Heil Air Motion Transformer
I have owned a pair of the AMT-1s since 1971 and still in use today. The high frequency response and accuracy is dead accurate. However, being the original version with the ported 10" woofer they are anemic in the lowest bass octaves. The published crossover frequency is 800Hz using a 12dB/octave passive crossover. The AMT Tweeter is so efficient that the is a 6ohm power resistor in series with the tweeters diaphram to pad down the delivered voltage. Since the voice coil is not wound, but instead folded, the unit is resistive, not inductive. That present a constant impedence to achieve high definition. Years ago I bought a set of "PolySwitch" resettable devices from Radio Shack and wired them in series with the AMT tweeters. Since then I have not had to replace them. Good thing since ESS was out of business until recently. These PolySwitch devices act like wire until an over-current condition occurs and then its resistance climbs (positive temperature co-efficient) to limit damaging current to the diaphram. As stated earlier, I used these since 1971 and haven't repalced diaphrams in over twenty years. My audio system consists of a Crown Straight-Line 2 Preamp and a DC-300A power amp (no light weight in terms os available power.). I would like to custom build a custom enclosure with one or two woofers for the low end and the HEIL's covering the highs. I have a Crown D-150A and a custom crossover for Bi-amplification of the respective drivers. Any suggestions on enclosures incorporating two woofers? All designs viewed so far so formulation for a single woofer.
I have owned a pair of the AMT-1s since 1971 and still in use today. The high frequency response and accuracy is dead accurate. However, being the original version with the ported 10" woofer they are anemic in the lowest bass octaves. The published crossover frequency is 800Hz using a 12dB/octave passive crossover. The AMT Tweeter is so efficient that the is a 6ohm power resistor in series with the tweeters diaphram to pad down the delivered voltage. Since the voice coil is not wound, but instead folded, the unit is resistive, not inductive. That present a constant impedence to achieve high definition. Years ago I bought a set of "PolySwitch" resettable devices from Radio Shack and wired them in series with the AMT tweeters. Since then I have not had to replace them. Good thing since ESS was out of business until recently. These PolySwitch devices act like wire until an over-current condition occurs and then its resistance climbs (positive temperature co-efficient) to limit damaging current to the diaphram. As stated earlier, I used these since 1971 and haven't repalced diaphrams in over twenty years. My audio system consists of a Crown Straight-Line 2 Preamp and a DC-300A power amp (no light weight in terms os available power.). I would like to custom build a custom enclosure with one or two woofers for the low end and the HEIL's covering the highs. I have a Crown D-150A and a custom crossover for Bi-amplification of the respective drivers. Any suggestions on enclosures incorporating two woofers? All designs viewed so far so formulation for a single woofer.
Hi all,
I bought a pair of the 'Grand heils' from a friend who was introduced to the AMTs' a long time ago. He also bought from the States a pair of the very cheap looking 12" woofers that ESS used to use. Having heard them I know they are a pretty good match for the Heils.
I see many are using quite high x/over points. ESS used to x at 600Hz but changed to 800-900Hz.
Surely it's better to keep the x/overs out of the 'intelligence band' or as low as possible.
The idea of using a rear baffle with the Heils, would appear to be sound.
I don't like the idea of 3-ways and I have been searching for a year to find a suitable 15" woofer.
The last thing I want to do is throw away the Heils 95/6 dB sensitivity.
I don't think big heavy pro woofers are what is required and to that end have been thinking about Pioneer A38GU40-52F - 15". They are 8 Ohms but if a 900Hz x/over is used they should be operating closer to 4 Ohms. This Pioneer may be cheap (about $46) but it's paper, 100W/200W max, which is more than enough and well made.
One thing I see nobody has mentioned - active x/overs. For a 2-way only one is required. No more phase problems and no more energy wasted as in passive x/overs. Control belongs with the amps (bi-amping) which is the way it should be.
Interestingly it appears that the only reason chipboard was dropped for MDF around 1980 was one of economics. It, chipboard makes for far better speaker cabinet material. So this is the material I shall use for the woofer cabinets.
Also has anyone thought about seperating the Heils from the woofer, by making a frame just for the Heils. With active x/over/s situated on your equipment racks, you are then free to move the two elements (with 2-ways) for best acoustic response.
I will use a Berhinger active x/over to start with and will get some knowledgeable friends to design a valve version if things pan out right - which they should.
I would appreciate any input on any paper, 15" / 4/8 Ohm/ 96dB + which I realise are becoming harder to find as time goes on.
Black Stuart
I bought a pair of the 'Grand heils' from a friend who was introduced to the AMTs' a long time ago. He also bought from the States a pair of the very cheap looking 12" woofers that ESS used to use. Having heard them I know they are a pretty good match for the Heils.
I see many are using quite high x/over points. ESS used to x at 600Hz but changed to 800-900Hz.
Surely it's better to keep the x/overs out of the 'intelligence band' or as low as possible.
The idea of using a rear baffle with the Heils, would appear to be sound.
I don't like the idea of 3-ways and I have been searching for a year to find a suitable 15" woofer.
The last thing I want to do is throw away the Heils 95/6 dB sensitivity.
I don't think big heavy pro woofers are what is required and to that end have been thinking about Pioneer A38GU40-52F - 15". They are 8 Ohms but if a 900Hz x/over is used they should be operating closer to 4 Ohms. This Pioneer may be cheap (about $46) but it's paper, 100W/200W max, which is more than enough and well made.
One thing I see nobody has mentioned - active x/overs. For a 2-way only one is required. No more phase problems and no more energy wasted as in passive x/overs. Control belongs with the amps (bi-amping) which is the way it should be.
Interestingly it appears that the only reason chipboard was dropped for MDF around 1980 was one of economics. It, chipboard makes for far better speaker cabinet material. So this is the material I shall use for the woofer cabinets.
Also has anyone thought about seperating the Heils from the woofer, by making a frame just for the Heils. With active x/over/s situated on your equipment racks, you are then free to move the two elements (with 2-ways) for best acoustic response.
I will use a Berhinger active x/over to start with and will get some knowledgeable friends to design a valve version if things pan out right - which they should.
I would appreciate any input on any paper, 15" / 4/8 Ohm/ 96dB + which I realise are becoming harder to find as time goes on.
Black Stuart
15"/96 db sound like a pro woofer to me. I think it will be a pretty hard job to find a suitable 15"woofer wich has a nice clean extension up to about 2kHz wich is what you will need when crossing at say 800-900 Hz. The only one's wich could do the job so far wich I have heard where some quite expensive TAD/Pioneer 15"woofers.
On the other hand it will be much easier to find a suitable 10 or 12" driver wich will be up to the task. Take a look at the range of PHL drivers. These drivers are also used by the very best PA compagnies as lowmid ranges. They've got some very good sounding 12"drivers with very good bottom extension, but as always (law of physics) the sensitivity drops a few db in exchange for this extension. In the end you will get aprox 92 dB sensitivity in an enclosure (wich is a whole lot more than the average 86db when typical "hifi" drivers are used)
I have read a lot about people using Eminence drivers with good results (like Bastanis and PI speakers) wich are cheaper but I don't have any experience with them. You might check on the PI speakers website and forum.
On the other hand it will be much easier to find a suitable 10 or 12" driver wich will be up to the task. Take a look at the range of PHL drivers. These drivers are also used by the very best PA compagnies as lowmid ranges. They've got some very good sounding 12"drivers with very good bottom extension, but as always (law of physics) the sensitivity drops a few db in exchange for this extension. In the end you will get aprox 92 dB sensitivity in an enclosure (wich is a whole lot more than the average 86db when typical "hifi" drivers are used)
I have read a lot about people using Eminence drivers with good results (like Bastanis and PI speakers) wich are cheaper but I don't have any experience with them. You might check on the PI speakers website and forum.
Dag, Sjef
do you have any website for me to look at these TAD/Pioneer woofers.
I sent an e-mail to Pioneer/Europe a couple of months ago, which incidentally is based in the Netherlands but got no response.
Hi JohnL, yes it can be done. In fact the only reasons that 15" woofers have not featured in many speaker designs are two-fold. One is the dreaded WAF (wife acceptance factor), which is of course their bulk and secondly the average size of living rooms outside of N. America.
Quite simply the style fascists have since the 80's demanded that speakers should have a small footprint, with multiple drivers - they just don't cut the mustard, compared to a 12" or 15" woofer and of course they don't have the efficiency either.
My reasons for wanting efficient speakers is that I will use less 'juice'with smaller output valve amps as I intend to build a house powered by alternative energy sources - PV ai'nt cheap.
Keep the info coming please.
do you have any website for me to look at these TAD/Pioneer woofers.
I sent an e-mail to Pioneer/Europe a couple of months ago, which incidentally is based in the Netherlands but got no response.
Hi JohnL, yes it can be done. In fact the only reasons that 15" woofers have not featured in many speaker designs are two-fold. One is the dreaded WAF (wife acceptance factor), which is of course their bulk and secondly the average size of living rooms outside of N. America.
