Got to love em. In a simple inquiry into the type (aluminum or Titanium) of tweeter my IS 350C has I sent an email to M&L. First response from a "live" CSR agent named "Dan" apologized but couldn't help me as I reached the home division but gave me a email address for automotive one. Fair enough. I thanked him.
The automotive division does not answer customer service questions on stereo equipment and advised me to call United radio or get in contact with the service department with Lexus.
I call United radio they don't know or work on speakers. I call Lexus and they don't know instead call M&L or Pioneer. I'm thinking Pioneer?.....
I write Pioneer and they don't know what type of speakers either.
Wow. An exercise in futility. Everyone just pushing the buck. I really like the sound of the tweeter and I know it's metal but what type? Timber, space, speed of the tweeter and best of all lack of ear fatigue make it a choice I'd like to buy for my RX 350.

"You have sent an inquiry to the automotive OEM business unit of Harman’s Infotainment and Lifestyle Audio divisions.* This business unit currently does not provide direct service or technical support to vehicle owners. If you are looking for technical details for the audio OE installed in your vehicle by the automotive manufacturer, please contact your local authorized vehicle service center for support."

 

Update: Their Ti. After some more back & forth "Kevin" stepped up and did some digging. Karma points for him.

 

The Mark Levinson system was definitely one of the worst systems ever made with respects to reliability and performance. I had a donor ML amp that I took apart and a $80 Best buy special had better parts than the overhyped ML.

As you already found out, ML, Lexus and Pioneer won't have a clue about anything with regards to the audio system. Cheapest parts possible, highest markup possible for mediocre performance.

If you want lack of ear fatigue, stay away from any of the hard domed tweeters. Aluminum, Beryllium, titanium...they ALL have ringing effects and fail to dampen properly. You can take the best Focal tweeters or the hyped Rainbow Reference series and they will still have the same problem. It's due to physics and the only way to partially dampen them is to make a "trap" in the crossover network, which is quite complex.

Best tweeter that I've ever heard, and I've heard MANY, would be the Dynaudio esotar series. Second best would be Dynaudio Esotec and they are worlds better than any hard dome tweeter when it comes to transient signal accuracy / reproduction. Silk dome tweeters with special coatings will dampen out after a transient whereas a titanium/aluminum/beryllium would still be ringing. The "empty pop can" effect as I call it. Sure you could always try to pad the backwave with some acoustic cotton or material, but the matter of fact is that the dome / driver itself is still ringing.

 

All solid points. One day I'll aim for the Dyn's and be done with it. Going off the book shelf speakers nothing compared to them. They literally opened a window to the music.
Otherwise your assessment on metal dome tweeters are not without merit. It just so happens that M&L got MY titanium tweets dialed in perfectly. Shocking I know. Every person who has listened to it their eyes give them away. It's funny. Crystal. Clear. The bass is very good also. I must have got a Thursday speaker special & extra tune up.

 

Last time I listened to the ML system was a couple of years ago. I'll have to give the one in the IS350 another listen to hear if they've solved the ringing issue. Probably the best one was in the LS430 which had horn loaded compression drivers for the higher octaves.