Infinity ES-300: The Elegant Fusion of Electrostatic Clarity and Dynamic Bass

Name: Infinity ES-300
Brand: Infinity

In the early 1980s, Infinity Systems, already known for its work in loudspeaker design, moved into high-end electrostatics with the ES-300. It is a tall floor-standing hybrid that pairs an electrostatic panel with conventional dynamic drivers. The idea was to get the transparency and speed of an electrostat without the usual trouble with bass response and efficiency. It is not as well documented as some of its contemporaries.

Historical Context and Design Philosophy

In the early 1980s, companies like MartinLogan, Acoustat, and Sound Lab were pushing electrostatic loudspeaker design hard. Their speakers were known for clarity, low distortion, and lifelike imaging. They were also criticized for limited bass extension, low sensitivity, and demanding amplifier requirements.

Infinity was known for its technical ingenuity, especially through co-founder Arnie Nudell’s engineering. The ES-300 was its hybrid answer to those shortcomings: a tall, slender speaker with a large electrostatic panel for the midrange and treble, and a dedicated dynamic woofer enclosure for bass. The approach mirrored Infinity’s earlier work with servo-controlled subwoofers and tapped horn designs, applied here to make a more practical, full-range electrostatic speaker.

A purely electrostatic speaker needs large diaphragms for bass, which means massive panels and high voltages. The ES-300 skips that. It hands the low frequencies to a sealed or ported bass cabinet mounted at the base. The electrostatic panel handles the mids and highs, and the dynamic driver handles the bottom of the spectrum.

Technical Specifications

Specification	Detail
Type	Hybrid electrostatic / dynamic speaker
Frequency Response	45 Hz – 20 kHz (±3 dB)
Sensitivity	89 dB (2.83V/1m)
Nominal Impedance	8 ohms (compatible with most amplifiers)
Crossover	Passive, integrated at ~450 Hz
Electrostatic Panel	Full-height stator-driven diaphragm
Bass Driver	10" or 12" dynamic woofer (exact size varies by production batch)
Enclosure	Separate bass cabinet with internal bracing
Recommended Amplifier	50–200 watts per channel, high current
Dimensions (H×W×D)	78" × 16" × 20" (approx.)
Weight	75 lbs (34 kg) per speaker
Inputs	Single pair of 5-way binding posts

The ES-300’s electrostatic panel operated on a high-voltage bias system, requiring internal power supplies (built into the base cabinet) to charge the stators. This eliminated the need for external power supplies or wall-wart transformers, a convenience compared to some competitors. The panel itself was constructed with precision-spaced stators and a thin, tensioned Mylar diaphragm coated with a conductive layer—technology refined from earlier Infinity electrostatic experiments.

Sound Characteristics and Performance

The sound of the Infinity ES-300 is effortless clarity, spacious imaging, and natural tonal balance. The electrostatic panel has a very fast transient response, so vocals, acoustic instruments, and string sections sound lifelike. The midrange has a "see-through" quality that many describe as holographic. Images appear with precise placement and depth, and the soundstage extends well past the physical edges of the speakers.

Treble is smooth and extended, without the harshness sometimes heard from dome tweeters. The electrostatic section has no voice coils or magnetic structures, so there is no inductance or mechanical resonance to color the sound. The top end comes out clean and open.

The dynamic woofer gives tight, articulate bass. It does not reach the subsonic depths of modern powered subwoofers, but it extends convincingly down to 45 Hz, enough for orchestral works, jazz, and rock. The crossover between the electrostatic panel and the woofer is well managed, with minimal overlap or phase issues. Careful placement and room integration still matter, or the bass sources become easy to localize.

The ES-300 does best with acoustic recordings, vocal jazz, and classical music. It is less suited to high-decibel home theater or electronic music, where deep bass and sheer output come first.

Notable Features and Innovations

Integrated Power Supply: Unlike many electrostatics of the era, the ES-300 includes a built-in high-voltage power supply in the bass cabinet, simplifying setup.
Hybrid Design: The marriage of electrostatic and dynamic technologies was ahead of its time, foreshadowing modern hybrid speakers from brands like MartinLogan.
High Sensitivity for an Electrostatic: At 89 dB, the ES-300 is relatively easy to drive compared to pure electrostats (which often dip into the 70s), making it compatible with a wider range of amplifiers.
Aesthetic Elegance: The tall, narrow profile with a satin woodgrain or black ash finish gives the ES-300 a stately, modernist appearance that blends well in living spaces.

Common Issues and Maintenance

As with any vintage electrostatic speaker, the ES-300 needs careful maintenance:

Panel Arcing: Over time, dust accumulation or humidity can cause arcing between stators. Regular cleaning with a soft brush or electrostatic-safe cloth is recommended.
Diaphragm Sag: The thin Mylar diaphragm can stretch or sag if exposed to high humidity or physical pressure. Store and operate in dry, stable environments.
Power Supply Failure: The internal high-voltage supply may degrade after decades. Capacitors and transformers should be inspected or replaced by a qualified technician.
Woofer Foam Surrounds: If equipped with foam-rimmed woofers, the surrounds may have perished. Replacement with butyl rubber equivalents is a common restoration step.

Owners are advised to keep the speakers away from walls, to prevent bass buildup and panel instability. They should also use current-capable amplifiers to prevent clipping, which can damage the delicate electrostatic elements.

Current Market Value and Collectibility

The Infinity ES-300 is a rare and underappreciated gem in the vintage audio market. It is not as well known as the ES-1 or the later IRSV. Well-maintained pairs in good cosmetic and electrical condition typically sell between $800 and $1,500 on the secondary market, depending on region and restoration status.

Collectibility is moderate. Buyers are mostly electrostatic enthusiasts, Infinity loyalists, and hybrid speaker fans. The ES-300 was produced in limited numbers and never became mainstream, unlike mass-market bookshelf speakers.

Conclusion and Legacy

The Infinity ES-300 stands as a testament to the ingenuity of early electrostatic hybrid design. It successfully bridged the gap between the ethereal clarity of electrostatic panels and the physical impact of dynamic bass, offering a balanced, engaging listening experience that remains compelling today.

It is overshadowed by more famous models, but the ES-300 is a thoughtful, well-engineered speaker that brought high-end electrostatic performance within reach of more audiophiles. It needs upkeep to stay in shape.