View Full Version : port distance from sub?

05-21-2004, 08:00 PM
I'm building a box for my 12" Type R using a 4" port. I believe Jmac helped me with this earlier, but I'm trying to fit a 22" port into a box with a gross volume of 2.15 ft^3. right now outside dimensions = 14" x 16" x 22"

I was told to keep the port a minimum of 3/4 Dia (or 3" in my case) away fromthe walls of the enclosure and i'm using a 90 Deg elbow to do it. My trouble is that the port runs under(or behind) the sub, but comes close to to bottom (magnet) of the sub - 1" to be exact. Is this way too close? Do the same distance rules apply for the walls and the sub?

I could move the port farther from the sub, but this would require that I make the box slightly bigger than originally calculated ( WinISO shortens the port length to compensate for this)


05-21-2004, 08:42 PM
I'll try to clarify..

box is 22" x 14" x 16"

The port opening and the sub are on the same side 22" x 14" with about 2" bewtween the widest part of the sub and the port.

The port centerline goes about 10" into the box (in the same direction as the sub) then 90 Deg turn for another 12". for the last 6" of length the port runs behind the magnet about 1" away from it, is this going to mess things up?

If I make the box 17" deep instead of 16" this will place the port 2" from the sub magnet and make the port about 2" shorter as well. so it will be 2" form the sub magnet for the last 4" or so of length...would this be a better option?


05-21-2004, 11:36 PM
Well the port runs beside the sub then turns 90 deg and runs along the bottom of the enclosure underneath the sub right under the magnet.

I guess since it under the magnet then air wont be blowing directly into the port from the sub then you say I'll be ok?

If I use the 1.848 ft^3 that WinISO predicted then the port will be 1" under the magnet but still 3" from the bottom of the enclosure for 14" x 16" x 22" box.

If I increase to 2.0 ft^3 the i go from 16" deep to 17" deep and the port will be 2" under the subs magnet, and a bit shorter....according to WinISO this doesnt change things too much. The air maximum velocity increases a little to 35 m/s but its way down at 23Hz.

This would be alot easier if I knew how to attach a picture. :)

05-22-2004, 03:58 PM
This is the picture...

your looking at the side thats 22" long x 16" deep using 3/4 MDF and a 4" port. The port is about 3" from the outside walls and 1" fom the subs magnet.

(The type r sub is 7" deep from underside of the flange to the magnet)

If I use 17" deep box then i can move the port 2" from the magent and still be 3" fromt the walls. How ever the box will be slightly bigger then WinISO suggested, but it just reduces the port length to compensate.

05-22-2004, 09:56 PM
oh...I guess I mustve misunderstood :crazy: that changes everything

Thats great though, I'll have lots of room for a port now, thanks again. :toast: