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jwgorman

Heil Air motion transformer for Cornwalls

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ESS is having a sale on The Great Air Motion Transformer tweets.  Their 4ohm, 96db/w/m rating made me think they might do well on Cornwalls. So I bought a pair of them, a pair of the large Dayton AMTs and the smaller Aurum Cantus Aerostiction tweet. For the last week I’ve been listening to them. 

I have the mids and tweets crossed over at 4k, LR2.  I unplugged the stock horn tweet and put them back in the cab. 

The Daytons were my least fave. The Aurum Cantus were very very sweet. The ESS sound the best to me. Plus I think I could play them loud crossed at 2k LR2. 

The ESS can give that Magneplanar ribbon type detail and dipole presentation only they can play really loud. I think I pad them a db. 

I think there’s a lot of improvement to be made in the crossover as I just used an online calculator and went from there. 

I can sometimes get the Maggie imagine thing going on where the image just sort of hangs there. 

https://essspeakers.store/collections/black-friday/products/the-original-great-ess-heil-amt-air-motion-transformer™

 

49D2EEE4-FA4C-40E4-8496-D35622894B89.jpeg

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I happened upon that sale looking for the eclipse crossover for my my mint AMT-1s. I have always wanted to build something that utilizes the great heil. Because they really are great, or amazing. I think builders have had issues mating these to a bass bin that will do them justice. Hmmmm.

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I ordered a pair last friday the price seems to good to pass up. I will be following your progress I have Belles and Cornwalls but bought them to play with Altec 420b that I have.

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I'm running a pair of Pyramid/Sequerra T1 Ribbons on my Belles. Works great!

 

I would expect the AMT tweeter to also work great.

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I love the sound of ribbons, usually and I always was mesmerized by the sound of Heils back in the late 70s. I think the "speed" of compression drivers might be easier to integrate with AMTs than cone mids!?!? Just a theory, but so far so good. I can say that after playing Pink Floyd's The Wall at more than moderate volume, these guys have no issues, show no strain and bring out very subtle details. I wonder how they would fare at 1.5KHz 4th order? This isn't a slam dunk, but I don't think I'm too far off with this baseline (1-2db down on the AMTs seems to be about right in my room) 

Claude has been working on his Super CWs for a while and I liked the idea of moving the x over point on the mids down to 4k. I think that helps a lot. 

 

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ESS is having a sale on The Great Air Motion Transformer tweets.  Their 4ohm, 96db/w/m rating made me think they might do well on Cornwalls. So I bought a pair of them, a pair of the large Dayton AMTs and the smaller Aurum Cantus Aerostiction tweet. For the last week I’ve been listening to them. 
I have the mids and tweets crossed over at 4k, LR2.  I unplugged the stock horn tweet and put them back in the cab. 
The Daytons were my least fave. The Aurum Cantus were very very sweet. The ESS sound the best to me. Plus I think I could play them loud crossed at 2k LR2. 
The ESS can give that Magneplanar ribbon type detail and dipole presentation only they can play really loud. I think I pad them a db. 
I think there’s a lot of improvement to be made in the crossover as I just used an online calculator and went from there. 
I can sometimes get the Maggie imagine thing going on where the image just sort of hangs there. 
https://essspeakers.store/collections/black-friday/products/the-original-great-ess-heil-amt-air-motion-transformer
 
49D2EEE4-FA4C-40E4-8496-D35622894B89.thumb.jpeg.f2bb765a73744dbb258183c54b250c49.jpeg

How did you decide on which Heil AMT's? I see the I, II, and III (and their specs).


Sent from my iPhone using Tapatalk

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13 hours ago, jwgorman said:

I love the sound of ribbons, usually and I always was mesmerized by the sound of Heils back in the late 70s. I think the "speed" of compression drivers might be easier to integrate with AMTs than cone mids!?!? Just a theory, but so far so good. I can say that after playing Pink Floyd's The Wall at more than moderate volume, these guys have no issues, show no strain and bring out very subtle details. I wonder how they would fare at 1.5KHz 4th order? This isn't a slam dunk, but I don't think I'm too far off with this baseline (1-2db down on the AMTs seems to be about right in my room) 

Claude has been working on his Super CWs for a while and I liked the idea of moving the x over point on the mids down to 4k. I think that helps a lot. 

 

You can take them down to 1.5 Khz. if you like. You would just need a bigger choke for the K55/K600 (which, BTW, goes down to 500 Hz.). I have 2 extra pairs of Heils, a third pair on top of a full Heil AMT-1A, which I refurbished with new woofers and passive radiators (also new diaphragms, which they really did not need, so I have an extra pair of those as well). I paid $200 each plus shipping USED, so $140 each NEW is an absolute STEAL deal, so don't wait.

 

The amazing part of those tweeters is the 3D effect of dipoles, which are second to none (except for my Carver Platinums, but that's beyond the scope of this text).

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12 minutes ago, baron167 said:


How did you decide on which Heil AMT's? I see the I, II, and III (and their specs).


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You want the biggest ones, of course!

