BL difference between Levels 3 & 4

[3stagevtec 2]

From the DC specs page i noticed that the BL for a level 3 15" is 22.18 TM and the BL for the Level 4 15" is 16.15 TM..

now from the specs, the level 3 has 17.5lbs of magnet, vs the level 4's 28.5lbs..

from my understanding, BL stands for magnetic strength.. how come the sub with less magnet material has a higher BL??

[KU40 173]

Bl isn't just magnetic strength, and weight of magnets has little to do with it. There are many more motor design factors that come into play. Motor topology, gap size, height of motor and top plate, where the coil rests in relation to motor parts.........

Many subs can get away with much less magnet, but don't often because of the wow factor. Take a look at the new FI BTL, for instance.

[3stagevtec 2]

so even with a low(ish) BL rating, a properly designed motor system can still be be very potent..

explain further with what you are saying about the BTL, i got lost there.. i saw it has an 11.25" wide motor! but the shape of the thing looks kinda odd..

in the tech info and how to forums, there is a nice thread on Linear BL Technologies.. does the DC / Fi subs use any of those technologies described?

thanks

[Duran 387]

well the old BTL had a big triple stack motor, this years had a wider single stack. The new one had more motor force than the old. It looks "weird" to accommodate the movement of the coil singe it isn't a triple stack they put more steel in it so they don't limit coil travel.

[3stagevtec 2]

the more steel is for a thicker top plate i assume?...

[Duran 387]

the more steel is for a thicker top plate i assume?...

From what I understand, yes.