Do you like AMT tweeters?

[Mort]

Ribbon with a wave form. Is that common?

 

[Frunse]

Ribbon with a wave form. Is that common?

There are some out i guess, i have that one laying around:

https://www.soundimports.eu/de/fountek-neocd35h.html

 

[Arindal]

I want to test this kind of Box:

Very very promising design so far. If it works, or has flaws which cannot be corrected, only a prototype and extended listening sessions can tell.

 

[DavidMcRoy]

Neither is the case with the majority of AMTs. You can EQ them to perfectly identical anechoic response and keep them well under heir threshold of producing audible distortion, they nevertheless can sound very very different. As they show no tendencies for resonance and compression issues as well as breakup (which is IMHO the main reason they in general tend to sound non-fatiguing and detail-resolving alike), it leaves basically two explanations for the very different sound:

directivity - although they do not have diaphragms following a pistonic movement concept, they nevertheless produce a pretty perfect even wavefront of rectangular pattern. As a matter of consequence, directivity pattern is highly dependent on diaphragm geometry and frequency. The transition between broad dispersion at lower frequencies thanks to diffraction and increasing tendency to narrow dispersion, is pretty suddenly, pretty angle-dependent and in most cases (as most of them are not quadratical), differing for vertical and horizontal behavior. In my understanding the reason why it is so difficult to design proper waveguides affecting both dimensions.

even response over a listening window - it is more or less a consequence of the same phenomenon. The closer you get to the frequency they start to narrow down dispersion, the response at angles being inside the window of even wavefront´ and those outside tend. to drift away forming pretty funny pattern. At this or that frequency, your listening window might touch this or that window of such behavior, resulting in pretty much unpredictable consequences for the perceived response.

As most of AMTs are tweeters with a more of less standard frequency range, their diaphragm dimensions vary between horizontal and vertical, but are tending to be bigger than comparable domes, you have pretty much all of the aforementioned effects well within the frequency bands defining sound quality.

To give you a visual impression of what I mean, this is a bunch or FR graphs at different angles (vertical) for one of the rather high AMTs:

View attachment 456035
Don´t get me wrong - this is IMHO one of the best AMT on the market in terms of sound quality. It is just an illustration of what any loudspeaker designer has to take into consideration, and in many cases this will lead to non-standards methods of optimizing tonal balance and combining it with a midrange.

Tonal issues differing over a narrow listening or measuring window might be also the reason why AMTs are attributed different sound characteristics. I never really experienced one sounding harsh or hard. If such impression occurred, it could be tracked down in most of cases to a narrow frequency band being overrepresented, so highlighting events in the recording which cause harshness. A sharp notch filter might fix this.

Thanks for an excellent treatise on the subject. Unaccustomed to listening in any other than an acoustically rather dead environment, nor outside midfield distances, I had overlooked the role dispersion can play.

 

[Ktacos]

Do I like them? Not really.

They seem to be in style mainly because they look different but I just don't see performance that makes them worth while. We have plenty of spins on AMT's and it seem that distortion tends to be higher than a cheap dome and dispersion isn't really any better. For whatever reason I assumed they might be wider at higher frequencies but seems like they don't beat physics and beam all the same. I'd argue most of the complaints about domes here are remedied by just buying a better dome. ~$50 usd gets you one of the best 1" domes out there, and you can waveguide it if you want. Seems most of the 'good' AMT's cost quite a bit more, some fall into the silly high "what are we even doing here" category of driver pricing like Mundorf.

Just seems like yet another driver tech that offers more marketing buzzwords than it does actual performance.

 

[egellings]

The tweeter that blew me away once was the totally impractical Hill Plasmatronic tweeter. This ionized a little ball of helium gas and then an electric current representing the music signal was passed though the ball causing it to pulsate with the music signal. Most transparent sound I ever heard, figuratively and literally.

 

[2020]

Do I like them? Not really.

They seem to be in style mainly because they look different but I just don't see performance that makes them worth while. We have plenty of spins on AMT's and it seem that distortion tends to be higher than a cheap dome and dispersion isn't really any better. For whatever reason I assumed they might be wider at higher frequencies but seems like they don't beat physics and beam all the same. I'd argue most of the complaints about domes here are remedied by just buying a better dome. ~$50 usd gets you one of the best 1" domes out there, and you can waveguide it if you want. Seems most of the 'good' AMT's cost quite a bit more, some fall into the silly high "what are we even doing here" category of driver pricing like Mundorf.

Just seems like yet another driver tech that offers more marketing buzzwords than it does actual performance.

Don't they generate planar waveforms?

