Questions about port velocity and "compression"

[MrAcd 10+ year member]

So i am designing a subwoofer box for my dodge ram 1500 2004 quad cab for two 10 inch SSA Dcons this box is going to be the entire rear cab and will be down firing and ported up. I was initially doing areo ports, but realized i had just enough amount of left over wood to build a slot port.

The box is going to be tuned to 33hz and inital volume is 3.75cubic space, after sub displacements i have 3.57 cubic feet so that is what i have been entering into calculators. The port will be 11.5 in height and 4 inches in diameter giving me 46 square inches of port area.

So my question is, when i put this stuff into WinISD and supply rated power i get around a max of 22m/s of vent velocity at 34hz... I have read a general rule is 17m/s with a max of 22m/s... It is clear that i do go over it. Will this become a problem? should i hear noise? How can i decrease this?more port area? Did i enter my info wrong?

My next question is compression. I have read compression is really bad and i do not know if i have any.. How can i figure out if i do? Also on a program called "Flare it" i enter my stuff into a table and it produces a graph and at the moment if i make my diameter 4 inches i will get cuffing but the compression is good, again is this true?

Also what is end correction? and do i need to add it on to my length of the port? Should i flare the ends instead? If so do i just round off the edges?

I will include a rough model of the box so i can get some feedback as well on the design.

Thanks, Addison

http://i.imgur.com/TnHP7kh.png

Click to read more...

 

[Jeffdachef 5,000+ posts]

normally you dont want to go higher than 30 meters per second or 100 feet per sec, thats generally when noise comes. However, minor things like 45s, sanding rough edges, proper flares along with fiberglassing the inside of the box can help airflow even smoother. thus you can get away with a little bit higher than 30 meters per sec if you take those additional actions. Too big of a port will cause the sub to lose control and not build up any back pressure if the sub is not designed for it.

 

[MrAcd 10+ year member]

Okay, I had actually fo got to mention the 45's. So do you think my port velocity is fine and I shouldn't have any issues? Also should I add 45's and Smooth the edges of the port or do you think that will cause issues? I can always down size it if I need to.

 

[MrAcd 10+ year member]

bump

 

[Jeffdachef 5,000+ posts]

Okay, I had actually fo got to mention the 45's. So do you think my port velocity is fine and I shouldn't have any issues? Also should I add 45's and Smooth the edges of the port or do you think that will cause issues? I can always down size it if I need to.

you are totally fine with the port area. 45s and smoothing edges is always recommended.

 

[denim 5,000+ posts]

I replied to your email earlier this morning. Check out the links I sent.