A hearing aid device comprising: a hearing aid device housing to be arranged behind the ear of a user, the hearing aid device including an input transducer, a signal processor adapted to process signal from the input transducer to compensate for the user's hearing loss, a hearing device connector , and a detachable speaker unit connected to the hearing aid device housing comprising a connector part having a set of contact pins for contacting the hearing device connector , a connecting element having an electrically conductive member, the connecting element connected to the connector part , a speaker unit housing configured to be positioned at least partly in the ear canal of the user, an output transducer included in the speaker unit housing , the output transducer being configured to provide an acoustic signal based on the processed signal from the signal processor, the speaker unit housing being connected to the connecting element , characterized in that a memory unit arranged in the connector part , the memory unit configured to store data relating to the acoustic properties of the output transducer and/or speaker unit housing, wherein the hearing aid device is configured to read the stored data via at least one of the contact pins. a hearing aid device housing to be arranged behind the ear of a user, the hearing aid device including an input transducer, a signal processor adapted to process signal from the input transducer to compensate for the user's hearing loss, a hearing device connector , and a detachable speaker unit connected to the hearing aid device housing comprising a connector part having a set of contact pins for contacting the hearing device connector , a connecting element having an electrically conductive member, the connecting element connected to the connector part , a speaker unit housing configured to be positioned at least partly in the ear canal of the user, an output transducer included in the speaker unit housing , the output transducer being configured to provide an acoustic signal based on the processed signal from the signal processor, the speaker unit housing being connected to the connecting element , characterized in that a memory unit arranged in the connector part , the memory unit configured to store data relating to the acoustic properties of the output transducer and/or speaker unit housing, wherein the hearing aid device is configured to read the stored data via at least one of the contact pins. a connector part having a set of contact pins for contacting the hearing device connector , a connecting element having an electrically conductive member, the connecting element connected to the connector part , a speaker unit housing configured to be positioned at least partly in the ear canal of the user, an output transducer included in the speaker unit housing , the output transducer being configured to provide an acoustic signal based on the processed signal from the signal processor, the speaker unit housing being connected to the connecting element , characterized in that a memory unit arranged in the connector part , the memory unit configured to store data relating to the acoustic properties of the output transducer and/or speaker unit housing, wherein the hearing aid device is configured to read the stored data via at least one of the contact pins. <EOS>