Altec 601 Duplex

Name: Altec 601 Duplex
Brand: Altec

1946 - 1954

Altec 601 Duplex - the original coaxial design (1946-1954)

The Altec 601 Duplex was the predecessor to the legendary 604 series, establishing the coaxial loudspeaker concept that would define Altec Lansing for decades. Using a 12-inch woofer instead of the later 604's 15-inch driver, the 601 laid the groundwork for what would become the world's most famous studio monitor lineage.

Specifications

Type	2-way coaxial loudspeaker (Duplex)
Low Frequency Driver	12" cone with 2.5" voice coil
High Frequency Driver	Compression driver with 1.5" diaphragm
Horn	Sectoral horn integrated into pole piece
Crossover Frequency	1,500 Hz
Nominal Impedance	8 Ω or 16 Ω
Power Handling	25W continuous
Sensitivity	95 dB/W/m
Frequency Response	40 Hz - 16 kHz
Magnet Structure	Alnico V
Weight	Approximately 35 lbs

Historical Context

The 601 Duplex was introduced in the immediate post-WWII era when Altec Lansing was establishing itself as a premier manufacturer of professional audio equipment. It represented an early attempt at creating a point-source loudspeaker where both low and high frequencies emanated from the same acoustic center—a concept that would prove revolutionary in studio monitoring.

The 601 found particular use in:

Early broadcast studio monitors
Film production monitoring
Small theater installations
Recording studio nearfield monitoring

The Evolution to the 604

The 601 established the basic Duplex formula that would be refined into the legendary 604 series. The key differences between the 601 and later 604 models were:

12" vs 15" Woofer: The 601 used a smaller 12-inch low-frequency driver
Smaller Voice Coil: 2.5" coil compared to the 604's 3" voice coil
Lower Power Handling: 25W vs 50W for later 604 models
More Compact: Lighter and smaller than the professional 604 series

Studio Monitor Heritage

The 601 was used in Altec's early studio monitor systems, including variations of the 9840 series monitors. While not as famous as its 604 successor, the 601 established the coaxial monitor concept that would dominate recording studios for decades.

The Duplex design offered several advantages for studio use:

Point Source: Single acoustic center for accurate imaging
Time Alignment: Inherent time coherence between drivers
Compact Footprint: Two-way performance from a single driver
Consistent Off-Axis: Uniform dispersion pattern

Collectibility Today

Vintage 601 Duplex drivers are relatively rare today, as they were superseded by the 604 within a decade and many were upgraded or replaced over the years. When found, they represent an important piece of audio history as the genesis of the coaxial studio monitor concept.

Restoration of 601 drivers requires similar techniques to the 604 series: