Carps right. I only ever had two ported captivators --- but i'm pretty confident it would take at least six, maybe eight sealed UM18-22 to even meet/beat the Caps performance level pretty much regardless. I don't think four would meet or beat in any room/regardless of boundary gain. The 2011 Captivator drivers I had were the same the Orbit Shifter uses.
JTR mates that driver with a 4000 watt speaker power amp, and his site states the sub should be good for 7,200 watt peak.
The UM-18 is 88dB efficient
The JTR driver was in the mid 90s efficiency IIRC, and Jeff states well over 100dB sensitive towards 100Hz.
So right out of the gate - with one watt applied it is at least 50% louder, maybe 2x's as loud based on the efficiency alone.
The JTR driver takes basically four times the power, and has about 50% more usable excursion.
So that's another doubling of volume based on power handling and excursion.
All that to say it's more than just the 9dB difference you get from going from a sealed box to a ported box.
Basically, - 2 things ---
1) even though I knew the lay of the land when I started this project - - - I'm surprised by how little output (if you try for a consistently flat FR, and don't get a load of free boundary gain) multiples of these sealed compare to monster ported subs.
2) thank goodness for nearfield
A co-worker who came to visit my place recently said I should ditch the sealed and go back to the Captivators that he had previously heard after listening to both ported caps and all eight sealed.
visited my new space, and basically said he remembered the 2 ported caps being more savage/tactile than the eight sealed. Since their visits I've reworked the amps - as mentioned a few posts back because it was in the back of my head that maybe it was just the fact that I was underdriving the subs with a mismatched impedance load and the amps were failing earlier than they should/could - if they were properly matched.
That's not the case...That's the experimentation I was doing last night.
I've considered dumping these and going with a pair of gjallarhorns - or a pair of Orbit Shifters or something - but Scott Simonian is right. Once you get to these levels the only time I need more output is for ear splitting demo volumes, and with a horn sub you have to navigate avoiding resonant frequencies, and lesser placement options, and lacking full bandwidth sound capability. It just sucks that to you would have to double down on subs, and amps to get 6dB more --- which might be my point of desire.
But --- back to reality - - the eight sealed UM18-22 fit my need/want, especially with a few near field and will probably stay a long time - I'm just reporting that if I, personally, had less than eight of these UM18-22 - I'd be disappointed with the outcome when compared to my pair of JTR ported Captivators. I'm going to hook up the three sealed nearfield today and get back to enjoying that tactile experience!