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3 Way Floor Standing Loudspeaker System

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The ESS AMT 3 rock monitor was developed to make available a hybrid system having perfect fusion between specialized cone drivers and the incredible clarity of the ESS Heil air-motion transformer midrange/tweeter.

It is so uncolored throughout its range, so detailed in its transient precision, and so powerful in its dynamic capability that no musical demands, from the purity of a solo voice to the visceral impact of a rock concert, will tax its resources.

To achieve performance at this impressive level, the ESS AMT 3 employs four drivers operating over three individual segments of the frequency range. Midrange and treble frequencies are handled by the ESS Heil air-motion transformer positioned to fully realize its unprecedented sound dispersion.

To carry the extreme definition of the ESS Heil air-motion transformer into the lower frequencies, a powerful six-inch driver, mounted in an internal transmission line, reproduces the lower midrange and upper bass. A new order of transient impact is carried into the deepest bass frequencies by the use of twin ten-inch, high gauss, foam surround woofers.

The result is a performance beyond classification, free of subtle colorations or shifts in spectral emphasis which tend to favor one musical form over another, and an unswerving full-bodied sonic accuracy that will remain an enduring value for years to come.

Styled in simple, contemporary lines. the ESS AMT 3 will blend easily into any decor; and like all ESS AMT systems, its extraordinarily wide dispersion allows complete freedom of placement with precise stereo localization at any listening position.

Uncompromising in any aspect of design, construction or performance, the AMT 3 is the most accurate hybrid system ESS can produce. A brilliant example of sound as clear as light.


Type: 3 way, 4 driver loudspeaker system

Frequency Response: 40Hz to 24kHz

Power Handling: 500W

Recommended Amplifier: 20W (minimum)

Crossover Frequency: 250, 700Hz

Impedance: 4Ω

Bass: 2 x 10" cone

Midbass: 1 x 6" cone

Tweeter: 1 x ESS Heil air motion transformer

Finish: oiled walnut veneer

Dimensions: 39-1/4 x 15-5/8 x 15-7/8 inches


instruction/owners manual   English - rcalvill

test report   English - rcalvill

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re: AMT 3

I see peeps picking up Rock Monitors, as the AMT 3 was known by in 1974. In 1974, I was living in Humbolt County, California. I decided to put together a sound system, that would just blow anything else away.
I put together a system, with the help of my friends at Sequoia Stereo in Arcata. I picked out the ESS Rock Monitors, AMT 3's. Hooked them up to a Marantz 2325, tuner/amp, 125 watts per channel, with a Sony turn table.
I still have, and use the system. The Sony turn table electronics died, so I no longer have that piece.

I want to rehab the speakers....any idea out there, on where to get components for the 6"?

Also, any feedback on the Marantz 2325, rehab and tweeking?

Thanks, Sageman

re: AMT 3

No tweeks for the 2325. A recap and adjust with good components can make it better than new. I have one and did a re cap/ restore about 4 years ago.
On the 6", the eminence Alpha 6A is a better speaker than original. Problem is you will have to cut, modify or remove the tube behind the 6" and replace with a tuned box larger than the hole. Original ESS 6 inch speakers can be found and Austin Speaker Works in Tx can restore to new shape.

If you need the best advice, contact Porkloin who commented below. He is a wiz with AMT 3 Rocks.

Porkloin Dubois's picture

re: AMT 3

The great Heil is addictive. The clarity coupled with the immersive qualities of a dipole driver makes everything else seem lacking. ESS did a commendable job bridging the woof-to-tweet gap of earlier two-ways with the 6" transition speaker.
To those of you that acquire a set and the state of the 40 year old crossovers is unknown to you, look into replacing the capacitors and resistors. It makes a noticeable difference.

re: AMT 3

Found a pair of AMT 3 Rock Monitors at the local thrift store for $40.00. Refoamed the four woofers and the the 2 mids. They make my Focal 706v's sound very sad. Have them connected to my Marantz PM 6004 amp and a Technics SL1700 and I couldn't be happier.

re: AMT 3

I am lucky enough to own a pair of these speakers that I
purchased from the original owner back in 1975. They were recently
reconditioned and new woofers installed. The sound must be heard to be
believed, absolutely incredible. Very neutral through out the entire sound range.
They were selling for $499 each in 1975 roughly $2300 in todays dollars.

re: AMT 3

Hi Richard,

I just picked up a pair of AMT3's this afternoon... One of the woofers is blown. I haven't opened it up yet to see what's going on but I see that you have replaced your woofers and love the sound...

If I can see what's wrong and fix it, I'll go that route, but if I can't, or if you saw a big improvement with your new woofers, I may be tempted to go that route...

Do you know the make and model of the woofers you used to replace the woofers (or were they just refurbished with new surrounds, etc)...

Thanks, Mike S.

This website is not affiliated with or sponsored by ESS. To purchase AMT 3 spares or accessories, please contact the company via their website or visit an authorised retailer.