jl w6v2 or jlw7?

Well here's the DUMAX report posted on Adire's site, and the one I was commenting on:

http://www.adireaudio.com/Files/DUMAX/JL-10W7.pdf

So the W6 is basically a stripped down, more affordable W7?  So the BL curve will be flat as well?

Dan Wiggins explained that although JL explains that the holes are there for cooling, they actually reduce stray flux.  By putting the holes there, it reduces the surface area, steering the flux into the gap where they want it.  But this doesn't reduce the amount of material in the pole piece by too much, so saturation isn't a problem.  Without those holes, the BL curve would be just as parabolic as any other overhung motor.

How did you think they got the flat curve?

Oh no, that 10W7 curve is very flat.  That's a flattering curve.

And I take it you mean the cooling vents that are... not the ones shown in JL's cutaway in their promotional material?

Dan was actually describing them to me when he visited my hotel at SEMA this year, but damn if we didnt' stay up until almost 2am... It's not the vents per-se that are having an effect on the flux.. directly.

My comment was more with regard to the outside, excursion extremes, than to the center of the BL curve that you speak of...

Dan's a great guy, and fun to hang out with.  I'm not surprised you stayed up so late.

So could you elaborate on what does effect the flux in the W7?

And there are ways to reduce the inductance.  For one thing, don't they only use 2 layer voice coils?  That cuts it in half.

i have sold both eclipse and JL. I have had the chance to hear demo vehicles of both and I have to say that the titaniums lacked the transient response that i heard in the w7.  And yes Eclipse is very "enthusiastic" about their numbers, in a training they told us that their decks put out 40watts rms!! 

On a side note, xmax numbers mean very little in reality because your car may be able to get up to 180mph but it is the 0-60 that really matters in SQ terms.

Very good point.  But you will find that the better SQ subs will have larger excursions.  This is because at lower excursions, the woofer will stay more linear.