Perhaps 10 years ago, I visted two electronic component manufacturers in quick succession. One made electret elements, and the other made electrolytic capacitors. Based on what I saw and was told on these separate field trips, I decided that it would be worth experimenting in modifying elecrolytic capacitors by changing the amount of compression and damping encountered by the metal can, and listening to the results using the methods that I described previously.
I recall that in this particular case I made up about 10 visually identical units, treated the electrolytic capacitors differently in each one, sealed them up, mixed them around, and labelled them randomly. I left them powered up for about 10 days, and listened while making notes.
Once I had finished noting my subjective impressions, I boxed up all of the units (without my listening notes), and sent them on to another person in charge of listening in our organization (at that time, I think there were 4 or 5 of us who formed a "listening panel". He also listened while writing down his subjective impressions, and once he had finished, sent the units on to the next person, and so on.
When the last person had finished, the units were sent back to our main workroom, we each brought in our listening notes, compared our notes to see what each of us thought of the sound of unit J, 7, *, etc. We then opened up the sealed units to see what was inside them, and figure out what modification was contributing to what sort of sonic change.
On the whole, we picked the completely peeled capacitors as offering the greatest, least ambiguous subjective sonic improvement for the least effort. We also concluded that it was better not to use the commonly supplied metal bands to secure the capacitors (changes in this area yielded measurable differences in distortion levels). Some other techniques were rejected because they resulted in divided opinions among our listening staff, were inaudible, or made the sound worse, while other techniques were deemed sonically worthwhile but likely to be too much of a PITA during production.
Even today, in my current products, some of the electrolytic capacitors have peeled sheaths.
