GROM Audio DSP for Select BMW Conversion KIT car Module You will need this part if your BMW stereo is equipped with DSP (Digital Signal Processing) and you want to install one of the aftermarket car audio integration adapters such as GROM Audio car kit or any other aftermarket integration adapters. The GROM BMW DSP Converter Kit converts the analog sound from your aftermarket integration adapter to the digital. Not all DSP radios have the coaxial connection in the trunk. Some have the standard 6 pin connection and do not require this interface.