Acoustic reflectors and piston drivers

[Bill poster]

I am guessing the B&O lens has less issues with room reflections, thats the way its designed

[Tom Danley]

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

[markus76]

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.

[gedlee]

Originally Posted by weltersys

The Soundsphere suffers from the same problem that the B&O / Sausalito lens has, wide horizontal dispersion, but extremely narrow vertical dispersion.

Of course, David Moulton seems to think that problem is a virtue .

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.

[gedlee]

Originally Posted by markus76

What are the problems?

Too much diffraction.

[gedlee]

Originally Posted by Bill poster

Eh? Are we talking about the same thing? B&O bought the Patent(s) and split the Rights of usage; its been instrumental in turning Bang & Olufsen's fortunes around.

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.

[6.283]

Originally Posted by gedlee

...but a wide horizontal directivity is a disaster IMO. So its the width thats a problem in my mind, not the vertical height.

Earl, could you please elaborate on this ? What is the problem with wide dispersion in your opinion ?

Oliver

[markus76]

Originally Posted by 6.283

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.

[Zero D]

Tom Danley

The "idea" goes back at least to when i worked at a TV store in the late 60's

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 ?

[6.283]

Originally Posted by markus76

Now that is a receipt for desaster

I don't think so ! It's a seriously meant question.