[JohnR]

Was just thinking about the vertical dispersion of the available (planar) dipole drivers and wondered if the "foam wedge" concept a la Raal might be worth exploring. For the long-ish drivers like Neo10 and AMTPRO-4 it might improve the vertical dispersion at high frequencies and/or make it easier to mate with other drivers.

As far as I can tell, the foam wedge absorbs more at higher frequencies and less at lower frequencies, so the effective length of the driver is reduced at high frequencies, improving vertical dispersion. I found these measurements on the Raal 140-15D driver: http://www.audioexcite.com/?page_id=2523 (scroll down to Vertical frequency measurements )

Has anyone tried something like this with another driver?

[FullRangeMan]

In my country many pro speakers manufacturers apply a 5mm felt layer as outside finish, which had the same effect this foam and very inexpensive, as the cabinet dont need painting or leather finish.
2 cents.

[JohnR]

Hi Gustavo, I think we're talking about something different. The foam I am speaking of actually goes in front of the driver element, not on the baffle around it.

[FullRangeMan]

Yes this is correct. The felt help to soft the mids and treble.
I wonder what effect this foam would do?

[matevana]

Dr Earl Geddes has spent a lot of time developing various densities and shapes of open cell foam to control directivity with his CD drivers. There's some interesting stuff on his commercial loudspeaker site as well as a short white paper here: http://www.gedlee.com/downloads/Philosophy.pdf

I haven't experimented with it but it occurs to me if you wanted to try out the concept you might start with the foam from a brush like this...

[Wind Chaser]

Some manufacturer's have used foam as a speakers grill, which would imply that it is acoustically fairly transparent, so I have my doubts as to whether it could make much of a difference? 

[InfernoSTi]

Dr Earl Geddes has spent a lot of time developing various densities and shapes of open cell foam to control directivity with his CD drivers. There's some interesting stuff on his commercial loudspeaker site as well as a short white paper here: http://www.gedlee.com/downloads/Philosophy.pdf

Very interesting read…thank you for posting.

John

[JLM]

Yes shorter ribbons, like those found on Adam's professional monitors, would be more desirable but I have my doubts about the effectiveness of foam or of smucking up a nice/expensive driver that someone has apparently thought long and hard about with hardware supplies.