I have been reading the SR-009 imbalance thread and I think it is better to post my questions here.
Humidity, diaphragm tension and diaphragm coating resistivity were already mentioned in this thread. But humidity is usually mentioned as a factor when using the drivers and I have not found any mentions of the relationship between humidity and the coating process.
This article describes the effects of humidity in very sensitive production processes:
Do you feel from your experience that coating the diaphragm in very humid days derives more drivers with imbalance?
I see that DIY drivers use a FR4 ring to hold the diaphragm. What material the SR-009's ring is made of? Is it metal like the stators?
I wonder if, contrary to the use of a FR4 ring to hold the diaphragm, a metal ring worsens the dimensional control of the ring/diaphragm structure.
Anyway, if it is such a precise process, a 95% reject rate is not bad at all. And congratulations to all DIYers of this thread that achieve such stability!