HEIL AMT DATA THREAD

[bimasta]

There've been several threads recently about the remarkable Heil AMT, in all it's forms, so I thought I'd try to start one dedicated to them. There've been entries about restoring the old ones, and about their recent revival by the original maker ESS. Also the patent expired, and so many new companies are using versions that their greatness is re-established. So the time seemed right.

I'll kick it off. I've been collecting them for about 25 years, after seeing a pair of the "pyramid" model in a thrift shop for $40/pair. The shape was intriguing but it was the Great Heil that really caught my attention. I had to hear it. I'd already owned many pairs of Quad electrostatics, and some Martin Logans — of course the AMT has no similarity to electrostatic speakers in any way — but I could see through the diaphragm, and that was enough similarity for me.

When I got them home, I had to make space for them. I moved the Quad 63's and Logans into a hallway, and moved JBL L200, L220, and stacked L65 Jubals aside. The small stand-mount monitors, the LS3/5A, Infinity Modulus et al were just stacked against the wall. I was exploring all technologies; they're all roads to the same destination. You could call me a collector, or addict, your choice.

The ESS woofer-foams were shot, so I disconnected them, and used the Jubals for bass. I put them in the space where the Quad 63's had been, with lots of space behind, so the set-up was ideal. The sound of the Heils was instantly captivating. They were even airier, clearer, more nuanced and more transparent than the Quads or Logans, and went remarkably deep into the midrange.

I started buying every Heil I saw. I even found a pair abandoned by the side of the road, they wouldn't fit in my car, Cops arrived to give me a $250 ticket because I wasn't allowed to stop there — but they ended up taking the speakers home for me, in their backseat normally reserved for perps.

I also grabbed every smaller model with the various different AMT's, including the "ring magnets" — which I think even better than the big ones.

I had a good little collection for awhile, but a couple of house-moves and downsizing perforce reduced it. I saved the tweeters/xovers when I could. I have 4 pairs of the Great Heils currently, and my recent system used 2 pairs recently, but replaced them with a single LS-8 tweeter using the ring-magnet — I prefer it.

Please add to this beginning, and I'll continue to do so — after 25 years I have a few more observations. It's been very reassuring to learn so many discerning ears feel the same way as I do about them, and many of you know far more than I. Please share that knowledge.

 

[nerdorama]

I'll join this thread. I have a pair of Great Heils but have to admit I haven't used them. When I first bought them I hooked them up with a series cap for some protection and played them just to be sure they worked.

Since then I have purchased several pair of Goldenear speakers which use an AMT type tweeter. I really like the clear and non-edgy treble from them. My son, who has a good ear I think, just bought a pair of Emotiva B1+ mini speakers. He has similar things to say about the AMT treble.

Wish I could share more experiences.
John

 

[Nixxuz]

Recently picked up a pair of the reissues from ESS via Simply Speakers. I'm using them in a tri-amped, 3 way configuration as supertweeters, being powered by an Elekit 8200R running Gold Lion KT88's. They have a 2nd order crossover with dual Audyn Plus 1.1uF caps in series, bypassed with a Miflex KPCU 0.1uF, which is in turn bypassed with a NOS Russian silver mica cap at 0.1uF. Inductor is an ERSE 0.15mH 18 AWG Perfect Layer.
Here's what I know;

Specs directly from ESS;

• Art of Pure Air Motion Sound™
• Weight: 14.5 pounds
• Height: 6″
• Width: 6.75″
• Depth: 4.25″
• Impedance: 4 ohms, Re: 3.9 ohms
• Power: 40 watts RMS, 160 watts max
• Response: 20 kHz - 800 Hz
• Sensitivity: 96 dB, 1 watt, 1 meter
• Fits ESS Cabinet and Driver Models:
• ESS: AMT-1. AMT1, AMT-1A, AMT-1B, and many more

