Originally Posted by chucky7
serith asked me that question so I will paraphrase my reply here...
Below is the comparison in output between 3 FV25HP and 2 4000ULFs:
Basically, from 12~50 Hz, the 4000ULFs will provide 50% more output and be almost twice as loud at 10Hz.
The ground shaking TR comes from output in ULF. Therefore, having this much more output at 10Hz will be sick.
IMHO, Jeff's secret sauce is from the driver he uses. I believe the TR is just the byproduct of the driver that he customizes that fits his design goal in producing JTR's signature sound: his desired level of THD - higher than Rythmik, but never too high to make the JTR subs sound bad.
At reference level, both systems will produce THD well under 10%. Therefore, both will sound really really good, but different. The JTR subs will just provide more TR.
PSA's 18" driver has a similar 20mm X-max as the 18" Rythmik driver, yet the PSA V1801 has more TR than the Rythmik FV18 Alum cone.
Originally Posted by serith
now the question is which profile captivator to buy. i'm still not sure.
*edit* - @chucky7
, can you show me the comparison between 3 cap4000 & 3 fv25hp? not sure how you are creating those data points but curious what it looks like. while i think i'll start with a pair i really would like 3 laying across the rear of the room like what i had before.
I think that the Cap 4000's will be relatively even stronger than what Chucky's chart shows. And, they will have an enormous advantage in tactile response. In my opinion, that will truly be a night-and-day difference!
With respect to the relative loudness at low-frequencies, we have to remember an ideosyncracy in the way our hearing works. According to the Equal Loudness Contours, an increase of 10db is perceived as a 100% increase in loudness at 1000Hz. But, that formula changes as frequencies drop below 120Hz, and it accelerates at frequencies below 70Hz. You can see the contour lines moving closer and closer together and leveling-off at around 30Hz. According to Linkwitz, and others, at 30Hz and below a 5db increase in SPL is equal to a doubling (100% increase) in loudness. Section VII-C of the Guide illustrates the Equal Loudness Contours, and shares a link to more information on this aspect of our hearing.
Most of us don't really hear frequencies below about 15Hz, but we feel them as low-bass energy, and they add weight to what we do hear. The point is that an increase of 8db at 10Hz isn't equal to nearly a doubling in loudness; it is equal to a loudness increase of about 160%. That is a huge
difference! And, even at 20Hz, the dual Cap 4000's will be about 80% louder than the three FV25's.
Part of the reason that I mention all of this is to suggest that serith may want to start with just two Cap 4000's. I know that money is no object in this exercise, but that's a lot of money to pay for just another 3db of headroom, when the increase he will already be getting is so profound. And, more could always be added later, if necessary. Just a thought!