The loudspeakers developed by James Bullough Lansing established the reputation of every company he was working at.

In 1939 Lansing’s partner with business and management skills died and 1941 his only way to keep the Lansing Manufacturing Company afloat was the merger with 'All Technical Services Corporation' to Altec Lansing.

Jim Lansing continued his work and perfected many manufacturing processes including winding of ribbon wire voice coils and hydraulic forming of aluminum diaphragms. During these years he also developed the model 601 Duplex (coaxial) loudspeaker and the first Voice of the Theatre system.

Introduced in 1944, the 604 briefly set the standard for critical monitoring applications. It continues in production to this day. Lansing's design concept for a coaxial speaker was to mount a modified Lansing 801 compression driver behind a 15" seamless paper cone bass and terminating in a small multicellular horn. The early models had 2" underhung voice coils and heavy field coils to generate high flux densities.

The field coil Duplex 601 was introduced in 1943 and was available as a component kit or could be ordered as the model 602 in a utility or in a furniture cabinet as the model 605. Lansing began the development of an Alnico V magnet version that was to become the legendary model 604 Duplex in 1944. This speaker outperformed the original 601 in efficiency and maximum output. Check this! My field-coil designs outperform the Alnico version with ease. The 604 was a great success and was sold as ubiquitous monitor in recording studios under different names. Among them UREI and Westlake.


The Kilimanjaro-Series A604 field-coil speaker driver is a further development and is equipped with a modern field-coil motor. It is the best Point-Source loudspeaker ever created. Enjoy music with this driver built in a baffle – and have a seat close to it...

LF section of A604S (pure copper coils for optimized power / flux ratio)

Frequency response = 30 – 2,000 Hz
Sensitivity = 98 dB @ 1W/1m
Paper cone with dampened corrugated surround driven by a 3-inch diameter voice coil
Flux density = 15,000 Gauss @ 16 V - 1.8 A (recommended 12 V and corresponding current)

HF section of A604S (curved inner core for optimized horn flare)

Frequency response = 1,500 – 20,000 Hz
Sensitivity = 104 dB @ 1W/1m
All aluminum dome driven by a 1.75-inch diameter voice coil
Flux density = 17,000 Gauss @ 12 V - 2.1 A (recommended 12 V and corresponding current)

© Wolf von Langa 2013