1. A device for adjusting a movable electroacoustic sound transducer to a specific reproducible position with respect to the mouth of a speaker comprising, an optical duct connected to the sound transducer and positioned between the speaker and an object such that the speaker can only fully visually observe the object via the optical duct when he is at a specific position in relation to the sound transducer such that a given reproducible frequency transfer function is maintained between the mouth of the speaker and the sound transducer for all separate uses of the device and for different speakers, and wherein the sound transducer and the optical duct are arranged on a pivotable elongate mount so as to be movable in parallel on a fixed holder by means of a parallelogram guide.