Paper cone woofers died in 1962 .... a look back

Had a pair of Leak Sandwich speakers . Very good sounding on low watt tube amps. Look them up. IIRC foil and styrofoam? Sorry about no paper ref.

bdp24  noted your comment on the KEF B139,
I finally bought commercial speakers, (Monitor Audios) and decommissioned my homemade KEF speakers.
Have to say the B110 (dextrene?) I think still sound fantastic.
I`m making small subwoofer boxes for the B139s,still going strong after 35 years!

@lastperfectdaymusic, the ESS Transtatic put the KEF B139 in a transmissionline enclosure (hence the "trans" part of the name; the "static" for the RTR electrostatic tweeters). That enclosure was very similar to that of the IMF Monitor, which also had a B139 woofer. Irving Fried (IMF were his initials) was a fan of transmissionlines.

Interesting that on both pair of Frieds I had in the 80s-90s it was the paper cones that eventually failed.