Just stumble overr this thread, @Horatio & rgd the ETF.10 shootout,
the meas taken by JMLC at the time were erroneously marked. The driver used was of own composition, mating Altec290 core with 288C diaphragm. In essence, a 288-8G. I took, perhaps unusually, a second horn/driver combo into that 2010 shootout with JBL2353+288-8K and perhaps caused Jean Marie's (may he rest in peace) mix-up of the comp driver names. Pretty evident in the photos the Melaudia / French ETF team took and published.
EV's HRx040 and HRx040A series differ significantly in lower mid freq response, see exchange on their history in AudioKarma between AK member abez0 and myself. Those posts were commented on by former EV staff elsewhere and provided here on this forum pointing to the possibility the changes were in fact mainly made due to easier manufacture (this was my initial guess, but the "A" series advantages then led me to believe otherwise).
Positive (mid/treble) and negative (lower cutoff) side effects of changing the HR series' initial expansion were maybe overlooked at launch as the majority of the horn bell, the parts facing the listener, stayed unchanged in expansion/shape. My (unconfirmed) guess is that when launching the "A" series, these went out from EV with data sheets previously compiled by Don Keele and actually show the non-"A" series radiation pattern details. Can some light on this be shed by someone more knowledgeable here, maybe?