Advent Model 400 (Early to mid-1970s)

Name: Advent Model 400
Brand: Advent

Compact mono FM radio receiver with acoustic suspension speaker, designed by Henry Kloss.

Overview

The Advent Model 400 is a mono FM radio receiver with a separate acoustic suspension speaker. Advent Corporation built it in Cambridge, Mass. during the early to mid-1970s. Henry Kloss designed it. It uses solid-state electronics and a geared vernier tuner for precise station selection. The receiver unit holds an integrated amplifier. It was one of the first FM radios reviewed in stereo magazines alongside high-end component systems. It descended directly from similar KLH units and came before the stereo 420S.

Specifications

Speaker Impedance	8-ohm driver
Driver Configuration	Single full range driver
Enclosure Type	Sealed enclosure (acoustic suspension)
Receiver Dimensions	Width 4-1/2", Depth 5-3/4", Height 6-1/2"
Speaker Dimensions	Width 11", Depth 5-3/4", Height 6-1/2"
Combined Weight	9 lbs
Tuner Type	FM only (mono)
Audio Output	Mono
Inputs	Aux-in
Outputs	Tuner out
Included Accessories	12-page owner’s manual, ~40 ft white speaker wire, dipole antenna

Design

The Advent Model 400 has a creamy-white plastic shell and is described as a "mini" size "little cube." The speaker is acoustic suspension. The receiver has a schematic printed on the bottom of the cabinet. According to the owner's manual, the idea was to distill techniques from high-end equipment into a simple system that "gets out of the way of the music." The white cabinets tend to yellow with age.

Context

Henry Kloss designed the Advent Model 400, and his work also runs through KLH, Acoustic Research, and Tivoli Audio. It was marketed as a compact, high-fidelity solution for FM listening and shared design lineage with earlier KLH models. A stereo version briefly appeared using two 400 speakers. The speakers were also sold in pairs as a budget option within the Advent line. The 420S succeeded the 400 as a stereo model.

Market

Common cosmetic problems are yellowed cabinets, scratched knobs, dented grilles, and surface blemishes. Used units turn up often in listings. Users report success connecting the receiver to external speaker pairs.