Infinity RS-4.5 (1980s)

A floorstanding speaker system so revealing it could make you love your music more, and make you question everything about your amplifier.

Overview

The Infinity RS-4.5 is big. It stands 65 inches tall, each cabinet weighs 150 pounds, and the system wants space and attention. It was introduced in the 1980s as part of Infinity's Reference Standard series, meant to bring the brand's high-end engineering to a broader audience. With an MSRP of $4500 (or $2000 as a system in 1979, depending on configuration), "broader" was still a relative term. This wasn't mass-market gear. It was for the serious listener who wanted transparency, extension, and every detail in the recording, warts and all.

It delivered, sometimes too well. Early units shipped to dealers were reportedly hard-sounding and lacking in lower midrange warmth. Infinity's chief designer, Bascom King, personally stepped in and modified the crossover network before full production. The version that reached consumers was the one Stereophile reviewed and praised as being so complete that “many audiophiles may never again feel the need for upgrading to something ‘better.’” That's not faint praise. That's a dare.

The technology inside is the real story. This is an active crossover system, so it doesn't use passive crossover components inside the speaker. Instead, a separate black box, the speaker control center, acts as both an electronic crossover and equalizer. This external unit measures 10" deep by 14" wide by 2" high, and the system needs it to work. Without it, the RS-4.5 is silent. With it, the crossover points can be adjusted with precision.

Specifications

Manufacturer	Infinity Systems, Inc.
Model	RS-4.5
Year Introduced	1980s
Type	Floorstanding loudspeaker system
Drivers	EMIM midrange, EMIT ribbon tweeters (4 total, one rear-facing)
Enclosure Type	Floorstanding with foam baffle
Dimensions (H×W×D)	65" × 27" × 15" (loudspeaker), 14" × 10" × 2" (equalizer)
Weight	150 lbs per speaker
Frequency Response	24 Hz – 32 kHz ±3 dB
Nominal Impedance	4 ohms
Power Handling	100Wpc minimum required
Crossover Frequencies	150 Hz, 5 kHz (lower point adjustable)

Key Features

The External Crossover/Equalizer: The Brain of the System

The RS-4.5 has no internal crossover. It relies on a dedicated external control unit, a black box that splits the audio signal electronically before it reaches the amplifier. It's an equalizer too, so users can fine-tune response and integration between drivers. The unit offers eleven selectable crossover frequencies for the low end of the midrange drivers and the upper end of the woofers, and these can be set independently. You can choose overlapping or separated crossovers depending on your preference or room acoustics. That kind of flexibility was almost unheard of in consumer speakers of the era.

EMIT and EMIM Drivers: The Heart of the Sound

The driver complement is where the RS-4.5 diverges from the pack. It uses electromagnetic-induction-midrange (EMIM) units and four EMIT (Electro-Magnetic Induction Tweeter) ribbon tweeters. Yes, four. One of the EMITs is rear-facing, designed to enhance spatial dispersion and create a more immersive soundstage. These aren't domes or cones. EMIT ribbons are known for their extreme speed and transparency, and they reveal high-frequency detail with startling clarity. Some listeners have called them “harsh” or “strident,” but as one reviewer noted, that reaction may come not from the speakers but from the flaws in recordings and electronics that EMITs reveal and other speakers politely ignore. If your source or amp is bright, the RS-4.5 will show it.

Build and Materials: Built Like a Tank, Aging Like Vintage Leather

Each speaker stands 65 inches tall with a broad 27-inch footprint. The cabinets are solid and massive, built to minimize resonance. They are not immune to age, though. The foam baffle pieces degrade over time, a common issue noted across listings and forums. Grill fabric is prone to holes, loosening, and sun damage. Cabinet surfaces can develop scuffs, splits in the wood veneer, and slight bubbling in the midrange panels. Plastic feet often go missing. These aren't dealbreakers, but they come with owning a 40-year-old floorstander. Replacement parts exist. A specific foam surround repair kit (model 2A12-12) is marketed for the RS-4.5, and both EMIT and EMIM drivers can be replaced, though sourcing them may mean digging through specialist suppliers.

Historical Context

The RS-4.5 was part of Infinity's Reference Standard series, a line intended to bring the brand's high-performance design to a wider audience. At a time when many manufacturers were chasing bass extension and cosmetic flair, Infinity focused on accuracy and transparency. Early production units were judged too hard-sounding and lacking in lower midrange presence. Rather than ship them as-is, Infinity's chief designer, Bascom King, revised the crossover network. The version that reached dealers, and the one Stereophile reviewed, was this corrected model.

Collectibility & Value

The Infinity RS-4.5 is no longer in production and is considered rare. TMR Audio lists it as “no longer available,” and current listings reflect its niche status. Prices vary wildly: a pair was listed for €4,700 in Spain (Como Ficho, 2023), while another sold for PLN 15,900 in Poland (OLX, 2022). A restored pair on Audiogon had new woofer surrounds and replaced EMIT/EMIM drivers within the last five years. The external crossover unit alone has been listed for €790.

Common failures center on age-related materials: foam baffles and surrounds degrade, grills deteriorate, and cabinet finishes suffer. The system is serviceable, though. Foam surround repair kits (2A12-12) are available, and driver replacement is possible. Given the 4-ohm impedance and 100Wpc minimum power requirement, these speakers need a strong amplifier, which is another thing for potential buyers to consider.

For collectors, the RS-4.5 is less a financial investment than a pursuit for the enthusiast. It's not for the casual listener. It's for the person who values engineering audacity and doesn't mind the quirks of vintage gear.

Similar items on eBay

No exact Infinity RS-4.5 listings are live right now — these searches show current Infinity and similar vintage audio gear on eBay:

Search Infinity RS-4.5 on eBay Browse Infinity audio gear on eBay

As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.