The best dome tweeter design on the earth! (what would you change?!)

[mike7877]

ATC's S-Spec tweeter is the best dome tweeter

Technology | ATC Loudspeakers

atc.audio

^you need to read that first. And the bulleted list below!
(tl;dr is under the - - - - - - - - - -)

Some information about the tweeter wasn't put on that page by ATC, so I typed it below. It's stuff I learned from press releases, articles, or reviews by people who asked ATC for the info. I'm rusty on the VC and magnetic gap lengths, but I'm 90% confident they're within 1mm...

- 1" soft, woven fabric, lightly doped, Dohm (dome lol)
- Underhung design
- Heat treated top plate
- Completely saturated magnetic gap 20,000 Gauss (evenly dispersed a.k.a. saturated!)
- Underhung voice coil
- 8mm peak to peak travel within gap
- +- 2mm peak to peak linear
- Double suspension: rocking modes are a dome's natural enemy - rears its FAT ugly head, screaming like a banshee at higher SPLs (including transients) and at lower frequencies (if encountered).
- Having a dual suspension allows for there to be an absolutely tiny magnetic gap. A two layer 3mm flat copper clad aluminum voice coil slid right into that gap enables an astounding 91.5dB efficiency, even with all the added weight of the added suspension, longer voice coil, damped doped fabric dome, and especially stiff Kapton former for fine control and double damping. Frequency response is very flat to above human hearing and is only down 2dB at 20kHz. 3dB down happens at 22kHz, and 6dB down happens at 25kHz. That graph in your mind, extrapolate it back to the top of your hearing range. Look at that nice, smooth curve! The dome kind of eats its own resonant modes with friction. Cool, eh?
No ferrofluid because it's not needed for cooling and it'll just dry out or change viscosity



Yes, I know "best dome tweeter on the earth" is a bold claim. I stand by it.
If you think the title is deserved by another tweeter, you can post it here too. And your reasoning, of course.
Sadly, I don't have the measurements of this tweeter... But I do know what some are and I know that I haven't seen ANY dome tweeter come close to this one's, so please post 2nd and 3rd at -6dB RMS power handling, and I will tell you approximately how far behind your tweeter falls. Remember: I'm not saying this is the most pleasant sounding dome to listen to on the planet, just that it appears to be made the best, and its measurements aren't incongruent.


- - - - - - - - - -
So:
If you could only change two things, what would you change? Why?
What else would be different if YOU were the last word before production?
Which design choices do you 100% agree with? Why?
You can also elaborate the same way about a different tweeter you think is better. Or about the likely reasoning behind one of the SH25-76S's design choices.

 

[mike7877]

I forgot to go myself!

OK... ATC is probably already butted right up against the maximum (reasonable) magnetic gap depth, as in, the magnet would have to be MUCH bigger to extend it just a little bit. But I want MORE!
(not for nothing, I have a plan!)

Gap would be expanded by 2mm fif possible without losing full saturation 2.0T / 20,000 gauss magnetic field strength. Saturated = maximized. A maximized uniform substance = uniform field
This uniform field (very rare in tweeters or any driver for that matter) is essential. It ensures force is always applied equally in both directions of a single tone. One side of the wave is not louder than the other, causing harmonic distortion, mainly the 3rd order variety (this tweeter's 3rd harmonic never peaks to above -70dB over its entire operation, and like most drivers, it remains significantly below its peaks for most of its bandwidth, probably especially in the area 2-2.5 octaves above resonance (~1000Hz, so 2.0-2.5kHz) up to 7-8kHz, the meat and potatoes!

The voice coil could then be wound the way I want - instead of the 2mm dual layer VC, it'd be 4mm single layer!! I forget if I mentioned that the voice coil is 2mm dual layer. Now you know!
I hope that this raises the -3dB point from 22kHz to 24kHz, so that the -2dB point is at 22kHz instead of 20kHz. This would ensure that the top end to 17.x kHz (most people's top end before age or damage gets 'em) would only ever be down by a small fraction of a dB, making even the pickiest, most obsessively astute among us happy!

