Do you like AMT tweeters?

[Killingbeans]

Apart from this: My AMT delivers up to 50KHz.

That's not an apart. It's the reason why the impulse response looks more pretty.

The frequency and time domains are interchangeable through math. If two drivers have exactly the same frequency + phase response, they'll also have exactly the same impulse response.

Wider bandwidth will always make the response to "illegal" signals look more impressive, but our hearing doesn't really care in the end.

It doesn't really make sense to talk about the "speed" of a tweeter, and there's far greater issuses to worry about.

Here's for instance an article from Purifi explaining why they used an AMT in their midwoofer demonstration kits, but is opting for a boring old dome tweeter as the basis for their own SOTA tweeter design:

The PURIFI Tweeter Project - Part 1

A Short Story of a Long Multi-Disciplinary R&D Effort

purifi-audio.com

 

[Few]

Late to the party, but I wanted to thank Killingbeans for the Purifi link. That was the most useful thing I’ve read in a long time.
Few

 

[Ian Knight]

That's not an apart. It's the reason why the impulse response looks more pretty.

The frequency and time domains are interchangeable through math. If two drivers have exactly the same frequency + phase response, they'll also have exactly the same impulse response.

Wider bandwidth will always make the response to "illegal" signals look more impressive, but our hearing doesn't really care in the end.

It doesn't really make sense to talk about the "speed" of a tweeter, and there's far greater issuses to worry about.

Here's for instance an article from Purifi explaining why they used an AMT in their midwoofer demonstration kits, but is opting for a boring old dome tweeter as the basis for their own SOTA tweeter design:

The PURIFI Tweeter Project - Part 1

A Short Story of a Long Multi-Disciplinary R&D Effort

purifi-audio.com

Full circle?... A dome tweeter with a catenary profile?... Invented I believe by Audax. so what's new?.

 

[Killingbeans]

If it ain't broke, don't fix it

 

[617]

I do wonder what the limits of HF dispersion are. Purely pistonic drivers will always have a directivity which gradually narrows, which is why we have things like ring radiators and BMRs which use some kind of non-pistonic motion to effectively turn the diaphragm into a series of smaller radiators at high frequencies, increasing dispersion at the top octave.

It is interesting that purifi is opting for an aluminum dome. Their argument that the dome is a non-esoteric material, easy to fabricate is very sensible (although 'sensible' is not necessarily a requirement for cutting edge transducer marketing) but aluminum wants to move pistonically, having a lower breakup frequency than other materials. If one of the design parameters is 'plays as loud as our crazy woofer', then that drives diaphragm size up, breakup point down, and top end dispersion with it.

I think the unstated direction purifi are going with is that the waveguide is integral to the design, and that their definition of 'top octave dispersion' is somewhat lower than the theoretical ideal - 10kHz instead of 20. Given the absorbance of rooms to these very high frequencies, and their low amplitude in most recordings, I think maximizing power and dispersion up to around 7-10k is a great approach if it comes at the expense of 10-20k.

I could of course be totally wrong, and these guys have basically done the impossible with their woofers, so who knows what this tweeter will look like.

 

[Few]

which is why we have things like ring radiators and BMRs which use some kind of non-pistonic motion to effectively turn the diaphragm into a series of smaller radiators at high frequencies, increasing dispersion at the top octave.

The Purifi calculations show ring radiators having less uniform directivity, with deep nulls off axis. The rings don't become effectively smaller at high frequency, although it would be grand if they did. And if aluminum “wants to move pistonically,” wouldn’t that move the break-up frequency higher, not lower? Maybe I’m misunderstanding your intent. I do agree they seem to love waveguides and “ coherers” (their word).

Strange that their white papers extol the virtues of domes and then they came out with an AMT. Maybe a future blog post will explain.

 

[617]

The Purifi calculations show ring radiators having less uniform directivity, with deep nulls off axis. The rings don't become effectively smaller at high frequency, although it would be grand if they did. And if aluminum “wants to move pistonically,” wouldn’t that move the break-up frequency higher, not lower? Maybe I’m misunderstanding your intent. I do agree they seem to love waveguides and “ coherers” (their word).

