ResonantLive Sound Archive

Equipment file · Coaxial (Duplex) loudspeaker

604 Duplex

Altec Lansing · 1944

Evidence status · documented

Identity and core specifications are documented; some historical fields remain unavailable.

The Altec 604 Duplex was a 15-inch coaxial loudspeaker whose compression-driver tweeter fired through the woofer's pole piece into a small multicellular horn. It followed the 1943 model 601 but used an Alnico V permanent magnet instead of a field coil.

Introduced
1944
Category
Coaxial (Duplex) loudspeaker
Intended use
Studio monitoring, later tour and installed sound
Production
Altec Lansing, 1944 into the 1990s (604B to 604-8K)

Equipment photographs · 1

Two vintage coaxial loudspeakers, one facing forward and one showing its magnet and basket

1 / 1 · Duplex coaxial loudspeaker

Duplex coaxial loudspeaker·Author unknown·CC0

Why it mattered

  1. 01

    It became the reference coaxial monitor of mid-century broadcast and recording control rooms.

  2. 02

    Its point-source geometry influenced later monitors, including UREI's 811/813/815 series.

Engineering record

Drivers
15-inch woofer with 3-inch voice coil on Alnico V, HF compression driver through the pole piece into a six-cell horn[1]
Power
About 30 watts[1]

Original pricing

No reliable period price located

2026 equivalent

Not calculated without a reliable original price.

Public price evidence was not sufficient to publish a defensible original figure.

Use in the field

Standard broadcast and recording monitor; basis of UREI's 811/813/815 line[1]

Manuals & original documents

No authoritative manual or original document has been located for this profile.

Sources

  1. 11944 Altec Lansing 604 Duplex SpeakerMix · technical paper · 2006-09-01

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