I agree Harbeth speakers don’t have the best crossover parts and best tweeters on market, but that Radial polymer midrange may be the best plastic midrange on market right now. We have to give credit to the designer. And we cannot forget that he has to build a product to a price point, so choices must be made in selecting parts. He has the right to make a living like everyone else who owns a company, so we should forgive him if he does not put a pair of Scanspeak beryllium revelators in his Shl5...
Sure , carbon, aluminium, titanium, beryllium and ceramic composite are more modern driver materials and they have their pros and cons.
Nevertheless, the first time I eard a pair of classic Spendors bookshelves I was very impressed by that midrange naturalness ! Only the bbc thin wall design can give you that kind of sound... Is it perfect , no. But it sure sounds special with voices, brass, winds, acoustic instruments.