 

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Claude, would you recommend crossing them at 1.5k? Is LR2 at 1.5K safe? 

Yes I totally agree, these tweets are a steal at this price.  

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2 hours ago, pzannucci said:

Thought those were used on an AMT-1 crossed at 800hz?

I think you’re right. I ended up calling the factory and the fella I spoke with alluded to 800hz 4th order. 

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Comments:

 

1) I recommend flipping your Cornwall upside down in order to get the woofer much closer to the AMT on top of the cabinet to reduce polar lobing and to get the midrange of the woofer much closer to the highs of the AMT.  This audibly coalesces the vertical soundstage image further.  If you have risers, just take the screws out and reuse the risers free-standing under what was the top of the Cornwall.  A little wood filler will hide the screw holes from the riser on what was the bottom of the Cornwall box. 

 

2) The electrical leads on the AMTs seem to be color coded opposite of the polarity that I'd guess.  The reddish-purple lead is actually the negative lead according to the SPL vs. frequency near the crossover region that I ran switching polarity.

 

3) The phase plot for the AMT-1 is almost unbelievably flat--less than 45 degrees of phase wander (measured in-room) until you get to below 2 kHz.  The harmonic distortion numbers are also amazingly low (all are less than -55 dB ref. a 90+ dBC on-axis). 

 

4) These are really dipole drivers--believe it.  The rear-wave shows up almost perfectly in the spectrogram plots. Recommend moving them out a little bit from reflective walls if you can.  It helps the spaciousness greatly (but basically decreases deep bass response...bummer).  I found that I needed about 1.5 ms of delay using Bessel 12 dB/octave filters if you reference the AMTs flush to the front of the Cornwall cabinet.  They're also much less sensitive than the Cornwall midrange and tweeter, so you'll likely need to bi-amp them (as I'm doing) in order to avoid having to pad down the bass bins further.

 

5) This is, on balance, a fairly spectacular upgrade to a Cornwall--or any Klipsch Heritage loudspeaker (JMTC).  $280USD for two.  They're stayin'...

 

Chris

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2 hours ago, Chris A said:

Comments:

 

1) I recommend flipping your Cornwall upside down in order to get the woofer much closer to the AMT on top of the cabinet to reduce polar lobing and to get the midrange of the woofer much closer to the highs of the AMT.  This audibly coalesces the vertical soundstage image further.  If you have risers, just take the screws out and reuse the risers free-standing under what was the top of the Cornwall.  A little wood filler will hide the screw holes from the riser on what was the bottom of the Cornwall box. 

 

2) The electrical leads on the AMTs seem to be color coded opposite of the polarity that I'd guess.  The reddish-purple lead is actually the negative lead according to the SPL vs. frequency near the crossover region that I ran switching polarity.

 

3) The phase plot for the AMT-1 is almost unbelievably flat--less than 45 degrees of phase wander (measured in-room) until you get to below 2 kHz.  The harmonic distortion numbers are also amazingly low (all are less than -55 dB ref. a 90+ dBC on-axis). 

 

4) These are really dipole drivers--believe it.  The rear-wave shows up almost perfectly in the spectrogram plots. Recommend moving them out a little bit from reflective walls if you can.  It helps the spaciousness greatly (but basically decreases deep bass response...bummer).  I found that I needed about 1.5 ms of delay using Bessel 12 dB/octave filters if you reference the AMTs flush to the front of the Cornwall cabinet.  They're also much less sensitive than the Cornwall midrange and tweeter, so you'll likely need to bi-amp them (as I'm doing) in order to avoid having to pad down the bass bins further.

 

5) This is, on balance, a fairly spectacular upgrade to a Cornwall--or any Klipsch Heritage loudspeaker (JMTC).  $280USD for two.  They're stayin'...

 

Chris

Thank you sir, I never would have thought to turn the Cornwalls upside down! And thanks for measuring them. I do enjoy them much more with a couple of feet between the AMT and the wall. 

I have contacted a cabinet maker to build a Cornwall with a M5N8 Faital Pro essentially where the tweeter is now on my stock Cornwalls.  I will have enough room to accommodate an LTH142 (or similar large horn) if I do not like the experiment with the M5N8.

Last weekend I actually ordered another pair of the ESS AMT1s. 

I really think this is a worthwhile experiment. 

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5 hours ago, Chris A said:

They're also much less sensitive than the Cornwall midrange and tweeter, so you'll likely need to bi-amp them (as I'm doing) in order to avoid having to pad down the bass bins further.

 

Or ... you can run an autoformer in reverse to lift the output. 

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]Man I think I found a sweet spot. Ok, I would never have considered flipping them over. First time I have ever run a MWT!  Ha.  D72BF56D-3E1A-4D76-A727-192BAA13E237.thumb.jpeg.2e7bab05034eabc58abd433fec8f488f.jpeg

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For those keeping score at home, I preferred the Cornwalls oriented normally, woofer on the bottom in my tests last night. I am using the squwaker in mine though. Chris was suggesting the Cornwall as a two way, bypassing the horns and changing crossover points. Just FYI. 

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