Strange that their white papers extol the virtues of domes and then they came out with an AMT. Maybe a future blog post will explain.

Aluminum, compared to denser and more esoteric dome materials, resonates at a lower frequency. It is a perfectly usable material for a dome tweeter and has been used by Scanspeak, sb acoustics and many others for a long time, but one would expect purifi to look to 'high end' materials such as Be or Ceramics or carbon fiber or whatever. I think the advantage of aluminum is that it is relatively easy to fabricate in a precise and repeatable way, so you can get your sinulated dome geometry to match your production units really well.

Aluminum 'wants to move pistonically' in the sense that it breaks up very suddenly and has sharp resonances which are within the audible band sometimes (esoteric materials have the same issue, but at say 30-50k). Soft materials, ring radiators and bmrs either intentionally or not have breakup modes which increase dispersion, albeit in a chaotic and inconsistent way, with the exception of the BMR, which breaks up according to small weights in the diaphragm.

Purifi is a very audiophilish engineering effort. I would argue the BMR is a far more important and interesting innovation than the purifi woofer, but one is made for high end speakers and one is only used in them incidentally. It will be very interesting to see what they get out our old friend the dome tweeter.

 

[SCR]

I think they are a great choice to complement the Bose 901. My AMTs have a passive crossover at12db/5kHz in front and the 901/AMTs are Dirac controlled.

 

[OldHvyMec]

Yes! I like a lot of ribbons too. Mids and tweeters. Strathearns, AC, and now GSR. GSR has a good lineup of ribbons. Arum Cantus has a really nice AST.
I like the G1. I use the G2SI, G1, and the AST/25120-8. It's hard to beat the G1 though, you can buy the replacement ribbon for most of the ACs.
Good drivers.

Aurum Cantus AST25120 Aero Striction Tweeter 8 Ohm​

Regards

 

[Killingbeans]

Strange that their white papers extol the virtues of domes and then they came out with an AMT. Maybe a future blog post will explain.

Huh? I must have missed that. Do you have a link to the final design?

All I can find is pictures of the Mundorf ATM they used for the old SPK4 demonstration design.

 

[Overseas]

I love my Piega Classic 3.0, even compared to Focal Aria 906. Dunno shit about technical data, but the sound resembles big standfloors in my perception.

 

[Few]

Here is one reference to the new speaker; I’ve seen others as well. Even The Audiophiliac has a review: https://www.youtube.com/channel/UC9wBmplRUhaCi-aNrkfgeTg

Few

 

[Killingbeans]

Here is one reference to the new speaker; I’ve seen others as well.

From the link:

And probably the most unique aspect of the Clarity 6.2 design was the use of a custom-designed, high-output Air Motion Transformer (AMT) tweeter, crafted for Radiant Acoustics by DALI.

So, DALI not Purifi.

 

[Few]

The title is "Peter Lyngdorf and Purifi Audio Announce New Radiant Acoustics Speaker Brand." Since Lyngdorf is a cofounder of Purifi, and Lars Risbo is the chief technology officer at Purifi, and they're the primary designers for the Radiant speaker, it sounds to me like the Purifi crew has formed a separate branch to handle the design and manufacture of complete speakers (as opposed to the components and amps made by Purifi).

"...custom-designed, high-output Air Motion Transformer (AMT) tweeter, crafted for Radiant Acoustics by DALI"
So DALI makes the AMT tweeter used in the Radiant (off-shoot of Purifi) speaker. Dali does not make the speaker.

I did find buried in the text a comment suggesting Purifi is still developing a dome tweeter. I have no idea if that will appear in a future Radiant Acoustics product, matched with Purifi woofers and passive radiators, but it would be a logical outcome.

Few

 

[Lars Risbo]

hi Few,

The only piece of the Clarity 6.2 that I or PURIFi have been designing is the waveguide. This was a paid consultancy job. The box design is done by Peter himself and the acoustic design including xover is done by Jens Schoeneman Paul.

We are about to release our first tweeter so stay tuned.

Cheers,

Lars

 

[Few]

Gotcha. Thanks for straightening me out. I'll look forward to the tweeter!
Few