People frequently
write to me asking how to install a PVC port in an MDF enclosure,
since it is usually cheaper and easier to use PVC as a port, rather
than a more expensive commercially available port. If you
install the PVC port correctly, it's as good or better than any of the
commercial alternatives.
If you follow this procedure steps, you
should have no trouble installing your port with ease and precision. The
drawback? You need the right tools.
First, measure the outer diameter of your
vent pipe and subtract 3/4". In my case, I have a vent tube with
an O.D. of 2 3/8". Subtracting 3/4", I come to 1 5/8".
That's the size of the hole I will cut in my MDF.
Baffle shown with 1 5/8" hole
Next, on the inside of the baffle, you
will route a 3/8" radius recess with a 3/8" rabbeting bit (this bit
has a bearing on it that allows you to follow the inside of the
circle).
3/8" rabbeting bit, ready for action!
Before you start rabbeting all
willy-nilly, you need to set your depth. To get the proper port
length, we measure from the inside end of the port tube to the outside
edge of the baffle. So, assuming the back baffle is 3/4" thick
and you want an overall port length of, say, 5", then you need to cut
your port to a length that when added to the thickness of the baffle (substracting
out the depth of the rabbet) you arrive at 5". More simply, if
we set a rabbeting depth of 3/8" (halfway through the baffle), then we
need to add 3/4" - 3/8" = 3/8" (the thickness of the baffle) from the
5" port. Thus, we cut our port to 4 5/8" and our router depth to
3/8", to make our final port length the desired 5".
Once the hole has been rabbeted, your
hole will look like this:
You are now ready to mount the port tube
in the hole. I like to use Carpenter's Goop as the adhesive, as
it had good bonding strength between the MDF and the PVC. A
fully Goop'ed up tube looks is shown below.
Finally, allow the glue to try overnight
and then put the final touches on it. Start by turning the piece
over and putting a roundover bit on your router. In this case, I
used a 1/2" radius bit.
Then, use the roundover bit to trim the
MDF from the inside of the hole, flush with the port tube. At
the same time, you'll round the outside edge of the hole, to smooth
airflow.
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That's it! Good
Luck!