Can't forget: I'd increase the diameter of the voice coil ever so slightly to account for lost girth!

 

[bigjacko]

Double suspension is cool, do we really need it? I don't really know if rocking mode is that bad. Also if we can buy it, how much is that?

 

[WillBrink]

In for responses. I'm no audio engineer by a long shot and yet I knew the thread would be about ATC.

 

[restorer-john]

Sadly, I don't have the measurements of this tweeter... But I do know what some are and I know that I haven't seen ANY dome tweeter come close to this one's, so please post 2nd and 3rd at -6dB RMS power handling, and I will tell you approximately how far behind your tweeter falls.

Where are the measurements of this supposedly magic tweeter to support your clickbait title and post?

 

[gene_stl]

Everybody knows that the best dome tweeters on earth are the Yamaha Beryllium domes. and perhaps some of their clones.

The ATC DOES look very good. I like that it is about a three inch (which is really a midrange not a tweeter). I am sure the double suspension doesn't hurt much but it probably comes with an efficiency and linearity cost. I like hard metal domes. One thing about the ATC that I find a bit surprising is the underhung voice coil. Efficiency is virtuous but not terribly important in this day and age of powerful amps. Back in the day underhung voice coils were more efficient but the overhung ones were supposed to be lower distortion.
(JBL Linear Efficiency and AR wooofers)

I would be interested in knowing how much the ATC midrange is , if it is available at all by itself.

Another method of making a powerful but good tweeter is the ring radiator which JBL had forever. This contruction allowed the voice coil and radiating surfaces to be tightly and rigidly coupled.

Also a newer and more recent development in dome tweeters are polycrystalline diamond domes, poly and possibly monocrytalline sapphire and corundum (aluminum oxide)and also various ceramics. These are very light and rigid and have very high breakup frequencies way into the ultrasonic. All are available and in use now. Diamond are very expensive but are not particularly expensive to make using new techniques (vapor deposition over a form similar to the way Yammy used to make Be) But these are being manufactured as substrates for integrated circuits which actally are not very expensive so I suspect in a farther distant future they may become reasonably priced. Revel has made extensive use of ceramics which are feasible to use.

 

[dfuller]

The ATC DOES look very good. I like that it is about a three inch (which is really a midrange not a tweeter)

ATC has a 3" mid dome and a 1" tweeter.

Back in the day underhung voice coils were more efficient but the overhung ones were supposed to be lower distortion.
(JBL Linear Efficiency and AR wooofers)

Underhung is better at high excursions (read: high SPL) and makes a lot more sense for a mid dome, since it improves LFX.

am sure the double suspension doesn't hurt much but it probably comes with an efficiency and linearity cost.

It certainly will cost efficiency by adding Mms; 91.5dB/2.83V isn't particularly high. Linearity, probably not - the entire point of it is to make the driver more linear.

I would be interested in knowing how much the ATC midrange is , if it is available at all by itself.

Used to be available for crazy money. $500+ a driver. No longer.

Where are the measurements of this supposedly magic tweeter to support your clickbait title and post?

I agree. Is it a good tweeter? To my ears, yes! But judging a tweeter on its own is difficult if not impossible, and I would love to see measurements of it "bare driver".

That said, I have used the SCM25A Mk1 and Mk2 (Mk1 has a Peerless D26NC-55-06, which is... not great...) and the Mk2 is substantially better sounding up top. Clearer, more extended, much less fatiguing.

 

[gene_stl]

I don't think the double suspension makes it more linear. It probably makes it less linear. But it prevents it from gyrating. (theoretically) But it can't do anything to prevent dome breakup.

@dfuller I like your signature lines.

 

[YSC]

The claims are as good as preaching.....

Ok I know (and probably a lot will agree) ATC did make good drivers, but without published data all those claims are no better than BS. just go to any snake oil company or Aliexpress and you will see lots of similar "best ever" claim with a lot of buzz word tech... without some FR, SPL and distortion plots one can say it's the world's best, I can claim similar in the tweeter torn from a 1990s car.