Altec Lansing 34647 Compression Driver

The Altec Lansing 34647 is a high-efficiency compression driver developed during the golden era of professional audio. Though its exact year of introduction remains undocumented, it was likely produced during the 1960s to early 1970s and became a staple in Altec's lineup of drivers designed for cinema sound, public address systems, and high-performance studio monitoring. Known for its robust construction and dynamic output, the 34647 exemplifies Altec’s engineering excellence during the analog audio era.

Specifications

Feature	Specification
Type	Compression Driver
Frequency Response	1.5 kHz – 18 kHz (typical with horn)
Power Handling	20W – 100W (depending on system integration)
Impedance	8 ohms or 16 ohms (model variant dependent)
Sensitivity	104 – 108 dB (1W/1m)
Diaphragm	Phenolic resin
Voice Coil	1-inch throat
Magnet Type	Alnico (Aluminum-Nickel-Cobalt)
Horn Compatibility	Exponential horns (e.g., Altec 802, 811)
Mounting	4-screw flange (standard Altec pattern)

Historical Context

The Altec Lansing 34647 was developed as part of Altec’s broader family of professional drivers aimed at commercial and industrial audio applications. During the mid-20th century, Altec dominated the cinema and theater sound market, and drivers like the 34647 were frequently paired with large-format horns and bass enclosures to create full-range systems capable of high sound pressure levels with minimal amplifier power.

Its alnico magnet and phenolic diaphragm construction reflect the materials and design philosophies of the time—prioritizing efficiency, durability, and sonic clarity. The 34647 was often used in conjunction with Altec’s legendary 515B or 518B crossover networks and paired with horns such as the 802A or 811A for optimal dispersion and response.

These drivers were commonly found in movie theaters, train stations, auditoriums, and even early rock concert PA systems. Their high sensitivity made them ideal for environments where amplifier power was limited but wide coverage was essential.

Sound Signature

The 34647 delivers a bright, articulate, and dynamic high-frequency response with a characteristic midrange presence that many describe as "lively" or "forward." Its alnico magnet contributes to a smooth, warm tonality that balances the inherent brightness of the phenolic diaphragm. When properly mated with a compatible horn and crossover, the driver offers exceptional clarity and projection.

However, due to its high efficiency and extended high-frequency response, the 34647 can sound harsh or fatiguing if used with poorly designed horns, mismatched crossovers, or excessive amplifier power. Proper system integration is key to achieving its best performance.

Maintenance and Restoration Tips

Like all vintage audio components, the Altec 34647 requires careful evaluation and potential restoration to perform reliably in modern systems:

Diaphragm Inspection: The phenolic diaphragm is prone to aging, warping, or cracking. If distorted or damaged, replacement with a modern equivalent (e.g., from Hahn or OEM restorers) is recommended.
Alnico Magnet Recharging: Over decades, alnico magnets can lose strength. Re-magnetizing using a proper magnetizer can restore original efficiency and output.
Terminal and Wiring Check: Inspect for corrosion, loose connections, or brittle insulation. Clean terminals with contact cleaner and replace wiring if necessary.
Horn Matching: Use with original Altec exponential horns for authentic response. Avoid modern plastic horns that alter dispersion and tonality.
Power Handling: Do not exceed 100W, and ensure amplifier impedance matches the driver (8Ω or 16Ω). Use a crossover to prevent low-frequency damage.
Environmental Care: Store and operate in dry, temperature-stable environments to prevent diaphragm warping and corrosion.

Collectibility and Market Value

The Altec 34647 holds moderate collectibility among vintage audio enthusiasts, especially those restoring classic theater systems or building high-efficiency horn speakers. With a collectibility rating of 7/10, it is valued more for its utility and historical role than as a rare collector’s item.

Market Value: $100 – $300 per driver, depending on condition, originality, and diaphragm status.
Restored Units: Drivers with replaced diaphragms or recharged magnets may command higher prices if professionally serviced.
Demand: Steady among DIY horn speaker builders and vintage PA restorers.

Conclusion

The Altec Lansing 34647 remains a respected driver among vintage audio aficionados for its efficiency, clarity, and historical significance. While not as widely known as the 285 or 802 drivers, it played a crucial role in Altec’s professional audio ecosystem. With proper care and system integration, the 34647 continues to deliver the powerful, detailed sound that defined an era of live and cinematic audio.