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Air Motion Transformers (Heil's) and New Diaphragms
Air Motion Transformers (Heil's) and New Diaphragms
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Old 24th February 2011, 11:39 PM   #151
spacetransient is offline spacetransient  United States
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I fried one of the original 1c diaphragms while making a new 2-way. I had no choice but to get a new, current production matched pair. The sonic measurements were virtually the same between the two but the new diaphragm material, mylar I presume sounded a bit colder, more extended and strident. After a couple weeks of break in either my hearing may have adapted or memory faded as they sounded very close to the originals albeit slightly tighter, more detailed at the cost of a bit of sweetness. Frankly, I like it this way. And they do seem to get better with age. Just my experience.
I use Altec 414c's as well in a transmission line configuration- without the passive woofer of course. The Altec's integrate well; fast, transparent, excellent transient response and timbre. By no means perfect but the experience convinces me the Heil's need the fastest most efficient pro-drivers to balance their sound. Audax PR17OMO might be another good choice if shooting for a MTM or three way with a JBL bottom. Me, I am still happy with the tight and flat 40hz I am getting out of mine. Next is to try a true isobaric dipole with dual altecs and see if I like that. I had the foresight to design the rear of my cabinet for that purpose but only tried that configuration briefly with my current 6,7 ohm Altecs (giving me about 3.3 ohms parallel). No dice as I was using the 1c crossover designed for an 8 ohm mid-woofer! A short in my cables had previously fried my Heils together with a good Marantz. That experience shied me away from trying this with an active cross again so I left well enough alone and upgraded the caps in the existing (AMT1c) crossover. Remember, the AMT1 series had a 4 ohm Heil coupled with an 8 ohm mid-woofer. Audio nirvana? No. But still better than any dome tweeter I have heard and the Altec's do their job as well. Overall I would still keep them over any other pair of speakers I have had in my living room, including a pair of Martin Logan's as they have the punch for rock, enough detail and soundstage for classical, while still maintaining enough immediacy for jazz. For me this combination of dynamics with transparency is tough to beat. Maybe the Carver Amazing's were a little more convincing top to bottom but the power, size and placement requirements put me on a different path. Just my 2 cents- as I hope this thread never ends.....
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Old 6th August 2011, 04:44 AM   #152
automaticmojo is offline automaticmojo  United States
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Originally Posted by el seven View Post
I recently found this to be the case. In point, i have been listening to my 1B pair of old heils (and we're talking original AMT units here) for some 17yrs without noticeable degradation when i decided to pull the amt's and put in new diaphragms. Something's amiss. The old diaphragms are 30something years old and they sound significantly brighter than the new ones. Threw both pairs on my dmm and they're all within .4ohms of each other but i removed the new ones again and left the old in place as they're the keeper in my mind. Who wants a pair of new diaphragms for cheap as they're for up for grabs now. They work, but the untrained ear is the new owner of these ESS bummers.

I'm losing faith now in their new stuff altogether.
I guess the thing I don't understand is that earlier (perhaps when you were still employed by ESS) these diaphrams were great-no problems and now-not so I great.
Am I sensing some sort of agenda here?
I have to wonder.......
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Old 6th August 2011, 05:43 AM   #153
el seven is offline el seven  United States
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Originally Posted by automaticmojo View Post
I guess the thing I don't understand is that earlier (perhaps when you were still employed by ESS) these diaphrams were great-no problems and now-not so I great.
Am I sensing some sort of agenda here?
I have to wonder.......
You would have to point to me where i stated the diaphragms were great earlier and in any post anywhere i may have implied being employed by ESS at any time.

Simply put again, the plates were reconfigured and the diaphragms were copied. It was not until test results were procured in an anechoic chamber that the new diaphragms fell measurably short and until this time i was unaware of any differences. Having come to these same conclusions both in the facility and my own sound environment (again, after test measurements) i will go on to say this; the 146 plate-build of your amt 3 is in my opinion still the superior build. Does that confuse you more? Sorry automojo my post(s) reflect my opinion(s) and those are subject to change. I liken the amt1/amt3 in the towers and the amt1a/b in the pyramids to be the pinnacle of the amt successors just like you do and finding product support for any of those is absent apparently. I no longer own the new amt's nor any of the new diaphragm(s) so all of my listening is to bias towards that which i find superior, until further notice of course. You will find my displeasure with what ess is doing at current to wit i am again biased as my constituents sidle my opinion(s) and mirror my sentiments. I also tend to base my ongoing findings on what works and what works well so since the end consumer pleads for more information based on my opinion(s) i give it to them rather furtively. Not the case on the public forums so take it fwiw that i am more candid here and more so with any other. Some details i won't release in print however but again it's a constituency factor and nothing personal mind you. These are less biased than anything else you might find in my post(s) but they are in fact embarking on trade infringement and my conscious won't allow me to go there in public. My opinions differ rarely from my findings both professional and personal. Anything else i can help with i will try. I am back out of state for another week and a half so i will see you around mojo!
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Old 6th August 2011, 06:42 AM   #154
coloradosound is offline coloradosound  United States
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I don't remember which year, but I recall the originals were teflon
and I think they switched to mylar.
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Old 8th August 2011, 07:21 PM   #155
Big Whitey is offline Big Whitey
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Hey all,

