Kevin's getting closer; here's an update from audiocircle (http://www.audiocircle.com/circles/i...pic=46027.20):
We have some updated pre-production parameters. We have had two pre-production units built and there is one more coming which will hopefully finalize the design. We are at the point now where we are just playing with suspension compliance & Mms to dial it in.
This is a dual 8 ohm VC design like the Shiva-X & Tempest-X. Parameters with VC in parallel.
Re: 3.1 Ohm
Le: 2.65 mH
Fs: 16.3 Hz
Cms: .200 mm/N
Sd: 1080 cm^2
Spl: 87.5 1W/1M
Wow.... this is serious output. The Tempest-X is no slouch at 4.3L of swept volume. The old Tumult had 5.0L so this is a driver reaching the limits of what can be done with traditional suspension components. We can design more motor travel but it becomes less and less usable due to the limitations of how much power can realistically be used in a driver (you need 1800W to reach full excursion in some designs @ 15A breakers are becoming a limit) and suspension components that operate well under >60mm of P-P displacement. I don't care how many spiders & what you do with the surround, they become non-linear the more you push them and the self-noise increases with throw so there are limits to what can be done with traditional suspension components and we are pushing up against them.
The motor BL is linear to within 10% out to about 27mm with the 30% down being our X-max. The inductance is managed with our AlCu motor technology that balances the Le curve for symmetry using variable width & thickness shorting rings made of either copper or aluminum depending upon the need. The VC is a 3" all copper design with black anodized aluminum former for maximum heat dissipation. Overall we pulled out all the stops on this one. Notice in the sectional drawing below both the notches cut for the XBL^2 motor and the two shorting rings of differing size/materials. This is all carefully designed to minimize inductance & BL based non-linearities. Not your run of the mill motor design.
This is working in slighly smaller boxes than the Tempest-X. Looks good in anywhere from 7-10 cubic feet for vented/PR alignments and it likes to be tuned down around 16-17Hz. Its going to take a PR or a big slot port because your not going to fit a big enough port with this kind of displacement in the smaller size boxes. You should be able to port the upper 10-12 cubic foot designs.
I have a 15" PR in the works but it will take four of them to keep this beast happy. No immediate plans for an 18" PR as two 15"s are cheaper and work well with the Tempest-X & Shiva-X also.
Price is holding steady @ $349 and they will probably start shipping sometime in April/May.