Microsoft Copilot AI:

Wavefront and propagation mechanics (short physics)

- A small pistonic radiator approximates a point or small-area source; at wavelengths similar to or shorter than its radiating diameter it becomes increasingly directional, creating a curved wavefront and stronger directivity (narrower beam). Planar panels act more like an extended, nearly uniform piston across their surface at higher frequencies, so the radiated wavefront is flatter and dispersion is smoother across angles.
- The “near field / Fresnel zone” around a source matters: a larger planar surface produces a flatter wavefront sooner with distance than a small dome, so the listening zone where the wavefront behaves evenly can be larger for planars of a given size.

 

[Lars Risbo]

no, narrower dispersion due to their large width and height. the planar source effect is only when the distance is small compare to the source dimensions. had no relevance at listening distance. AI got it wrong again.

 

[Salt]

no, narrower dispersion due to their large width and height. the planar source effect is only when the distance is small compare to the source dimensions. had no relevance at listening distance. AI got it wrong again.

That is, looking at was is available today, not quite right. You can select AMT with different horizontal and vertical size, to adjust beaming to your needs.
I just scrolled through Mundorf's versions and that is a lot, besides all other offers globally.

 

[mhardy6647]

The tweeter that blew me away once was the totally impractical Hill Plasmatronic tweeter. This ionized a little ball of helium gas and then an electric current representing the music signal was passed though the ball causing it to pulsate with the music signal. Most transparent sound I ever heard, figuratively and literally.

The Plasmatronic used (almost) full-range plasma transducers. The use of helium rather than room air as the matrix (so to speak) for plasma generation was fairly revolutionary.
The famous Ionovac (air) plasma tweeter was -- perhaps -- the most successful plasma driver, sold by several different companies.
I think of Electrovoice's T3500 variant... but that's mostly because I am a dyed-in-the-wool EV fanboi.

Everybody's favorite audioiconoclast engineer*, Nelson Pass, famously was foolin' around with prototype air plasma loudspeakers many years back... and ended up in the hospital due to over-imbibing ozone.

a very young Nelson Pass, from Stereophile...

______________
*well... OK... everybody who's not at ASR...

 

[dfuller]

Do I like them? Not really.

They seem to be in style mainly because they look different but I just don't see performance that makes them worth while. We have plenty of spins on AMT's and it seem that distortion tends to be higher than a cheap dome and dispersion isn't really any better. For whatever reason I assumed they might be wider at higher frequencies but seems like they don't beat physics and beam all the same. I'd argue most of the complaints about domes here are remedied by just buying a better dome. ~$50 usd gets you one of the best 1" domes out there, and you can waveguide it if you want. Seems most of the 'good' AMT's cost quite a bit more, some fall into the silly high "what are we even doing here" category of driver pricing like Mundorf.

Just seems like yet another driver tech that offers more marketing buzzwords than it does actual performance.

This is my experience too. Every single one I've heard just doesn't sound good - the distortion is seemingly quite high compared to good quality domes (which, as you note, need not be particularly expensive...), and the dispersion behavior is all over the place. Moreover they don't seem to have any meaningful advantage as a tradeoff - they're not meaningfully more sensitive, they can't cross lower, they don't have better frequency response behavior, they don't have better distortion behavior. The only thing that you could maybe give them is they're less prone to compression. But that's it, and not often a meaningful problem for tweeters most of the time.

Adam is particularly infamous in my book for making spectacularly awful sounding AMTs - we have a few where I work and they sound... poor. Sandpapery and sharp in the treble, I'd say.

no, narrower dispersion due to their large width and height. the planar source effect is only when the distance is small compare to the source dimensions. had no relevance at listening distance. AI got it wrong again.

Shocker.

 

[posvibes]

I have a built in prejudicial preconception as to how AMT's will sound, just from the look of them, I always think they are going to sound piercing or tinny or bright.

Lately I have been playing my AdamTv5's with their version of AMT called ART (I think), and I have been playing them without the recommended EQ that Amir came up with when he tested them, because I cannot get Windows 11/RealTek to play nice with Peace/APO to equalize the top end.

But using the boundary switches I have taken 2db of the tweeters and I suspect that I have suffered a further degradation of my HF hearing capacity and am listening to them from ca. 3m away in a domestic setting.

I think the wave guide is helping a bit, but there is subjectively speaking still a sparkle to them. Probably still due to that 5Khz leap they have. With the EQ settings from Amir's review from various posters (and I tried them all, Lord I miss Windows 10) they were really wonderful and the tweeter integration was first rate.

 

[2020]

no, narrower dispersion due to their large width and height. the planar source effect is only when the distance is small compare to the source dimensions. had no relevance at listening distance. AI got it wrong again.

Well AI isn't just LLMs anymore. It sourced this website for its takeaway https://audiohorn.net/sciences/wavefront-propagation/

 

[Rick63]

I'm about to find out as I have ordered a pair of Hedd Type 07 A-Core monitors from Sweetwater.

