Altec 604-8G Super Duplex
1973 - 1979
The 604-8G Super Duplex represents the culmination of nearly 30 years of Altec coaxial speaker development. This legendary 15" driver was used in countless recording studios worldwide and is considered by many to be the definitive version of the iconic 604 series.
Specifications
| Type | 2-way coaxial loudspeaker (Duplex) |
|---|---|
| Low Frequency Driver | 15" cone with 3" voice coil |
| High Frequency Driver | Compression driver with 1.75" diaphragm |
| Horn | Sectoral horn with vanes (40° x 90° dispersion) |
| Crossover Frequency | 1,500 Hz |
| Nominal Impedance | 8 Ω |
| Power Handling | 50W continuous, 100W program |
| Sensitivity | 98 dB/W/m |
| Frequency Response | 30 Hz - 22 kHz |
| Magnet Structure | Alnico V, 5.2 lbs (LF), 2.5 lbs (HF) |
| Mounting Depth | 8.5" |
| Weight | Approximately 47 lbs |
Key Features
- True Coaxial Design: HF compression driver mounted coaxially behind the LF cone for point-source radiation
- Improved Transient Response: Enhanced suspension and voice coil design for better detail retrieval
- Symbiotic Magnet Structure: Integrated LF and HF magnet assemblies
- Tangerine Phase Plug: Proprietary phase plug design for improved high-frequency dispersion
The 604 Series Evolution
The 604-8G was the final production version of the 604 series before Altec shifted to newer designs. Key improvements over earlier versions included:
- Improved rubberized woofer surround for better longevity
- Enhanced heat dissipation for the HF section
- Refined crossover network (external N-1601-A recommended)
- Better consistency in manufacturing
Applications
The 604-8G found use in:
- Recording studio main monitors (Western Electric/Altec cabinets)
- Broadcast facilities
- Home high-fidelity systems
- Commercial sound installations
Recommended Enclosures
Altec recommended several enclosures for the 604-8G:
- 620/620A: Compact studio monitor cabinet
- 621: Larger studio monitor with extended bass
- 9844: Professional studio monitor system
- Custom: Many users built custom open or closed baffles
Legacy
The 604-8G remains highly sought after by vintage audio enthusiasts and studio engineers. Its combination of high sensitivity (98 dB), wide frequency response, and natural, uncompressed sound quality makes it ideal for low-powered tube amplifiers and critical listening applications.
Today, Great Plains Audio manufactures a modern version of the 604 (604-8H-II) that honors the original design while using updated materials.
Related Models
- 604E Super Duplex - Predecessor to the 8G
- 605A Duplex - Alternative with different magnet structure
- 604 Series Overview - Complete history of the line