Altec 909-8A Compression Driver
1988 - 1990s
The Altec 909-8A is the top of Altec's compression driver line. It has the Tangerine radial phase plug and the Pascalite diaphragm structure. Altec introduced it in 1988 for professional work that needed the highest performance, durability, and power handling.
Specifications
| Type | High-frequency compression driver |
|---|---|
| Model Variants | 909-8A (8Ω), 909-16A (16Ω) |
| Throat Diameter | 1" (25mm) |
| Diaphragm Material | Pascalite structure | Voice Coil Diameter | 45mm (1.77") |
| Voice Coil Bobbin | Aramid fiber (high heat resistance) |
| Magnet Type | Ceramic (ferrite) |
| Magnetic Flux Density | 18,000 Gauss |
| Phase Plug | Tangerine radial phase plug |
| Nominal Impedance | 8 Ω (909-8A), 16 Ω (909-16A) |
| AES Rated Input | 30W (500Hz+), 40W (800Hz+) |
| Continuous Program Input | 60W (500Hz+), 80W (800Hz+) |
| Peak Power | 120W (500Hz+), 160W (800Hz+) |
| Output Sound Pressure Level | 144 dB SPL (with acoustic tube) 108 dB SPL (with MR994A or 511B horn) |
| Frequency Response | 500 Hz to 20 kHz |
| Dimensions | 140mm diameter x 69mm depth |
| Weight | 2.9 kg (6.4 lbs) |
Advanced Technologies
The 909-8A used several technologies that set it apart from earlier Altec compression drivers:
Tangerine Radial Phase Plug
The Tangerine phase plug used radial slots instead of the usual circular slots. That gave it several advantages:
- Improved Phase Coherence: Better time alignment of sound waves
- Reduced Distortion: Smother frequency response with fewer anomalies
- Higher Efficiency: Improved energy transfer from diaphragm to horn
- Extended High-Frequency Response: Better performance above 10 kHz
Pascalite Diaphragm Structure
The Pascalite diaphragm was a significant step forward in diaphragm technology:
- Enhanced Durability: More resistant to fatigue and failure
- Improved Heat Dissipation: Better thermal management for high-power operation
- Consistent Performance: More stable characteristics over time
- Reduced Breakup Modes: Cleaner reproduction at high frequencies
Aramid Fiber Voice Coil Bobbin
The voice coil bobbin was made of aramid fiber, similar to Kevlar. It provided:
- High Temperature Resistance: Withstands continuous high-power operation
- Dimensional Stability: Maintains shape under thermal stress
- Lightweight Construction: Contributes to high efficiency
- Longevity: Extended service life in demanding applications
Performance Characteristics
Altec designed the 909-8A for professional applications that needed the highest performance:
- Exceptional Power Handling: Up to 160W peak power capability
- High Output Capability: 144 dB SPL maximum output
- Wide Frequency Response: 500 Hz to 20 kHz usable range
- Low Distortion: Advanced phase plug design minimizes distortion
- Thermal Stability: Designed for continuous high-power operation
Compatible Horns
Altec designed the 909-8A to work with various Altec horns:
- MR994A: Medium format horn specifically designed for the 909 series
- 511B: Popular 90° x 40° exponential sectoral horn
- MRII500 Series: Large format Mantaray horns (with 21216 conversion throat)
- Other 1" Throat Horns: Compatible with any horn designed for 1" compression drivers
Comparison with Earlier Models
| Feature | 902-8B | 909-8A |
|---|---|---|
| Introduction | Mid-1980s | 1988 |
| Phase Plug | Conventional | Tangerine radial |
| Diaphragm | Aluminum | Pascalite structure |
| Voice Coil Bobbin | Conventional | Aramid fiber |
| Power Handling | 30W AES | 30-40W AES (higher at 800Hz+) |
| Maximum SPL | ~110 dB | 144 dB (with tube) |
| Throat Size | 1.4" | 1" |
Professional Applications
The 909-8A was used in demanding professional environments:
- Concert Sound Reinforcement: Large venue PA systems
- Studio Monitoring: High-end control room monitors
- Theater Systems:
Cinema and live theater installations - Tournament Installations: Sports arenas and stadiums
- High-End Home Audio: Custom installations for audiophiles
Sound Characteristics
Users and engineers describe the 909-8A as:
- Exceptionally Clear: Outstanding detail and transparency
- Smooth High-Frequency Response: Extended highs without harshness
- Dynamic and Powerful: Capable of very high output levels
- Low Distortion: Clean reproduction even at high volumes
- Professional Character: Accurate, uncolored sound suitable for critical listening
Maintenance and Service
Replacement parts for the 909-8A:
- Diaphragm: 26420 (8Ω), 26421 (16Ω)
- Gaskets: Standard Altec gaskets available
- Hardware: Standard mounting bolts and hardware
The heavy construction means 909-8A drivers typically need less maintenance than earlier models. Diaphragms may still need replacing after extreme use.
Historical Significance
The 909-8A represents:
- Technological Peak: The most advanced compression driver Altec produced
- Professional Standard: Set new benchmarks for power handling and output
- End of an Era: One of the last great Altec designs before the company's decline
- Collector's Item: Highly sought after by vintage audio enthusiasts
Legacy
Today, the 909-8A is highly regarded for:
- Technical Excellence: Still competitive with modern compression drivers
- Durability: Built to withstand decades of professional use
- Sound Quality: Exceptional performance that has stood the test of time
- Collectibility: Command premium prices on the vintage market
Well-maintained 909-8A drivers typically sell for $400-$600 per pair, and mint examples go higher. They are still used in professional applications and in high-end home audio projects.
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