Infinity Quantum Series

Name: Infinity Quantum
Brand: Infinity

The record on the Infinity Quantum series is thin. The speakers weren't unremarkable. "Quantum" was a family of models, not a single speaker, and surviving documentation tends to blur them together. The period sources do agree on this much. It was Infinity's mid-to-high-end line during the late 1970s, a more attainable step down from the Quantum Line Source. Critics praised the Line Source as musically accurate beyond anything previously made. According to Infinity's own advertising in Audio (May 1977, p.55), the Quantum 3 was "very probably the finest" of the line short of the full Line Source.

The series covered a wide price range. At the top, the Quantum Reference Standard ran $6,500. The bookshelf-sized Qa sold for $105 to $150, and the company pitched it as a way to get "state-of-the-art" Infinity sound without the flagship investment, per High Fidelity (July 1977, p.24). The Quantum 5, at $355 each, shared much of the same technology on a smaller scale, including the EMIT tweeter and a high-definition dome midrange. A later ad in High Fidelity (October 1978, p.51) claimed the Quantum 5's output shared an electrostatic's delicacy while beating electrostatics, cones, and dome tweeters in power handling.

The models known to exist in the series are the Qb, Q2, Q3, Q4, Q5, Q7, Q8, plus the WTLC and WTMC. The WTLC and WTMC use the Watkins Woofer™ and were well received in the audiophile community for their unique bass output. That detail comes from a single forum source, so treat it as unverified.

Several things are missing here: a unified spec sheet for any single Quantum model, production years, original pricing beyond the ad references above, and dimensions and weight. The series clearly held a significant place in Infinity's lineup, but the crossover, enclosure, and driver complement of each model aren't documented in the available sources. If you own a pair and have the original literature, the archive would like to hear from you.