Altec 601 Duplex
1946 - 1954
The Altec 601 Duplex came before the 604 series. It set up the coaxial loudspeaker concept that Altec Lansing would build on for decades. The 601 used a 12-inch woofer where the later 604 used a 15-inch driver. It started the lineage that became the world's most famous studio monitor line.
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
Altec Lansing introduced the 601 Duplex in the years right after WWII, when the company was making a name as a maker of professional audio equipment. It was an early try at a point-source loudspeaker, with the low and high frequencies coming from the same acoustic center.
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 set the basic Duplex formula that was later refined into the 604 series. The key differences between the 601 and the 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
Altec used the 601 in its early studio monitor systems, including variations of the 9840 series monitors. It isn't as famous as the 604 that replaced it, but it 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. The 604 superseded them within a decade, and many were upgraded or replaced over the years.
Restoring 601 drivers takes the same techniques as the 604 series:
- Reconing with appropriate surround materials
- Diaphragm replacement for the compression driver section
- Crossover capacitor replacement
- Magnetic structure inspection
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Documentation
- Altec Datasheets - Historical specifications
- Altec Lansing Unofficial - Historical documentation
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