one question about the SVG motors

jbl said in tech notes volume 1 number 22
-------------------------------------------------
1. Thicker top plate and magnet structure. These
afford better heat sinking and greater flux in the gap for a
higher B1 product (magnetic flux times voice coil length).
This provides higher electromechanical damping and
increased motor strength
--------------------------------------------------
these drivers , 2227 and 2242 did not have a high flux density and neither do the old thick plate e145s and le15's and stuff they run from .9? to 1.1 or so that's about it .

I thought that increasing the thickness of the top plate and pole piece reduced flux density ??

or are they stating that even though the flux density is reduced there is a bigger surface area exposed to the voice coil which ultimately results in a higher BL ?

I think its the latter but wanted to run it by you guys just in case :D

EDIT : I did find this in a search for "magnet"

http://www.audioheritage.org/vbullet...agnet+material

which states "If both the flux density and voice coil gap dimensions are known then the total amount of useful flux can be calculated".So the new question is does anyone happen to know the actual math formula ?