Anyway, I finally have samples that look to be 99% of the way there. They are based upon a traditional 26mm (1") dome format with the following "extras".
* Beryllium/Copper Matrix dome. Beryllium is all the range for good reasons, it is light and stiff and you typically get a measurable improvement in distortion. They are so light and stiff that the dome stays pistonic at higher frequencies than most other materials. Most Be domes are made on an aluminum/Be matrix with only about 1% Be content. Our dome is a CuBe with about 97% copper, 3% Be. There isn't any 100% Be domes. Our CuBe matrix is better than a standard BeAl dome for a couple reasons. It has better damping properties that results in less break-up. The break-up of most Be domes is way above 20K but high Q break-up has some relation to distortion products. If you excite a break-up, the distortion products are excited to some degree also. Having well behaved break-up, is always better than having high Q resonances.
* XBL^2 motor technology. Typically, people think of this as a method for increasing stroke. It allows us to make the BL field of a transducer more linear with stroke, which tends to have a big impact on woofers and midwoofers. Tweeters don't see large excursions but they do benefit from a linear BL field so the approach is not without merit, especially when you are pushing the envelop for a device lower in frequency. The other feature of XBL^2 designs that is beneficial, is low native inductance. That IS important to tweeter performance and there really was no downside to using an XBL^2 motor, only an upside in terms of lower distortion at the bottom-end and lower native inductance.
* Suspension: The suspension termination of tweeters often has profound influence over the response. This is always a balancing act and there are some real tweaker engineers who focus on soft-part development. It is part materials science, part acoustics and partially an art of trail-error and experience. With a high-stroke tweeter we had to have a suspension that not only provided good termination for FR issues, we had to have plenty of travel (at least from a tweeter perspective).
* Horn Design: The primary maxim here was that of the medical profession. First, do no harm. That meant no response issues or stored energy issues. The reason for the horn, was to gain more headroom on the bottom-end and have the benefit of some directivity control elsewhere. We achieve that and kept the form-factor in a usable range (5" overall).
* Phase Plug: That thing in the middle is there for more than just keeping your kids fingers off the dome (although that is nice also). It provides some shaping of the response that was impossible to achieve without it. Some people might worry about early diffraction, it is close enough that it's in the near-field pressure range of the device so its affects are all on the initial wave front. Speaking of diffraction, this design also removes any of the early baffle related diffraction issues you typically see on-axis with a traditional tweeter.
Kan detta bli något? Låtter det som en vettig diskant? Eller pratar han bara strunt
Jag frågar för jag har ingen aning
Här är en bild: http://www.diycable.com/main/pdf/ExodusWG.pdf