Specs from Simply Speakers,

• ESS AMT Speaker Air Motion Transformer Part # AMT-HEIL
• Original ESS AMT design
• Factory new direct replacement Air Motion Transformer
• Weight: 14.5 pounds
• Height: 6"
• Width: 6.75"
• Depth: 4.25"
• Impedance: 4 ohms, Re: 2.9 ohms
• Power: 40 watts RMS, 160 watts max
• Response: 800 Hz - 20 kHz
• Sensitivity: 92 dB, 1 watt, 1 meter

Specs sheet from TestHobbyHiFi2017;
https://www.hifisound.de/out/media/pdf.php?r=WGZpbv7SiCEfoDbzCVRCIvfRyj9FdLa+dKeJ+iJl46QuD0ECHBJ6nCbap8P//ZTdTJAKEofNDkEOSML4uLjEpA==.pdf
Specs sheet from the same source for the older version;
https://www.hifisound.de/out/media/pdf.php?r=fnVzQ5uLXCDkcm+LdgmayPCvQiCx4S8e3ZOUK7C2u3ZB/+X/JJI0FoOjBwhI4aCrPcdYhm6QCmkprvGdSla8lA==.pdf

Now I can't read german, but those spec sheets claim a whopping 100dB efficiency, unless I'm missing something in the translation. I know for a fact that mine are not that efficient. My guess is closer to the 92dB listing from Simply Speakers. Another thing I do know, is that mine measure over 20khz, used with the equipment I have now. Now the amp I'm using to power them may NOT actually have any usable output much past the complete dropoff point, which is roughly 22khz. So I can't verify the claim of going up to 32khz, (not that any of us could hear it). I also know that, based on my real time spectrum analyzer measurements, they don't have a serious shelf at 14khz, which some people seem to have experienced.

This article puts the (maybe original?) around 98dB efficient and also claims 35khz extension;
https://www.tnt-audio.com/casse/ess_amt_e.html

 

[jcidave]

As I have posted in other threads, my interest in ESS Heil products began the summer of 73 when I worked for a small ESS audio dealer. During that time I got my first 2 pair, AMT1s and AMT3s with salesmans discount. There were lots of good speakers we didn't carry, but of what we had I liked the ESS Heil the best.
Over the decades, I've added other ESS Heil products and never looked back. I have ESS speakers stacked on top of others and have converted small bookshelves with Great Heils shoehorned in them. The sound room has 30 Heils. Soon to be 32 when I finish this add on Heil tweeter project which I will post more of in a separate thread.

 

[toddalin]

AI have ESS speakers stacked on top of others and have converted small bookshelves with Great Heils shoehorned in them. The sound room has 30 Heils. Soon to be 32 when I finish this add on Heil tweeter project which I will post more of in a separate thread.
View attachment 1977127 View attachment 1977165

A group discount on stands perhaps? These are smoked acrylic with all the right holes.

 

[Dmartn149]

I have a pair of AMT 1d's that I bought in the mid 80's. They were the store floor models so I got them for $350 for the pair. They still sound good to me, though the crossovers probably should be rebuilt.
In lieu of rebuilding the crossovers I have a plan to bi-amp them with a minidsp doing the crossover duties, while making it easy for the next owner (after I die) to use the internal crossover if desired.
My plan is to leave the original spring terminals connected to the internal crossovers, and terminate the outputs of the crossovers with spade connectors which will exit the cabinet near the new binding posts. The binding posts will be wired directly to the speaker terminals. This way if someone wanted to use the internal crossovers, all they need do is hook the spades to the binding posts and connect their receiver to the old spring terminals. While bi-amped, the leads with spades will be pushed into their holes so that the body of the spade plugs the hole and only the ears stick out. Amps would then be connected to the new binding posts.
If anyone can think of a better way to accomplish this quick change option, I'd like to hear it.

 

[bimasta]

...this add on Heil tweeter project which I will post more of in a separate thread.
View attachment 1977127 View attachment 1977165

What is the purpose of the horizontal orientation?

