I pull both Tweeters out, open, take apart, check the Voice coil, the gap in the Magnet is very clean and no trace of Ferro-fluid.
Put everything back together and test, those Tweeters are sounded fine.
They are very much exactly sound like before I open them up.
I open them up suspecting they they are using Ferro-fluid, they are not. My Rega Ela is Mk1 and I bought it Brand-new from a Dealer.
The Bass/Mids Drivers are fine also, only Crossover that left.
Any suggestion to What, where, how or else to check, upgrade, replace or whatnot to those Rega Ela Crossover?