BillFitzmaurice.info

I'm looking into port options on my DR200's. I'd planned the standard PVC 4" ports at 2" diameter per the plans. I'm also curious to run them sealed since I have T48's to go with most of the time.

My question is, how does port diameter affect length? I'm trying to use some port calculators online to see the affect of changing the diameter slightly in the mouth, almost like a flared port but not really.

2" PVC has an "average ID of 2.047in". I found this little gem at Menards Mechanical Test Plug and I now have access to a 3D printer that will print ABS plastic. My plan was to make a 4" long pipe, with a 2" ID, but I need to flare the last inch out to 2.25in to allow the test plug to seat. it's meant for cast iron thread ID, not the nominal bore of PVC. Every port calculator i've tried shows the port goes longer when I increase the ID to 2.25in, by like an inch. Granted i'm only changing the first inch, and tapering the next inch back to 2 ID, but it still seems extreme.

I'm hoping Bill or someone has some port wisdom to share.

I've attached a crude 3D model of what I'm proposing. I need to print a prototype to even see if the plug will even hold before I make more sawdust.

You can't use a port calculator, you would have to model the entire enclosure in HornResp. I don't see the need to use anything other than the 1/4 inch option with subs.

Thanks Bill, I was thinking a bit backwards about this. I went back and reread the tuning section after your comment. For some reason I was thinking sealed gave best response used with a sub, so my plan was to seal for that, and I wanted the option for 4" port bass extension for times when I won't haul the Titans around. Now I'm thinking I'll stick with the 1/4" like you recommended, since sealed, you lose some in the middle.