 

[bimasta]

Recently picked up a pair of the reissues from ESS via Simply Speakers. I'm using them in a tri-amped, 3 way configuration as supertweeters, being powered by an Elekit 8200R running Gold Lion KT88's. They have a 2nd order crossover with dual Audyn Plus 1.1uF caps in series, bypassed with a Miflex KPCU 0.1uF, which is in turn bypassed with a NOS Russian silver mica cap at 0.1uF. Inductor is an ERSE 0.15mH 18 AWG Perfect Layer.
Here's what I know;

[I deleted Specs from ESS and Simply Speakers to save space.]
Specs sheet from TestHobbyHiFi2017;
https://www.hifisound.de/out/media/pdf.php?r=WGZpbv7SiCEfoDbzCVRCIvfRyj9FdLa+dKeJ+iJl46QuD0ECHBJ6nCbap8P//ZTdTJAKEofNDkEOSML4uLjEpA==.pdf
Specs sheet from the same source for the older version;
https://www.hifisound.de/out/media/pdf.php?r=fnVzQ5uLXCDkcm+LdgmayPCvQiCx4S8e3ZOUK7C2u3ZB/+X/JJI0FoOjBwhI4aCrPcdYhm6QCmkprvGdSla8lA==.pdf

Now I can't read german, but those spec sheets claim a whopping 100dB efficiency, unless I'm missing something in the translation. I know for a fact that mine are not that efficient. My guess is closer to the 92dB listing from Simply Speakers.

This article puts the (maybe original?) around 98dB efficient and also claims 35khz extension;
https://www.tnt-audio.com/casse/ess_amt_e.html

It's confusing, with all the variations out there, and ages ranging from New to 40 years old.

I have an old pair of Great Heils, but I think it's a Series 2 (or whatever it's called) as it has the V-cutouts top and bottom, front and back.

I estimate Sensitivity at 96dB. This based on the rated Sensitivity of the Woofer and Midrange I'm using with it, both of which are rated at 92dB by their manufacturers, which I think are reliable. If your estimate of 92dB were correct, my three drivers would be in balance. But my Great Heil is much louder — I have to reduce it by 4-5 Ohms (using resistors) to reach balance.

Of course it may just be the difference in our Heils, and their ages. I have 3 other pair I could try, but they're all the same age more or less, thus untrustworthy. This is all so vague, and based on "ear readings", that I'd like to hear any counter-theories from you that could reinforce your 92dB estimate.

 

[jcidave]

What is the purpose of the horizontal orientation?

No real reason other than I can. The cabinet and mounting hardware will allow orientation in either position. They will sit on top of, ( of course ) ESS AMT IIs which have the hard frame grill which should support the weight.

 

[bimasta]

Heil AMT's have great horizontal dispersion, about 120°, but awful vertical dispersion, about 20°. ESS tried to claim it was intentional: "... to prevent ceiling reflections in your room." No, it's a weakness inherent in the design.

By laying the Great Heil on its side, the great horizontal dispersion becomes vertical. The sound-image becomes 3D, with W - D - and H. You hear reflections off the ceiling in the place the recording was made, and the overtones and phase anomalies that make the music alive.

There's not much point adding yet one more Heil in the standard position; maybe the volume increases by 3dB, barely noticeable. But rotating it makes the music bigger and you'll hear it instantly. You're halfway there — you should explore that potential.

 

[Nixxuz]

Heil AMT's have great horizontal dispersion, about 120°, but awful vertical dispersion, about 20°. ESS tried to claim it was intentional: "... to prevent ceiling reflections in your room." No, it's a weakness inherent in the design.

By laying the Great Heil on its side, the great horizontal dispersion becomes vertical. The sound-image becomes 3D, with W - D - and H. You hear reflections off the ceiling in the place the recording was made, and the overtones and phase anomalies that make the music alive.

There's not much point adding yet one more Heil in the standard position; maybe the volume increases by 3dB, barely noticeable. But rotating it makes the music bigger and you'll hear it instantly. You're halfway there — you should explore that potential.

