Altec 605A Duplex
1959 - 1964
The 605A Duplex was Altec's attempt to evolve the 604 design with a modified magnet structure. Though it offered some technical improvements, the market ultimately rejected it in favor of the classic 604 formula, making the 605A a fascinating footnote in Altec history.
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 |
| Crossover Frequency | 1,500 Hz |
| Nominal Impedance | 8 Ω or 16 Ω |
| Power Handling | 35W continuous |
| Sensitivity | 95 dB/W/m (3 dB less than 604C) |
| Frequency Response | 35 Hz - 20 kHz |
| Magnet Structure | Modified Alnico V (shared flux path) |
| Finish | Green hammertone with gold decal |
| Weight | Approximately 42 lbs |
The 605A Controversy
The 605A was intended to replace the 604C with an improved magnet structure. However, several factors led to its poor reception:
- Reduced Sensitivity: The modified magnet assembly resulted in 3 dB less output than the 604C
- Name Recognition: The "604" was an industry standard; customers wanted a 604, not a 605
- Cost Reduction Perception: Some viewed the changes as cost-cutting rather than improvements
Interestingly, some listeners actually preferred the 605A's slightly different voicing, finding it smoother in the midrange for home listening.
Technical Differences from 604
The 605A differed from the 604 series in several ways:
- Shared Magnet Assembly: The LF and HF sections shared a common flux path, reducing the total magnet weight
- Reduced Efficiency: The trade-off for the shared magnet was lower sensitivity
- Similar Components: The cone, voice coil, and diaphragm were essentially the same as the 604C
The Green Hammertone Finish
The 605A is easily identified by its distinctive green hammertone paint finish with gold Altec Lansing decal. This finish was also used on some 604C production and has become iconic among vintage Altec collectors.
Collectibility Today
Despite (or perhaps because of) its limited production run, the 605A has become collectible. Some enthusiasts specifically seek out the 605A for its:
- Unique history as the "rejected" Altec
- Slightly more "domesticated" sound compared to the 604
- Distinctive green hammertone appearance
- Rarity compared to the abundant 604 variants
Paul Veneklasen's Objection
Audio historian Paul S. Veneklasen, who worked in Altec's acoustic research department, later noted that he had objected to the horn design changes (from true multicellular to vaned sectoral) that occurred around this period, believing they were cost-motivated rather than acoustically beneficial. His objections were overruled, and the vaned horn remained standard through the 604G and 605A production.
Historical Outcome
Due to customer demand, Altec reintroduced the 604 as the 604E "Super Duplex" in 1964, effectively ending 605A production. The 604E restored the full separate magnet assemblies while maintaining some of the technical improvements developed during the 605A era.
Related Models
- 604E Super Duplex - The 604 that replaced the 605A
- 604-8G Super Duplex - Final evolution of the 604 series
- 604 Series Overview - Complete history of the line