15" titanic subwoofer

[cap765]

I have a 15" titanic mk3 woofer and when I run the numbers I get a box of 30913 cubic inches 4 ports 6" dia 28" long for a qb3 I find this box a little to big for my set up would like to make it smaller with out losing bass out put any ideas would be great

[Alex]

Hmmmmmm......are you doing it right? 30913 c.i. is around 18 cu. ft. which is one big honkin' box. It should come out to about half that for a vented alignment but even that's ridiculous and I don't see how you can make the vents work. That said - this woofer (I'm looking at the Dayton TIT400C-4 15" Titanic Mk III Subwoofer 4 Ohm - assuming that's the one you have) is optimized for a closed box and would reside quite nicely in an 18 inch cube w/ an f3 of 43 Hz. Whatcha think?

Alex

[cap765]

If I go with a closed box I'm giving up a lot of bass f3 of 43Hz is high when I use the manufactures numbers fs=20 qts=.38 vas=7.79cu.ft I get a box 9932 cu.inch port 5" by 16.8" f3=22.3Hz fb=21Hz the last time I was using numbers that I got using a SL woofer tester 2 I'm not sure how accurate it is I am hoping to find a prove design with max bass out put so far the designs have been small closed boxes that don't go very low is it the driver or are the designs for size not bass out put

[Alex]

Actually, now that I look at it, this woofer in a closed box is a dandy solution. I may have to get me a couple.
Yeah - I get what your concern is but are you taking into consideration room gain & boundary effects? (what are the dimensions of your room by the way?)

With subs you have to look at things differently - look at the -6 dB and -12db points. Room gain can boost the output of a sub by as much as 12 dB at some frequencies. And in the real world subs need some EQing anyway so you'd have an easy time flattening it out. ..... The Titanic in a closed box is down only about 7 dB @ 30 Hz and about 12 dB @ 20 Hz. ( By way of example, my subs have f3s of 39 Hz and in-room response is up 6dB @ 45 Hz, up 3 dB @ 30 Hz and down 6 dB @ 22 Hz., all of which I flattened out with EQ )

Sure the vented alignment gets more output at lower frequencies but you could very well overwhelm the room and have too much gain to eq it down. You might get the dreaded one note bass. Other things to consider are that with a vented box you'll have a huge group delay starting at 40 Hz and going off the chart at 26 mSec @ 20 Hz. With vented, there's going to be some cone flop - which could muck things up. Chances are if you get 20-30 Hz. bass w/ the vented alignment - it won't sound right anyway. There's always a price for the lunch.

Okay- so what to do?

I don't think a vented box is practical with this woofer. I just can't get a reasonable vent size to start with. So that means passive radiator. Now I don't know much about PRs so I'm just throwing this out - but it looks like a cool solution ...... If you squash the alignment down to 5 c.f., you can get an f3 of ~22 Hz. You can get 26 Hz in 4 c.f. . Ya can't complain about that. ...... So - build a box say 20" x 20" x 28" or maybe a 22 in. cube (5 c.f.), get the appropriate passive radiator, plug it in and try it out. If it doesn't work out, slice the box in half and make it a closed box

here's some stuff:

http://www.linkwitzlab.com/rooms.htm#Standing%20waves

http://www.htguide.com/forum/showthread.php4?t=10872

-awp