Wouldn't you hear reflections in the place the speakers currently reside? Like, if your ceilings are 10', and the recording space was 8', it's not going to magic the illusion of 8' ceiling reflections. I've always gone with the idea that, if you want height for your sound stage, you mount a pair of tweeters higher than you normally would, or add in a set of up-firing tweeters. Besides, for me at least, I have sound treatments on the ceiling of my listening room, specifically to negate first order HF reflections.

 

[Stepwise]

Some years ago I scrapped two bookshelf speakers and this is what remains.
Can someone identify them so I can use the information here to decide what to
do with them. The number 8 lingers in the braincell as a possible part of a model name.

The foam in the woofers had rotted and the position in the bookshelf was tricky to get
right and when furniture was moved/changed they were replaced. The fake veneer started
"sweating" but I was always very satisfied with how acoustic instruments sounded.
The lower register was less impressive, the crossover was really simple.

 

[puppet]

Fortura? Anyway, that's ess's "power ring".

 

[jcidave]

View attachment 1977554
Some years ago I scrapped two bookshelf speakers and this is what remains.
Can someone identify them so I can use the information here to decide what to
do with them. The number 8 lingers in the braincell as a possible part of a model name.

The foam in the woofers had rotted and the position in the bookshelf was tricky to get
right and when furniture was moved/changed they were replaced. The fake veneer started
"sweating" but I was always very satisfied with how acoustic instruments sounded.
The lower register was less impressive, the crossover was really simple.

Yes. The PS 8. A pair for sale now on Ebay. Some of the Tempest series bookshelves we sold also used the power ring. So did the AMT 5. For us in the store, the lesser speakers of other major brands like AR, KLH, JBL and others used lesser quality tweeters. But these lower cost ESS Tempest speakers still had this Heil. There was just no comparision. At lower price points, dollar for dollar, anything with a power ring was clearly superior.

 

[jcidave]

Heil AMT's have great horizontal dispersion, about 120°, but awful vertical dispersion, about 20°. ESS tried to claim it was intentional: "... to prevent ceiling reflections in your room." No, it's a weakness inherent in the design.

By laying the Great Heil on its side, the great horizontal dispersion becomes vertical. The sound-image becomes 3D, with W - D - and H. You hear reflections off the ceiling in the place the recording was made, and the overtones and phase anomalies that make the music alive.

There's not much point adding yet one more Heil in the standard position; maybe the volume increases by 3dB, barely noticeable. But rotating it makes the music bigger and you'll hear it instantly. You're halfway there — you should explore that potential.

I appreciate and agree with your comments. This project is really adding some back room fill in the area where I sit. So for right now, they will play at a much lower volume than their potential. Plus, its using some pieces of scrap wood I had taking up space. Using ESS AMT1B bookshelf crossovers that will fit in the slot underneath. Xover at about 1000hz. Picture is testing the setup.

 

[bimasta]

@Stepwise I'm using a pair of those "L'il Heils" now. They sound better than the Great Heils, though more limited. In fact, I was using G Heils until two weeks ago, when I got these — swapped them to test, and never went back. Best tweeters I've heard, plus very sensitive (±95dB). Also, the Great Heils get "screechy" above a certain point, and these remain sharp as a knife but never cutting.

PS, it someone has a way to "tame" the screechiness of the Great Heils, please share.

 

[toddalin]

@Stepwise I'm using a pair of those "L'il Heils" now. They sound better than the Great Heils, though more limited. In fact, I was using G Heils until two weeks ago, when I got these — swapped them to test, and never went back. Best tweeters I've heard, plus very sensitive (±95dB). Also, the Great Heils get "screechy" above a certain point, and these remain sharp as a knife but never cutting.

PS, it someone has a way to "tame" the screechiness of the Great Heils, please share.

I'm assuming the peak is to what you refer. BION, there are some "parrot heads/bird brains" who say they prefer this to a flatter frequency response. Maybe some birds are not sensitive to higher frequencies. I've never even seen a bird with noticable ears, so in the grand scheme of things in the animal kingdom, their hearing probably isn't all that good.

