I used the Solens as an example of the type (film caps) not as THE recommended cap. However, they perform quite well for the money and are a good way to start on the diy upgrade path. Much of what is discussed here IS a matter of personal taste. I am not sure what application you have used the Solens in, but the stock mylars in the Pi 4 crossovers are not as resolving or extended as film caps, including the Solens. The Solens also do not generally sound harsh and 'cruchy' unless the signal contains that sound character. That is a problem frequently encountered when upgrading mid or 'downstream' in the system. With upgrades to the speakers you often hear problems originating in the amplifier or source. I have heard that you can have too many film caps in the signal path and too much silver interconnect (the sound becomes overly analytical or worse), but I have not been burdened with that experience. System voicing can get pretty involved and expensive.

In any case, items 1 and 2 are quite inexpensive as system upgrades go, and certainly less expensive and involved than a super tweeter that at least matches the quality of the Eminence driver in the 4 Pi's. So I suggest that he try a few inexpensive tweeks before spending a bundle on a horn or ribbon tweeter. If, in his opinion, the sound is improved, then he is ahead for very low cost. Trying an inexpensive super tweeter like a piezo or the Radio Shack pod tweeter could also yield some improvement.

With respect to your experience with Solens, how were they being used (power supply, coupling, crossover, etc.)? What did you bypass them with that improved the sound?

Regards,

AstroSonic