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5 inch Port or square? (1 Viewer)

JerryD

Grip
Joined
May 15, 2000
Messages
24
I'm doing a Sub for my son as a graduation present for him to take to the dorm next year. I have settled on the Dayton 12" DVC for the driver and the PE 250W plate amp. (I have two of the 15" DVCs in an IB for our home theater.)

Unibox shows good results in vented boxes from 85 to 112 liters, but a 4 inch diameter port goes over the maximum recommended air speed and a six inch port gets way to long. A five inch dia. port, 27 inches long gives an F3 of 20 Hz in a 112 liter box with an Fb of 21 Hz.

The problem is I can't seem to find a vendor of a 5" flared port (or any 5 inch port for that matter). I also can't seem to find a source for 5" ID PVC pipe. Does anyone know a source for a 5" ID port? Failing that, does anyone know where to find any kind of rigid tubing with a 5" ID suitable for service as a port?

If I can't find a round 5" tube, how well would a square port of equal area work? Would the length needed be the same? I could easily make one from 1/4" hardboard. Any other creative thoughts on what else might work here?
 

Dustin B

Senior HTF Member
Joined
Mar 10, 2001
Messages
3,126
I've had no problems with the 4" flared ports in the twins. I wouldn't worry too much about it, a 4" flared port will work fine with the DVC12".

The two subs I built are DVC12" with the PE300-792 tuned to 20hz with 4" flared ports in 125L enclosures. One of them is currently in a room pretty close to the size of a dorm room and it is quite impressive there. He'll have to be very careful as he could easily get himself kick out of a dorm with it.
 

Brian Bunge

Senior HTF Member
Joined
Sep 11, 2000
Messages
3,716
Dustin,
I was modeling your subs the other day and I fully see why you went with 125L tuned to 20Hz! :) Did you use the port at full length or did you trim it a bit? From what I could tell from unibox it looks like the 125L enclosure with 20Hz tuning would be right around the 17" length of the 4" flared ports.
Brian
 

Eduardo

Agent
Joined
Apr 10, 2002
Messages
47
Dustin - I have the 4" flared port kit from Madisound.

I am currently building my sonosub and I haven't cut the port yet. My understanding is that if the port is flared at both ends then the total length should be 1" greater than the desire port length. Can you confirm this.

Thanks for the great website too.
 

Dustin B

Senior HTF Member
Joined
Mar 10, 2001
Messages
3,126
That's what the instructions with the Adire port kit I received said. I did exactly that. I modelled a 17" long port in LspCAD and the actual total length with flairs of the port was 18".

I don't have the measuring equipment to confirm the tuning, but the sub sounds fine to me.
 

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