Infinity RS-1B (1985)

Name: Infinity RS-1B
Brand: Infinity

A flagship floor-standing system that paired planar clarity with servo-controlled bass. On paper, a masterpiece. In practice, a handful.

Overview

Infinity released the RS-1B in 1985. It was not a bookshelf box or a conventional floorstander. It was a modular system of separate treble/midrange panels and woofer columns, tied together by an outboard electronic crossover with servo feedback. It was Infinity's flagship, the top model in the Reference Standard series, and it was priced that way: $12,000 per pair, a lot of money at the time. The goal was simple enough - near-perfect full-range sound, with the transparency of planar magnetics and the authority of servo-controlled bass.

Owners report it could deliver on that, when everything was aligned. The EMIT planar tweeter and EMIM planar midrange brought a level of detail and speed that cone drivers couldn't match. The sealed woofer columns, each housing a 12-inch driver, were meant to give tight, articulate bass. But this was no plug-and-play system. It needed correct polarity, compatible amplifiers and a large room. Get it right, and reviewers said the sound was "wide open and dynamic, just superb." Get it wrong, and the system could oscillate, distort, or simply underperform.

Specifications

Manufacturer	Infinity
Model	RS-1B
Type	loudspeaker system with an active controller (electronic crossover)
Drivers	One 12" woofer, two 5" midranges, one EMIT planar tweeter, one EMIM planar midrange
Enclosure type	Sealed (acoustic suspension)
Frequency response	25 Hz to 32 kHz
Crossover frequencies	150 Hz, 700 Hz, 3 kHz, 8 kHz
Impedance	6 ohms
Sensitivity	86 dB
Power handling	400 watts
Dimensions (H×W×D)	43.5" × 19.5" × 11.5" (1105 × 495 × 292 mm)
Weight	125 lbs (56.7 kg)

Key Features

Modular Design: Panels and Columns

The RS-1B was not a single cabinet. Each channel used separate components: a main treble/midrange panel and dual woofer columns. The main towers housed two 5-inch cone midranges, one EMIM planar midrange, and one EMIT planar tweeter, while This physical separation aimed to reduce intermodulation distortion and allow independent placement tuning. In practice it took serious floor space and careful setup.

Planar Magnetic Drivers

The EMIM (Electro-Magnetic Induction Midrange) and EMIT (Electro-Magnetic Induction Tweeter) drivers did the heavy lifting. These planar ribbons offered exceptional transient response and low distortion, which built the RS-1B's reputation for transparency and detail. They don't last forever, though. Owners note the mylar diaphragms tend to deteriorate over time. Replacement kits are available from specialists like MillerSound, but restoring them isn't trivial.

Active Servo Control and Electronic Crossover

The RS-1B wasn't passive. It relied on an outboard electronic crossover with servo feedback, connected via banana jacks to the amplifier and speakers. This active controller ran the four-way crossover at 150 Hz, 800 Hz, and 3.5 kHz, and included a feedback loop to correct woofer behavior in real time. The catch is that the system is "very fussy about polarity," and incorrect wiring could send it into destructive oscillation. It also won't work with all amplifiers - monoblocks without a common ground are a no-go.

Four-Way Configuration

Distinct drivers handled bass, mid-bass, midrange, and highs, so the RS-1B was a true four-way system. The sealed enclosure avoided port noise but demanded serious amplifier control. With 6-ohm impedance and 86 dB sensitivity, it wasn't easy to drive. It could handle up to 400 watts, and it needed quality power to sound its best.

Historical Context

Introduced in 1985, the RS-1B was Infinity's answer to the high-end speaker wars of the era, a statement product designed to compete with the best in the world. As the top model in the Reference Standard series, it represented the peak of the company's engineering at the time. It was built to show that servo control, planar magnetics, and active electronics could work together in a single system. At $5,000 a pair, it was never going to be mainstream. It did cement Infinity's reputation among audiophiles as a brand that pushed boundaries, even if the results were sometimes polarizing.

Collectibility & Value

Today the RS-1B is a rare sight. A pair sold for $4,500 on US AudioMart in 2023, which suggests strong collector interest. Buying one takes nerve. The active controller is a known weak point: capacitors fail, op-amps (like the LF353N) degrade, and the tiny 33-ohm and 62-ohm resistors in the feedback circuit can burn out, causing oscillation or hum. Grounding is also finicky. The chassis isn't a true ground point, and there's a 50- or 100-ohm resistance to ground depending on the version. The planar drivers are the other problem - EMIM and EMIT units fail as their mylar diaphragms age, though replacements exist. Anyone considering a pair should assume both the electronics and the ribbons will need service.

Market Value

┌──────────────────────────────────────────────────────────────────────────┐
│ INFINITY RS-1B                                                  Nov 2026 │
├──────────────────────────────────────────────────────────────────────────┤
│ High      $4,140                                  Latest            $244 │
│ Median    $2,327                                  Trend                — │
│ Low       $244                                    Volume           ~1/mo │
├──────────────────────────────────────────────────────────────────────────┤
│ $5,000 ┤                                                                 │
│        │                                                                 │
│        │.                                                             .  │
│ $2,943 ┤                                                                 │
│        │                                                                 │
│        │                                                                 │
│        │                                                                 │
│   $200 ┤                                                  .             .│
│        ├─────────────────────────────────────────────────────────────────│
│    vol │█                                                 █           █ █│
│        └─────────────────────────────────────────────────────────────────│
│         2026-03                      2026-05                      2026-08│
└──────────────────────────────────────────────────────────────────────────┘

eBay completed sales. Excludes accessories, parts, and non-working units. Hover points for details.