A HEARING AID COMPRISING A SPEAKER UNIT

A hearing aid adapted to be worn at an ear of a user comprises a multitude of microphones, each providing an electric input signal representative of sound; and a processor configured to apply one or more processing algorithms to the multitude of electric input signals and to provide a processed signal in dependence thereof. The processor comprises a feedback control system for estimating a feedback path from said output transducer to at least one of said multitude of microphones; an output transducer for converting said processed signal to an acoustic signal. The hearing aid further comprises a BTE-part adapted for being located at or behind the ear of the user and comprising at least one of said multitude of microphones; and a speaker unit adapted to be located at least partly in an ear canal of the user, the speaker unit comprising said output transducer and a cable electrically connecting said BTE-part and said output transducer. The processor is configured to estimate a speaker unit size in dependence of said estimated feedback path, wherein the feedback path is estimated while said hearing aid is located in a specific position away from the user's head. A method of operating a hearing aid is further disclosed. The invention may e.g. be used in hearing aids comprising a behind-the-ear part as well as an exchangeable speaker unit located in the ear canal.