Electrostatic Speakers Vs. Horn/component Tweeter

It might help if you clarify which ESLs you have...  I have the original Motion ESLs...  Did drive them with a Yamaha AVR...  No thermal issues...  Now drive them with a small McIntosh MC152...  No problem with those autoformers...  You might want to find an AMP that "maps" to your ESLs and does not just double as ohms dip...  As those ESLs will dive into the lows ohms at high frequencies, unlike orthodox speakers which dive towards low ohms at low frequencies...

I’m running ESL X’s on a Denon 4520CI

Ok... So, crossover between panel and woofersx2 at 400Hz... I don’t think I would try and bi-amp with an AVR like that... You could be pushing 150 watts x 4 just for RMS... And when panels dive to 2 ohms your pulling 150 x 2 per channel (std) for the woofers and 150 x 3 (8, 4, 2 ohms with a doubling AVR/Amp) per channel... Ouch!!! No wonder you would have a thermal problem and clipping... Wonder what the total wattage output of that AVR can handle is... Spec is 150 watts per channel in _Stereo mode_ I read that as 2 channel... And I don’t see anything about multichannel mode... Also not sure how you would drive 2 left and 2 right stereo channels to bi-amp from an AVR like that... And how would driver time alignment work out... Speaker placement and time alinement is critical with these ESL hybrids... Hoping you have your room acoustics in order and use something like REW to get your speaker placement and room right...

The receiver is a 9 channel receiver with 9x150w 8ohn channels.  Designed to do a 9.1 or 9.2 setup.  Instead of doing front left and right and front high left and right, there is an option to bi amp the left and right which is what I’ve done.  Since the speaker nominal power is something like 320w RMS (I don’t recall exactly, been a while since I looked it up), it gives the power, and it says you can run it at 8ohm, but we all know that a speaker will suck down every bit of juice it can, and if a speaker can run down to 2ohm, it will try to suck that out of your receiver, whether the receiver can handle it or not.  I don’t have the clipping issue since I added the sub, however, there has definitely been a degradation of quality.  I believe it to be because of the limitation of setting the speakers to “small” and having the receiver apply it’s own filters/crossovers as it sees fit with no ability to manually adjust those.  That said, there isn’t much I can do to avoid clipping otherwise, unless I get a nice amp that will cost thousands I don’t have atm until I can get a reliable source of income.  You work with what you’ve got!  On the bright side, I don’t have a piece of crap Arcam receiver to ruin my day with constant failures ;)

ML suggests a power amplifier in the 20 to 400 watt range... I think they should do just fine with 150 watts... Although the ESL X are rated at 6 ohms which will cause your AVR to run up 190 watts per channel... Again more than enough to properly power your ESL Xs...

Back to you initial question about how your speakers may be damaged... The mylar may decompose with age, sun, dust... There is no voice coil like in a cone speaker which may deform or melt in an overpower situation...

I would be curious how the ESLs sound running as a vanilla 2 channel with out that extra subwoofer and set as large speakers in the AVR... You may be able to connect that subwoofer to other left and right channels or even tap directly to the standard left and rights... There is no reason to run them as anything less than full range speakers... You could then crossover your subwoofer in your subwoofer, given it has the capability to manage its own gain, crossover and phase or polarity...