Infinity RS-3: A Compact Pioneer of High-Frequency Innovation

Name: Infinity RS-3
Brand: Infinity

In the late 1970s, as high-fidelity audio began to move from bulky console systems into more refined, component-based setups, speaker manufacturers were racing to deliver both sonic accuracy and technological innovation. Among the most forward-thinking brands of the era was Infinity, a company founded in 1968 by Arnie Nudell and Cary Christie, known for pushing the boundaries of loudspeaker design. While Infinity would later become famous for large floor-standing models and advanced servo-controlled subwoofers, the RS-3, introduced around 1977, represented a more modest yet still ambitious product: a compact bookshelf speaker that brought the brand’s signature ribbon tweeter technology into an affordable and space-conscious format.

Though not as widely documented as some of Infinity’s flagship models like the IRS or Servo-Statik series, the RS-3 holds a quiet but important place in the company’s evolution. It was part of a broader effort to democratize high-end audio, making advanced transducer technology accessible to a wider audience. At a time when most bookshelf speakers relied on conventional dome or cone tweeters, the RS-3 stood out by incorporating a high-frequency ribbon driver—a hallmark of Infinity’s design philosophy.

Technical Specifications

The RS-3 was engineered as a two-way bookshelf speaker, designed for nearfield listening, small rooms, or use as a secondary system. Its compact cabinet housed a modest mid-bass driver paired with Infinity’s signature "ionovac" or electrostatic-like ribbon tweeter, though not a true electrostatic. This ribbon element was lightweight and responsive, capable of delivering exceptional transient detail and extended high-frequency response with minimal distortion.

Specification	Detail
Model	Infinity RS-3
Type	Two-way bookshelf speaker
Driver Configuration	1 x 5.25" mid-bass cone, 1 x ribbon tweeter
Frequency Response	~60 Hz – 22 kHz (estimated)
Crossover Frequency	~3.5 kHz (estimated)
Sensitivity	~86 dB (1W/1m)
Nominal Impedance	8 ohms
Recommended Amp Power	20–60 watts
Enclosure Type	Sealed (acoustic suspension)
Dimensions (H×W×D)	~13" × 7.5" × 8" (33 × 19 × 20.3 cm)
Weight	~15 lbs (6.8 kg) per speaker
Finish Options	Walnut vinyl veneer

The sealed cabinet design contributed to tight, controlled bass response—typical of the era’s acoustic suspension trend popularized by speakers like the AR-3. However, due to its small size and lack of porting, the RS-3 did not produce deep bass extension, making it best suited for midrange and treble clarity rather than full-range reproduction without a subwoofer.

Sound Characteristics and Performance

The Infinity RS-3 delivered a sound signature that was remarkably detailed and transparent for a speaker of its size and era. The ribbon tweeter was the star of the show, offering a level of high-frequency clarity and speed that outperformed many dome tweeters of the time. Cymbals, strings, and vocal sibilance were rendered with a lifelike, airy quality that many listeners described as “effortless” and “open.”

The 5.25-inch mid-bass driver handled the lower frequencies competently, though with predictable limitations. Bass response rolled off below 60 Hz, and the speaker lacked the punch and authority of larger designs. However, within its range, the midrange was clean and well-articulated, making the RS-3 particularly well-suited for vocal-centric music, acoustic jazz, and classical recordings.

When paired with a quality tube or solid-state integrated amplifier of moderate power, the RS-3 could produce a surprisingly spacious soundstage, with good imaging and separation. Its ribbon tweeter contributed to a wide sweet spot and excellent off-axis dispersion, allowing for flexible placement in small listening environments.

Notable Features and Innovations

What made the RS-3 stand out in the crowded bookshelf speaker market of the late 1970s was its use of ribbon high-frequency technology in a relatively affordable package. While ribbon drivers were typically reserved for high-end or experimental speakers due to their cost and complexity, Infinity managed to integrate a simplified version into the RS-3, showcasing their commitment to bringing advanced engineering to more listeners.

The ribbon tweeter operated on electromagnetic principles, using a thin aluminum strip suspended in a magnetic field. This design offered extremely low mass and high responsiveness, resulting in minimal phase distortion and excellent high-frequency extension. Unlike dome tweeters, which could sometimes sound harsh or fatiguing, the RS-3’s ribbon provided a smooth, natural top end.

Additionally, the sealed cabinet design ensured a time-coherent response and reduced phase anomalies, contributing to the speaker’s accurate transient reproduction. The compact size and modest power requirements also made the RS-3 ideal for dorm rooms, offices, or secondary systems—places where space and amplifier power were limited.

Common Issues and Maintenance

As with many vintage speakers from the 1970s, the Infinity RS-3 can suffer from age-related degradation. The most common issue is tweeter failure. The delicate ribbon element, while innovative, is fragile and susceptible to damage from overdriving, electrical spikes, or simply decades of use. Some units may exhibit reduced high-frequency output or complete tweeter silence due to broken conductive strips or deteriorated adhesives.

The mid-bass driver is generally more robust, but foam surrounds—common in speakers of this era—can dry out and disintegrate over time. If the speaker has not been re-foamed, users may notice a loss of bass response or “rubbing” sounds at higher volumes. Replacement foam kits are available from specialty restoration suppliers.

Another consideration is the internal crossover. While simple by modern standards, the crossover components (particularly capacitors) may have aged, leading to imbalanced frequency response or increased distortion. Replacing these with modern equivalents can restore the speaker’s original performance.

For collectors and restorers, finding original parts can be challenging, as Infinity did not widely document the RS-3 in service manuals or brochures. However, its driver configurations were shared with other models of the era, allowing for some cross-compatibility.

Current Market Value and Collectibility

The Infinity RS-3 is not a highly sought-after collector’s item like the IRS V or the EMPIRE series, but it holds niche appeal among vintage audio enthusiasts, particularly those interested in early ribbon technology or the history of Infinity’s design evolution. Pairs in good working condition typically sell for $150–$300, depending on cosmetic condition and whether restoration has been performed.

Restored units with re-foamed drivers and repaired tweeters can command higher prices, especially if paired with original grilles and documentation. However, due to the fragility of the ribbon tweeter and the lack of widespread parts support, full restoration can be a labor-intensive project.

Despite its obscurity, the RS-3 is appreciated for its historical significance—a bridge between Infinity’s experimental beginnings and its later commercial success. It represents a moment when high-end audio innovation began to trickle down into more accessible products.

Conclusion and Legacy

The Infinity RS-3 may not have been a flagship model, but it embodies the spirit of innovation that defined Infinity in its formative years. By incorporating a ribbon tweeter into a compact, affordable bookshelf speaker, Infinity demonstrated that advanced audio technology didn’t have to be reserved for the elite.

Today, the RS-3 serves as a reminder of the bold experiments taking place in speaker design during the 1970s. For vintage audio collectors, it’s a rewarding project—a chance to restore and experience a piece of loudspeaker history that helped pave the way for modern high-resolution audio. While it may not fill a large room with bass, the RS-3 delivers a listening experience that is detailed, engaging, and unmistakably vintage. For those who appreciate the marriage of engineering ambition and musical fidelity, the Infinity RS-3 remains a quiet classic worth rediscovering.