Mirage, Wilson, and titanium-dome tweeter designs

To Doug Schneider,

I always enjoy reading your reviews. They’re very insightful and very helpful especially when you’re reviewing speakers.

I have a question for you regarding the Mirage OMD-28s. I am very intrigued by omnidirectional speakers, but I have not listened to the OMDs. In reading the specs, I read that the tweeter is a titanium-dome variety. As I’ve gotten older (I’m 52) my ears have become very sensitive to certain metal-dome tweeters. Some of the metal-based tweeters give me major fatigue, including the Wilson inverted tweeter they use on their newest speakers [that’s] made by Focal. With that said, is the metal tweeter used in the OMD-28 fatiguing based on your experience?

If not, I may go ahead and purchase a new pair, because the prices right now ($2800 per pair) are hard to beat.

Thank you in advance.

Michael Coleman

Audiophiles will often generalize about the sound of tweeters, based on the material that the diaphragm is made of. The reason has to do with various materials’ breakup characteristics and what that does in the audioband. Frankly, I’ve found some truth to some of it. On the other hand, I know it’s more important to look at the overall driver design, since that has more bearing on the final outcome. For example, one of the very best tweeters I’ve heard is used in Vivid Audio’s speakers. The tweeter, which they call the D26, uses an aluminum dome, a material often used in low-priced tweeters. Aluminum gets criticized for having a severe breakup mode at about 20kHz, which some consider too close to the audioband. Through clever engineering (the diaphragm has more of a catenary shape), Vivid pushes the severe breakup mode above 40Hz, far past the audioband. Materials matter, but good design matters more.

Insofar as titanium goes, in my opinion, the Focal-based tweeters that Wilson is using are not indicative of what good metal-dome designs sound like, despite their speakers’ high price. We’ve measured a number of their speakers that use these modified Focal tweeters and found that they’re not very linear and that there’s a severe breakup near 20kHz that’s worse than regular aluminum and is very audible. Don’t blame the age of your ears -- I found the same fatiguing sound you mentioned. Quite simply, I don’t think that the tweeters they’re using are very good, nor are they even remotely competitive to some of the state-of-the-art tweeters that companies such as Vivid Audio, Revel, and Paradigm are producing that not only measure much better, but sound superior too. I don't even think Focal uses that old titanium-based tweeter model anymore. (Revel and Paradigm use beryllium for the tweeter diaphragms in their top models, a material that does seem to have distinct advantages over other metals. Focal also uses beryllium in their own top-of-the-line speakers, but I've never listened to those speakers long enough to comment. The downside of beryllium is that it’s very fragile, difficult to work with, and very expensive.)

Mirage calls the tweeter in the OMD-28 a Pure Titanium Hybrid (PTH) design. If the engineers who created this speaker still worked there I’d call them and ask exactly what that means, but they don’t anymore (see comments below). It could be a pure-titanium dome, or it might be titanium and something else. Whatever the case, the tweeter in the OMD-28 is not quite up to the standard that Vivid, Revel, and Paradigm produce today, but I found it far and away better sounding than Wilson’s Focal-based tweeter, and it is superior to many of the other less-refined-sounding metal-dome designs. Overall, the OMD-28 sounded very good in the high frequencies when I reviewed it, and listening fatigue was never an issue.

One final word of caution regarding my comments about the OMD-28: I agree that the $2800 asking price for the OMD-28s is hard to beat. But I have received so many e-mails in the past about this speaker and the low price it’s being offered at that I’ve decided that it would be prudent to warn people that the OMD-28 model that I reviewed came directly from Mirage when Audio Products International (API) owned the brand and I'm not 100 percent sure that the speaker being offered at this low price is the exact same. Shortly after my review, the Klipsch Group bought API and took with it the Mirage, Energy and Athena Technologies brands. I had heard that the OMD-28 and the smaller OMD-15 were going to be discontinued by Klipsch for good, but then they started showing up for sale online for $2800 per pair, brand new, and seem to still be selling for that today. That surprised me but brought to mind these questions: Are they built the exact same way? Do they measure similarly? Do they sound identical to the ones I had here? I don’t know the answers to any of these questions, but I find it very hard to believe that a speaker that once sold for $8000 could be offered for 35 percent of the price for so long. If they are the same in all respects, then it’s a staggeringly good deal. But if they’re not the same anymore, then what’s being offered online is not really they same speaker I reviewed and I can’t say how good a deal they actually are now. Buyer beware! . . . Doug Schneider