Quite simply the style fascists have since the 80's demanded that speakers should have a small footprint, with multiple drivers - they just don't cut the mustard, compared to a 12" or 15" woofer and of course they don't have the efficiency either.
My reasons for wanting efficient speakers is that I will use less 'juice'with smaller output valve amps as I intend to build a house powered by alternative energy sources - PV ai'nt cheap.
Keep the info coming please.
Hi dshortt9,
they look great - one in the eye for the small footprint brigade.
Is that a port on the side or a passive radiator?
I was going to bid on a pair of 12" Klips here in Europe but they went for a pretty penny.
Are you using a passive or active x/over? Anyway I'd like to hear them.
Have you considered removing the Heils from any possible woofer cabinet vibration, or is there any vibration coming from your cabs.?
they look great - one in the eye for the small footprint brigade.
Is that a port on the side or a passive radiator?
I was going to bid on a pair of 12" Klips here in Europe but they went for a pretty penny.
Are you using a passive or active x/over? Anyway I'd like to hear them.
Have you considered removing the Heils from any possible woofer cabinet vibration, or is there any vibration coming from your cabs.?
There are 2 4" ports, one on each side. One 10" woof on front and one on the rear. I am using a passive series crossover, just one cap and inductor. This contributes to the excellent performance. Higher order parallel crossovers can work but are much harder to design and IMHO can arguably degrade performance. Maybe I am just going through a phase of minimalism. I like to keep it simple as possible. The drivers seem to match well since the woofs were meant to be used with a horn they are fast enough to keep up with the ribbon. The series crossover is easy since it is very flexible - regardless of the values used they will mesh the drivers well. I calculated the original values and tweaked them by ear. No boom or overhang, very articulate. can seperate 2 basses playing with no problem.
The fronts are 1" plywood and have no vibration to speak of, especially on the edge. The Heil's weigh 12 pounds so are not easily shaken anyway. They go down to an honest 32 hz and will startle you with transients like the 1812 Overature has. I literally jump at times. Always available for an audition.
The fronts are 1" plywood and have no vibration to speak of, especially on the edge. The Heil's weigh 12 pounds so are not easily shaken anyway. They go down to an honest 32 hz and will startle you with transients like the 1812 Overature has. I literally jump at times. Always available for an audition.
Hi dshortt9,
you can never go wrong keeping it simple. Using the Klipsch woofers is exactly right - as you say they keep up with the Heils.
I'd love to hear your speakers but Andalucia to Wisconsin is some trip.
Active x/overs - take a look at Rod Elliot's, Elliots Sound Products site & TNT-Audio for the articles on active x/overs. Until I read Rod's take on it, I just did'nt realise how much of an amp's power is dissipated in heating up the components in a passive x/over.
I've bought a Berhinger to start with but I can see a valve active x/over in the pipeline.
you can never go wrong keeping it simple. Using the Klipsch woofers is exactly right - as you say they keep up with the Heils.
I'd love to hear your speakers but Andalucia to Wisconsin is some trip.
Active x/overs - take a look at Rod Elliot's, Elliots Sound Products site & TNT-Audio for the articles on active x/overs. Until I read Rod's take on it, I just did'nt realise how much of an amp's power is dissipated in heating up the components in a passive x/over.
I've bought a Berhinger to start with but I can see a valve active x/over in the pipeline.
Hi all
I've got two questions. 1st, - can anyone input on the following Pioneer woofers;
A30GU40-51D 12" poly 96dB/23-1,500Hz - 6 Ohms
A38GU40-52D 15" poly 96dB/24-2,500Hz 6 Ohms
A38GU40-52F 15" paper 96dB/20-3,000Hz 8 Ohms
My preference will always be for paper coned woofers and I've been told that mostly woofers will be working around 4 Ohms even if they are rated at 8 Ohms.
As the woofers have to work with the AMT's which are a steady 3.6 Ohms, I am steered towards the Pioneer polys about which I know nothing. I have read on another forum that the paper coned Pioneers are sonically excellant and a 'steal' @$50 a piece.
I have no intention of reigning in the Heils and would like to think that I could use the 15" Pioneer. The other solution is to parallel (2) of the 12" polys or (2) of the paper 15" or is this overkill.
Most important though is info on the poly woofers.
2nd, can anyone give me an address on the European mainland, where I can buy pioneer woofers. I may have an address for the UK but would prefer it if I can buy in Spain - either of these will save me a fortune in postage if I have to buy from the States.
I've got two questions. 1st, - can anyone input on the following Pioneer woofers;
A30GU40-51D 12" poly 96dB/23-1,500Hz - 6 Ohms
A38GU40-52D 15" poly 96dB/24-2,500Hz 6 Ohms
A38GU40-52F 15" paper 96dB/20-3,000Hz 8 Ohms
My preference will always be for paper coned woofers and I've been told that mostly woofers will be working around 4 Ohms even if they are rated at 8 Ohms.
