I received my AMT's 1/3. Man, these are everything I was hoping for. I haven't taken any measurements yet, but I will. I paired these my Eminence BP102 10" woofers using miniDSP crossed @ 800Hz.
Of course the $140 sale is over now, but ESS lowered their regular prices now. The BIG one is $170, $160 for the II and $150 for the III. Still, a pretty good deal.
HEIL AMT – ESS Speakers USA
Of course the $140 sale is over now, but ESS lowered their regular prices now. The BIG one is $170, $160 for the II and $150 for the III. Still, a pretty good deal.
HEIL AMT – ESS Speakers USA
Because Parts Express?
The AMT patent expired a few years ago. That's why you see Parts Express selling AMTs and Legacy using them in their loudspeakers.
The AMTs from ESS predate the patent's expiration. So either they own the patent or they pay a licensing fee.
OK, just to muddy the waters further:
EP2158789B1 - Diaphragm arrangement for an air motion transformer (amt), and sound converter comprising such a diaphragm arrangement
- Google Patents
Here is the patent. It was granted in 2010, which would seem to indicate that you'd need a license to sell these until 2020 at least. PE has been selling AMTs for a few years. No idea if they have a license.
ESS Factory Air Motion Transformer, AMT Tweeter, AMT-HEIL
Here's a link to the ESS AMT, from seven years ago, when it sold for $340 each
Best dipole tweeter?
Some discussion from seven years ago. Since the patent was "in force" during that time frame, possibly Aurum Cantus had a license?
Manufacturing companies love to find ways around patents, so who knows? For instance, there were something like four or five different split-gap technologies being used about ten years ago. That was during a timeframe when Adire, Creative Sound, and Ascendant were selling woofers licensed from Adire, while TC Sounds had a competing solution. Pioneer and Orion briefly sold woofers with split gap, but that didn't last long.
A primer into XBL2, LMT, and Split Coil Subwoofer design | Audioholics Home Theater Forums
EP2158789B1 - Diaphragm arrangement for an air motion transformer (amt), and sound converter comprising such a diaphragm arrangement
- Google Patents
Here is the patent. It was granted in 2010, which would seem to indicate that you'd need a license to sell these until 2020 at least. PE has been selling AMTs for a few years. No idea if they have a license.
ESS Factory Air Motion Transformer, AMT Tweeter, AMT-HEIL
Here's a link to the ESS AMT, from seven years ago, when it sold for $340 each
Best dipole tweeter?
Some discussion from seven years ago. Since the patent was "in force" during that time frame, possibly Aurum Cantus had a license?
Manufacturing companies love to find ways around patents, so who knows? For instance, there were something like four or five different split-gap technologies being used about ten years ago. That was during a timeframe when Adire, Creative Sound, and Ascendant were selling woofers licensed from Adire, while TC Sounds had a competing solution. Pioneer and Orion briefly sold woofers with split gap, but that didn't last long.
A primer into XBL2, LMT, and Split Coil Subwoofer design | Audioholics Home Theater Forums
Keep in mind that the larger ribbons will generally have greater power handling, but the vertical directivity gets pretty ridiculous. A three inch tall ribbon has zero degrees of vertical beamwidth above 4500hz. IMHO, one of the reasons that people like the sound of ribbons is that the extremely narrow directivity can be a feature or a defect, depending on how you implement them.
I own a pair of the original '70's heil with newer diaphragms. I've paired mine to a FaitalPro 15pr400 driver mounted in a 180 liter sealed enclosure. Heils set on top. XO is @1240hz LR4, not much drama. Sounds great.
This is an active system so tweaking isn't a big deal. My opinion however is that when you begin trying to flatten the response of the heil the airiness of the overall sounds starts to diminish. A trade off between "eye candy" and overall sound quality. I've since decided to let it be. I'm an older user so perhaps some of these higher frequency anomalies don't offend me as much as the missing "sparkle" would/does. YMMV
This is an active system so tweaking isn't a big deal. My opinion however is that when you begin trying to flatten the response of the heil the airiness of the overall sounds starts to diminish. A trade off between "eye candy" and overall sound quality. I've since decided to let it be. I'm an older user so perhaps some of these higher frequency anomalies don't offend me as much as the missing "sparkle" would/does. YMMV
This is exactly what I describe in the previous post: when you have a loudspeaker with rapidly changing directivity, getting it to sound "right" can be tricky because of pattern flip.
I do a lot of work with car audio horns, and this is the single biggest challenge with them, IMHO. You can equalize them flat and they won't necessarily sound right, because of pattern flip and power response.
