Anyone hear or own Musical Technology (Heil AMT's) speakers?

I’m in Venice for work reasons, and looking around for audio to check out.
I came across a place that carries MT (Musical Technology) speakers. They use ESS Heil technology,

From the website:

"MT speakers offer together the qualities which usually can be found only separately in high quality speakers of different technologies: transparency and three-dimensional stage (electrostatics), dynamics and high efficiency (horn systems), Iinearity (dynamic systems).

The main driver is the AMT (Air Motion Transformer) by Oscar HEIL, which for us is the best mid-high in the market. Using a planar diaphragm it has the transparency of the electrostatics, it is a dipole and it’s probably the fastest (15 ms square wave rise time) driver in the world. It overcomes dome tweeters on every aspect: efficiency (100 db), dynamics (50 db of difference), dispersion (1200, front and rear), impedance (it behaves Iike a resistor), mid frequencies reproduction(from 900 Hz), low distortion and power capability (over 1000 W peak power), air driving area (3.5 times). It’s the only one which can reproduce real instruments dynamics and attacks, with its “instant acceleration”. It’s not easy to match traditional drivers to a so advanced component Fast, efficient and powerful woofers, using polypropylene cones, massive magnets and copper voice coils, bonded with high temperature epoxy to precision aluminium form, have been developed to give warmth to the mid-bass and at the same time to follow accurately the violent dynamics of the AMT.

Optimal blending of the drivers is achieved by sophisticated crossover networks which utilize high voltage, high quality capacitors, precision air core inductors and heavy duty wire-wound level control. The slopes between the AMT and the woofers are soft to obtain a very good phase and dynamic response without energy holes in the crossover points.

Speaker cabinets are weIl engineered components where care has also been taken with appearance. They are strategically braced and reinforced for structural rigidity in order to minimize cabinet-induced resonance. Their baffle boards are rounded to avoid holes in the frequency response out of axis. They are constructed from mdf and solid wood board and veneered with the highest furniture grade walnut or lacquered.
     The result of all this work and of exhausting listening sessions is “a speaker of incredible performances. The successful matching of the classic qualities of a home speaker, there is a flat response, transparency and musicality, and the dynamic qualities of the best professional monitors makes them very special speakers” (AMT330: Audio Review Oct. 91).They can achieve awesome undistorted sound levels, or can be driven by small power class A or tube amplifiers in a small room. Detail and clarity, wide dispersion and consequently an overall spaciousness to rival the live concert, the infinite dynamics, the coherence of the instruments and of the stage at any volume and in any Iistening point in the room, puts them among the few realistic speakers in the world."

Anyone have these? Or have heard them? I’m curious.


But they don’t have my mods. Note the flairs. Maybe they will if they see this. Still, it doesn’t show the rear mods which are most significant. BTW, I and another on the JBL Forum, have found that the Heils image better if you block off the rear wave.


I mate them with JBL 2251Js and JBL 2241H (18"). The 2251J is probably one of the "fastest" "10"ers" (actually ~9.5") out there (dual 3" voice coils, differential drive, neo magnet) and can take 400 watts all day long.


BTW, You can buy the Great Heils directly from ESS and they will typically have ~twice yearly sales of $250/pr including the mounting hardware and rubber gaskets.  Best I can tell, my pair came from a pair of AMT1Ds.

"@toddalin Best I can tell, my pair came from a pair of AMT1Ds".


Yes, that is correct, originally from the "1D" model series.

BTW, this is the SACD on an Oppo95 through a Yamaha RX-Z9 RECEIVER in "Pure Direct" mode.  There is no eq or room correction being used, electronic or physical.  The room volume is ~5,000 cubic feet.



@toddalin fyi, they've been sold out of the full kits with Great Heil AMT and mounting kits for a while.  Just for grins emailed them this morning to see when there might be more in stock. I may order a 3rd set of spare diaphragms too just to have them. If the crossover is set up properly, the last longer.  I have not been onsite for a while, last time was 4 years ago. Will check in again with them soon. Seem to be back to minimal parts supply and seeing some 1Ds pop up again, which seem to be on limited production again lately, if at all.   


