Altec 908 Compression Driver

Name: Altec 908 Compression Driver
Brand: Altec

1980s - 1990s

The Altec 908 is a high-frequency compression driver from Altec's 900 series, representing the company's continued refinement of compression driver technology in the ceramic magnet era. Often confused with or converted to 902 models, the 908 offers robust performance for professional audio applications with some distinctive technical characteristics.

Specifications

Type	High-frequency compression driver
Model Variants	908-8A (8Ω), 908-16A (16Ω)
Throat Diameter	1.4" (35mm)
Diaphragm Material	Aluminum
Voice Coil Diameter	2" (50mm)
Magnet Type	Ceramic (ferrite)
Magnet Weight	Approximately 4.5 lbs (2.0 kg)
Nominal Impedance	8 Ω (908-8A), 16 Ω (908-16A)
Power Handling	30W AES, 60W program
Sensitivity	109-110 dB SPL (1W, 1m)
Frequency Response	500 Hz - 18 kHz
Recommended Crossover	800 Hz or higher
Weight	Approximately 8 lbs (3.6 kg)

Design Characteristics

The 908 shares many design features with the 902 series but has some important differences:

Centering Rings: 908 drivers typically include centering rings that block the diaphragm from the space in the magnet chamber
Voice Coil Assembly: Similar to 902 but with different suspension characteristics
Phase Plug: Precision-machined phase plug optimized for smooth response
Magnet Structure: Large ceramic magnet providing strong magnetic field
Cooling: Adequate thermal management for professional use

908 vs 902 Comparison

The relationship between 908 and 902 drivers is complex and often misunderstood:

Feature	908 Series	902 Series
Centering Rings	Typically present	902-8A: Usually absent 902-8B: May have rings
Conversion	Can be converted to 902-8B	902-8A preferred by many purists
Sound Character	Slightly different due to centering rings	902-8A: More open, natural 902-8B: Similar to converted 908
Applications	Professional installations, some monitors	Wide range including studio monitors

Conversion to 902-8B

A common practice in the Altec community is converting 908 drivers to 902-8B specifications:

Diaphragm Replacement: Installing a 902-style diaphragm
Removing Centering Rings: Some conversions involve modifying or removing the centering rings
Re-labeling: Converted drivers are often referred to as "902-8B"

It's important to note that true 902-8A drivers (without centering rings) are generally preferred by purists for their more open, natural sound character.

Technical Performance

The 908 offers professional-grade performance characteristics:

High Efficiency: 109-110 dB sensitivity allows for high output with modest amplifier power
Wide Frequency Response: Capable of reproducing frequencies from 500 Hz to 18 kHz
Good Power Handling: 30W AES rating suitable for most professional applications
Low Distortion: Well-designed phase plug minimizes distortion
Durability: Built for continuous use in demanding environments

Common Applications

The 908 was used in various professional and installed sound applications:

Sound Reinforcement: Concert systems, theater installations
Installed Sound: Churches, auditoriums, conference facilities
Monitor Systems: Some studio and stage monitor applications
Custom Installations: High-end home theater and music systems

Sound Characteristics

Users describe the 908 as:

Detailed and Clear: Good high-frequency reproduction
Efficient: High sensitivity for dynamic performance
Robust: Can handle demanding professional use
Slightly Constrained: Some users note a slightly more "closed" sound compared to 902-8A, possibly due to centering rings
Versatile: Works well across various applications

Maintenance and Service

Common maintenance considerations for 908 drivers:

Diaphragm Replacement: Original diaphragms may need replacement after heavy use
Cleaning: Phase plug slots can accumulate debris affecting performance
Inspection: Regular inspection of voice coil alignment and suspension
Gasket Replacement: Original gaskets may deteriorate and need replacement

Historical Context

The 908 represents Altec's ongoing development of compression driver technology during the ceramic magnet era. While not as famous as the 802 series or as advanced as the later 909 series with Tangerine phase plugs, the 908 filled an important role in Altec's product line:

Cost-Effective Performance: Offered professional performance at a competitive price point
Technical Refinement: Incorporated lessons from earlier designs
Market Position: Positioned between entry-level and premium compression drivers
Transitional Design: Bridges earlier Alnico designs and later advanced ceramic designs

Legacy and Collectibility

Today, 908 drivers are valued for:

Conversion Projects: Popular for conversion to 902-8B specifications
Budget-Friendly Performance: Often more affordable than 902 or 802 drivers
Professional Reliability: Built for demanding applications
Historical Interest: Part of Altec's compression driver evolution

While not as collectible as Alnico models or as advanced as Tangerine-equipped drivers, the 908 remains a solid choice for practical applications and conversion projects. Prices typically range from $200-$400 per pair depending on condition.

Images

The following sources may have images of this equipment. Always verify license terms and provide proper attribution when required.

Source 1: HiFi Wiki

Link: HiFi Wiki
License: Varies - check individual image
Attribution Required: Yes
Commercial Use: Unknown - verify on site
Notes: User-contributed content. Attribution recommended.

Source 2: HiFi Engine

Link: HiFi Engine
License: User-contributed manuals
Attribution Required: Yes
Commercial Use: Reference only
Notes: Great for specs/manuals. Request permission for images.

Source 3: Audio Database

Link: Audio Database
License: User-contributed
Attribution Required: Yes
Commercial Use: Unknown
Notes: Verify license before use.

Source 4: Radio Museum

Link: Radio Museum
License: User-contributed
Attribution Required: Yes
Commercial Use: Unknown
Notes: Attribution required for user photos.

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