Not to get into the details of patent law, but ring radiators have been on the market continuously since JBL introduced the 075 "Bullet" tweeter in 1954, 65 years ago!
There were loads of manufacturers making them prior to CV, BMS, Eminence, Faital, and B&C.
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I understood that BMS had a patent on a certain manufacturing process which allowed them to make non-metal ring radiator diaphragms quickly, cheaply and precisely.
I never thought they had a patent on ring radiators as such but then I had a pair of 075 on my first speakers. 🙂
I never thought they had a patent on ring radiators as such but then I had a pair of 075 on my first speakers. 🙂
That's a good catch!
I would expect that a 1" wide ribbon would have similar directivity to a 1" wide tweeter. But if you look at those measurements I posted, the ribbon DOES have wider directivity.
If I had to speculate, my 'hunch' is that the narrower beamwidth is due to this:
Basically a soft dome tweeter behaves like a ring at high frequencies. This is because the tip of the dome becomes 'decoupled' from the rest of the diaphragm. We have this soft material that's trying to vibrate at 20,000 cycles per second that's clamped to the voice coil at the edge, and at high frequency, only the edge is moving.
That's great if you're putting a soft dome on a waveguide.
But if it's on a flat baffle, the two edges of the dome will generate an interference pattern, as if there were two sources seperated by an inch. (Because the dome is behaving like a ring at high frequency.)
My mind is officially blown! 🙂
Here's what that interference pattern would look like, from a 1" dome, at 15khz.
If what I just wrote makes sense, than you can see why BMS and JBL put these big conical waveguides inside their compression driver throats. It must be there to keep the two sides of the ring from interfering with each other as much as possible.
Here's what I can see, from a cursory look at Google:
1) US6320970B1 is The Big Kahuna. This is the ring radiator compression driver patent. This is the patent that prevented anyone from selling a ring radiator compression driver, without a license. BMS must have had a license, because this isn't their patent, it's Cerwin Vega's.
2) JBL must have liked this patent a lot, because they hired the inventor and he's patented a whole bunch of ring radiator tech for Harman. For instance, the dual diaphragm ring radiator: US20110085692A1
3) Eugene Czerwinski passed away, and his ring radiator patent expired when the fees weren't paid. And that opened the flood gates from Faital and B&C. Eminence jumped the gun; their ring radiator came out while the patent was still active.
I am no lawyer, but from what I can see, Czerwinski simply patented something that no one else had bothered to patent. For instance, Yamaha had a patent on ring radiators that preceded Czerwinski's patent by THIRTY years, but Yamaha's patent only covered dual voice coil ring radiators:
https://patentimages.storage.googleapis.com/b4/94/57/47b0ebfed19ca0/US3665124.pdf
The problem I have with these tests, is the levels arent absolute, at least in the comparison plots.
Comparing the Vifa D26NC55 and Neo ribbon, there is little to choose between them.
Zaph even included both plots with overlays reversed for clarity and when you compare the two different overlays, they are very close.
I should point out that I predominantly use dome tweeters, but the 'something' about ribbons, is due to a lot more than just a THD test.
Ribbons are known to be poor at lower frequencies, as are domes, perhaps less so, but still poor.
Ribbon users will often, fully aware of their low frequency failings, use them at a XO point to mitigate the THD rise.
What I think also has an impact on the sound are:
1.The entire diaphragm is driven and as a result, I postulate that they do not suffer from break up, or that the mechanism of break up is very different (whether it can be measured I dont know)
2. The ribbon is far lighter than the dome.
3.THD being generalised as higher in ribbons, probably has a lit to do with motor design, as there are no underhung, overhung coils, shorting rings or other THD reduction methods I know of. It's purely geometry, magnets and assembly precision.
4. Sensitivity and efficiency are generally higher, and though you can find 96dB dome tweeters, I've not heard one, mainly as I havent found one that looks usable enough for me to pay to hear it.
Perhaps I like efficient tweeters, and an efficient dome would enamour me?
CD/horns in general don't inspire me at all, I always feel like something is off with the EQ on the desk. But I probably haven't heard a really good CD horn combo yet.
By nature a simpler motor, and accompanying THD may be higher, than a more conventional dynamic driver.
Listening to some ribbons now, and for the last week Fountek NeoCD3.5H.
My mother usually comes round on the weekend, and this week she walked right in and said how clear everything sounded, what had I done to my speakers. Then I show her the tatty boxes with the ribbon perched on top.
"What THAT P.O.S.?", "Yes mum that P.O.S."
These are crossed about 5k.
Even with perfect 20-20k hearing, I wouldn't be too worried about tall orders of harmonics, H2 and H3 are about all I'd worry about, the latter even less. Everything else isnt audible anyway....
What I love about the ribbons, the ones I'm using at least, is the immediacy, clarity and intelligibility.
Vertical pattern control helping rather than being portrayed as an enemy, I guess does wonders in my living space.
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Yes and if you look at a 2405/2403/2404/2402 and a 2408 the only difference is the 2408 is a polymer as opposed to aluminum. The diaphragm shape and position of the voice coil are the same.
Rob🙂
^not too shabby!
102dB!!!
I especially like when I can pad down the tweeter by at least 12dB, more is better; then the tweeter is never really strained
102dB!!!
I especially like when I can pad down the tweeter by at least 12dB, more is better; then the tweeter is never really strained
So far, not a single cumulative spectral decay plot to be seen. FR graphs on their own don't mean much, especially in this age of DSP.
There’s 3rd party CSDs around for the Fountek Ribbons......very clean in their intended passband of 3khz and up.
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