Easily the best highs out there. Better than ribbons or pretty much any dome, or horn. They are so clear and dynamic. They make everything else sound slow and veiled, less powerful and dynamic. More enjoyable to listen to than the Infinity Kappa 8s, Thiels, JBL, or Carver Amazing Loudspeakers, and dozens of othes over the years.

Better through the lower midrange with new upgraded ESS woofers, and passive radiators. High current SS amplifiers are best, not as good sounding with tubes.

Extremely coherent and easy to listen to. Much better than any piston style speaker, ribbons an electrostatic speakers included. Fast, dynamic, true tonal balance, large sound stage, sound as clear as light. Dipole sound. Huge sweet spot.

The bass can sound disconnected unless you have the right high current amplification.

Sounded great in 1982 and after refoaming they still are in daily use. Parts still available 40 yrs later. Clearest cleanest highs you’ve ever heard.

They are big and heavy, but that is also a good thing.

Have had my ESS AMT's since 2004 and have gradually been improving due to some built in design flaws, most of which are bass driver and crossover related. First thing to go was the Bass driver...replaced by a taiwanese made kevlar bass driver ( 4 ohm design to match crossover values and also efficiency match to the Heils. This lasted a few months before getting stuck into the crossover and replacing with polyprops and also adjusting the values to close up the hole that exists at the crossover point. This obviously requires some calcs and common sense and blackmagic "feel for it" guesswork. I had better mention that mine are AMT1a's and don't have a passive built in and are ported instead. Final change thou is the one that really made some impact. Connected underneath each cabinet now is a subwoofer and crossover inside and the 2 x Kef bass driver ( total 4 ohm to match efficiency) and 2 x Kef passives in each lower cabinet with crossover at 150 hz - then the Taiwanese Kevlar bass driver does upper bass ( approx 200 hz up) and lower midrange to about 900 hz. The Heil takes off at about 1000 hz. Perfectly calculated 12 db crossovers are used throughout as have found any greater roll off removes too much dynamics no matter what...12 db is acceptable and the pros outweigh the cons. The upper bass cabinet with the 10 inch Kevlar is now a sealed cabinet and the damping material has increased so its almost full of damping wadding ( mix of poly fibre and wool now). One last mod thou is interesting and that is the standing wave effect of the shape of the large heil...I have placed thin felt, stick on panels to the front and rear 45 degree inner surfaces on the hanging Heil
(using bungee cord hanging from an alloy frame shaped around the heil - to eliminate microphony, forgot to mention earlier) ...anyway the thin felt panels front and back dampen the reflecting waves that would happen due to the hard reflective 45 degree surface. This means now that I run the heil on its max setting on the crossover due to reduced efficiency but the slight harsh hi end that is always there on all large heils has disappeared. This last mod is a fix that everybody who has a large heil should try out...also the hanging heil is another fantastic mod that should be looked at as well...After all this, the ESS cabinet can still have its cover on and it looks pretty much the same as it did when it came out the factory although all ESS 1's should be stand mounted as the speaker is just a bit too low on the floor by itself. Having the Keff loaded bass cabinet underneath raises speaker up to about the right amount...Have done 2 x set now to this spec and other friend and myself are very happy with the final product. All glitches with the original design are eliminated and these are sound like light at all frequencies now - not just the top end...
Thanks and hope that this helps other people to realise what these speakers are capable of.

I grew up with AMT 1b's in the house and have never heard another loudspeaker that compares for music. I finally picked up a pair for myself (AMT 1a's) and could not be more satisfied with the purchase. As many others have mentioned, you'd be hard pressed to find a better speaker for the money and perhaps at any price.

These excell at creating a wide sound stage, are incredibly efficient and can play very loud with outstanding clarity. My old man fed these with a 70's Onkyo 60w/ch, I've used an entry level pioneer vsx822 av reciever and I currently use an old Yamaha M45 120w/ch. All were more than adequate. The system gets loud driven with just 1w and I have not been able to tolerate above 60w letting em stretch their legs.

