Altec 515B / 515-8G Woofer

The Altec 515 series represents the most powerful 15-inch cone woofers in Altec's lineup, designed specifically for horn-loaded applications in the legendary Voice of the Theatre systems. The 515B and its successor the 515-8G delivered exceptional efficiency and deep bass when installed in the front-loaded A7 cabinet.

Specifications

Type	15" (380mm) Low-Frequency Loudspeaker
Voice Coil Diameter	3 inches (76mm)
Magnet	Alnico V
Nominal Impedance	8 Ω (515-8G) / 16 Ω (515B)
Power Handling	50W continuous, 100W program
Frequency Response	20 Hz - 1,000 Hz
Sensitivity	~100 dB/W/m (in horn-loaded cabinet)
Recommended Crossover	800 Hz (with 288 or 291 compression drivers)

Design Overview

The 515 series was engineered specifically for horn-loaded cinema applications. Unlike direct-radiating woofers designed for sealed or vented boxes, the 515 was optimized for front-loaded horn operation in the A7 and similar cabinets.

Key design characteristics:

Horn-Load Optimized: Magnetic circuit and suspension designed for front-loaded horn operation
High Efficiency: Capable of 100+ dB sensitivity when properly horn-loaded
Extended Bass: Reaches down to 20 Hz in A7 cabinet for full-range cinema sound
Alnico V Magnet: Provides stable, high-flux magnetic field
Large Voice Coil: 3-inch diameter for excellent power handling

Applications

The 515 series was the foundation of Altec's cinema and professional systems:

Voice of the Theatre A7 - Primary woofer in the legendary cinema speaker
Voice of the Theatre A5 - Mid-sized cinema system
825B Cabinet - Front-loaded enclosure for the 515
Professional sound reinforcement systems

In the Wild

Featured in Resistor Magazine's restoration profile of Iwan Arjanto's vintage speaker collection. The 515 woofer (in its various iterations) is the low-frequency foundation of the Altec A7 speakers that Arjanto has built four pairs of for customers.

When restoring or building A7 systems, Arjanto has learned to carefully test each driver before installation. The 515's robust construction means that even decades-old examples can often be returned to full performance with minimal service.

Evolution: 515B to 515-8G

The 515 underwent refinements throughout its production life:

515B: Early version, typically 16 ohms
515-8G: Later version with improved suspension and 8-ohm impedance
515-16G: Later version maintaining 16-ohm impedance
515-8GHP: High-power variant

The "G" series incorporated refinements to the cone and suspension materials while maintaining the same fundamental magnetic structure and performance characteristics.