft gross - I added this to a box design for 2.5cft internal volume (plus 0.15 sub displacement) to get a box that seems to just fit with total external dimensions of 21" wide 17.5" high and 26.74" deep.

Will making the slot port a U inside, change the length/tune that I am not thinking off?

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Since your port is using 3 common walls you only need to add one wall of 3/4" when calculating port displacement, which gives roughly 1.4ft^3 for the port. That makes your gross box dimensions about 4ft^3. Using 17.5"x26.75",  It looks like you can get your width down to about 18.5" or 19" with bracing displacement also. 

(I did these calcs on paper so someone might want to check my math) 

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Thanks, I think I doubled up a wall internally like you said equals about 1.42cft for the port now...which brings it down to about 19" wide like you say which is good to know!

Is the tuning length as easy as measuring the port from the middle? or do the 2 turns and inside port somehow change the way I should be l looking at it?

image.png.fce73cde13622a83df0b05e9b1c5121a.png

Edited by airofu

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Nope you're exactly right. The blue line is the tuning length. You might also want to put 45's in the corners of the port to help guide the waves and prevent turbulence. 

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Thanks all, seems like I am on the right track. Will look at 45 or rounding all the port edges (assuming it might drop my port length by an inch or two)

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1 minute ago, airofu said:

Thanks all, seems like I am on the right track. Will look at 45 or rounding all the port edges (assuming it might drop my port length by an inch or two)

It won't drop the length. What it will do, however, is keep the port width the same around the bends. 

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