Harbeth blog

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.

There are indeed quite a few more. Harbeth, however, are unique in that with a government research grant they developed a special polymer (which they call Radial) that was optimed for this application. Others mostly used ordinary polypropylene. There is quite a bit of documentation about this on the Harbeth website.

@shadorne 

I suppose it really depends on what one considers "intrinsically damped." One could argue that only plastics fall into that category, but a case can be made for some alloys and composites as well.

The issue I have with Harbeth is they dominate the BBC market on somewhat false pretenses, as though they're the only ones who know how to make a stiff plastic driver or lossy cabinet. Don't get me wrong. I think they're good speakers and I'd recommend an audition to anyone shopping for a BBC inspired monitor. However,  the others I listed are equally competitive and worthy of a listen. Unfortunately for them, they lack the marketing skills of AS.

@willemj

No, the others don’t just use generic polypropylene.

Sorry, that is what I thought. Anyway, the Harbeth material is a proprietary compound to have just the right mix of properties. See here for some of their explanation: http://www.harbeth.co.uk/usergroup/forum/the-science-of-audio/213-harbeth-radial-v-other-cone-materi...