What cause tweeters hiss ?

Consider the obvious.  The tweeter is a transducer, it has no intrinsic energy of its own (other than the kinematic energy imparted to it by gravity which will not produce a sound unless you drop it on the ground).  If you take the tweeter out of the speaker and hold it to your ear you may hear noise.  Obviously the tweeter alone has no power going to it so it can't be 'transducing" so what you hear is similar to what you hear when put a seashell to you your ear at the beach (go look that up, the education will be good for you).

Tendinitis is another possibility for a un-powered tweeter appearing to be hissing.  If you have a mild case of it there is there is a chance that by concentrating on the tweeter, you are perceiving the results of this medical issue.

Otherwise this question is wrong.  One must as 'Where the signal coming from?"  The answer would have to be the electronics driving the driver.  Something is producing energy, this is a great trouble shooting exercise to sharpen you inductive (not deductive, no matter what you think of you readings of Sherlock Holmes, he was a master of inductive rather than the deductive reasoning processes.  Again, do some homework, it will be good for you.

@itsjustme @perazzi28 @oldrooney @gs5556 @jb1 @clearthinker @erik_squires Dear all, thanks for your advise and sharing thoughts.

Finally I have discovered the culprit, it’s my 15 years old Cardas XLR interconnect. (even I have had tried phase invert at both Ares II and E280) .

After I replaced with a normal decent Ugreen XLR interconnect. No more hiss on both tweeters.

Should I get a better XLR interconnect?

@perazzi28 all high-end audio equipment here are 3-pin UK with ground connected and with IEC 60320 C13 power cable.

Interesting.

So premium interconnect can worsen SQ as well as improve it!

@auronthas I’m glad to hear you solved your problem. Getting a better interconnect is up to you. The purpose of spending more money is to get better sound, and to give yourself peace-of-mind that you’re doing everything, within your means, to achieve it. 
 

I would be interested to learn more about the XLR cable you replaced. Have you opened it up to check its connections? One of them could be loose or the victim of a cold solder joint. A poor connection would, I think, add a great deal of capacitance to the line.
Have you checked the cable with an Ohmmeter? I have found pin 3’s (ground) and even pin 1’s (opposing signal) tied to the XLR shell’s tab, sometimes at both ends. Pin 3 (ground) should only be tied to the cable’s shield at one end if it is to perform its proper function. If it tied to ground at both ends it is no longer a shield, but a conductor, connecting one chassis’s ground to another, or even connecting signal ground to chassis ground.
I think I’ve read, on this forum, that the connection should be made at the ‘male end.’ Which begs the question, for me, if it is the XLR connector or the actual pins which are referenced. The male XLR connector houses the female pins; whereas the female XLR connector houses the male pins. The male XLR connector plugs into the ‘source;’ the female XLR connector plugs into the ‘destination.’ Others on the forum have recommended ‘grounding at the preamp,’ which is the destination for an analog source or a DAC; but a source for the amp. Perhaps someone with more insight can clarify matters for us both. 
 

Again, I’m glad you managed to solve your problem. 

@oldrooney hi, thanks for your detail explanation on the XLR pin terminals construction,  i am not electronic savvy, and furthermore this XLR interconnect may have reached its life span after 15 years ? I will leave it, lucky that I have a spare XLR that connect to my headphone amp. Temporary this will replace my old Cardas. Thanks again.