I'm looking to build a sub that has similar response to the captivator 4000 below 30hz or better. Above 30hz I'm good. I've got a labgroupen clone to play ball with. Any designs out there that will get me in the playing field?
most of the commercial subs are limited in size. that can be used to your advantage in diy.
you could use a lesser driver, such as the UM18, use three of them, in a nice big enclosure and outperform it.
notnyt designed a dual um18 cab here:
since having multiples is good, perhaps that could be another option.
essentially, figure out how big of a sub you have space for and it is relatively easy to create a custom ported cab to fit in the space.
and if going for only 30Hz and lower, a 6th order bandpass might be another option.
6th order bandpass gives some additional output from the front port in exchange for less output above the upper corner.
max output is pretty close on the low end, excursion limited region (the droop in the graphic).
i've got 28mm as xmax for the driver. usable is higher than that, but i'm not sure how high. backing out data-bass numbers suggests somewhere around 34mm or so.
this is the jtr4000ulf from data-bass.
add 6db for comparison to the winisd models above which are 1m. data-bass is 2m.
so to get the same max output, would require roughly 10db more than the single um18. so 3 um18's in a properly ported cab would be about the same, perhaps a little more, max output. (3 drivers give 9.5db or so vs. a single and 34mm vs 28mm would give a little bit more).
the um18 drivers do not have as powerful of a motor as the driver in the jtr cab, so if looking to do the same output in the same size cab, they wouldn't be the best choice. big motor, big excursion, 18's are expensive. for under 30 hz, maybe something custom from stereo integrity could be an option if size is critical.