Infinity 2000-II: The Pioneer of Passive Radiator Technology

Name: Infinity 2000-II
Brand: Infinity

In the mid-1970s, Infinity Systems was making a name for itself in loudspeaker design. The Infinity 2000-II was a compact speaker that brought passive radiator technology to audiophiles. It isn't as widely known as some of its contemporaries, but it was one of the first commercially successful designs to skip the traditional ported or sealed enclosure for a tuned passive radiator system. The result was deep, articulate bass from a relatively small cabinet.

Released in 1975, the Infinity 2000-II came out while speaker designers were pushing bass extension and efficiency. Many high-end speakers of the time relied on large enclosures or complex transmission line designs for low-frequency response. Infinity, founded by 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 fit in a home listening room.

Technical Specifications

Specification	Detail
Model	Infinity 2000-II
Manufacturer	Infinity Systems, Inc.
Production Years	1975–1979 (approximate)
Type	4-way, 4-speaker floor type loudspeaker
Driver Complement	1 x 12" passive radiator, 1 x 8" active woofer, 1 x 1" dome tweeter
Frequency Response	28 Hz – 28 kHz (±4 dB)
Crossover Frequency	800 Hz, 4 kHz, 10 kHz
Sensitivity	91 dB (1W/1m)
Nominal Impedance	8 ohms (compatible with most tube and solid-state amps)
Enclosure Type	Reportedly sealed with passive radiator tuning
Dimensions (H×W×D)	36.5" × 22.2" × 17.0" (927 × 565 × 432 mm)
Weight	73.9 lbs (33.5 kg) per cabinet
Finish Options	Walnut or black ash veneer
Recommended Amp Power	Approximately 20–100 watts

Sound Characteristics and Performance

The Infinity 2000-II was designed for balanced, dynamic sound with tight, extended bass, which was a rarity in compact speakers of the era. A 12-inch passive radiator (sometimes called a "drone cone") let the system reach bass response down to 38 Hz, rivaling much larger floor-standing models. Ported designs can suffer from chuffing or delayed bass transients. The passive radiator gave a more controlled, articulate low end, especially with complex musical passages.

The 8-inch polypropylene woofer handled midbass and lower midrange with good clarity. The 1-inch soft dome tweeter gave smooth, non-fatiguing highs. The crossover is relatively simple by modern standards, but it was well done for its time. It minimized phase distortion and gave a coherent handoff between drivers.

Listeners often describe the 2000-II's sound as warm yet detailed, with a natural midrange that works well with vocals and acoustic instruments. The soundstage is surprisingly wide for a speaker this size, and imaging is precise, particularly when the speakers sit away from rear walls.

Notable Features and Innovations

The passive radiator is the main event in the 2000-II. A port uses a tube to tune the cabinet's resonance. A passive radiator is a speaker-like diaphragm with no voice coil or magnet. It moves in response to internal air pressure from the active driver, which extends bass response without 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 advanced for the 1970s. It used a mass-loaded passive radiator that could be tuned by adding or removing weights, a feature more commonly seen in modern subwoofers. Dealers or enthusiasts could use this to tailor the bass response to their room acoustics.

The 2000-II also had 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 whole assembly was finished in real wood veneer, which matched its high-end positioning.

Common Issues and Maintenance

As with any vintage speaker, the Infinity 2000-II needs 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.

Keep the speakers away from humidity and direct sunlight, which can warp the veneer and speed up foam breakdown. Clean them with a soft, dry cloth. Avoid polishes, which 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 appeals to audiophiles interested in how speaker technology evolved. 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

It isn't as famous as the later IRSV or Beta series, but the 2000-II was a step toward Infinity's 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 was a quiet pioneer in loudspeaker engineering. Infinity embraced the passive radiator when most manufacturers stuck to ports or sealed boxes, 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.