Hi all
The "idea" goes back at least to when i worked at a TV store in the late 60's, see link. We sold these;
Zenith Circle of Sound Record Player – 1965 The Invisible Agent
Best,
Tom
The "idea" goes back at least to when i worked at a TV store in the late 60's, see link. We sold these;
Zenith Circle of Sound Record Player – 1965 The Invisible Agent
Best,
Tom
Varied the distance of the reflector from the driver. Here's data from around the listening axis.
70°, 80°, 90° without reflector:
70°, 80°, 90° with reflector:
70°, 80°, 90° with reflector, increased distance by 10mm:
70°, 80°, 90° with reflector, decreased distance so the reflector tip is about 5mm from the driver's cone:
Last graph shows the lowest variation. Not too shabby.
70°, 80°, 90° without reflector:
An externally hosted image should be here but it was not working when we last tested it.
70°, 80°, 90° with reflector:
An externally hosted image should be here but it was not working when we last tested it.
70°, 80°, 90° with reflector, increased distance by 10mm:
An externally hosted image should be here but it was not working when we last tested it.
70°, 80°, 90° with reflector, decreased distance so the reflector tip is about 5mm from the driver's cone:
An externally hosted image should be here but it was not working when we last tested it.
Last graph shows the lowest variation. Not too shabby.
I would agree that narrow vertical directivity is a virtue if well controlled, but a wide horizontal directivity is a disaster IMO. So its the width thats a problem in my mind, not the vertical height.
B&O took out a limited time exclusive license on this. They didn't buy it. When it ran out they did not renew and no one else has taken it up. As to its commercial success for B&O, thats kind of beside the point even if it is true.
Earl, could you please elaborate on this ? What is the problem with wide dispersion in your opinion ?
Oliver
Now that is a receipt for desaster 🙂 I left out the "why" question in my initial post to this thread on purpose.
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You don't look old enough 😀
@ markus76
Interesting tests you did. I'm wondering though what the graphs might look like if you made the cone larger, and/or also curved ?
Also with much smaller supports ?
I was hoping other would contribute too 🙂
The supports are acoustically small when viewed from the drivers perspective. It's just cardboard.
Yes sure but what is the downside if the listening window and the power response is smooth.
Fact- ALT has made Bang & Olufsen a highly profitable company through a recession. Its specced in many top brand cars. SAW sold the ALT patents to Bang & Olufsen and Sausalito Audio retained the rights to develop certain products with ALT. A huge success story, but I guess thats beside the point, right?
I think Marcus handled this one to my satisfaction.
Diuffraction in and of itself is a negative thing regardless of the listening window and power response. Diffraction in nonminimum phase and always audible at some SPL level, completely independent of the response of the system in any other regard. Very often the diffraction effects are so small in the frequency domain as to be hardly even noticable, but that does not imply that they are not audible, because it is primarily a time domain aberation. My obsession with minimizing diffraction in all its forms has paid me back big dividends in sound quality. However, there is only scant published supporting data in this regard (basically all our own), but no data that says that its not true.
To keep things on topic: is there a preferable design for such a reflector that minimizes time domain aberrations (at least for the listening window)?
Diffraction is one reason this sort of set up might be disappointing. Another is that the acoustic loading on the cone will be frequency dependant as it forms a sort of truncated 360 degree horn together with the reflector.
see Markus - there is the answer to Your question:
so the philosophical answer given by Doctor of Philosophy Himself is: "the pattern of early reflections should be clearer" 😉
there are certainly some blauertian papers corroborating this, You can surely easily find them 😉
so "facts are beside the point"? impressively philosophical approach to facts, quite Hegelian I would say, but what are the facts?
Fontana in Hobby HiFi 5/2001
Metronom in Hobby HiFi 3/2011
(both in German only)
Rudolf
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