The application relates to a hearing aid system comprising a hearing aid device comprising a configurable signal processing unit, a programming device configured to program the configurable signal processing unit, and a communication link allowing the exchange of data between the hearing aid device and the programming device. The application further relates to a method of programming configurable signal processing unit to provide an increased speech intelligibility by frequency lowering. The hearing aid system is configured to program the configurable signal processing unit of the hearing device according the claimed method. The invention may e.g. be used in hearing aids.