I've never owned or heard AMT/ribbon tweeters and for the last few years I've contemplated a pair of Adam A7Vs, but I've read too many people saying their tweeter was bright and harsh and that scared me off.

Then recently the new Hedd A-Cores were released, and based on the limited reviews and comments from people who've heard them that say they're much smoother and non-fatuiging to listen to, I decided to try them out. I also like that the Hedd is all analog with no DSP, and though it matters less than sound I like their looks way more. Honestly I'm more concerned about their hiss levels than whether I'll like the tweeter. My listening position is exactly 2 meters from my monitors and I'm hoping I won't hear any from there. I own a pair of Dynaudio BM5 MKIIIs and they have low hiss. I can't hear it at all from my MLP and have to be within 6" or less to hear it.

I can't wait to try them out and I'm fairly confident I'll like them. If not I'll simply return them.

@Amir, what were your findings regarding hiss on the A-Core 05 you recently tested? My decision to try the 07s was also particularly due to your review of those. And also in general do like AMT tweeters?

 

[Lars Risbo]

Well AI isn't just LLMs anymore. It sourced this website for its takeaway https://audiohorn.net/sciences/wavefront-propagation/

the web resource looks very solid but more applicable to PA line arrays etc. not so much for tweeters in a hifi system where the wavefront get spherical in the typical listening position no matter what type of tweeter you have.

 

[ThatSoundsGood]

That is, looking at was is available today, not quite right. You can select AMT with different horizontal and vertical size, to adjust beaming to your needs.
I just scrolled through Mundorf's versions and that is a lot, besides all other offers globally.

This is exactly what I did for my living room speakers. They ended up being the flattest response, best integrated speakers I have designed. The Mundorf AMT's are on a different level than any other I have heard or worked with. In this situation, the restricted vertical axis got me somewhere a dome couldn't.

 

[JohnnyAudio]

This is exactly what I did for my living room speakers. They ended up being the flattest response, best integrated speakers I have designed. The Mundorf AMT's are on a different level than any other I have heard or worked with. In this situation, the restricted vertical axis got me somewhere a dome couldn't.

Dear SoundsGood,

Are the Mundorf AMT's much better/ different than the ESS AMT's? I have 6 ESS and like them but there is an edge to them that I wish was better.

 

[Salt]

Dear SoundsGood,

Are the Mundorf AMT's much better/ different than the ESS AMT's? I have 6 ESS and like them but there is an edge to them that I wish was better.

What do you mean by edge?

 

[Arindal]

They seem to be in style mainly because they look different but I just don't see performance that makes them worth while.

Many tweeters (like planar magnetostats) have a different look as well and are not in style, that does not really explain why AMTs are popular.

Regarding performance advantages, they are not as easily visible in the data. Transparency and subjective clarity are much easier to achieve with an AMT, while it offers an inherently higher level of directivity in the upper frequency bands compared to a small dome, and a very low level of diffraction/cancellation issues within the listening window.

We have plenty of spins on AMT's and it seem that distortion tends to be higher than a cheap dome and dispersion isn't really any better.

Distortion is only a problem with AMTs which are too small or the crossover freq is overly low. If sized and driven properly, they can be exceptionally clean.

Dispersion I would rather see as an advantage. It might be less broad and less homogeneous than a dome, but it is inherently more focussed in the upper bands, particularly vertically, which brings a lot of advantages in the room.

Seems most of the 'good' AMT's cost quite a bit more, some fall into the silly high "what are we even doing here" category of driver pricing like Mundorf.

Not all good drivers are available for DIY, and not all DIY prices translate to similarly inflated OEM prices. There are pretty capable AMTs for 50 bucks on the DIY market, and probably manufacturers like ADAM are paying significantly less per unit as they buy in large quantities.

I have a built in prejudicial preconception as to how AMT's will sound, just from the look of them, I always think they are going to sound piercing or tinny or bright.

Indeed a prejudice, and I have a good idea where it might come from: speaker designers not properly implementing the typical directivity behavior of an AMT, i.e. either letting it blow out too much of lower treble energy into the room compared to the midrange cone, or trying to correct the decreasing off-axis level in higher frequency bands by in creasing it on axis (or both).

A textbook implementation of an AMT will rather sound the opposite, i.e. lacking a bit of energy in the highest audible bands in the room.

 

[Audionaut]

As is so often the case, there are far too many generalizations here.
There are good and bad dome tweeters, and there are bad and excellent AMT tweeters.
In both cases, the problem lies not with the principle, but with the technical implementation.
An AMT has great potential for technical excellence, but in some implementations it fails due to a lack of experience and technical implementation.
The diaphragm, which is the heart of the AMT, must be folded and installed very carefully.
Unfortunately, this results in very large variations in quality at some companies.
I have not yet encountered any outliers at Mundorf, but I have at other companies.