Beryllium Tweeters

My mid 1980s Pioneer DSS9D speakers have current-driven Beryllium ribbon tweeters inherited from the PT-R series. A USA market re-style of the japanese S-1800DV, itself an evolution of the original S-180 from 1979.

I think of them as the ultimate conventional 3-way old-style box rock loudspeaker. The tweeters and mids are a bit more refined sounding than most and way louder. It a little hard to explain the sound because it came out of trying to one up the JBL L100 and Pioneer HPM-100 but somewhere along the design process, they made a bit of a detour into a more flexible, as I say, refined sound that works OK with classcal, folk, and acoustic as well as power rock and combo jazz.

And they do have a different sound. It’s less distorted, more etched without losing any of the guilty pleasure of rock blasters. Though I have to say they are not nearly so clean, refined or flexible as the Thiel CS3.5 I recently rebuilt with about $1500 of completely conventional drivers, just very high quality. And they do not really compare to my Apogee Stages with enough power thrown at them.

I suppose the difference and what makes these Pioneers so special is that a 35 watt tube amp can achieve orbital velocity with Zeppelin’s "Whole Lotta Love" and there is simply no more distortion than if one were making them whisper. So a lot of popular Japanese hifi makers were playing around with exotic materials, beryllium, tungston, carbon fibers, since the late 1970s to good effect.

A few years ago one could pick these 80’s experiments up for free. But I had to pay $500 for mine last year crumbling foam surrounds and all. And I expect the prices will keep climbing till they might as well be coated with vaporized unobtainium.

Specifications for the DSS9 wich was the DSS9D’s lower powered version: Type: 3 way, 3 driver loudspeaker system, Frequency Response: 30Hz to 50kHz, Power Handling: 240W, Impedance: 6Ω, Sensitivity: 91dB, Bass: 1 x 12" dual voice coil, dual crossover carbon fiber cone, Midrange: 1 x 4-3/4" tungston cone, Tweeter: 1 x beryllium ribbon, Enclosure: bass reflex, Dimensions: 15-3/8 x 26-3/4 x 13-7/8 inches, Weight: 57.3lbs, Year: 1986

My Yamaha NS1000m use those tweeters. Howevwr the B&W Nautilus 803 sounds way better.

I think dome compound is just a piece of the puzzle. I’m currently listening to a tweeter that’s made of aluminum, lithium and magnesium and hand on heart, my last 4 speakers used BE tweeters and I don’t hear any dropoff in detail coarse’ I probably can’t hear above 12k anymore. When I first heard the 1028be it was like a magnifying glass for my ears, but nowadays I think the rest have caught up. 
  

Given it appears in various sources that Materion (the sole supplier) is going to be discontinuing the manufacture of beryllium foil that is used in tweeters, is there any insight as to what will be replacing that material? Carbon fiber? Silk? 

Apologies if this is too off point.