While these provide satisfying, well defined, floor shaking, chest pounding bass; they don't have the low extension of a good powered sub in a modern system. Consequently, they're not as revelatory when listening to modern music with electronic bass engineered to kick the crap out of a sub woofer or av applications in my opinion. Outside this caveat, a wide range of electronic and all acoustic instruments are reproduced exceptionally.

Another consideration with the low pass is room acoustics. The AMT sounds great in every room I've listened in, however, the room can have a remarkable effect on the woofer/radiator combo. When I picked up the 1a's I was disappointed to the point I thought there was something wrong with them. After moving them to a bedroom with carpet and a mattress I was blown away by how much better they sounded. After buying a large heavy rug and some more furniture I've got em sounding great in my listening room. While you can coax some incredibly satisfying bass out of these, I have not dealt with such pronounced room variance with modern subs.

These are available today new from Ess for $4400 a pair with the classic styling or updated cabinets.

I recently met a guy on Craigslist that I bought a vintage Pioneer Reel to Reel from that mentioned that he had an old pair of ESS AMT 1b's that needed to be repaired and he might be willing to part with them in the future. He saved my number and low and behold he called about six weeks later. He said he was moving and needed to clear some space and wondered if I was still interested in the speakers, I said of course and how much did he want for them? He responded $150.00 for the pair. I was at his house before I set down the phone. Fast forward 3 weeks and a little elbow grease and some newly re-foamed speakers and radiators and presto! Like new speakers for less than $400. I placed them in my theater room that is walled with soundproofing for acoustic balance, plugged in the speakers, lit the amp, and put in a classic Van Morison CD and the magic happened. I do not profess to be an audiophile or be capable of explaining every little nuance, but I can tell you this... Listening to these speakers makes me want to rush home to listen to all my music again. And in many cases it's like hearing it for the first time. I guess having two subs supporting the low end may have an impact, but the base produced by these speakers is definitely distinguishable from the subs so together they make beautiful highs and lows with a clarity I've never before experienced.

I have used the ESS AMT 1b, ESS Rock Monitor, and ESS AMT Monitors since 1979. AMT tweeters are the HF driver to use in any serious loudspeaker and monitor designs. Many reviews here are very old. To update, have a Google at AMT/Heil tweeters to see how many manufacturers have seen the light. The revelation starts with how one has entered into the HiFi realm. If you were raised on a diet of dome, ribbon, planar, and compression horns your brain may not grasp the AMT's immediately. To see what you have been missing just refrain from listening for a 30 day stint, I would barely make it, and then begin to listen to a AMT equipped speaker equivalent to price range of your existing speakers to level the playing field. Listen to all your favorites that you know every nuance to for 30 straight days of dedicated listening. Most (without substantial hearing loss) will rediscover their music collection within the first two weeks. At the end of the 30 day all AMT listening, hook your non-AMT speakers back up and go through your music collection again. It will be readily apparent that so much is now missing when listening to your non-AMT equipped speakers. AMT's have immediate/instantaneous response, with a what is put in comes out. Keeping this in mind there are faults with the matching of woofers in ESS' original designs. SPL is one, as ESS did not mate a quality LF unit to the AMT with near the sensitivity or the transient response to match the AMT. Keep in mind that you only gain 1db loudness when amplifier wattage doubles, so when all say there is a definite difference when there is a 3db gap between drivers, they mean it. To match a woofer to the AMT look for a 8 to 10 inch driver with a Le of .35 or lower, and voila.....AMT heavens gates open up. Some here that curse the AMT with utterances of detail/accuracy, there is no more detail and accuracy than immediacy with the Heil AMT tweeters. I too once sought detail and accuracy. When I put together my Yamaha CX 1000 pre amp, MX 1000 amp, and NS 1000 speakers there were right ther in spades. Yet it only took a couple of days to realize this is not what I wanted. I ended up hating my music collection. It exposed all the flaws of recordings. Showed me that only the big names in music could be assigned/afford a sound engineer that could provide a truly good recording in the studio. Every audio enthusiast needs to introduce our younger generation to real HiFi instead of the LoFi, NoFi, and ChiFi that is out there today such as earbuds, Beats "Pill" etc. streaming horribly compressed music that in no way conveys emotion, meaning, or thrill of MUSIC. CES show planners should allow ALL children and youths in for free. These are the future of HiFi, consumers, researchers, and possibly even performers. Otherwise HiFi will die with the generations that know and truly appreciate real High Fidelity music playback. For now it is amazing to see so many manufacturers making and using AMT tweeters in their designs. I love the AMT tweeter speakers for all leisure/semi-critical listening, but still prefer Horn designs when I crank things up to concert levels. My 10 watt Air Tight Amp with the cornerhorns is still magical. All in all still buy with your ears, not your eyes. Everyone has different taste in music and preferences in sound of playback, so don't be swayed.