This is the Heil @ ~1' with a second order, 3.3 mfd ClarityCap and 0.6 mH air core inductor, 8 ohm L-pad, and 4 ohm Mills series resistor on the Heil. Note the spread of ~9 dB from 4KHz.

But I am like you and prefer a flatter response. So, I created a diffraction lens that does this. Note the spread from 4KHz is now reduced to about 4-5 dB as is that screech.

I did this and have threads on it. look for Give Oskar a Wedgie and He'll Straighten Out" or something to that effect. IIRC, that recalls the original concept and development, and there may be another thread on the finished piece.

 

[bimasta]

@toddalin I studied your wedgie when you first posted it a couple years ago, and again when you reposted it recently. I thought it was all about dispersion, and had nothing to do with the screechiness. I guess I wasn't reading closely.

I was misled a little, a few weeks ago, when you wrote you were trying a choke (wound it yourself) to tame the screech.

If the wedge does the job, why the coil?

 

[toddalin]

@toddalin I studied your wedgie when you first posted it a couple years ago, and again when you reposted it recently. I thought it was all about dispersion, and had nothing to do with the screechiness. I guess I wasn't reading closely.

I was misled a little, a few weeks ago, when you wrote you were trying a choke (wound it yourself) to tame the screech.

If the wedge does the job, why the coil?

Not sure they two are quite related. Can you refer me back to the post about the choke?

 

[bimasta]

Not sure they two are quite related. Can you refer me back to the post about the choke?

Here it is — in the thread "GREAT HEIL" AMT EXPERTS — QUESTIONS... page 2, April 20, 2018. I edited a little for continuity/brevity, but some non-sequiturs remain, sorry —

"VanAm wrote: Jeff Poth is correct and his explanation is exactly how the pleats perform the dipole action. I understand he may also be the first person to describe the rising with frequency ( approx. 6 dB per octave) response of the ESS AMT HEIL , a function of the low mass diaphragm ( which is easily corrected) and is a characteristic that is unfortunately ignored by the majority of users , employing the AMT in a speaker system."

"[bimasta said:]↑

I owe a mea culpa, as I was wrong on the di- vs bi-pole question — but first I hope VanArn can provide more details on his claim about amplitude rising with frequency. It strikes me as far more serious than the other question..."

"[Toddalin replies]

"I've noted this same thing and in fact provided the JBL 075 as an example of this same sort of thing.

"What I've done with my Heils is to put a 0.06 mH coil in series in the crossover, in effect making the high pass filter a band pass filter. At 0.06 mH, there is still plenty of high end available, but it removes peakiness at the high end of the band that I found irritating. In removing that peakiness, it helps the lower frequencies come through to the ear. I would rather give up a bit of the highest frequencies to remove this irritation and "flatten" the high end of the band a bit.

"BTW, for the choke, I just bought a couple 15 foot rolls of 16 gauge enamaled wire. I was shooting for ~0.03-0.05 mH, but this works fine without trimming the wire, which would be on the order of inches. And, it doesn't have to be 16 gauge, which is probably way over-kill. The gauge of the wire has little to do with the inductance, except that you can put more turns in a given area with a smaller gauge."

https://www.ebay.com/itm/TEMCo-Magn...-G__wHT7V9QYqSg:sc:USPSFirstClass!92705!US!-1

Last edited: Apr 20, 2018
toddalin, Apr 20, 2018

@toddalin Hope this freshens the memory. And I'd appreciate a bit more info on the choke: did it work? I may need to use one. It really gets shrill — as VanAm noted: "it is a characteristic that is unfortunately ignored by the majority of users employing the AMT in a speaker system."

I too ignored it, for years, and now I can't understand how — it's really irritating. Adding resistance to lower the overall level of the Great Heil helps, but at the cost of losing other Treble info, not just the offending frequencies.