ESS Performance PS-9 (1980–1982)
The pyramid cabinet is just under half a meter tall. The quiet highs from the Heil AMT tweeter are the main attraction.
Overview
The ESS Performance PS-9 came out between 1980 and 1982 as part of ESS's mid-tier line, built in the USA. At the time, Air Motion Transformer (AMT) tweeters were still rare outside high-end audiophile circles. ESS doesn't officially brand the PS-9 as an "electrostatic" speaker, but it uses the Heil Air-Motion tweeter. That tweeter has a pleated conductive diaphragm that squeezes air more efficiently than a conventional dome. It gives the tweeter its speed and clarity, especially with tube amplification. Owners report soundstage depth and spatial imaging that belie the speaker's modest footprint, with midrange and high frequencies delivered with absolute clarity. The 2-way configuration and compact cabinet mean the bass is somewhat lacking. That's the trade-off for the focused upper register.
The pyramid shape is acoustically efficient and allows unobstructed dispersion of mid and high frequencies, but the PS-9 has still drawn criticism. Forum reports on similar variants, such as the PS-9a, suggest a noticeable gap in the midrange frequency response, where the woofer and tweeter fail to blend well. It remains unclear whether this affects all PS-9 units, but it's noted often enough to give cautious buyers pause. The Heil AMT tweeters themselves are consistently praised. They are solidly built, with 6-pound ceramic magnets adding heft and stability to the high-frequency driver. The speakers were designed to work best with low-power tube amplifiers, where their efficiency shows, and they reportedly underperform with solid-state gear.
Specifications
| Manufacturer | ESS (ElectroStatic Sound Systems) |
| Model | Performance PS-9 |
| Type | Loudspeaker |
| Production Years | 1980–1982 |
| Country of Origin | USA |
| Design | 2-way speaker |
| Tweeter Type | Heil Air-Motion tweeter |
| Cabinet Finish | Walnut |
| Dimensions (WxHxD) | approximately 26x46x26 cm |
| Front Coverings | Removable |
| Terminal Instructions | Strip about 7 mm of insulation from speaker wire |
Key Features
Heil Air-Motion Tweeter with Pleated Diaphragm
The Heil Air-Motion tweeter is the main part of the PS-9. It folds a thin, conductive membrane into pleats and mounts them within a powerful magnetic field. When current flows, the pleats expand and contract laterally, "squeezing" air forward faster than a piston-driven dome can. The result is exceptional transient response and low distortion in the upper frequencies. Owners note the tweeter delivers openness and detail that remain impressive even by modern standards, particularly with acoustic and vocal recordings. According to available documentation, all ESS AMT units were built to high mechanical tolerances, with substantial ceramic magnets contributing to long-term reliability.
Pyramid-Shaped Cabinet for Unobstructed Dispersion
The pyramid form has a clear acoustic purpose beyond looks. By tapering upward, the cabinet minimizes baffle edge diffraction and lets the midrange and tweeter radiate sound freely in multiple directions. This contributes to a wide, stable soundstage and precise imaging, qualities that collectors rate highly. The shape also reduces internal standing waves compared to rectangular enclosures, though the compact size limits bass extension. The solid wood construction with walnut finish adds rigidity and a degree of damping, supporting cleaner driver output.
Woofer with Critically Damped Magnetic Circuit
The 8-inch woofer (exact size not confirmed for PS-9, but consistent with ESS 2-way models of the era) uses a magnetic circuit designed to critically damp the moving assembly. The cone motion is tightly controlled, which reduces overhang and resonance after the signal stops. The goal is faster, more accurate bass within the limits of the cabinet volume. The bass is described as somewhat lacking, likely due to physical limitations rather than poor execution, but the damping helps keep the lower mids coherent. The transition to the tweeter appears to be a weak point, with user reports indicating a potential mismatch in the crossover region.
Collectibility & Value
The PS-9 originally cost approximately 574 Deutsche Mark per piece and sat in the mid-range of the German hi-fi market during its production run. Collectors value it mainly for the Heil AMT tweeter and the pyramid form, though critical reception is mixed. Some owners report excellent performance with tube amplifiers, rating imaging and clarity at the highest level. Others cite a noticeable gap in the midrange frequency response, particularly in variants like the PS-9a, and raise concerns about the crossover implementation. Common maintenance issues are not explicitly documented for the PS-9, but similar ESS models often need woofer refoaming and crossover capacitor replacement. Units typically show minor cosmetic wear consistent with age, described by some as "Wabi Sabi" - a patina of use rather than damage.
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