Specification of headphones
 

What values of impedance and sensitivity does one expect from "high impedance" headphones as used, for example, with early radios and military sets (e.g. R1116, R1155)?

Re: Specification of headphones
 

They're normally 2K. Sensitivity varies a lot, but if they've got to work with a crystal set they must be fairly sensitive :D

Best regards, Paul

Re: Specification of headphones
 

Headphones for crystal sets do need to be high impedance, and sensitive as Paul says. Those for military radios (ie DLR5s) are normally low impedance (but high impedance will work OK). I don't know the R1116, but the R1155, like all similar vehicle/aircraft fit radios to this day, is designed to feed several sets of headphones via a system of "control boxes". The output will be typically 50-100mW, and the impedance from tens to the low hundreds of Ohms.