Altec Lansing 604-8G Duplex

The Altec Lansing 604-8G Duplex uses a coaxial driver design in which the high-frequency compression tweeter is mounted at the center of the low-frequency woofer. This creates a single-point sound source, which helps produce accurate phase response and coherent imaging.

The 604-8G has a sensitivity rating of approximately 98 dB, making it highly efficient by modern standards. This high sensitivity means the speaker can produce substantial volume from relatively low-wattage amplifiers, including tube amplifiers.

The 604 Duplex series was historically favored by major recording studios and mastering engineers because its coaxial design delivered accurate, time-aligned sound from a single point source. Studios like Capitol Records and RCA used 604-series monitors as primary reference speakers through the mid-20th century.

Due to their 98 dB sensitivity, the 604-8G speakers work very effectively with low-wattage tube amplifiers, including single-ended triode (SET) designs. Many audiophiles also pair them with solid-state amplifiers, as the speakers' efficiency gives broad amplifier compatibility.