Looking for a 20hz sub for an already existing custom enclosure

What amp are you using?

high pass filter at just under tuning?

The only one with a high pass filter is the sa1000, and that is to much power. (Dont know anything about the butkicker actually)

Here's an odd-but-worthwhile suggestion - seal the ports and use the new Dayton Ultimax 15" which happens to be on sale for $170.

Comparing the RSS390HO vented vs. the Ultimax 15 sealed, both in a 5.8 cu ft box:
Driver . . . F3 . . . F10
RSS390 . 18.7 . . 15.4 Hz
Umax15 . 20.1 . . 16.7Hz
... with no need for an infrasonic filter to protect the driver below box tune... you hear 15Hz rather than filtering it out.

Now, double your box size and drop tune to 15Hz, and the Umax gets an F3 of 15Hz and F10 of 11Hz. But you like your box...

The key point is that U-max drivers are very conservatively rated for Xmax. 19mm is geometric. Klippel testing puts it in the low 20's and Xmech is ~30mm. Can't find the reference, but this is from PE. You should be able to drive it just as hard as the RSS390HO, but with an extra 15mm of travel before anything hits, so think 800W @ 15Hz yielding 104dB. The HO at that power/frequency is self destructing (at 30mm on its way to 43mm).

Like I said, odd, but not bad at all.

Have fun,
Frank

PS Umax 15's bolt circle's 372mm, so it's closer to the Titanic than the 368mm for the RSS390... but in a 6mm smaller hole.

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.
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.

HAve fun,
Frnak
Edited by fbov - 3/13/13 at 10:01am