Comparison of Neo vs SmCo EMIM Strength

[Maxamillion]

So I picked up a bunch of assorted EMIM/EMIT parts from the auction place - two neo EMIMs and four SmCo EMIMs w/o diaphragms, along with two EMITs with bad diaphragms. I was able to get one good neo EMIM out of the two (minus corroded/detached magnets), so my RSIIbs now have a complete neo set (yeah!). All the SmCo EMIMs are fine, as they don't corrode.

Just out of curiosity I did an experiment to see the relative strength of the neo vs SmCo magnets. On my EMIM jig, I suspended the front plate over the back plate for each of the EMIMs and measured the gaps with the top plate level. The neos all had a gap between the plates of 3/4", while the SmCos all had a gap of 9/16"; it was a noticable difference, and remarkably consistent. The force required to push the plates together was also noticably higher with the neos. I would guess the stronger field would translate into higher efficiency and a bit lower range for the neos.

Just thought you might want to know...

 

[cbrworm]

I have a related question.

I have RSIIIa's which came with SmCo Emits. At some point in the past (not knowing the magnets were different) I replaced the ribbons and back magnet assembly with Emit K parts. At the time infinity showed the ribbon itself as the same - it didn't occur to me that there would be different magnet strengths.

So I now have one set of tweeters with Neo backplates and SmCo fronts and one set with SmCo backs and Neo fronts. I never noticed any sound difference and wanted to keep the front plates on their matching speakers. If there was a sound difference I would have attributed it to nice tight new ribbons, not magnetic differences.

Does anyone know if mismatched front and back magnets will affect SQ? I could not tell a difference side by side, but when I listened to them side by side they were running without the rest of the speaker, so differences may not have been as noticeable.

I still have both sets, so if I need to swap them back I can, but I hate to disturb working speakers.

 

[Maxamillion]

If they sound good to you, then leave them alone. I know that would drive me crazy, though, probably to the point of taking them all apart and trying each of the different combinations. It may not make much difference in sound - the higher field strength may just make then a little more efficient. I believe though that in the EMIMs, the higher field of the neos extends their lower cutoff point a bit, allowing them to mesh with the woofers a little better.