Harbeth blog

He is a curious mix of engineering and listening. He designs everything himself and tunes with his ear alone. He dismisses “Rock Speakers” entirely. Definitely quirky as his musings tend to convey. His interest is acoustic and classical at low to moderate levels. This has had a big influence on design.

Alan’s big focus is on damped cone material. I know of only one other speaker maker with such a focus - ATC. All the rest are chasing light weight rigid cone materials that look great under frequency measurements but sound terrible due to added intrinsic coloration from cone vibration. Latest ATC designs include CLD - constrained layer damping - this places damping material in a sandwich between two light weight cones.

http://atcloudspeakers.co.uk/technology/cld/

The key understanding that Alan latched on to early in his career with Dudley Harwood is that all cone materials impart a coloration to the sound (as seen on waterfall plots but best assessed with critical listening). The key realization is that you use engineering design for a flat frequency response but you use intrinsically damped cone material to reduce subsequent tonal coloration after the transients. The sole purpose of the radial damped cone was to get away from polypropylene foggy or nasal sound.

If you examine Harbeth and ATC mid range and tweeters you will find they are damped with highly viscous semi-solid semi-fluid material. ATC mid range are sticky.

This approach differentiates Alan’s work from all other transducer makers except ATC. The difference between ATC and Harbeth is that Harbeth are engineered (voiced) to play at low volumes where they sound best. ATC are engineered for realistic loud volumes where they sound best. This is a design choice based on equal loudness contours and preferred listening level.

Anyhow, a thread about Harbeth must necessarily start with a recognition and realization about what makes Harbeth sound so amazing. It is all about intrinsic damping within the cone material - this is what makes Harbeth sound so natural and revealing - the usual clutter from cone vibration after the initial transient is absent. Quad electrostatics achieve similar results in mid range clarity but they are hopeless at providing a wide even sound field/sweet spot (too much beaming)  and are dynamically severely limited (much more than Harbeth.)

Two cents

Thanks Yogiboy! That interview really exposes Alan’s critical realization and understanding about transducer material. Alan really is quite exceptional. I have never owned a Harbeth but I have listened extensively and hear exactly why everyone raves about them. Great unique speaker designs that refuse to follow the trendy exotic rigid lightweight cones espoused by the rest of the industry. Harbeth sales keep growing because Harbeth do much more right than most everyone else’s latest and greatest diamonds and metals.

Thanks Helomech. I suspected there were a few more. Yes plastic/polypropylene is intrinsically damped and was popular in the 80’swith Mission. Harbeth mid range cones are even more damped - so it has been taken further than the old Rogers Ls3/5 design. All those you happen to mention are UK BBC style. I have heard of Spendor but not the others. I still think I am correct that the vast majority of designers have gone in the direction of lightweight rigid material over the last 30 years - ceramic or metal etc. as it is cheaper and it uses smaller drive units (more efficient)

I guess Harbeth is quite a bit less unique than I stated. Maybe it is a UK thing as these styles of heavily damped mid range design aren’t often found in North America.

Here is a close up of Radial mid cone

http://www.harbeth.co.uk/usergroup/forum/the-science-of-audio/1119-fast-and-slow-speakers-should-fas...

Here is is a close up of ATC mid dome

http://www.stereomojo.com/ATC%20SCM50ASLT%20SPEAKER%20REVIEW/images/ATC-Soft-Mid.jpg

Harbeth is injection molded (entirely plastic). ATC apply the “dope material” to a woven fabric. Both have a similar look and feel. Both are hydrocarbon based plastics. Both are softer than polypropylene and cannot be used for large cones (not stiff enough). Specifically designed material just for the mid range. What ATC use is even softer (tacky to touch) but the fabric and dome shape provides the necessary rigidity.

I am not aware of any others using this type of material but after so many years of use I can only assume the cat is long out of the bag and others do use it.