ESS Heil AMT, yet more questions...
I am used to seeing a tweeter on a baffle, even in an open baffle design.
Normally tweeters in free air are a bad idea.
Why isn't diffraction a big issue with this design?
Is the Great Heil ever used in a monopole fashion on a baffle?
Or is monopole a waste of this gem?
I am used to seeing a tweeter on a baffle, even in an open baffle design.
Normally tweeters in free air are a bad idea.
Why isn't diffraction a big issue with this design?
Is the Great Heil ever used in a monopole fashion on a baffle?
Or is monopole a waste of this gem?
Attachments
According to a german article that 5k spike is the result of sound waves leaking between the ends of the focus plates and the plastic cover.
Their fix was to fit a felt "belt" from the diaphragm slot, over the focus plate, around the plastic housing to the other side, returning on the back focus plate to the backside diaphragm slot. This of course did half the unit and was repeated on the opposite half.
Hifi-Selbstbau - ESS AMT-1 Air-Motion-Transformer
Their fix was to fit a felt "belt" from the diaphragm slot, over the focus plate, around the plastic housing to the other side, returning on the back focus plate to the backside diaphragm slot. This of course did half the unit and was repeated on the opposite half.
Hifi-Selbstbau - ESS AMT-1 Air-Motion-Transformer
There are two reasons.
Firstly, the big AMTs got, unlike domes and cones, a very narrow vertical dispersion. They simply don't hit as much as other dipoles or 360° speakers. That leads to reflections reaching the ear within a shorter period of time, which often is heard as more precise. The reflections (especally on dipoles) usually make speakers sound broader, more depth, 'air-ier', and that's pretty much dependent on the enviroment, the reflecting surfaces (furniture, walls, windows) and absorbing characteristics (courtains, sofa, bed, pillows etc). So if you aren't satisfied with the room impression, it will change much more than with 'just' direct radiating speakers to different speaker positions and angles.
Secondly, most drivers got a much different dispersion over the frequency, they 'beam', get narrower. For dipoles with cones or dome drivers that usually means, the sound energy balance in the room is quite non-linear and any reflection will sound different, depending on where from they come and what and how much reflected/absorbed they are. That isn't a good thing because the reflections actually do add up to the preceived tonal balance. For cones i.e. the backwards radiated sound differs a lot from the forward radiated sound, even without the reflections, because the magnet, basket and spider are in the way, combined with the beaming towards higher frequencies/very broad dispersion at the lower end, the sound gets 'muddier'.
At the big AMT you don't have any of these, the backwards dispersed sound is identical in response to the front-wise (except for the phase) and they have still exactly the same dispersion, a quite good horizontal dispersion and same narrow vertical one aswell.
Yes, there were some which got an absorption chamber behind them (i.e. the ESS amt-bookshelf) and ofcourse there are still the smaller AMT monopoles. If you want to use the big dipoles, you'll want the dipole characteristics, otherwise you'd be better off to just buy different ones which don't pose that much needed effort and time in experiments on how to tame the back energy in the way you want them to sound.
Yes, that's pretty much sums uip what I wanted to say.
The ESS AMT-1 was manufactured over a long time and was modified a lot and without any note or explanation on how to recognize it. The membrane units are often not compatible, differ in thickness, membrane material, response and spl. That means, they can actually sound a lot different. So generally, you'll want to buy them in pairs or matched. You'll also want to measure them in response/spl, distortion, decay and impedance. Some differences can be compensated for by developing/modifying the crossover for each one (and don't forget to mark which xo is for which AMT!).
The tape trick is well known and cannot harm in any way, even if you got a different version which does not have that problem. And since costs practically nothing, it's a very good idea to do it.
The foam on the back side is different though. You'll have to experiment a lot with it because of the nature of absorption of sound, it will change the tonal balance of the (quieter but still audible) backwards radiated sound. And while it does improve the mechanical resonance around 650-900Hz (depending on which model, membrane unit slot and membrane unit you've got, some got several, lesser resonances, some got different frequencies), I'm not very thrilled by the 'construction' of the foam part. See, the problem is, in the middle the sound has a shorter distance till it leaves the foam, near the magnets the sound runs through a lot more foam than in the middle, that means, it filters there a lot more and lower frequencies than in the middle, that means, the response will be much different, especally under angles. I did not measure it how relevant it is but it's definitely not enough to absorb all the back energy. The easy solution would be, if you want to use that foam at all, to use a wedge of a circle (don't know how to describe it, like a piece of a cake with the front angle cut off). IMHO it's much better to just try different speaker positions to keep the advantage of the dipole or just use different AMTs or experiment with the reflecting back surfaces.
