“ These are amazing. If you can get them for a low price, do so. They are a bit uncomfortable, so you might not want to use them for long periods of time. Their clarity is fantastic though, the bass while not being big in quantity is extremely accurate and with a decent amp (I'm using the 300 Ohm version of the headphones) it is just fantastic in quality. Despite being a closed headphone...” --FirsToStrike
From an old MB Quart brochure (circa late 80s): The Quart Phone 50 Dynamic, semi-open headphone. Coupling: circumaural. Frequency response: 10 Hz - 22 kHz. Nominal Impedance: 120 ohms (x2). Sound Pressure Level: 96 dB. Rated Power Handling: 0.1 watt. Distortion <0.5%. Weight (without cord): 245 grams.
High-end offering from German headhpone company 'Manta' (manufactured by Calrad Imports Inc.*) in 1974. *Reference Needed Impedance Rating in Ohms 4.0 minimum and 16.0 maximum Frequency Response Range Hz 30.0 to 15000.0 Headset Cord Length 84.0 inches nominal Earphone Element Type Dynamic Earphone Cushion Material ...