New to the forum, I was sent over here by the good boys over at AVS. I recently came across as set of ESS HEIL Tweeter as well as the crossovers from a pair of ESS AMT's. So first off the crossover is as confusing as hell but hopefully I can figure it out. Maybe some of you could give me a hand with that. Now I am looking to rebuild these bad boys. Starting off with woofers, what would pair up well with these Heils?

I am BRAND new to the DIY scene but am great with electronics and have a wood working shop and carpenter at my disposal, so although it may take me longer than the normal person, I should be able to accomplish the task.

I've also just thought of contacting ESS and seeing if I can buy some boxes off them depending on the price. So back to the woofers, any suggestions??

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Old 8th August 2011, 08:44 PM   #156
Adioss is offline Adioss  United States
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Cool ESS AMT-3s

Hello All, I'm the original owner of a pair of ESS amt-3's from late 1970 or early 1971. WOW that"s 40 + YEARS & YES I'm an old bird!!! I'm looking for some current general info about these speakers. Value etc. I have had all the speakers rebuilt with Original parts as directed from ESS. I do use my amt-3's daily and really enjoy the clarity of sound reproducion. I still have a turntable and about 300 vinyl albums that sound great thru my amt-3's. I power the system with an ADCOM amplifier
which gives me lots of power. Oh! by the way I do still have the original
literature and warranty registration cards, No. 97440 & 97442, from when ESS was in Sacramento Ca. Any information is greatly appreciated...
Thanks in Advance, Tom
PS: I will be on the lookout for the current email address for ESS in Europe
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Old 15th May 2012, 01:56 PM   #157
Cobra71 is offline Cobra71  Germany
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Default It's time to lift this thread up...

Hello, I'm using the ESS AMT 1C since ~10 Years and they sound great.
But I know about the Problems that this Speakers have with the midrange.
In Germany there are some companys like "Klangmeister" that exchange the xo with a new one without pots and set the AMT a little bit away from the front.
But they take ~700,- Euro / ~900,- USD for this modification, I think thats pretty much for some coils, foils, resistors and two new holes in the housing. ;-)

Does anybody here have succesfully built a new xo with a higher xo-point than 800Hz and could show the plans here?

Some weeks ago I was happy to get a cheap pair of AMT 1C Tweeters.
I think I will build some speakers with them, I saw some interesting projects with 8" or 10" Broadband drivers with ~97dB/w/m, like the Celestion Truvox 1020.

I use my AMT's with Transistor-Amps and with Tube-Amps, and they sound good on both Amps.

I don't pay for Voodoo...I like turntables, Tubes and diy.

Last edited by Cobra71; 15th May 2012 at 01:58 PM.
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Old 15th June 2012, 08:28 PM   #158
Buck R0gers is offline Buck R0gers  United States
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I use the Heils w/active crossover at 1K, KEF 10's and two 500 watt subs.
Custom 150wpc amp on the Heils and 300wpc amp on the KEF's.
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Old 12th June 2013, 06:36 PM   #159
Horizons is offline Horizons  United States
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I hope this Heil thread lives forever as I just bought an old pair of Heil AMTs to run on top of the Hornshoppe horns. Will use a series crossover to the Fostex. I might go active at some point to try 4th order around 1.5k. I first heard the Heil around 1978 and I will never forget the experience to this day. It was in a small college dorm room playing Aerosmith "Sweet Emotion" of all things. From about 2K up, there is nothing better IMO.
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Old 11th October 2013, 10:55 PM   #160
HeilHeir is offline HeilHeir
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Old thread. I come, not to boast, but more to ask for help. I have the golden egg! I married Oskar Heil's granddaughter and now have most of his stuff, including boxes of unassembled AMT membranes and the plastic housings that they sit in. Sadly, I know nothing about engineering audio equipment (although I have done some tinkering with Oskar's ESS Bass Cube and his Connoisseur BD1 turntables). I guess it's possible that I learn to assemble these membranes and eventually can get them to other AMT enthusiasts (probably for a heck of a lot less than ESS, or the guys on Ebay sells them fo r). Enlighten me and I may be of some service. As for now, I'll just sit in Oskar's basement looking at all the loot collecting dust, because I have no clue as to how to make it work. Cheers all.
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