The BLD has a really well controlled directivity and is virtually diffraction free at least up to 12-13 kHz (where the CD takes it over anyway). The only downside I see at the moment is that it's somewhat ugly. I'll try a rectangular/baffle version as well. There's still plenty of what to try out on that design.
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Okay - here we go. Some measurements:
1) BLD - Horizontal Polars - 0 - 70
2) BLD - Vertical Polars - 0 - 70
3) KVAR - Horizontal Polars - 0 - 70
4) KVAR - Vertical Polars - 0 -70
I tried to keep the measurements as consistent as possible (i.e., same distance - approximately 0.55m, same gate time (4ms), same driver, same mic location, etc.)
The BLD was printed as one piece
The KVAR was printed in two pieces, and just merely taped together.
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Harman wrote some software that iterated through thousands of different waveguide profiles, to find the optimal shape. When it finished, it ummm...
It looks like an anus
I don't think they ever ended up selling it in any designs.
Patent: https://patents.google.com/patent/US20200077180A1/en
There's even one with a phase plug that looks like... Well, umm, I think we all know
Attachments
A possible M2 successor.Harman wrote some software that iterated through thousands of different waveguide profiles, to find the optimal shape. When it finished, it ummm...
It looks like an anus
I don't think they ever ended up selling it in any designs.
Patent: https://patents.google.com/patent/US20200077180A1/en
There's even one with a phase plug that looks like... Well, umm, I think we all know
That phase plug is doing too much, haha.
If anyone is wondering whats the difference I say the basic circular ST260 performance is great, been listening to one for few months. I would not hesitate use any of these variations and would suggest anyone to select by the looks (and coverage angle). Perhaps there is small audible difference, but these all seem to be pretty much problem free and thus as good as they need be, better than 99.9% out there. Just select directivity that suits the application and fits together with rest of the system.
For context I'm using ST260 in a home hifi three way system with 8" mid in minimal 21cm baffle, passive cardioid. Crossover around 1.1kHz seems to work nicely. I think ST260 should fit 20-30cm wide baffles / drivers but I have not simulated, measured or listened other than the system I have. Subjectively it is better sounding than Faitalpro STH100 and RCF HF100 commercial waveguides I have for same application. I used those freestanding as well on the same system. There is possibility I had misconfiguration on any of the setups and have not done AB tests. Assesment is based on factoids that the system is sounding and measuring better than ever, measurements are as good as they get but I have no idea what the absolute sound quality as I don't have much anything to compare to. Definitely happy for the performance and I'm not able to identify problems due to the waveguides. Hopefully enough context
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Approaching design as a problem solving endeavor, I can only imagine making the waveguide white would help hide the sphincter-like attributes of such a series of convolutions. Making the phase plug a gold or copper color might be the best choice after that. I dunno, just trying to see how to troubleshoot the elephant in the room with such a design.
Honey I bought some new speakers!
I think there weren't many other options how could it end up (I mean the Samsung optimization exercise), given their constraints on the profile curves - the way they parametrized the splines. It was an easy and straightforward approach but inevitably leading to a shape like this. Employ e.g. the OSSE curve and it will look different - see the ST260. What I find actually intereting on their results is that it worked.
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