Marantz HD77

HD77 is a model name of Marantz 4-way high-fidelity loudspeakers produced during the mid-1970s. They were bass reflex speakers but came with a cylindrical piece of foam which fit into the bass-reflex port of the enclosure, allowing listeners to achieve more accurate bass response similar to that of airtight speaker boxes. Although this configuration wasn’t fully airtight in theory— technically considered aperiodic—the plug used was actually made of closed-cell foam, which did seal the cabinet completely. The plug was cut slightly larger than the port opening, and when inserted and tightened with a retainer screw, it compressed to create an airtight seal, effectively converting the speaker into an acoustic suspension type.

The HD77 was designed by former JBL engineer Edmond May. The speaker’s front baffle included resistive potentiometer controls that adjusted the response curve of each driver from soft to bright, offering great versatility and allowing users to tailor the sound to a wide range of listening environments.