If you measure the capacitance with a multi meter the difference could be in that.
I always felt the SA Clarity Caps were soft compared to the Mundorf Supreme.
We added a Auricap 0.01 uF and it vastly improved the balance.
One of the problems with capacitors is that the winding structure which can cause inductance. The effect of the inductance
is to soften (reduce ) high frequencies. Oil damps the windings from microphony.
In general terms metal diaphragms or piston range transducers are best used with a polypropylene film and foil capacitor (not metalized film which can be noisy and sound harsh). CC Solen 350 Volt Fast CAPs are much more dampened that non CC. Clean out of
The vintage JBL 2/3/4 ways are a bit live sounding so the above applies.
The acquaplas dusted diaphragms are less live sounding but may lack the air of a dedicated light weight HF transducer.
Some great alternatives to the 077/2405 are evaluated here
http://www.troelsgravesen.dk/The-Lou...er.htm#DRIVERS
According to Troels the Loudspeaker 1 rules above any other system he has designed.
He knows what he is talking about with a full suite of measurements and a perspective on graphs and real listening tests.
He discusses how to use graphs and what he aims for.