Vd is the measurement that is critical here...this is the swept displacement of the driver, peak to peak (linear)...when the driver was first released, the stated xmax was 34mm linear...winisdpro autocalculated:
34mm /Sd=829.6 cm^2 and Vd=2.82, or 5.64 liters swept/ 109.5 dB @ 20 Hz
Later the xmax was dropped to:
30mm /Sd=829.6 cm^2 and Vd=2.49, or 4.98 liters swept/ 108.5 dB @ 20 Hz
Discussions with kyle, indicated that the excursion envelope extends out to around 46mm, assuming you have the power to drive it to that point...this would be over 7.5 liters displacement, of course distortion would be high, but it's more protective than usable...watching a single driver during "F' Irene" would "illustrate" this capacity quite vividly...point of the fact is that it has much more excursion headroom than the TC-1000...more linear xmax and sensitivity (+3 dB)to boot. Tale of the tape?
15 liters (3x15") vs. 13 liters (6x12")...and the cost would be a tad less for 3 15's (3x395) vs. 6 12's(6x198)...you may save more on shipping also...
Keep in mind that the TC-3000 is probably the best for this application, given size and budgeting, but it's not the best 15" driver offered...the LMS 5400 series should have a 4" peak to peak excursion envelope, retaining all of it's motor force over 38mm one-way...of course you'd have to pay twice the price of a tc3000 for this performance...
It's hard to say how much i felt at 8 Hz...
I'll disconnect the mains and run the 8 Hz tones tomorrow and let you know more...a high load on the ep2500 though:help: ...it causes severe flickering with my lamps while playing it back...:blink:
While the threshold for hearing is supposedly ~110 dB @ 5 Hz, how much spl does it take to feel this frequency? that's the question...i'll see if i can find Ed Mullen's findings on VLF. I think Mark Seaton has done some work in this area also.
The Linkwitz transform is more efficient/accurate than shelf filtering but there "is" a limit to how much you can "squeeze" from a driver. I will say this though...below 9 Hz, the response falls off at a more rapid rate...the FBQ 2496 and Audigy2ZS soundcard have a stated FR of < 10 - 44/46 KHz...who knows what the < 10 means but it would appear to be accurate given the 7 dB loss between 8 and 10 Hz...the ep2500 is also on its way out at 5 Hz (-3 dB)...the cones are still moving down past 4 Hz, but they are'nt producing anything tactile...:thumbsdown:
I'll check this all out tomorrow though. I'll run trueRTA also and be looking for the 2nd and 3rd harmonics...i won't be able to "see" the fundamental though so it'll be hard to measure actual distortion for the 8 Hz signal.:rolleyesno:...I may also bypass the Yamaha and run the signal straight from the soundcard to the ep2500 and see if that makes a difference.:scratch:
That said, you may not be able to overcome both the room and the electronics roll off without considerable expense in new electronics and SOTA drivers...again that 99.9th percentile thingy...that's why i was saying that maybe 8 Hz would be a more feasible goal...
Btw...i want that cat!!!...i'll trade you for a snooty himalayan named "Sasha" with tons of fur...hehe