Ii have been rebuilding loudspeaker Xovers for over 20 years
Tony Gee from Humble homemade hifi capacitor test
have a cook book of each brands rankings and sound and is roughly 90% accurate
many time he doe’s not not have time for them to fully open up
higher voltage say 800 v or foil types normally take longer .
Newer Sonus Faber use Mundorf Evo Aluminum oil caps Which are decent but you can do much better and get a big improvement , the resistors too absolutely
mundorf supreme are prettygood , Path Audio are my favorite andi use Jantzen waxed paper Copperfoil inductors , open coil is very good after theCopper foils awg 14 for me ideal ,,Jantzen Alumen Z aluminum foil not too pricy and muchbetter then Anythung Sonus Faber uses just the caps and resistors alone a solid 10% upgrade better in every respect ,and these are Aluminum foil type
inside youcan read theUF or size on the capacitors ,
theresistorstoo should show how many ohms ,ifyou can’t read them ,leave them the caps are by far most important , the loudspeakerterminals WBT next gen excellent value , and the flat on the inside made for crimping slide on. WBT or Furutech
VH audio sells both ,highpurity Copper then gold plated ,much better conductivity
then solderehich is mostly tin ,for caps use Cardas solder excellent sound and has flux rosin built in flows nice , Donot use a solder pen spend $100+ on a good-solder station