Absolutely. The BC-1s, widely regarded in vintage circles of being an unmatched legend, were undeniably embarrassed by the Harbeths... if one was to look at them strictly from overall performance/sonic presentation and not thinking of them as a historical loudspeaker landmark. The gulf between the ESL-63s and the SHL-5s was much smaller, but the ESL-63 needed a radically different approach totally outside of the mainstream it was contemporary to, to achieve those results. The Harbeth did it with an approach not unlike the BC-1s, just with 40 years of learning attached to it.One of the best examples was the comparisons we did between your Spendor BC1s, your ESL-63s and the Harbeths. Never has progress been more evident.
So the BC-1 "idea" caught up to the ESL-63, and even surpassed it, but had to become nearly something else entirely to do so. Only the 2 cubic foot thin-walled cabinet, and tweeter/super-tweeter/woofer ideas carried on. Maybe things are plateauing a bit, as the newest SHL-5+XD aren't -that- much different than my nearly 10-year-old SHL-5s, but I wouldn't say mine are better. They're just not as far behind.
As for my BC-1s, the woofers had been sent to England and serviced by Derek Hughes himself and the crossovers had been redone. They were as healthy as a pair of mid '70s BC-1s could get. They were what they were, and they wren't bad speakers but they were by no means unmatched today. They weren't even unmatched in my little house.