As the woofers have to work with the AMT's which are a steady 3.6 Ohms, I am steered towards the Pioneer polys about which I know nothing. I have read on another forum that the paper coned Pioneers are sonically excellant and a 'steal' @$50 a piece.
I have no intention of reigning in the Heils and would like to think that I could use the 15" Pioneer. The other solution is to parallel (2) of the 12" polys or (2) of the paper 15" or is this overkill.
Most important though is info on the poly woofers.
2nd, can anyone give me an address on the European mainland, where I can buy pioneer woofers. I may have an address for the UK but would prefer it if I can buy in Spain - either of these will save me a fortune in postage if I have to buy from the States.
At first I was going to discourage you from the use of these drivers: but they're pretty nice seeming. However: you'll be hard pressed to get even the best 15" to keep up with the heils. You're talking about a 99% reduction in moving mass at the driver transition, so the 15" might not be able to reproduce the transient response you want for them to blend well. My own design for the heils (which hasn't been built yet) uses a 6.5" to go between the 15" and heil.
Whatever you do, good luck!
Whatever you do, good luck!
Hi Badman,
I'm a complete novice at building speakers, so I am really open to all educated views.
I bought a s/hand pair of Great Heils from a friend in the UK and had a good listen to his copy of the ESS AMT-1 ( it uses the same woofers and x/over.
The secret of this speaker was using a relatively lightweight paper woofer, which many thought was crap but was key to melding with the Heil. It's for this reason that I will not use a pro woofer.
I like the idea of using the 15" Pioneer but have not ruled out using a Klipsch K33E, trouble is I can't find out it's frequency range. As long as it goes reasonably low (30Hz) and up to 2500Hz that's fine, also it's 4Ohm and has an SPL of 97.4dB
Can you explain why you want use a mid-range unit when the whole beauty of the Heils is that they are a true mid/high unit, which makes the whole x/over thing that much simpler.
ESS used to x/over at 4/600Hz but quickly changed that to 800Hz. I intend to x/over at 900Hz and use an active x/over. This in turn means that both units are totally seperate (the Heils will be slung from their own frames) so making it simple (relatively) to time align them with the woofers in their cabinets and to deal with room nodes.
The other option, which is a no-no for many because of the WAF factor is to use huge OBs and when sorted can be used as artworks - just a thought.
I'm a complete novice at building speakers, so I am really open to all educated views.
I bought a s/hand pair of Great Heils from a friend in the UK and had a good listen to his copy of the ESS AMT-1 ( it uses the same woofers and x/over.
The secret of this speaker was using a relatively lightweight paper woofer, which many thought was crap but was key to melding with the Heil. It's for this reason that I will not use a pro woofer.
I like the idea of using the 15" Pioneer but have not ruled out using a Klipsch K33E, trouble is I can't find out it's frequency range. As long as it goes reasonably low (30Hz) and up to 2500Hz that's fine, also it's 4Ohm and has an SPL of 97.4dB
Can you explain why you want use a mid-range unit when the whole beauty of the Heils is that they are a true mid/high unit, which makes the whole x/over thing that much simpler.
ESS used to x/over at 4/600Hz but quickly changed that to 800Hz. I intend to x/over at 900Hz and use an active x/over. This in turn means that both units are totally seperate (the Heils will be slung from their own frames) so making it simple (relatively) to time align them with the woofers in their cabinets and to deal with room nodes.
The other option, which is a no-no for many because of the WAF factor is to use huge OBs and when sorted can be used as artworks - just a thought.
The response curves I've seen for the heils show a dip from 1k-2k, and, apart from that, using a true mid will let me push the mid/woof XO down lower. Right now I'm using them 4th order@1k with a pair of sealed 8"s, and it doesn't suck. Another nice feature: As a true 'tweeter', the heils will be able to soak up more power: I'm all for a huge amount of headroom.
The real issue, for me, is optimized transient behavior. I want to use a mid, as I want to have a low mass transducer (10g) between the super low mass heil (1g) and the relatively heavy 100g 15".
But that's all theory. The reason I build my speakers in a modular way and use an active crossover is because I try things many many ways.
The real issue, for me, is optimized transient behavior. I want to use a mid, as I want to have a low mass transducer (10g) between the super low mass heil (1g) and the relatively heavy 100g 15".
But that's all theory. The reason I build my speakers in a modular way and use an active crossover is because I try things many many ways.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.