This new speaker module fits wherever 20mm x 40mm rectangular speakers were previously installed. With the help of the built-in passive radiator in conjunction with a high-performance rectangular speaker, the module achieves significantly improved bass reproduction and achieves a considerable sound pressure even in the highs and mids. The module is particularly suitable for diesel or steam locomotives where contemporary bass reproduction is important. The speaker fits perfectly with LokSound 5 micro, LokSound 5 or LokSound 5 L decoders.