the benchmark for me was a pair of circa 1982 maggie tympani III panel speakers demo'ed @ definitive audio in north seattle. precise imaging that could be heard all over the room without getting too warped. AND depth that made [on the right recordings] one think there was room beyond the end of the room where the speakers were speaking. a direct-disc recording of some cathedral organ transformed the room into the original recording venue, but for an almost palpable "cloud" of surface noise between me and the speakers. the music was back behind [literally] the surface noise cloud. prolly the least efficient speakers ever made, a pair of class A monoblocks each the size of a dorm room fridge, were effectively heating the room too near to sauna levels for my long-term comfort. after sweating some, i left the room to listen to their little brothers, the SMGs. like a tiny version of their big brothers, without their seamless wall-to-wall omnipresent imaging, but with the essential tone quality and stereophonic imaging/depth, i was sold. they were the first truly high-quality speakers i had. before i had a pair of nova 6 acoustic suspension compact boxes, they were probably the mellowest speaker i'd heard outside of a pair of advents. neither could image anything like those maggies.
Sound quality of Newer versus Older speakers
From a sound quality perspective, is there anything that newer speakers are doing better than older speakers. For reference, I have a pair of Monitor Audio Silver 300s which are amazing me with their ability to balance detail retrieval with an ability to avoid harshness (with the right ancillaries). My subjective perception is that this type of balance between resolution and refinement was more difficult to find in speakers from 20-30 years ago.