Car Audio Central - Ultimate Car Audio Forum and Community

[quote="Jonathan"]Ripple is more a description of what it looks like
For reference, since you are limited in bandwidth:
Extremis: Centered around -1.25mm, around 9.4 TM at that point. Rises to around 10.2 TM at +4mm, and rises to a bit over 10TM at -6mm excursion. Falls sharply to 70% at +8.5mm, and -11mm, but suspension limits it to +8 and -7.5.
XXX: Centered right around 0, around 3.8 TM at that point. Rises to ~4.4TM at +7mm, and ~4.1 TM around -7mm. Falls to 70% at +/- 12mm. Suspension limited to +12, -10.
Excel: Center at 0, 7.7 TM at that point. Stays flat to +/-5mm, then a gradual rolloff with 70% occuring at +10, -11mm. Suspension limited to +9, -8.
CSS FR125: Center at 0, BL of 4.05. Flat to 2.5mm, rolloff to 70% at +/-6mm.
I was a bit curious seeing those BL curves, but after checking things this also shows up in the Dumax tests of drivers like the Brahma (Brahma Mk I Dumax is on Adire's site). And the Extremis Klippel analysis looks almost exactly the same as that of the Brahma on the PDF file, though it is a bit more extreme in variance. In case you don't have it on tap, the Brahma Mk I Dumax has around a 5% variance within +/- 7.5mm excursion, then past that BL rises to around the same value of the motor at center at around 15mm each way (the "ripple", if you will ). Enough of a variance to be notable as something other than a picnic table ]
Coil length relative to the gaps is absolutely 100% critical.

If you make the coil slightly short, you develop a dip in the center - heck, you could make the coil short and create a twin camel hump out of the
curve.

If you make the coil slightly long, you start to create a curve that looks like... well, a nipple - one that shows a bump within a short range of excursion (where "more coils" are suspended in the gap), that then falls quickly down to a lower level where it plataus for a while (once the coil moves far enough to stabilize the number of coils in the gap) before rolling off like it normally would for an XBL^2 curve. You could create an XBL^2 driver with MORE intermodulation distortion than a traditional sub, if you wanted.

I can't speak to the design intent of those drivers you cite - I'll assume all the tests were run appropriately (I've talked to npdang about Klippel testing, and he's aware of the statistical centering issue, and how to mitigate it, and DUMAX tests on Adire's site were usually backed up with a second test for confirmation).

Bear in mind that there are other factors to consider when designing a sub - particularly with regard to impedence... the impedence you get is a function of how much wire you have. Remember JL's explaination as to why the W7 has such an odd impedence? Their goal was to create as perfect of a subwoofer as they could, and those impedences are what resulted.

The designer of the speakers you mention may have had that as a higher priority...
With our sub, we worked the dimensions to our advantage - our Re is only slightly high for a dual-2 - which should work well for most people, it's an easy load on an amp.

I attached two plots for you to view, direct from our FEMM and modelling tools:

BABL.jpg shows the designed BL curve, given our exact coil dimensions, all magnetics and hard parts considered.

BABL2.jpg shows a magnified view of the BL curve "ripple" - note the scale on the Y-axis!

these are the kinds of threads I love to sticky just for people wishing to delve into more about the mechanics of things like speakers, but who hate having to search entire forums to find the meat of what they want. heh

I was considering doing one sub AP, and one sealed, and switching between them to compare, and so forth. It'd be the perfect comparison since one amp is dedicated to each sub, and all else is controlled.
I'll definitely play with different boxes since I have the tools and time to do so. I'd be happy to give you all the feedback and digital images you care to have.

when did you say release was scheduled? May'ish?

Beautiful!

Right - buildhouse estimates are for mid-April... (originally was April 1, to begin with)
So I'm going to be a bit wiser, and call that "May".

Well then, mmaayy your drivers bring joy to many :)

I hope so - that's the goal.

If it works, we'll have a success on our hands - that's also a goal!

did you say price range was $300-350 ballpark per twelve?
that's a terrific target range for market competition.
just above the type R strata, but well below drivers in it's catagory of performance.

oh in regards to the membrane, I was going to see waht I could find for a thicker material for the membrane to withstand the pressures, at last to sandwich something lighter to fine tune with.. then probably squish all of that between stel mesh not unlike a screen door material to hold it firm, maybe over a wire bead. That'd allow it a lot of rigidity and I could still cover it with an acousticly transparent grille cloth dyed to match the interior for a stelthy appearance.
Just some ideas I've tossed around. I knew the displacement would be a factor to be concerned with on a sub like that just like it was with the XXX12.

The 2250SX on one of these won't be an issue will it? Albiet they won't see the full power (I feel like Darth Vader) of the deathst, er, amplifiers, I'd like to make sure I don't kill them by accident. I'd hate to pet a bunny with a bulldozer ya know.

I know what you meant about the AP membranes and older subs, too. I still have my (at the time formidable) Cerwin Vega LE12D subs, with all of their 14mm Xmax.. haha circa 1989, but they were madly efficient so even with 160 watts each two of those babies could really give my car a workout for the era. I have seen S12L7 and S15L7 solobarics in AP enclosures though so it's still done sometimes with newer drivers.. though I'll admit if ever there was a sub that could use more control and better SQ, it's a solobaric.. haha

Ballpark, yes.
Still have some finalizing to do - researching shipping rates, awaiting final billing, etc.

Anyway - with the XXX moving right up out of there into an expensive driver (it does look cool), and the Brahma becoming scarcer and scarcer, there's an opportunity I think with an already existing customer market - although we've really technically been targeting the W7 as our benchmark standard, driving a lot of the design, a lot of our modeling comparisons, if you will.

But I'm a longtime JL fan, so maybe I just gravitate that way.

Oh -
I promised a preview picture.
So anyway, this is just a picture of a preproduction test mule:
(looks like I took it in a photography studio, no? )
The finalized version is going to have a few upscale cosmetic touches.

GlassWolf wrote: I'd hate to pet a bunny with a bulldozer ya know.

thats an awsome referal to kicking the crap out of a sub i might have to use that some time.

thanks. just made it up :)

thanks for the image. looks lovely. I like these new terminals everyone uses now with posts instead of the old spade terminals.. man I used to hate those things. ugly, wires fell off half the time from resonance, no ay shy of solder to keep em fixed, and did I mention ugly?


I beg of you, have a sexy cone though. I like the simple elegant cone designs like the eclipse Ti has, and even the XXX, if any design is used at all. Nothing gay like kicker et al, with raised fancy designs and explosions etc. bling drives me up a wall, although a little tasteful chrome is always the sex :)