I regularly lust for these, remember the AMT1s and the great clear and open top. Could not find any specs on the ESS site, I saw somewhere that they are around 100dB/1w. is there a difference in the bandwidth and efficiency of the "medium" and "large" Heil element? I have some Altec 515-8Gs and Altec 620 and 828 cabinets ( and many power amplifiers 
) to play with. Could be fun to try a 2 way with electronic crossovers.
) to play with. Could be fun to try a 2 way with electronic crossovers.I have a pair waiting to be used - some quick and dirty measurement here (in the first post): ESS AMT-1 in my projects
I can only compare these to my other measurements (using UMIK) and these are the best I ever saw, especially the IR. IIRC, there is no smoothing, just gating the reflections and not even all of them. The FR is sort of horizontal polar measurement with on axis, off axis and even more off axis without specific angles.
Due to the virus, neither of the speakers or flatpacks to be used with them arrived yet
I can only compare these to my other measurements (using UMIK) and these are the best I ever saw, especially the IR. IIRC, there is no smoothing, just gating the reflections and not even all of them. The FR is sort of horizontal polar measurement with on axis, off axis and even more off axis without specific angles.
Due to the virus, neither of the speakers or flatpacks to be used with them arrived yet
Thats correct
And used 18 dB per octave slope witch gives a more complex filter (read expensive) but using a (as far as i know) constant voltage crossover is unique in that it has no phase distortion, and the step response is perfect.
So the ESS guys knew what they where doing if above is correct.
I think ESS actually crossed them over at 800Hz
I wanted tod do a 3 way with KEF139 woofer, Kef midrange and Heil tweeter.
Wait maybe that's Nelson had. Hard to remember the 70s
And used 18 dB per octave slope witch gives a more complex filter (read expensive) but using a (as far as i know) constant voltage crossover is unique in that it has no phase distortion, and the step response is perfect.
So the ESS guys knew what they where doing if above is correct.
Amt crossover
And then You met your Wife and it all had to go ?
Btw who constructed the cross overs for AMTs and am I right that they were made as 18 db constant voltage crossovers ?
That could be the reason why they need some space around/behind them before they really shines (because you pay for using that with the off axis performance) as you maybe saw on the pictures from my setup.
If you did (yeah I know you have too many things to do and too little time to do them but you are the only NP) a youtube video like "Nelson pass do ESS" with some nice stories and pictures etc. that would be really nice and loved by the community I am sure.
I sure had my eyes on the B139 in a TL, but initially Navy work didnt pay that well so it took some years before i could buy the ESS amt 1c and they seemed to be a good compromise, especially after i took the passive bass unit out (and filled up with long haired african sheeps wool (from Denmark) and just boosted the bass at was it 30 or 35 Hz at the amp.
And then You met your Wife and it all had to go
?Btw who constructed the cross overs for AMTs and am I right that they were made as 18 db constant voltage crossovers ?
That could be the reason why they need some space around/behind them before they really shines (because you pay for using that with the off axis performance) as you maybe saw on the pictures from my setup.
If you did (yeah I know you have too many things to do and too little time to do them but you are the only NP) a youtube video like "Nelson pass do ESS" with some nice stories and pictures etc. that would be really nice and loved by the community I am sure.
I sure had my eyes on the B139 in a TL, but initially Navy work didnt pay that well so it took some years before i could buy the ESS amt 1c and they seemed to be a good compromise, especially after i took the passive bass unit out (and filled up with long haired african sheeps wool (from Denmark
) and just boosted the bass at was it 30 or 35 Hz at the amp.Data
ESS AMT-1 AIR Motion Transformer 'Great Heil', Selected buy at hifisound.de
There is some to be found at above link
I regularly lust for these, remember the AMT1s and the great clear and open top. Could not find any specs on the ESS site, I saw somewhere that they are around 100dB/1w. is there a difference in the bandwidth and efficiency of the "medium" and "large" Heil element? I have some Altec 515-8Gs and Altec 620 and 828 cabinets ( and many power amplifiers
ESS AMT-1 AIR Motion Transformer 'Great Heil', Selected buy at hifisound.de
There is some to be found at above link
Yes you have to turn the "brilliance" totally down and the "midrange presence" totally op.
Se my picture no. 58 on imgur.
And have a good free space behind them and a well damped room like mine with wooden floor, best sound is off cause if its made of 120 years old "unobtanium" boards like here
Joke aside a good thick cotton or wool carpet will do the job, just do not try to damp with foam etc. around the heil.
That doesnt work that well for what ever reason just keep it as is and work on the room around the speakers instead.
I have a pair waiting to be used - some quick and dirty measurement here (in the first post): ESS AMT-1 in my projects
I can only compare these to my other measurements (using UMIK) and these are the best I ever saw, especially the IR. IIRC, there is no smoothing, just gating the reflections and not even all of them. The FR is sort of horizontal polar measurement with on axis, off axis and even more off axis without specific angles.
Due to the virus, neither of the speakers or flatpacks to be used with them arrived yet
Nice measurements THX.
Didnt you get them eventually cause i bought from Germany w/o problems.
ESS | hifisound.de | Your online hifi specialist
I think ESS actually crossed them over at 800Hz
I wanted tod do a 3 way with KEF139 woofer, Kef midrange and Heil tweeter.
Wait maybe that's Nelson had. Hard to remember the 70s
The AMT unit has dynamics enough to get up and run away from the KEF drivers. Decent efficiency too.
I had to service a few of those for party dudes. When you really take out the tweeter, the diaphragm assembly comes out in pieces, and you'll spend some time scraping melted bits from the magnet plates.
Yes i got some (unwanted) attension beeing the first in DK that actually burnt my 2 AMTs Diaphragms.
History was that i got the brilliant idea that removing the ceramic condensors in my Sentic PA8 could improve the sound from my system.
So open AMP, desolder snaffy ceramichs and initially things was ok.
Then i noticed the PA8 was running hot and suddenly no sound from one amt.
Took the PA8 to the lab at the Navy, connected to a dummyload, scope on output, and the PA8 occillated happyly at 70 Khz.
Phoned the store where i bought the ESS (Audioscan) and asked if they had 2 new AMTs Diaphragms.
And they said they had them on stock.
When i arrived the guy at the counter called out the tech cause the tech had said to him he wanted to talk with the customer who had burnt the AMTs.
The tech at the service counter looked curiusly at me and inquired carefully as to how on earth i had burnt them and I told him.
Then he said that I was the first that had burnt the AMTs in Denmark and so to be nice I got a first "mover" discount on the Diaphragms
Btw when you remount the Diaphragms you have to scrape off the "window" putty and re apply putty so the Diaphragms wont rattle (and off cause have the wires running out at the correct side so they are oriented correctly, but that sounds more difficult than it actually is, it was actually a quite easy operation.
That normally only can be done on pro PA drivers so its one more nice feature of the heils.
So what can we learn here ??
Its always expensive to be a first mover
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Ordered. You're an evil man.
( and bring a pair, in pockets)
I remember a friend owning a transmission line with a KEF B139 in it. Just one, he lived in a smallish house and it dominated the loungeroom. Those drivers were reputedly the best you could get for bass in those days. Fantastic deep and natural sound.