What Yamaha has to say:
Open-ear headphones with a neutral tone that is ideal for listening to digital musical instruments
Product Specs:
Driver TypeDriver UnitImpedanceMaximum InputSound Pressure LevelFrequency ResponseWeight (with Cable)Cable LengthConnectors HPH-150 Headphones / Earphones Driver Type Dynamic, open air Driver Unit Φ40 mm Impedance 48 ohms Maximum Input 1,000 mw Sound Pressure Level 101 dB Frequency Response 20 Hz - 20kHz Weight (with Cable) 163 g with cable Cable Length 2.0 m (Single Cable) Connectors 3.5 mm (1/8") stereo, 6.3 mm (1/4") stereo