Tuning round ports?

[AltarCrystal 10+ year member]

dunking your ports in water wont work because the ports will fill up with water, just figure out the volume of a cylinder, http://www.the12volt.com/caraudio/boxcalcs.asp

I thought it was jsut the acual space taken up by materal of the box? I have to accomadate for the actual volume of the pipe? Hm, alright, thanks for the heads up!

Anyone know if running my ports like I mentioned (along the back wall, braced, and have a few elbows in there) will work if I calculate everything correctly? Would 2 4" ports sound much better than one 4" port? One 4" would only have to be like 15.9" long, much more managable (Half the width of my box, about.

 

[Trixter 10+ year member]

first off, when finding port displacement, you need to account for the material the port is made of and the air space it takes up. however, if your using 3/4" mdf for your box, then you can subtract 3/4" from the length...this is only for finding it's displacement. since you use the internal volume of the box, the thickness of the wood is already accounted for.

secondly, the port must stay at least the port's width away from the back of the box.

third, why don't you put the ports on top?

fourth, if you use pvc, use the pvc 90deg. elbows (remember to measure down the center for port length). a single 4" port will need to be 15.75" long to tune a 2cu' box to 30hz...this is 2cu' net...after all displacement is accounted for...you may be better off going this route.

 

[AltarCrystal 10+ year member]

first off, when finding port displacement, you need to account for the material the port is made of and the air space it takes up. however, if your using 3/4" mdf for your box, then you can subtract 3/4" from the length...this is only for finding it's displacement. since you use the internal volume of the box, the thickness of the wood is already accounted for.
secondly, the port must stay at least the port's width away from the back of the box.

third, why don't you put the ports on top?

fourth, if you use pvc, use the pvc 90deg. elbows (remember to measure down the center for port length). a single 4" port will need to be 15.75" long to tune a 2cu' box to 30hz...this is 2cu' net...after all displacement is accounted for...you may be better off going this route.

Well, the reason I don't want to put the ports up top is because the box 14.5" tall, and my trunk is only about an inch taller than that..

And yeah, I guess I'll just go with a singl 4" port. It's not going to be a drastically noticable difference, will it?

Edit: Here's the design I did a quick sketch of real quick. Everything is to scale. It's actually EXACTLY 2 cubes after ALL displacements (Including the pipe).