Ess Air motion AMT1 Meassurements

[c2cthomas]

So the AMT is bipolar? I assumed it was dipolar. I just bought a pair of the new ones and looking at the diaphragm it looks like it must move "side to side" in a compressing accordian sort of way? I guess I can see how this bipolar and not dipolar. I had planned on using them for an open baffle, but now I'm wondering how it will work since the other drivers are naturally dipolar on an open baffle?

http://en.wikipedia.org/wiki/Air_Motion_Transformer = dipole

Go for it

 

[augerpro]

Hmmm, the author uses the term dipolar but the mechanism described strikes me as bipolar. To be dipolar the motion on both sides would have to be equal and OPPOSITE. But the description appears to me to be equal and the same. When the air is being compressed on one side it is also being compressed on the other, and vice versa.

Of course I had planned on using BW3 filters so actually, it would not matter as the AMT would end up 90 degees out phase versus the mid either way. No LR filters for OB though.

 

[Keith Taylor]

Augerpro, There is no doubt whatever that the Heil is a dipole. When alternate pleats come together veiwed from the front air is expelled to create a compression. While this is happening alternate pleats on the rear side are moving apart to create a rarefaction. The contribution of the individual pleats sum in phase to increase the efficiency of the device.
Keith Taylor

 

[augerpro]

Thanks Keith. See that is how I originally thought it worked, kind of like a BG planar. But looking at the patent application I think we are both mistaken. The membrane doesn't appear to move front to back like a normal planar, but instead accordian style. If it moves accordian style compression or rarefaction occurs at the same time on both sides. I don't don't know, I'm still not convinced it's dipole. It does move like and accordian correct?

 

[Neil Davis]

Thanks Keith. See that is how I originally thought it worked, kind of like a BG planar. But looking at the patent application I think we are both mistaken. The membrane doesn't appear to move front to back like a normal planar, but instead accordian style. If it moves accordian style compression or rarefaction occurs at the same time on both sides. I don't don't know, I'm still not convinced it's dipole. It does move like and accordian correct?

The accordian analogy is a poor one, because the distance from edge to edge remains constant. As Keith noted, the pleats either move together and push air out or else they move away from each other and suck air in. The opposite happens on the other side of the diaphragm: while one side is pushing out air, the other side is pulling it in. See the first drawing in the link below:

http://home.comcast.net/~neilandbarbaradavis/DIYHeil/ART.pdf

 

[augerpro]

I think I understand now. The (new?) Loudspeaker book from Newell and Holland had a pretty good diagram of the diaphragm under +/- current that helped. I suppose as I have them I could have just measured them and see for myself