Advent Model 400 (Early to mid-1970s)

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, manufactured by Advent Corporation in Cambridge, Mass. during the early to mid-1970s. Designed by audio pioneer Henry Kloss, it features solid-state electronics and a geared vernier tuner for precise station selection. The system includes an integrated amplifier in the receiver unit and was one of the first FM radios reviewed in stereo magazines alongside high-end component systems. It was a direct descendant of similar KLH units and preceded the stereo 420S model.

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 features a creamy-white plastic shell and is described as a "mini" size "little cube." The speaker uses acoustic suspension technology, and the receiver includes a schematic printed on the bottom of the cabinet. The design philosophy, as stated in the owner's manual, was to distill techniques from high-end equipment into a simple system that "gets out of the way of the music." The white cabinets are prone to yellowing with age.

Context

Designed by Henry Kloss, the Advent Model 400 reflects his legacy across companies like 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, and 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 issues include yellowed cabinets, scratched knobs, dented grilles, and surface blemishes. The system is frequently found in used and sold listings, and users report success connecting the receiver to external speaker pairs.