Danley BC-subs reverse engineered

[Kravchenko_Audio]

The real xmax is much more complicated then a very simplified gap-coil-ratio. Very high Bl drivers routinely have a somewhat larger xmax then the simplified mathematic formula indicates. The magnet field does not abruptly end at the exact edge of the pole-piece. With strong modern Nd magnets and well saturated pole-pieces the field will extend a considerable distance outside the gap.

I agree with part of this statement. It is true in a sense that high BL motors can have greater usable X-max. But that is a function of the motor design. There is a great paper available that is actually quite readable:

http://www.xlrtechs.com/dbkeele.com...bute to Ray Newman, Underhung Voice Coils.pdf

Also within this paper are detailed simulations of how the magnetic field behaves in a motor. A well designed motor actually is very good at keeping the magnetic energy within the gap area. That's the entire reason for the engineering in the first place.

What does happen in some high BL motors especially when they are tall gap and short coil is that there is greater excursion capable that the simple math tells you. Greater excursion because there is still enough force from the gap to push the coil out farther and in farther than you would consider likely.

What I enjoy is the loudspeaker driver application work you guys are doing. I learn news things from time to time and I really appreciate it.

 

[papasteack]

What does happen in some high BL motors especially when they are tall gap and short coil is that there is greater excursion capable that the simple math tells you.

So should be easy to verifying with bcspeaker and sica speaker if taller gap got more xvar-xmax. I'll take a look using bcspeaker and sica datas, cosidering neo appart.
It's not so much intuitive for me. Bigger gap mean less shorting flux since it got more ways to pass. On the contrary, small voicoil big motor let few ways for flux, so there will have probably (intuitively) for flux escaping around...don't know at all, but it's really interesting to exchange, thanks.
If flux going out is let say 5mm outside (even if it cannot be measured of course) for a 10mm gap, we suppose that it will be 10mm for a 20mm gap. Wich mean 50% the size of flux outside in each case.
But of course, twice the size with twice gap of outside flux, wich can help a lot since voicecoil are still limited in size/weight...
And counting of this outside gap flux means worth BL curve VS excursion.
What the receipe for a flat BL curve vs excursion ? trying to study klippel internet measurement, it's not so easy to understand.

 

[Abielpanggabean]

I know this is an old thread. I might experiment building the bc412 with 4 12tbx100. Do you know the size of the mouth for the build?

 

[weltersys]

You can download drawings on DSL's website, the plan view of the outside dimensions of the BC 412 depicts the mouth exit at 26" x 19.5", the "boundary" of the mouth 50" x 50". The internals are probably similar to a scaled down version of the BC415, post #13 shows a possible layout of that horn.