vented fibreglass enclosures
yeah, so how would you do this? assuming you didn't want it to look like butt, of course (i.e. a 4-foot piece of pvc sticking out of a 'glass box)... i'm wanting to glass my sub into a vented box in a corner of my trunk over the summer (for several reasons, delineated below), but I can't for the life of me figure out a good way to wind a long port around inside a 'glass box, and still be sure that the diameter of the port is constant all the way through...
ooh... a thought... since a port does its thing by restricting airflow (which is why a larger port must also be longer), why don't i use a small port inside, like 3" diameter, to keep the length way down, but then have a huge flare to the outside of the box, to keep port noise down... see, the only reason i need a 12" x 3" port is to keep the air in the port below approximately the speed of light (actually, you want it below like 5% of the speed of sound, but up to 8% is okay... with a smaller port than this ~6" diameter equivalent, the speed of the air rises above 10%, which will cause horrific port noise)... so i'm thinking, if i tune it to my 31.45 Hz with a much smaller port, like 3" or 4", i can keep the vent down to a sane length, but by flaring the outside like a tuba (and nearly to that scale, at least along the long axis), i can keep the noise down...
from the little bit of horn research i've done, i don't think that horn-loading effects will be apparent with this setup, which is a good thing...
finally, my reasons:
1) my audio has taken over my trunk, which i sorta need
2) i can't put my top down, the box is too big
3) i want better sound, and the current box is too small (much too small - the vented box i'm planning will get me anywhere from 1 to 9 more decibels, from 20-80 Hz, and at smaller excursions to boot!)
4) i like the look of a 'glass enclosure much better than mdf
ideas? comments? references? abuse?