I read every one of the reviews here, because on getting these speakers into the workshop for repair of the cone surrounds and passive radiators for the owner a friend, I was stunned by the detail of the Heils, and the firm controlled bass down to very low frequencies. I went looking for info on what exactly I had found. After listening some more and reading all those reviews to see if I should believe my ears I ended up buying them from the owner for $600 Ca. They are the 1B model which has crossover control via two pots one for midrange presence and the other for Brilliance. I found online ESS have posted the circuit diagrams for these crossovers and all the early AMT speakers using the Heils. Notably the new reformed ESS company is also building these speakers again almost 40 years later at a price of $4400 a pair with what appears to be essentially the same arrangement as the past. Go figure ! Replacement parts are also available to repair Heils and perished speaker cones and surrounds.

The vast majority of reviews here tell the story,these are wonderful speakers and if found used, worth restoring and then treasuring and listening to perhaps for the rest of your life as many of the owners here already are. .

For all the fussing audiophile people do with audio gear, turntables, amps, wires and CD players etc nothing can make as much difference to the end sound as a pair of really good speakers like these, properly placed in a good room. The fact you can still find these for a few hundred bucks should wake everyone up to the fact that an audiophile level steal is still possible.

The criticism of some good ears in the reviews here is that in really crowded music content there is a loss of detail in the lower mids due to the use of the Heil down at such a low crossover ( 800 Hz). Some claim there is a large frequency " hole " between the two drivers. but others contradict this. Numerous very serious audiophiles review and rate the Heil transformer as one of the very best tweeters EVER.

For myself Im just sitting back and enjoying all my music anew.

Thanks to this site for the encouragement !

Had a pair about a month, then found DQ 10 it was over. good speaker for its time.

I own a pair of the original AMT 1's. Not the A, B, C, or D models with the 12" and passive radiator. Mine have 10" drivers in ported cabinets. Aside from that, the differences between mine and the A's and B's are minor.
These are some of the most honest speakers you're ever going to hear. The air-motion transformer on any AMT 1 is extremely clear and uncolored all the way down to 800 Hz. The complaint you often hear about the AMT 1 line is that the woofer can keep up with the air-motion transformer, which is true, especially for the models with 12" woofers. This is hardly a glaring flaw, however, and shouldn't be overstated as such. There is no such thing as a functionally massless woofer and that's what it would take to match the AMT. Bass is solid, balanced, and crisp overall. The models sporting the 12" gain lower bass extension at the cost of speed and accuracy whereas the 10" ported model drops off sharply below 45 Hz.
These are speakers I'd put up against the best names and find comparable, if not better. Numerous companies are making knock-offs of the air-motion transformer, such as Martin-Logan and hearing them makes the reasons obvious. If you're looking for a very honest speaker that lacks failings which relegate it to a select few genres of music, which is truly capable of reproducing a three dimensional sound stage, this speaker may be what you're looking for. I consider them vastly superior to B&W's middle weight offerings. In fact, I'd go so far as to say there are extremely few speakers at any price that use conventional drivers that can compare. That's a bold statement, but I think it's honest and I'd invite you to test that statement.
ESS is back at it, by the way, with a new and broadened product line.