Thiel Owners

tomthiel,

Your mention of your work on modifications on the faceplate surface for the CS 2.2 tweeter reminded me that the tweeters on my 1992 2.2 speakers have an anomaly that I've always wondered about. Many years ago, I noticed that the black metal frame protecting the face of the tweeter has a small gap where the top prong (of the 3 prongs) looks like it should attach to the round center piece of the structure. The tweeters are identical on both of my speakers, with only the top prong not connected to the center disc. The tweeters themselves have no dents or creases and they seem to work well.

What is the purpose of the black metal frame in front of the tweeters (protection, waveguide, something else?) and are all 3 prongs supposed to attach firmly to the center disc? I obviously haven't been too concerned about this issue since I've ignored it for years, but your explorations into reflections off the surface of the speaker got me thinking about other issues that might affect tweeter performance/vibration in some way.

Thanks for any insights you can provide.

Sdl4 - this is the first time I've heard of one leg being disconnected. They all three should hold the center plug in place. If those tweeters were mine, I would repair them with aluminum filled epoxy. You might consult Rob before doing anything and see what he thinks.
That fore-structure performs multiple functions. It protects the fragile dome. It also spreads the on-axis energy for broader dispersion at the high end. It also acts something like a phase plug in that it retards the leading energy at the apex of the dome to average it with the circumferential energy closer to the surround. The hex shape of the center plate is engineered as superior to a round one.
Considerable effort went into developing that structure, so I find it interesting when various pundits recommend removing it. I suggest trusting Jim's work, those kinds of details represent the meticulous care he took in the design process.

What I am looking at is the sharp edges on the back side of the structure, both the 3 arms and the plug. We didn't address that level of detail in the 80s, but I wish we had, and I now am attending to unfinished business. I do not yet have confirming measurements (working on it), but I (believe that I) can hear improvement via contouring the edges of all members and coating with soft agents. Work in process.

tomthiel,

Very interesting comments! Thanks for taking the time to explain some of the issues involved with the structures in front of the 2.2 tweeters. I didn't even notice that the center plate was actually a hex shape until you mentioned it.

I'm fascinated by your work on the sharp edges on the back of the structure, and I hope your mods will have sonic benefits.

I think I will hold off on attempting to epoxy the detached legs/prongs until you figure out what sort of contouring or edge-coating may be helpful on the structure. I also want to consult Rob before I do anything.

Thanks again for the great info! 

Something funny ...
I was having a few beers late last night then I found myself listening to a pair of beautiful CS7.2 in a large mansion no less ... then I woke up, no speakers, no mansion, no beef :-)  Maybe I should stop working on speakers for awhile.  

Beats having nightmares