Very true. The “driver seeing frequencies they weren’t meant to see” is the only reason I’m considering recapping my Mach 3s. They sound great for the most part, but how do you ever KNOW that the cutoffs are where they intended?
Regarding the “trying another brand or type”, that part is harder for me to personally get behind. Not only does that become expensive (especially given some of the caps people recommend here), but the worst part is, some speakers are a chore to get to the x-over boards on. I hate the thought of trying a cap, hating it, and having to pull the woofers a bunch of times. Not sure how many tries you get with wood screws in particle board before they strip, etc.
I’d love to be one and done and upgrade to poly caps. For me though, the biggest worry is trying an “expensive” poly cap and hating it. The problem there lies in that, not only is everyone’s taste different, but so is their hearing and perception. So what some say sounds great, may be too bright or harsh for others. Sibilance is one thing that drives me NUTS, but again, how do we say “this cap won’t cause it for sure”?
Just my thoughts

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Joe