Harbeth mid range uses a soft cone material that is inert. Some form of polypropylene that remains soft and stable. Similar to ATC which use a doped fabric both drivers are intrinsically damped. I believe this is the trick to audibly superior mid range - others are chasing highly rigid materials for cones and these all have a characteristic resonances that are imparted on top of the music. An intrinsically damped cone has blacker blacks to use a visual analogy. This is why Harbeth mid range sounds so clean.
FWIW - the other BBC designs with the harder polypropylene material a la Rogers etc. can not compare to Harbeth. The harder polypropylene cones used in most other BBC knock offs imparts a nasal character to the mid range.
How on earth did you come to this conclusion? It couldn't be any further from reality. Harbeth by far uses the hardest polypropylene. It's obvious by simply tapping on them. The surface-doped cones of Stirling, and Spendor's EP77, and the clear cones of Graham and Spendor's EP38 are much softer to the touch. It's easy to understand how they're considered intrinsically damped - not at all like the Harbeth Radial material.
as for believing my own experience, i do. first, i believe in good procedure when testing and comparing gear: level matched AB testin: any other test have been proven to be very susceptible to bias. then using a well treated room, with the same electronics.
you clearly never did such extensive pre requisite or even went close to this to compare the graham ls59 and harbeth shl5plus. you never even heard both in the same room. yet, you go around multiple forums claiming youve heard them all bbc speaker companies and that harbeth is the worst of the bunch.
I really don't need to do such tests. They've been proven to be unreliable anyway, as has been discussed to death in SHF. I claim they're the least good of the bunch, because to my ears, they don't even belong in the same conversation. Their sound doesn't justify the price. An example: the $1350 Vandersteen 1Cis blow the C7s away in almost every regard. The SHL5s have good clarity but they do nothing significantly better than many $2k speakers. Their resolution is lacking and they struggle to do the disappearing act. Harbeths as a whole are slightly warmer than many brands but are much brighter than all other BBC derivatives. One doesn't even have to listen to them in person, let alone the same room, level-matched with the same gear to hear it. It's a glaring difference that's obvious even in YouTube clips. I suppose I can understand the "warmth" claim if it's coming from an old timer, assuming that person has considerable high-frequency hearing loss.
Once again, I'm not a Harbeth hater as you claim. I simply believe they offer the lowest value proposition out of the BBC family. Again, I really wanted to prefer them, as they have the best aesthetics by far. Unfortunately, their sonics just don't compete. And next time a thread like this pops up, I will certainly chime in with my opinion, especially now that I know how much it gets your goat. Bye Bye now.