Airborne AMT tweeter...

[Wolf]

From Solen:

http://www.solen.ca/pub/cms_nf_catal...au2=1&niveau3=

Certainly looks intriguing!!! Too bad it's BO'd.

And more....
http://www.solen.ca/pub/cms_nf_catal...eau3=&niveau4=

Later,
Wolf

[neildavis]

Re: Airborne AMT tweeter...

Certainly looks intriguing!!!

Looks like Hygeia:
http://www.hg-audio.com.tw/product_air_tweeter.html

I've always liked their circular ribbon driver: http://www.hg-audio.com.tw/notes/UHFS-001.html

Any one know of a source other than Solen?

[Paul Carmody]

Re: Airborne AMT tweeter...

From Solen:

http://www.solen.ca/pub/cms_nf_catal...au2=1&niveau3=

Certainly looks intriguing!!! Too bad it's BO'd.

Seems awfully inexpensive for an AMT ribbon.

[Wolf]

Re: Airborne AMT tweeter...

Why do you think I'm intrigued?? :D
I think it's due to physical size...

This would be cool to pair with a dome-mid/tweeter as a supertweeter:
http://www.hg-audio.com.tw/notes/RAT-4003.html



Later,
Wolf

[Mark65]

Re: Airborne AMT tweeter...

I think the silk dome is intriguing, 25 mm dome with a 75 mm faceplate and 721 HZ Fs? For 10 bucks??? Hmmm...


Mark

[Wolf]

Re: Airborne AMT tweeter...

I think that's the set I got to look at at Iowa in 2008. They look reasonable, and fairly solid- especially for the $$!
Wolf

[Face]

Re: Airborne AMT tweeter...

I think the silk dome is intriguing, 25 mm dome with a 75 mm faceplate and 721 HZ Fs? For 10 bucks??? Hmmm...

What about all the wobbles in it's impedance curve?

[neildavis]

Re: Airborne AMT tweeter...

From Solen:

http://www.solen.ca/pub/cms_nf_catal...au2=1&niveau3=

Certainly looks intriguing!!! Too bad it's BO'd.

Later,
Wolf

Another source for the larger version: http://meniscusaudio.com/airborne-rt4001-p-1201.html

[Taterworks]

Re: Airborne AMT tweeter...

Grr...I want the round neo planar tweeter from Hygeia's line, for a project. I wonder if an email to Solen could bring that about.

RT-1101

It looks way more legit than the Beston POS...

[spasticteapot]

Re: Airborne AMT tweeter...

These look an awful lot smaller than the old Heils, and they seem to be specific to a pretty high crossover point.

Which does raise the question:

Why not use a Neo3PDR instead?

[Jeff B.]

Re: Airborne AMT tweeter...

Another source for the larger version: http://meniscusaudio.com/airborne-rt4001-p-1201.html

I should have a sample coming my way to test soon. I will report out then.

Jeff B.

[neildavis]

Re: Airborne AMT tweeter...

These look an awful lot smaller than the old Heils, and they seem to be specific to a pretty high crossover point.

Which does raise the question:

Why not use a Neo3PDR instead?

Hard to tell for sure from the data sheet, but it looks like these are closed-back. If so, the high crossover point is mostly due to the size of the chamber.

Heils use a clever magnet structure that can result in lower distortion than planars. The big advantage for the Heil is that the magnetic field is both symmetrical and uniform: no matter where the pleats are in their movement, the magnetic field is always the same. This is what Klippel refers to as BL vs displacement. You can see how the BL remains constant in the side view of the Heil below: the pleats are moving along the x-axis, and at any point between the pole pieces the magnetic field (oriented along the y-axis) is the same.

Some planars such as the Maggies don't have a symmetrical magnet structure, and it should be obvious from the picture in the middle that the field is going to be different as the diaphragm moves. As the diaphragm moves away from the magnets, the current will cut fewer lines of magnet flux. That is, BL vs displacement is not going to be constant.

The Neo3PDR uses a symmetrical magnet structure that gives it an advantage over most of the other planars--this is shown in the picture at the bottom. However, you can see from the picture in the middle that the magnetic field for the planar is oriented along the x-axis, and that as the number of lines of magnetic flux (those curved lines in the middle picture) is still not going to be consistent across the entire diaphragm travel. The Neo3PDR magnet field is symmetical, which helps reduce distortion, but it is not completely uniform, and as a result there should be some distortion due to BL vs displacement. At least, that is how it looks from a geometric depiction of the magnet field. Maybe in a well-implemented design this distortion is negligible, but it certainly looks to me like the Heil magnet structure has an inherent advange in reducing BL vs X distortion.

So that is why I would *consider* the Heil over the Neo3PDR. Of course, if the Airborne AMT implementation is poor (such as poorly designed diaphragm materials), then the Neo3PDR would be the better choice.

[spasticteapot]

Re: Airborne AMT tweeter...

So that is why I would *consider* the Heil over the Neo3PDR. Of course, if the Airborne AMT implementation is poor (such as poorly designed diaphragm materials), then the Neo3PDR would be the better choice.

If I may, I'd point out that most Heil tweeters measure very poorly indeed. While it's ugly and somewhat cheaply made, the Neo3PDR measures very well indeed.

[neildavis]

Re: Airborne AMT tweeter...

If I may, I'd point out that most Heil tweeters measure very poorly indeed.

?
The only recent measurements I've seen were done by Zaph on those poorly build Mark & Daniel units. The only other published distortion and frequency response measurements that I know of were from ADAM (see link below) and Klang & Ton (for the ER-4). Both of these other measurements were done differently than Zaph's tests, but they were quite favorable. I would be interested in seeing other measurements--if you know of any, I'd appreciate the link. I know Dennis Murphy tested some of the older "great Heils" and did not see the frequency response anomaly that Zaph saw for the M&D units, so my inclination is to totally discount the M&D drivers.

Usually the Heil performs very well for frequencies above 1-2KHz. Below that, the distortion rises rapidly--most likely due to the "suspension" non-linearity of the diaphragm. This suspension issue corresponds to the Klippel distortion mode of "Stiffness Kms(x) versus voice coil displacement x". But above this lower range, the Heil can be a great sounding driver that, according to some sources, also measures well.

I did some listening tests a while back comparing a Heil to the PT2. It was interesting:
http://techtalk.parts-express.com/sh....php?p=1425239


AES article (ADAM)

[framus]

Re: Airborne AMT tweeter...

Hi Neil Great set of posts, as usual. I have done a couple of designs with the original AMT--the Big Hog--and it certainly measures better than that M&D disaster. It's much less even than most conventional tweeters, however, and needs a whole lotta crossover contouring. And It's very hard to mate with a conventional front-radiating woofer. And did I mention the limited vertical dispersion? Compromises, as usual. S0--have you finished any interesting projects that would motivate another D.C. DIY get-together?
Dennis