Kevin McMurtrie wrote:
In article 3FFC3E2A.2070204@usefirstinitialandlastnameATerol s.com,
Simon Juncal
wrote:


Kevin McMurtrie wrote:

I wouldn't use a port at all. It's asking for trouble when the box is
undersized and conditions aren't perfect. Most likely it will leak out
the low-end and buzz rather than create a mild resonation to help the
lowest frequencies. It will sound really bad if it buzzes badly enough
to make your CD player skip on certain notes.

I'll try without the port first but I worry about the sub not having any
access at all to outside air, all fully sealed boxes I've seen (where
the sub is mounted entirely inside the box I forget what this mounting
style is called), have had vents to let it push some outside air around.


The hole isn't to let out air. It is to set up a resonance at a low
frequency (resonate like a large glass bottle does) where a sealed
enclosure would begin to perform poorly or have too much excursion.

Tuned port enclosures are common because they're louder than sealed
enclosures. Also, a large sealed enclosure may cause overexcursion in
the speaker because there's too little of an acoustic load. Adding a
tuned port increases the acoustic load at the tuned frequency. The
downside of a tuned port is that it can easily sound very bad when done
wrong. A sealed enclosure has a smooth frequency roll-off where a tuned
port enclosure has a very sharp drop-off below the tuned frequency.
Below the tuned port frequency, the port is just a big air leak.

Small enclosures are almost always best without a tuned port. They're
inefficient but they at least produce some deep bass. A small enclosure
with a tuned port will hum or buzz and produce no deep bass.

Excellent explanation. I've got the sub temporarilly inside the console
(which is a work in progress) with no port and I'm getting the idea that
it will actually sound decent. It actually sounds pretty good just
sitting free inside (not rattling on anything), which is obviously very
inefficient. It thumps a lot harder mounted, once I get the walls
reinforced with fiberglass, and fabricate a sealable top and polyfill
it, it should thoeretically smooth out again right?

--
Simon
"I may be wrong, but I'm not uncertain." -- Robert A. Heinlein