Originally Posted by dominguez1
Originally Posted by Archaea
So how do I calculate for my JTR Captivators?
They don't play below 15hz, but they'd put a whalloping on many (or most) of the subs on databass. The specs are unpublished.
Follow me on this one...
Looking at the SVS PB12 and SB12...at tune of 20hz, the PB12 has 11db increase over it's sealed brother.
The closest thing to the JTR Cap driver (30mm xmax) is the UXL-18 (34mm xmax). The UXL at 16hz is 102.1. The tune of the Cap is 17.5 hz. I'd say it's safe to add 8db to the UXL number factoring in the slight loss under tune, and slight difference in xmax.
That makes the cap 110.1db at 16hz. Using the ULF Calculator, that equals 4.12 SI's. Since you have two of them, it would be 8.24 SI's @ 16hz.
What's your room size? 3500? If so, 3500 / 8.24 = 425@16hz.
What do you think?
Sounds like some guesswork would have to be in order to come up with any idea. Further complicating the matter is the fact that power handling and sensitivity comparison between the drivers is not really known without comparison measurements. Jeff Permanian, owner of JTR speakers, ran 4000 watts RMS and 7,200 watt peak into the JTR driver in the 2011 Captivators and Orbit Shifters drivers. I've got the older Captivators, from 2011, that were tuned to 20hz, but could use a port plug to get them to 15hz. The UXL-18 is said to be 1,200 watt RMS. The sensitivity on the Captivator/Orbit Shifter drivers was quoted as really high by JTR - at 100dB at 60hz, or 91dB at 20hz as shown in this old capture of Jeff's website from 2011 using the wayback machine.
The UXL-18 is quoted as 94 dB sensitivity with no frequency given so you can assume it's the peak output frequency?
So between the sensitivity differences and the power handling differences there will be more confusion than just the cabinet alignment and xmax numbers alone provide.
I guess it boils down the fact that since my sub is unmeasured by Ricci, I'll just stay out of the numbers game in this thread cause anything would be a bit of a guess.
My remaining question is why 10hz was chosen as the measuring stick? It is inaudible, it is below the capability of lots of source, and amplification components, and it seems a bit of an odd benchmark. Any sub but sealed alignment would be producing mostly distortion or harmonics at that frequency - yet - you can't discredit all alignments except sealed -- - especially when evidence exists to the contrary - - - like in the blind KC subwoofer meet of 2012 our group of nine voting enthusiasts couldn't even tell the difference in the alignments with similar similar playback volumes close to reference levels -- with anything from eight 15's in dual opposed sealed, to a pair of ported HSU VTF-15h, to ported Caps, to horn alignment Orbit Shifters etc.
The scoring system being based on 10hz scoring system minimizes subs like the Orthorns (as I understand - these are Ricci's favorite sub he's ever used/measured), the Orbit Shifters, The Captivators, etc. Any THD numbers on any commercial ported subs at 10hz would be darn near worthless - loaded with distortion and harmonics and not really desirable. However. I'd put a pair of JTR Captivators, Orbit Shifters, or Othorns up against a great many of the sealed systems that are touted on this board and I'd wager the majority of auditoners would pick the higher tuned, more powerful horn or ported subs, and never even miss the 10hz stuff (this of course excludes the systems like notnyt, or popalock, or carp, or beast, or etc have). I will stop my rambling with this note: I had considered DIY in the past I was thinking about buying eight Dayton 15's at one point back in mid 2012 when they were on a good sale at parts express. I opened a PM with notnyt, bosso, scott simonian, guys I respect on the forum to know quite a bit about the DIY world and subwoofers in general, and was told that eight Dayton 15's by the math would likely not keep up - or at best just be equitable to my pair of Captivators. That sort of extinguished my DIY flame at the time, and I'm glad the guys were honest with me so I didn't pursue a rabbits trail. When the SI group buy came through I was also considering buying 8 or 12 of them, but by that time I'd been to at least 3 or 4 other meets and pretty much personally and subjectively decided that I didn't care about frequencies below about 15hz because they didn't seem to make any difference to me in the various meets I'd been to when a sub could or couldn't supposedly play those frequencies. The Captivators are already well beyond the volume capability I need and not having much use for the sub sonic frequencies - well I just stayed put.
All the above said - Carp and I agree that his eight SI drivers seem more powerful in his room than my dual captivators, so the math above still doesn't quite work out that two caps are equal to eight 18" SI. I think we also both believe that two orbit shifters would be more powerful than his eight 18" SI if we had to guess based on our past audition experiences. So unless we have the published numbers it really just becomes a guessing game. I think your idea here is cool and I applaud the concept and open request for feedback! I hope the system continues to be discussed and evolves into a very workable metric!Edited by Archaea - 8/28/13 at 9:14pm