Do you understand this?
The cause of the ripple of our ESS AMT-1 at 5 kHz was the sound leakage at the end of the Disc packs (red arrow) over the entire height of the slot. Once you have the with textile adhesive tape This ripple was fixed.
Cause is probably a part of the radiated from the outer lateral regions of the membrane Sound that gets into the inner workings of the AMT-1. Unfortunately, you can not open the chassis as it is in the
Image is shown, because then you should also bring absorption material in the outer areas(pink hatched area).
Another irregularity occurs at 12 kHz. This could be due to an absorbent pad
be linearized the "disk pack". As a "combination measure" we therefore have the disk set taped with d-c-fix® velor, in total height (= 138 mm) from the beginning of the "closed" Disc packs to the back (= 264 mm long). Here then the side part was also complete pasted over. The effect for the break-in at 12 kHz was very low, but this break-in only occurs Axle up. With stronger absorption on the disk pack, the range was> 7 kHz too heavily damped.
We strongly assume that even newer versions of the ESS AMT-1 still have this weakness at 5 kHz and benefit from this conversion.
To dampen the mechanical resonance at 870 Hz, we also recommend using one Basotect triangular block (height 138 mm, base area s.u.) complete the rear triangle fill. The Basotect block increases the mechanical losses and thus dampens the Resonance frequency. In addition, the radiation is reduced to the rear, which is too low Wall clearances to the rear is usually very beneficial.
I personally see a lot of inaccurate or misleading information regarding what you'll get with a new pair of AMT-1s from ESS (California) in the last couple of pages. While some of the historical information here might be interesting (i.e., thread drift), understand that much of what I've read is not accurate or not applicable to the present AMT-1 based on measurements of new units. Many of the arguments above have no material relevance to the drivers mentioned by the OP. Try a pair for yourself rather than suffering the angst from "expert opinion".
I've found that the ESS AMT-1 enables excellent configurations for 2-way loudspeakers using a DSP crossover with first order (IIR) filters without the type of phase/group delay growth that you see with typical higher order IIR filters, especially when looking at the combined step response. The AMT-1 transient response is second to none that I've measured or listened to. I would assume that DSP with FIR filtering will take this combined performance to an even higher level.
I can recommend that the AMT-1s can be used down to their stated 800 crossover point (or even slightly lower) without issues of significant distortion or loss of polar control...and the sound is superb.
While most here will opt for a direct radiating woofer in a vented cabinet, I can highly recommend a fully horn loaded Belle or La Scala type bass bin as improved choices--which will give you coverage control down to below 100 Hz (i.e., below your listening room's Schroeder frequency). The tightness and cleanness of sound and quality of the "tinkles" is outstanding, subjectively coinciding with the aforementioned good measurement results.
Chris
I've found that the ESS AMT-1 enables excellent configurations for 2-way loudspeakers using a DSP crossover with first order (IIR) filters without the type of phase/group delay growth that you see with typical higher order IIR filters, especially when looking at the combined step response. The AMT-1 transient response is second to none that I've measured or listened to. I would assume that DSP with FIR filtering will take this combined performance to an even higher level.
I can recommend that the AMT-1s can be used down to their stated 800 crossover point (or even slightly lower) without issues of significant distortion or loss of polar control...and the sound is superb.
While most here will opt for a direct radiating woofer in a vented cabinet, I can highly recommend a fully horn loaded Belle or La Scala type bass bin as improved choices--which will give you coverage control down to below 100 Hz (i.e., below your listening room's Schroeder frequency). The tightness and cleanness of sound and quality of the "tinkles" is outstanding, subjectively coinciding with the aforementioned good measurement results.
Chris
@davefred
No, I don't speak the language but the text can be copied to a translator easy enough.
I have to wonder why, except to pretty them up, that a simple welded plate across the angle iron (top and bottom) wasn't used thus ditching the black "resonance" chamber created by the cover. Actually, you could drill a hole dead center on each cover and shoot "great stuff " in there.
No, I don't speak the language but the text can be copied to a translator easy enough.
I have to wonder why, except to pretty them up, that a simple welded plate across the angle iron (top and bottom) wasn't used thus ditching the black "resonance" chamber created by the cover. Actually, you could drill a hole dead center on each cover and shoot "great stuff " in there.
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