Before and After Rebuild of Ferrofluid Tweeter/Midrange by Richard So

[Glitch]

 Has any measured the tweeter/midrange characteristics before and after having Richard So rebuild them?  I'm interested in things like SPL vs. frequency, impedance vs. frequency, and T/S parameters.

I have replaced the ferrofluid in several pairs of my ADS speakers.  I am curious if my results match those of others.  Thanks.

[DavidDru]

Yeah, many wonder if it is needed.  I think some do and some don't but it would be nice to know what the actual results of the $ spent is.  Can't imagine it hurts.  I did it on my 1590's but not my 910's which seem fine as-is.

[Glitch]

It is hard to say if rebuilding is necessary. 

I can say that the drivers (mids/tweets) that I rebuilt are measurably different.  However, almost all of the differences are in the lower frequency of the driver, well below the crossover cutoff frequency.  Aside from the quantitative measurements, I also did some qualitative A-B testing using a speaker switch.  In general, the tonality of the speakers didn't change.  The measurements appear to correlate to the listening tests. 

I used the Ferrotech ferrofluid from PE.  This fluid is noticeably thinner that the ferrofluid that I removed.  What I don't know is if the ADS ferrofluid is supposed to be more viscous than the Ferrotech ferrofluid.  One could make the argument that the original fluid was thicker because it "evaporated" over the years.  An equally plausible argument is that the fluid start off thicker and hasn't changed.  I'd love to be able to pick the brain of some of the engineers that designed the drivers.

Does anyone know what ferrofluid Richard So uses when he rebuilds the drivers?  Does he use Ferrotech or does he have a supply of the original fluid?

I'm still on the fence on whether it could "hurt" or not.  If the drivers "need" the original ferrofluid (and the original ferrofluid is not available), yes, it could hurt.  The place that it is most likely to "hurt" is marking up the cabinets trying to remove the drivers.  There is also the possibility of not getting the voice coils properly centered.  The ADS drivers do not have a positive indexing system between the cone/coil and the magnet.  I found the alignment to be extremely sensitive (i.e. time consuming to get right).  If this part of the job is done carelessly, the driver performance will be diminished.