What do people mean by 4th order box ?

[bbeljefe]

I will do that... in the AM. Right now I am having a few adult beverages...

[john253a]

Your not the only one

Except its only lunch time here

[bbeljefe]

Okay....

Here it modeled four ways.

Obsidian recommends 4.5 to 6 cubes tuned @ 28 to 32 so I modeled:

Green: 6 cubes @ 28 hz

Red: 4.5 cubes @ 28 hz

Purple: 6 cubes @ 28 hz

Yellow: 4.5 cubes @ 32 hz

All of the above boxes use two 4" ports.

Lowest -3dB alignment is green, at 23.41 hz and highest acoustical peak is purple... +~7 dB @ ~42 hz.

As an interesting aside.... When you first choose a driver(s) and alignment in WinISD, it models a box that is optimized for the driver at the flattest possible curve which would yield the widest possible bandwidth for that driver. Since this sub is not well suited for ported enclosures, that optimum box was a little over 35 cubic feet, tuned at 14 hz.

If you're using WinISD or another modeling program that optimizes for the driver by default and it comes up with a ridiculously large box for your driver... it's a good idea to think about either changing drivers or changing alignments for that driver, as it is clearly not well suited for the box you're wanting to build.

EDIT: Another thing to consider is that if you don't have the correct TS numbers for a driver or of you don't have all of them, then the software will also sometimes model an incorrect box or report an incorrect curve. For this driver, I had everything but the actual Sd of the piston, so I had to guess. Since I'm probably less than ~2% off on that guess, these curves should reflect real world responses. Of course, the curves shown are representative of real world performance in an anechoic chamber, so once in a vehicle cabin or listening room, they will change. Typically, low end response will be extended slightly and depending on the environment, acoustical peaks can increase or decrease considerably.

[john253a]

Lookin at that compared to 6th

Personaly 6@30 is what idd do

Something Inbetween