Btw, some of the early original AMT-1 series line was cross down as low as 800hz, then later bumped up to 1000hz on the later generation models. I had the AMT Monitors and the AMT 1C series back then both.  Decades later, when I built my custom DEC-AMT28s, I chose dual 8" Nomex woofers in MTM configuration (Heil in between), and its crossed over at 1,200hz instead at my choosing, also helps to save the diaphragms a bit longer.  

I cross them over ~3kHz and run the speakers as "2.5-ways."

Audyns are Q4s, 400 volts

ClarityCaps are filmcaps, 630 volts

Resistors are Dale, 1%.

Chokes are air core, 14 gauge.

Lpads are typically run "flat out"

BTW, these can "rock" with the best of them at any sane/insane volume level. Ever wonder what an overdriven Hammond sounds like played through a Marshall at live/concert levels in your living room? Not a great recording, but great PR&T!

As always, the recording was made in the approximate sweet spot and is played on an Oppo95 through a Yamaha RX-Z9 RECEIVER in "Pure Direct" mode with no eq or room correction, electronic or physical.


Something to keep in mind. The beauty of the sound from the ESS Great Heil AMT is the lower midrange, imo. I worked at ESS Laboratories in the early 1980s, and listened to most of the models in that era, and owned several different units over the years. This has been a bit of a debate for decades, about the crossover point that is. There are tradeoffs going in either direction. Finding the sweet spot is key.

While I chose to cross last two custom speaker builds I did at 1,200hz, and some folks like to cross them lower, I did not do any lower so for diaphragm longevity reasons. Some of the later units in production were crossed at 1,000hz. I’ve tried it at 2,500hz too, and do like it at 1,200hz for the reasons I mention. While its not the most precise or overly accurate device, its fast, it provides a nice and engaging sound, fwiw. My other traditional speaker builds do not duplicate this same sound.   

Best of Luck.

My thought is that for the most coherent vocal presentation, it makes sense to keep the vocals in one speaker rather than spread them across a few drivers. And I never wanted to replace surround foams.

The 2251J is a very special ~9.5" driver that plays very well, way above the region I cross them over at and this allows the fundamentals to all be portrayed from a single source. They use dual 3" voice coils in a differential drive system with neodynium magnets and will take 400 watts RMS all day long. AND, the cones are light and use an accordion, rather than foam, edge. JBL actually used these in a horn enclosure.

Of course there is no free lunch, and the 2251Js roll off significally below 300 Hz which is why I run them as a 2.5-way augmented by a JBL 2241H 18". These also have an accordion edge. I am of the belief that the accordion edge presents a more textured, realistic bass guitar. Also, if you see a bass player playing/recorded through an 18" speaker, there is a pretty good chance that it may be a JBL 2241.

The dispersion on the 2251s may suffer a bit at the upper end, but it makes little difference because I always listen alone in the sweet spot. In fact, by limiting horizontal dispersion, I also limit side bounce and the soundstage and imaging are so real its unreal.

I, and others, have found that soundstage and imaging of the Heil are increased/bettered by blocking off the rear rather than letting this signal bounce willy-nilly about the room. But you need to be careful what and where you place things back there because it can cause good or bad reflections at the diaphragm.

The natural gently rising slope of the Heil may blend well with a woofer that has a gently declining slope, but the 2251J gets brighter above 3kHz very quickly and I augment the slope by increasing roll off a bit.

This then would leave a depression in the crossover area, but I modify the Heils by adding rear half-rounds that totally change their slopes by orders of magnitude.

In fact, with the addition of the half rounds, the actual slopes remain relatively the same even if you were to use a 1st order crossover down at 800 Hz (not recommended BTW). I also add curved flairs to their fronts for a smoother exit transition.


I know..., it don't mean a thing without pictures.

Heil crossed over at ~3kHz without half-round behind:

And with half-round behind:


Actually, the placement of the half-round is fairly critical and since these were taken, the Audyn Q4 cap was changed to a Mundorf EVO Oil and adjustments to the placement of the half-round make the plateau even flatter.  This added area under the curve is where the real detail lies!