See:
Heil Air motion transformer for Cornwalls
Double Stack ESS AMT-1 with Wings--Possible Kit for Heritage
I currently run doubled AMT-1s (top AMT-1 leaned back ~15 degrees to improve vertical polar coverage) on top of Belle bass bins as surround loudspeakers in my 5.1 array (bi-amped with a miniDSP 2x4 HD). This was a very large improvement over the stock tweeter and midrange horns/drivers in the Belles--even compared to when I was tri-amping the Belle drivers and correcting the time misalignments and the non-flat SPL response.
Chris
Heil Air motion transformer for Cornwalls
Double Stack ESS AMT-1 with Wings--Possible Kit for Heritage
I currently run doubled AMT-1s (top AMT-1 leaned back ~15 degrees to improve vertical polar coverage) on top of Belle bass bins as surround loudspeakers in my 5.1 array (bi-amped with a miniDSP 2x4 HD). This was a very large improvement over the stock tweeter and midrange horns/drivers in the Belles--even compared to when I was tri-amping the Belle drivers and correcting the time misalignments and the non-flat SPL response.
Chris
They seem to go on sale often. Dennis Murphy designed a crossover for a custom speaker built for a client thru SALK using the Heil. The driver is very dynamic but the response is tough to even out and when comparing the Heil to a Fountek ribbon …the ribbon tweeter seemed to be more defined and transparent. I would like to try it again someday but only enclosed and as a upper midrange(1-5k) crossed to a ribbon up top.
Not at all...It's quite easy, in fact. It takes a few minutes to measure and correct.
That seems odd (to be honest). Why throw away three quarters of the frequency response for a ribbon that's got polar issues?
Well no even going passive it's easy to flatten the response. I was using a pair in a bi-amp set-up crossed at 800hz with a passive network to tame the response and increase the Imp. Still have them they are fun !
It was great being able to selectively absorb the back wave to be able to adjust focus and spaciousness.
Rob
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they're currently on sale for $250 for a pair including the mounting kits......times are tough all over
Woah…that’s quite a null you’ve got there……is that consistent with the Heil?…..gosh I hope notWell no even going passive it's easy to flatten the response. I was using a pair in a bi-amp set-up crossed at 800hz with a passive network to tame the response and increase the Imp. Still have them they are fun !
It was great being able to selectively absorb the back wave to be able to adjust focus and spaciousness.
Rob
You mean at 7K or so? It was real and was also repeated in a separate Hi Fi mag measurement mine is red. Could be measured at same distance and on center not sure. It's not audible as most "nulls" are not. Don't base a purchasing decision on it. If your are curious the $250 a pair delivered with mounting hardware is well worth the price to "play" Also attenuating the back wave is a real eye opener with the effects on imaging and finding a balance between spaciousness and imaging that works best in your room.
Rob
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Google translate:
"Modification of an ESS AMT-1
The cause of the ripple in our ESS AMT-1 at 5 kHz was the sound exiting at the end of the
lamellar pack (red arrow) over the entire height of the slot. As soon as you cover it with textile tape, this ripple was eliminated.
The cause is probably part of the sound emitted from the outer side regions of the membrane, which reaches the inner workings of the AMT-1. Unfortunately, you cannot open the chassis as shown in the picture, because then you would also have to add absorption material to the outer areas (pink hatched area).
Another irregularity occurs at 12 kHz. This could be linearized by an absorbent layer on the “lamellar pack”. As a "combined measure" we therefore covered the slat pack with d-c-fix® velours, covering its entire height (= 138 mm) from the beginning of the "closed" slat pack to the back (= 264 mm long). The side part was then also completely covered. The effect of the dip at 12 kHz was very slight, but this dip only occurs on the axis. With stronger absorption on the slat pack, the range > 7 kHz would otherwise also be dampened too much. We strongly assume that newer versions of the ESS AMT-1 still have this weakness at 5 kHz and will benefit from this conversion measure. To dampen the mechanical resonance at 870 Hz, we also recommend completely filling the rear triangle with a triangular block made of Basotect (height 138 mm, base area see below). The Basotect block increases the mechanical losses and thus dampens the resonance frequency. In addition, the radiation to the rear is reduced, which is usually very advantageous when the distance to the wall is too small"
PDF with pictures but without measurments:
https://www.diyaudio.com/community/...kQFnoECBIQAQ&usg=AOvVaw2a5FOV5Wm2JGTb5nVgfZ1h
"Modification of an ESS AMT-1
The cause of the ripple in our ESS AMT-1 at 5 kHz was the sound exiting at the end of the
lamellar pack (red arrow) over the entire height of the slot. As soon as you cover it with textile tape, this ripple was eliminated.
The cause is probably part of the sound emitted from the outer side regions of the membrane, which reaches the inner workings of the AMT-1. Unfortunately, you cannot open the chassis as shown in the picture, because then you would also have to add absorption material to the outer areas (pink hatched area).
Another irregularity occurs at 12 kHz. This could be linearized by an absorbent layer on the “lamellar pack”. As a "combined measure" we therefore covered the slat pack with d-c-fix® velours, covering its entire height (= 138 mm) from the beginning of the "closed" slat pack to the back (= 264 mm long). The side part was then also completely covered. The effect of the dip at 12 kHz was very slight, but this dip only occurs on the axis. With stronger absorption on the slat pack, the range > 7 kHz would otherwise also be dampened too much. We strongly assume that newer versions of the ESS AMT-1 still have this weakness at 5 kHz and will benefit from this conversion measure. To dampen the mechanical resonance at 870 Hz, we also recommend completely filling the rear triangle with a triangular block made of Basotect (height 138 mm, base area see below). The Basotect block increases the mechanical losses and thus dampens the resonance frequency. In addition, the radiation to the rear is reduced, which is usually very advantageous when the distance to the wall is too small"
PDF with pictures but without measurments:
https://www.diyaudio.com/community/...kQFnoECBIQAQ&usg=AOvVaw2a5FOV5Wm2JGTb5nVgfZ1h
What I like? More of a defined directivity than a dipole where lots of high frequency energy is reflected off the back walls. You get a sense of spaces and an image that you can't tell where it's coming from but it was very diffuse at least in my room. I ended up attenuating the back wave and that improved the imaging.
Still have them at some time I will give them another go.
Rob
