Hello to you

. I too collected them . I have had 4 of them , acyually hold 2 + 1 on borrow from quite a time now . They sound slightly different the one from the other and express their maximum potential on a balanced configuration , that is how I use them only , one with an ofc balanced cable and the other with a mixed copper/silver balanced cable ; cable apart , one produce a more open and close sound and more surprising or exciting at first , the other little more distant but slightly more natural and more right tonally , this is the one I used the most lately . I always wondered about this difference as in some high end headphones and brands it can happen, and this is the case too ; the third I have on borrow is again a different sounding pair has it has a more pitchy accent -or more resonant- on sone highs and is more fatiguing for me. Slightly different but audible .
Speaking of the two on current use , they both add some hollow honkyness or what is some sort of hamony overlap or glare on some low-mids ( harmonic distortion?) , it is hardly noticeable on casual listening but I decided for some eq for reducing it so I use them only equalized, i suspect this is house sound and slight problem of all a800.
Also because the upfront open sound can be quite murky and dark on first and before ears adapt , eq helps in this regard too.
I also added some thick angled pads as the one mentioned in this thread , lambskin pads on a pair and velvet pads on another , to furtherly distance the drivers from ears ( if you dare to remotely think at Abyss 1266.. ) , the house sound remains gross rich with airy and seducing bass nuances , but the extra distance definitely helps in defining soundstage ; a800 have a preference to portray drums guitar in pop rock etc, and strings in orchestra , in fact I was surprised to hear so frequently drums so close and upfront with them Vs other headphones set as a drummer ; also archs ( viola in particular ) can be emotional . They pair well with clear trasparent sources ; a slightly bright source can benefit them whereas they pair badly with warm sources ; a matched tube amp can help add some life in vocals or mids, not my preference for them anyhow.
I would comment or define their sound as rich seducing and dark , gross and sinking well down on bass frequencies ; depending on music and tracks sometimes it can vibrate pads on cheeks and it is impressive and rich ; while other times it seduce with good manner handle body and presence ; tone accuracy for different drums or skins of drums is nice too to have.. , this is on balanced configuration and my setup ; unbalanced they sound more polite and edcuated , still rich and lush but more gentle , the bass or drums are sill beefy but not under hands and conducting as when they are cabled balanced ; in both cases they are some of the most un-fatiguing headphones ever tried , this is likely due to a combination of very low distortion on highs as well as a sort of absence in the attack region , they prefer core and decay of the sound to attack at least my ears say so ; i feel they are quite much better then recabled hd600 ; not better then recabled hd650 but not worse , still better then hd650 for bass resolution and low frequency range as well as behind for vocal rendition and orchestra or classical music rendering.
I bought the extra angled pads for them on Aliexpress , they do the job and are both comfortable .
As for the balanced cables copper is their preference as silver will sound 1mm more resolving and a little bigger on bass but less natural, as usually happens with silver cables