The ring diaphragm design offers an advantage in reducing H3, but it has a smaller radiating surface compared to a plain diaphragm. This means it must move more for the same SPL, which adds more H2. It’s not a big issue, but at very high SPL it becomes something to consider, the Honey Bar in Brooklyn first use HF1440, they burn it (well there was a mistake in power compressor too ^^). This isn’t about patents, it’s simply physics.
There’s no technology transfer between B&C and 18Sound (I know 18S very well); they actually have opposite design philosophies. This was clear in their joint interview on YouTube: B&C accepts the breakup behavior, believing that many listeners actually want that character (they literally said so in the interview). Meanwhile, 18Sound aims for technically perfect compression drivers.
This different of philosophy is very important to note, you can see it here :
I’m not against annular diaphragms. For polar response, they are the best, since they exhibit almost no breakup and produce a near-perfect plane wave at high frequencies, they match FEA simulation almost perfectly (especially the 5530). My own drivers are:
- BMS 5530 / 18Sound 1090
- JBL 2450SL / 18Sound 1460/80 / HF1440
I just recognize when one type is better suited than another. “High-end” doesn’t mean buying the most expensive driver, it means choosing the one best adapted to the application and the need, not following hype or fashion.
Moreover, psychoacoustics shows that aiming for perfectly constant directivity at very high frequencies isn’t very useful, since in most drivers the wavefront is already strongly disturbed by diaphragm breakup. Directing too much energy into that very high frequency will also even reduce the on-axis HF response, as some of the energy is redistributed off-axis. In practice, this is why plain diaphragms are often prioritized over annular designs.
B&C are good in 8" for ex, the new compression driver, not so much.
I can give you another example: the phase plug of the ND3 is more modern than that of the 1460/80 in the 18S lineup, but in practice it doesn’t make a huge difference. Since the ND3 is smaller than the 1460/80 (designed to be stacked in groups of three in line array lenses), its rear chamber and overall design are different. As a result, the “older” 1460/80 extends lower with less distortion. For our applications, we therefore choose the 1460, whereas in line arrays—where it is crossed higher—the ND3 is preferred. I know both professionals and DIYers who have switched from the newer ND3 to the 1460/80 for this reason.
Forget the hype and take what is the more adapted to your needs, generally it also help to save money.
Edit: About patents: 90% of them are almost meaningless. They mainly exist to communication, marketing, inflate shareholder value, facilitate resale, or give lawyers grounds to attack other companies. Of course, there’s still that remaining 10% that truly matter.
For B&C I think you speak about the HEX Phase Plug :
View attachment 475051
It's a way to facilitate impedance match between path, it's very related to facilitate conception but a complex or helical phase plug could make the sound travel a longer path, causing slight viscous and thermal losses.
I made it for tweeter with the same result of a regular phase plug, it's interesting yes, but don't really change something for the end user.
For JBL it's the last ring phase plug iteration, that BMS doesn't have:
View attachment 475052View attachment 475053
In practice the diaphragm remaining the same, the H2 problem remains due to ring diaphragm lack of surface, but it's a good evolution too.
For Celestion you can look the Corrugation, it aims to create a cylinder wavefront (so not for our use case) in line array, in a way it's a derivative of HEX :
