Marantz HD 77


HD77 is a model name of Marantz 4-way high-fidelity loudspeakers which were 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 if the listener preferred the more accurate bass response provided by airtight speaker boxes. However, they were not fully airtight this way, but rather what is known as aperiodic.

Power handling: 250 watts RMS, 330 Watts peak
Impedance: 8 ohms

Marantz HD77s had a total volume of 2.8 cubic feet each. The cabinet dimensions are:

Dimension:
Depth: 12 inches
Width: 15 inches
Height: 28.5 inches

Drivers
The four drivers of the Marantz HD77s were a woofer, mid-range, tweeter and super tweeter. The given frequency responses are what the crossover circuit fed to each speaker, not what each speaker would respond to with no crossover circuit. The mid-range, tweeter and super tweeter have controls for switching between a laboratory flat and neutral response and a room EQ response.
Woofer
The woofer was 12 inches in diameter with a frequency response of 30 to 500 hertz.
Mid-range
The mid-range was 4.5 inches in diameter with a frequency response of 500 hertz to 3 kilohertz.
Tweeter
The tweeter was a soft dome-type. The tweeter\'s frequency response is from 3 to 8.8 kHz Linear Polyester Film Dome
Super-tweeter
The super-tweeter responded from 8.8 to 23 kHz, which extends 3 kHz above the nominal range of audio frequencies which can be heard by the human ear. Linear Polyester Film Dome

źródło: en.wikipedia.org/wiki/Marantz_HD77#References