Recone: Still Bugging Me

[toddalin]

I know we've been through this and I've seen the postings with the list of speakers that can be reconed with 2235 kits including the D130 and 136A, BUT:

We've been told that 130As are different and can't properly be reconed as 2235s because the voice coil is 1/8" deeper and the 2235 coil doesn't center. My D130s reconed as 130A have been called Frankensteins on this forum. Fair enough..., BUT:

The 136A and D130 are listed as having a 12# magnetic structure and a depth of 5-5/8". The 130A is listed as having a 13# magnet and a depth of 5-3/4". This explains the extra 1/8" of depth that people have noted.

Now examine the literature on the 2205 and 2231A, both listed as having the 13# alnico magnets, but both reported to be reconable with 2235 kits. To me, the extra pound of magnet would then infer the extra 1/8" of depth associated with the bigger magnet. I would then conclude that this would then make these speakers more comparable to the 130A as opposed to the D130 and 136A. Is it that the "shallow coil" cones can be used in the "deep frame" magnet structures but vise versa is not recommended?

Any others have thoughts on this? I know it's an old horse.

[GordonW]

It's not the depth of the frame... it's the thickness of the top plate of the magnet assembly. The D130/2205/2231/136 have the .281" thick top plate, while the top plate of the 130A/2220 is much thicker (almost .500"). The problem that occurs, is that if you install a 2235 kit into a 130A frame, the "extra" thickness of the top plate is NOT uniformly oriented on the 2235 voice coil... the center of the top plate is now "biased downward" on the voice coil winding, so that there is a greater downward X-max than upward X-max. That's enough to cause non-linearities and distortion, at any appreciable cone excursions...

Now, if you're willing to use aftermarket components, it IS possible to use a longer-winding voice coil (ie, one of about 1" long winding, instead of the .75" long 2235 winding), a 2235 cone, spider and dustcap, and a modified (ie, slightly less weight) mass ring in a 130A/2220 frame, and wind up with something that will test reasonably close to a 2235... it's possible to manually adjust the up-down centering of the coil winding, so it's centered in its travel at rest, before bonding the voice coil into the cone. But, there's no way to do this with factory recone kits...

Regards,
Gordon.

[toddalin]

It's not the depth of the frame... it's the thickness of the top plate of the magnet assembly. The D130/2205/2231/136 have the .281" thick top plate, while the top plate of the 130A/2220 is much thicker (almost .500"). The problem that occurs, is that if you install a 2235 kit into a 130A frame, the "extra" thickness of the top plate is NOT uniformly oriented on the 2235 voice coil... the center of the top plate is now "biased downward" on the voice coil winding, so that there is a greater downward X-max than upward X-max. That's enough to cause non-linearities and distortion, at any appreciable cone excursions...

Now, if you're willing to use aftermarket components, it IS possible to use a longer-winding voice coil (ie, one of about 1" long winding, instead of the .75" long 2235 winding), a 2235 cone, spider and dustcap, and a modified (ie, slightly less weight) mass ring in a 130A/2220 frame, and wind up with something that will test reasonably close to a 2235... it's possible to manually adjust the up-down centering of the coil winding, so it's centered in its travel at rest, before bonding the voice coil into the cone. But, there's no way to do this with factory recone kits...

Regards,
Gordon.

So then, I take it that the magnets are identical and the extra pound of the 130A over the D130/136A is related to the weight of the extra thickness of the top plate??? If this is the case, wouldn't the 2205 and 2231A also use the thicker top plate becase they have the extra pound of magnetic assembly???:hmm: