Infinity BETA-ES250: The Electrostatic Elegance of a Forgotten Hybrid

Name: Infinity BETA-ES250
Brand: Infinity

In the mid-1980s, as high-end audio was undergoing a renaissance of innovation, Infinity Systems—already renowned for its groundbreaking speaker designs—introduced a unique and ambitious product: the BETA-ES250. Unlike traditional dynamic loudspeakers or full-range electrostatics, the BETA-ES250 was a hybrid electrostatic design that merged the precision of electrostatic midrange and treble reproduction with the punch and authority of a dynamic bass driver. Positioned as a premium offering in Infinity’s BETA series, the ES250 represented the company’s attempt to deliver the best of both worlds: the speed and transparency of electrostatic panels with the low-end extension and room-filling power of conventional cone drivers.

Though not as widely recognized as the iconic IRSV or the mass-market Beta series bookshelf models, the BETA-ES250 occupies a special niche in vintage audio history. It reflects a bold engineering philosophy and a moment when manufacturers were pushing the boundaries of what was possible in home audio reproduction.

Technical Specifications

Specification	Detail
Type	Hybrid electrostatic / dynamic speaker
Frequency Response	35 Hz – 22 kHz (±3 dB)
Sensitivity	89 dB (2.83V/1m)
Nominal Impedance	8 ohms (compatible with most amplifiers)
Crossover Frequency	500 Hz (electrostatic to woofer)
Tweeter	Full-range electrostatic panel
Woofer	12-inch treated paper cone (1 per side)
Enclosure Type	Transmission line / hybrid cabinet
Recommended Amp Power	50–200 watts per channel
Dimensions (H×W×D)	48" × 16" × 24" (122 cm × 41 cm × 61 cm)
Weight	78 lbs (35.4 kg) per speaker
Finish Options	Black ash, walnut veneer

The BETA-ES250’s design centers around a large, vertically oriented electrostatic panel that handles frequencies above 500 Hz. This panel, constructed with a thin, electrically charged diaphragm suspended between perforated stator plates, delivers the near-instantaneous transient response and low distortion characteristic of electrostatic transducers. Below 500 Hz, a dedicated 12-inch dynamic woofer takes over, housed in a transmission-line cabinet that enhances bass extension and reduces resonance.

The crossover between the electrostatic panel and the woofer is carefully engineered to ensure a smooth transition, avoiding the “crossover dip” or phase anomalies that often plague hybrid designs. The result is a speaker that aims for both accuracy and emotional engagement.

Sound Characteristics and Performance

The sonic signature of the Infinity BETA-ES250 is nothing short of captivating. The electrostatic panel delivers a level of clarity and airiness in the midrange and treble that few dynamic drivers can match. Vocals are rendered with startling realism—individual breaths, subtle inflections, and harmonic textures are all preserved with exceptional fidelity. Instruments like violins, acoustic guitars, and cymbals shimmer with lifelike presence and spatial precision.

The 12-inch woofer, while not as fast as the electrostatic panel, is well-integrated and provides deep, articulate bass down to 35 Hz. Thanks to the transmission-line design, the bass is taut and controlled, avoiding the boominess that sometimes plagues ported enclosures. The overall balance is neutral to slightly warm, making the ES250 equally at home with classical recordings, jazz trios, and rock music.

One of the most praised aspects of the BETA-ES250 is its soundstage. The electrostatic panel produces a wide, three-dimensional image with excellent depth and instrument separation. Listeners often report the sensation that the speakers have “disappeared,” leaving only the music suspended in space.

However, like all electrostatic designs, the ES250 has a directional dispersion pattern. The sweet spot is relatively narrow, requiring careful placement and listener positioning. Additionally, while the sensitivity is respectable at 89 dB, the electrostatic panel demands clean, stable amplification—especially in the upper frequencies where voltage swings can be high.

Notable Features and Innovations

The BETA-ES250 was not just another speaker in Infinity’s lineup—it was a statement of technological ambition. Among its most notable features:

Hybrid Electrostatic Design: At a time when full electrostatic speakers (like the Quad ESL-57 or KLH Model Nine) were admired but limited by bass performance, Infinity’s hybrid approach offered a practical compromise. The ES250 delivered electrostatic clarity without sacrificing low-end authority.

Transmission-Line Bass Cabinet: The woofer is housed in a long, folded transmission line that acts as an acoustic labyrinth, absorbing rear-wave energy and reinforcing bass output. This design reduces distortion and enhances low-frequency extension.

Modular Construction: The electrostatic panel and woofer section are built as separate modules within the same cabinet, allowing for easier servicing and alignment.

High-Voltage Power Supply: Each speaker contains an internal power supply that generates the high voltage (typically 2–3 kV) required to charge the electrostatic diaphragm. This eliminates the need for external power units, a convenience compared to some electrostatic competitors.

Aesthetic Elegance: With its tall, narrow profile and fine wood veneer finishes, the ES250 was as much a piece of furniture as it was audio equipment. The perforated metal stator grille adds a futuristic touch, hinting at the advanced technology within.

Common Issues and Maintenance

As with any vintage electrostatic speaker, the BETA-ES250 requires attentive care. Over time, several issues may arise:

Diaphragm Degradation: The ultra-thin Mylar diaphragm in the electrostatic panel can become brittle or develop static cling, leading to distortion or “crackling” sounds. Re-lacing or re-paneling by a specialist may be necessary.

Stator Corrosion: If exposed to high humidity, the metal stators can corrode, causing arcing or reduced output. Keeping the speakers in a dry environment is essential.

Power Supply Failure: The internal high-voltage supply uses aging capacitors and transformers that may fail after decades. A recapping by a qualified technician is often recommended for long-term reliability.

Woofer Surround Deterioration: The foam or rubber surrounds on the 12-inch woofer may dry out and disintegrate. Replacement surrounds or full reconing are common restoration steps.

Owners are advised to avoid placing the speakers too close to walls, as this can increase the risk of arcing due to humidity buildup. Regular dusting with a soft brush or anti-static cloth helps maintain performance.

Current Market Value and Collectibility

The Infinity BETA-ES250 is a rare find today. It never achieved the commercial success of Infinity’s more mainstream Beta speakers, and production numbers were relatively low. As a result, working pairs in good condition can command prices between $800 and $1,500, depending on cosmetic condition, functionality, and whether they’ve been restored.

Collectors of vintage hybrid speakers, particularly those interested in the evolution of electrostatic technology, value the ES250 for its engineering ingenuity and sonic character. While not as iconic as the Quad ESLs or the Acoustat models, the BETA-ES250 represents a fascinating chapter in American speaker design.

Its hybrid nature also makes it more practical than full electrostatics for modern use, especially in larger rooms or with dynamic music genres.

Conclusion and Legacy

The Infinity BETA-ES250 stands as a testament to a bold era in audio engineering—one where manufacturers weren’t afraid to experiment with radical technologies in pursuit of sonic perfection. By blending electrostatic clarity with dynamic bass, Infinity created a speaker that offered both refinement and realism.

Though overshadowed by more famous models, the BETA-ES250 deserves recognition as a sophisticated, forward-thinking design. For the vintage audio enthusiast, it offers a unique listening experience: the speed and transparency of electrostatics, grounded by the warmth and power of a well-engineered woofer.

Today, the BETA-ES250 is more than just a relic—it’s a bridge between two worlds of speaker design, and a reminder that innovation often lies at the intersection of seemingly opposing technologies. For those willing to restore and appreciate it, the ES250 remains a compelling choice for high-fidelity listening with a touch of vintage elegance.