Beyond the Ariel

[gainphile]

Hi Mige,

Your measurements looks very interesting.

How do you attach the waveguides to the AMT? And would something like Neo PDR3 work?

Any pics would be much appreciated

Would mounting something like this back to back reasonable?

[mige0]

plug your AMT , electrostat or NEO8 magnetostat (or any other planar speaker suitable for dipole operation) put a bottom and a top plate and you are ready for lift off



Michael

[soongsc]

Originally posted by mige0








plug your AMT , electrostat or NEO8 magnetostat (or any other planar speaker suitable for dipole operation) put a bottom and a top plate and you are ready for lift off



Michael

I knew that would come up sooner or later.

[Rudolf]

Originally posted by mige0
plug your AMT , electrostat or NEO8 magnetostat (or any other planar speaker suitable for dipole operation) put a bottom and a top plate and you are ready for lift off

Somewhere in the waveguide thread Earl Geddes recommends a torus with an OS profile - if he would ever do a dipole.

[Jmmlc]

Hello Mikael,

as I told you using such quasicylindrical waves horn result in some diffraction at the horizontal edges of the mouth.

Eventually in order to reduce the effect of those diffraction you may use the idea expressed by Thend (a French audiophile having a strong education in acoustics):

http://thend.chez-alice.fr/Audio/Media/transparent.gif

(the horn is seen in transparency)

http://thend.chez-alice.fr/Audio/2_voies_de_course.html

The idea is taken from the Northrop Grumman Stealth bomber,

http://en.wikipedia.org/wiki/B-2_Spirit

Best regards rfom Paris, France

Jean-Michel Le Cléac'h

Originally posted by mige0
plug your AMT , electrostat or NEO8 magnetostat (or any other planar speaker suitable for dipole operation) put a bottom and a top plate and you are ready for lift off. Michael

[soongsc]

Originally posted by Jmmlc
Hello Mikael,

as I told you using such quasicylindrical waves horn result in some diffraction at the horizontal edges of the mouth.

Eventually in order to reduce the effect of those diffraction you may use the idea expressed by Thend (a French audiophile having a strong education in acoustics):

http://thend.chez-alice.fr/Audio/Media/transparent.gif

(the horn is seen in transparency)

http://thend.chez-alice.fr/Audio/2_voies_de_course.html

The idea is taken from the Northrop Grumman Stealth bomber,

http://en.wikipedia.org/wiki/B-2_Spirit

Best regards rfom Paris, France

Jean-Michel Le Cléac'h

Hello Jean-Michel ,
That analogy is totally different from what stealth aircraft shape indends, and is misleading. Although such shape will reduce the diffraction as intended, it really more closly resembles baffle edge diffraction reduction design mthods and theory.

The stealth aircraft shape is to concentrate reflection and diffraction in a different direction so that waves will not return to the radar.

[gedlee]

Originally posted by Rudolf


Somewhere in the waveguide thread Earl Geddes recommends a torus with an OS profile - if he would ever do a dipole.

A Torus, yes, but its not OS profile. A torus is a seperable coordinate and so it will have an exact solution. In all other cases that I have looked at, when this occurs, the diffraction is minimum. This is exactly why I would look at a torus for an OB if I were to do one.

Get an old truck inner-tube and use it to make a mold!!

Originally posted by soongsc

The stealth aircraft shape is to concentrate reflection and diffraction in a different direction so that waves will not return to the radar.

Soongsc

Its both actually. The diffraction and reflection are reduced AND they are sent in non-return directions. Either effect alone is not nearly as effective.

[soongsc]

Well, yeah, I guess you're right. But it's not self canceling as one picture shows.

[cuibono]

Will there be substantial vertical lobing from using a 100mm source and an even larger horn? It seems like the distance between drivers would become significant. Or do people not consider that an issue?

On the other hand, using a horn might make it easier to get the acoustic centers aligned wrt the baffle.

Michael and Jean-Michel, thanks for your work!

[mige0]

Thanks Jean-Michel !
Yes I already was thinking about that when building my prototype.
We always will have to deal with diffraction issues whatever route we take. As for the current double hemisphere horn I'm pretty happy that there are no severe irregularities I can see or hear so far – hence I take that particular issue cool.

Quick question – what you think is the deep notch at 600Hz – not that I'm concerned – just curious if this happens in standard horn as well

Originally posted by soongsc

I knew that would come up sooner or later.

I was pretty much surprised too to find out that nobody else did it any “sooner”

Originally posted by soongsc

The stealth aircraft shape is to concentrate reflection and diffraction in a different direction so that waves will not return to the radar.

We see all angels to be 90 deg on that war machine.
Put together two mirrors in the same angle and look at it from different directions – seems the explanations given fall short.
Also there is no substantial diffraction for micro wave at such macro structures.

Originally posted by cuibono
Will there be substantial vertical lobing from using a 100mm source and an even larger horn? It seems like the distance between drivers would become significant. Or do people not consider that an issue?

On the other hand, using a horn might make it easier to get the acoustic centers aligned wrt the baffle.

Michael and Jean-Michel, thanks for your work!

Vertical lobing is (pretty much) always there once you go with non coax / multi way speaker designs.
The AMT's – as any tall (with respect to wave length) planar speakers do not have very broad dispersion in the vertical direction.
So – as for me – I didn't give up too much with putting a “cylinder wave shape ” horn in front.

Originally posted by gedlee


A Torus, yes, but its not OS profile. A torus is a seperable coordinate and so it will have an exact solution. In all other cases that I have looked at, when this occurs, the diffraction is minimum. This is exactly why I would look at a torus for an OB if I were to do one.

Get an old truck inner-tube and use it to make a mold!!

You mean to put a fat donut around the speaker?
I thought the same line but came to the conclusion that adding well defined directivity give us the extra bonus of additional gain compared to just spreading diffraction over the rounding of the torus.
At some point you end up with creating some cavity anyway - and there we have to ask how to deal with – this you are especially familiar with (honk)...



Michael