A hearing aid device (10, 44) comprising: a hearing aid device housing to be arranged behind the ear of a user, the hearing aid device (10, 44) 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 (12, 46), and a detachable speaker unit connected to the hearing aid device housing comprising a connector part (14, 24, 34) having a set of contact pins (38, 52, 54, 56) for contacting the hearing device connector (12, 46), a connecting element (20, 32) having an electrically conductive member, the connecting element (20, 32) connected to the connector part (14, 24, 34), 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 (20, 32), characterized in that a memory unit (22, 68) arranged in the connector part (14, 24, 34), the memory unit (22, 68) 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 (10, 44) 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 (12, 46), and a detachable speaker unit connected to the hearing aid device housing comprising a connector part (14, 24, 34) having a set of contact pins (38, 52, 54, 56) for contacting the hearing device connector (12, 46), a connecting element (20, 32) having an electrically conductive member, the connecting element (20, 32) connected to the connector part (14, 24, 34), 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 (20, 32), characterized in that a memory unit (22, 68) arranged in the connector part (14, 24, 34), the memory unit (22, 68) 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 (14, 24, 34) having a set of contact pins (38, 52, 54, 56) for contacting the hearing device connector (12, 46), a connecting element (20, 32) having an electrically conductive member, the connecting element (20, 32) connected to the connector part (14, 24, 34), 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 (20, 32), characterized in that a memory unit (22, 68) arranged in the connector part (14, 24, 34), the memory unit (22, 68) 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.