Infinity 2000-II: The Pioneer of Passive Radiator Technology

Name: Infinity 2000-II
Brand: Infinity

In the mid-1970s, when high-fidelity audio was undergoing a renaissance of innovation, Infinity Systems emerged as a bold new force in loudspeaker design. Among their most revolutionary offerings was the Infinity 2000-II, a compact yet sonically ambitious speaker that introduced audiophiles to the potential of passive radiator technology. Though not as widely recognized as some of its contemporaries, the 2000-II holds a special place in audio history as one of the first commercially successful designs to eschew the traditional ported or sealed enclosure in favor of a tuned passive radiator system—ushering in a new era of deep, articulate bass from a relatively small cabinet.

Released in 1975, the Infinity 2000-II was developed during a period when speaker designers were pushing the limits of bass extension and efficiency. At a time when many high-end speakers relied on large enclosures or complex transmission line designs to achieve low-frequency response, Infinity—founded by audio pioneers Arnie Nudell and Cary Christie—took a different path. The 2000-II was a direct descendant of their earlier 2000 model, refined for better performance, reliability, and integration into domestic listening environments.

Technical Specifications

Specification	Detail
Model	Infinity 2000-II
Manufacturer	Infinity Systems, Inc.
Production Years	1975–1979 (approximate)
Type	2-way, passive radiator loudspeaker
Driver Complement	1 x 12" passive radiator, 1 x 8" active woofer, 1 x 1" dome tweeter
Frequency Response	38 Hz – 20 kHz (±3 dB)
Crossover Frequency	~2.5 kHz
Sensitivity	91 dB (1W/1m)
Nominal Impedance	8 ohms (compatible with most tube and solid-state amps)
Enclosure Type	Sealed with passive radiator tuning
Dimensions (H×W×D)	24" × 14" × 12" (61 × 35.5 × 30.5 cm)
Weight	48 lbs (21.8 kg) per cabinet
Finish Options	Walnut or black ash veneer
Recommended Amp Power	20–100 watts

Sound Characteristics and Performance

The Infinity 2000-II was designed to deliver a balanced, dynamic sound with an emphasis on tight, extended bass—a rarity in compact speakers of the era. The use of a 12-inch passive radiator (sometimes referred to as a "drone cone") allowed the system to achieve bass response down to 38 Hz, rivaling much larger floor-standing models. Unlike ported designs, which can suffer from chuffing or delayed bass transients, the passive radiator provided a more controlled and articulate low end, especially with complex musical passages.

The 8-inch polypropylene woofer handled midbass and lower midrange duties with commendable clarity, while the 1-inch soft dome tweeter offered smooth, non-fatiguing highs. The crossover, though relatively simple by modern standards, was well-executed for its time, minimizing phase distortion and ensuring a coherent handoff between drivers.

Listeners often describe the 2000-II’s sonic signature as warm yet detailed, with a natural midrange that excels with vocals and acoustic instruments. The soundstage is surprisingly wide for a speaker of its size, and imaging is precise, particularly when the speakers are properly positioned away from rear walls.

Notable Features and Innovations

The passive radiator is the star of the show in the 2000-II. Unlike a port, which uses a tube to tune the cabinet’s resonance, a passive radiator is a speaker-like diaphragm without a voice coil or magnet. It moves in response to internal air pressure generated by the active driver, effectively extending bass response without the drawbacks of port turbulence.

This design offered several advantages:

No port noise at high volumes
Tighter bass transient response
Greater design flexibility in cabinet size and shape

Infinity’s implementation was particularly advanced for the 1970s, using a mass-loaded passive radiator that could be finely tuned by adding or removing weights—a feature more commonly seen in modern subwoofers. This allowed dealers or enthusiasts to tailor the bass response to their room acoustics.

Another hallmark of the 2000-II was its modular construction. The cabinet was heavily braced and built with high-quality MDF (medium-density fiberboard), which was still a novelty in consumer audio at the time. The front baffle was slightly curved to reduce diffraction, and the entire assembly was finished in real wood veneer, giving it a premium look that matched its high-end positioning.

Common Issues and Maintenance

As with any vintage speaker, the Infinity 2000-II requires careful inspection before purchase. The most common issues include:

Aged foam surrounds on the woofer and passive radiator: Many original units have deteriorated foam, leading to rattles or loss of bass. Replacement foam kits are available from specialty vendors, but refoaming should be done by an experienced technician.
Capacitor degradation in the crossover: Electrolytic capacitors in older crossovers can dry out, leading to dull highs or imbalance. Replacing these with modern equivalents can restore original performance.
Tweeter failure: While the soft dome tweeters were robust, some early units suffered from oxidation on the terminals or diaphragm fatigue. Testing with low-level pink noise is recommended.

Proper maintenance includes keeping the speakers away from humidity and direct sunlight, as these can warp the veneer and accelerate foam breakdown. Cleaning should be done with a soft, dry cloth—avoiding polishes that can damage the finish.

Current Market Value and Collectibility

The Infinity 2000-II is a niche collectible rather than a mainstream vintage icon, but it holds strong appeal among audiophiles interested in the evolution of speaker technology. Well-restored pairs in good cosmetic and sonic condition typically sell for $400–$800 in today’s market, depending on finish, provenance, and location.

They are particularly sought after by:

Vintage Infinity enthusiasts collecting the brand’s early innovations
DIY audio tinkerers who appreciate the modularity and upgrade potential
Small-room listeners looking for compact speakers with real bass

While not as famous as the later IRSV or Beta series, the 2000-II represents a crucial step in Infinity’s journey toward high-end credibility. Its influence can be seen in modern passive radiator designs from brands like KEF, PSB, and even some Bluetooth speakers.

Conclusion and Legacy

The Infinity 2000-II may not have the star power of some of its larger siblings, but it stands as a quiet pioneer in loudspeaker engineering. By embracing the passive radiator at a time when most manufacturers stuck to ports or sealed boxes, Infinity demonstrated a willingness to challenge conventions—and the 2000-II delivered tangible sonic benefits as a result.

Today, it serves as a reminder of the bold experimentation that defined the 1970s high-end audio scene. For the vintage audio collector or the curious listener, the 2000-II offers a unique blend of historical significance, innovative design, and satisfying musicality. Restored and properly driven, it remains a compelling choice for those who appreciate the roots of modern speaker technology.

If you stumble upon a pair in good condition, consider giving them a second life—few speakers from this era offer such a smart balance of size, performance, and engineering ingenuity.