Originally Posted by dece870717
...Why not leave the ports open?
...This box has no polyfill or anything in it
...Also, what exactly should I plug the ports with?...
When using a woofer simulator, one can look at several alignments. The Umax 15 driver works well in 5.8 cu ft sealed.
- 1/2 rated power is just ticklinig Xmax, so no need for low end filters and an opportunity for boost
- System Q is adjustable in the 0.65-0.75 range by adding fill, so response is flat
- a comparably good vented alignment requires 2.5x larger box.... and I don't see a point in an F3 of 13Hz.
Other drivers behave differently.
I use dense fill in sealed subwoofers. Acoustically, fill acts to raise the apparent volume seen by the driver, lowering Q and smoothing out response. You may want to experiment. With 5 cu ft, think 5-15 lb of fill, with a clear area around the driver so it doesn't touch (remember the cone moves +/- 1"). Densities as high as 4 lb/cu ft aren't bad.... Love actual fiberglass, but pillow stuffing is a common alternate. I suggest starting with 5 lb and adding another 5 to see how the sound changes, or just go right to the whole 15lb packed densely into the corners to make room for the driver basket.
Plug the ports with foam. Nerf footballs are popular. Fabric stores that sell piloow stuffing also sell foam.
NOTE ABOUT MY SETUP: Right now I have the RSS390 paired up with the SA1000 amp and frequency cut off to just do 40hz and below, since after measuring with my UMIK it shows at around 37hz and under there is a significant drop in db, have the RSS390 for boosting that low end drop.
With a sealed sub, you don't need that filter. the air volume in the box provides the driver with protection from overexcursion. I get strong output, in room, into the low teens, using a bit of boost plus room gain. I can go 1 step lower, but don't see the need... and I start getting untoward sounds. This with a Tempest X driver that's very comparable to the Ultimax 15.
FrnakEdited by fbov - 3/13/13 at 10:01am