ESS AMT 1-AM

The ESS AMT 1-AM shows up in enough places to be real, but rarely with much detail attached. What the record shows: it was a floor-standing loudspeaker built around the company's Heil air-motion transformer tweeter - the "AMT" in the name - paired with a 12" original paper-cone woofer. Some listings also mention a 12" flat passive radiator, which would make it a two-way-plus-radiator design. No midrange driver is confirmed for this model in any of the surviving documentation.

The "AM" or "aM" suffix remains unexplained. A diyAudio thread from someone restoring a pair asks which of two woofer variants from an old ESS catalog belongs in the cabinet - a 12" rated at 350 watts max, or a 12" CF rated at 200 watts max. The thread never resolves the question. A forum post refers to a "1982 mod" version, and one owner on Pinterest simply called them "beautiful sounding speakers." A 1973 ad and brochure exist for the related AMT-1 Heil Air Tweeter, which suggests the family goes back to the early days of ESS. The 1-AM itself has no confirmed production dates.

Two practical notes from owners. A forum member testing a pair measured a 9 dB drop in frequency response around 11-12 kHz, and a YouTube repair video documents a failure where the transformer/tweeter produced no sound. Both point to the AMT driver as the part to check on a used pair. A Russian-language video series also documents a full restoration with crossover ("filter") modification, which fits the general collector advice that these benefit from refreshed crossovers.

Asking prices vary widely. A professionally restored pair was listed at $1,999 and another at $3,599, while unrestored pairs in Europe have appeared around €799 - €840. A Sacramento Craigslist pair went for $1,174. That is a snapshot of what's been asked recently, not a reliable market guide.

Known Specs

• Type: Floor-standing loudspeaker / monitor
• Tweeter: Heil air-motion transformer (AMT)
• Woofer: 12" original paper cone
• Passive radiator: 12" flat (per some listings)
• Woofer power rating (two catalog variants): 350W max or 200W max (CF)

No dimensions, weight, impedance, sensitivity, or frequency response figures have surfaced for this model. If you own a pair or have an original manual, the Archive would like to hear from you.

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