Special Micro Rectangular Planar Dynamic Driver -[High] Crisp and Dynamic Treble Sound The Micro Rectangular Planar Dynamic Driver is a driver specifically developed to deliver high frequencies, featuring advanced technology that allows a planar driver to be used in IEMs, despite the extreme difficulty in making it small enough to fit in such a small cavity. A team of tuning engineers selected a light yet sturdy planar membrane to minimise frequency loss and applied a trembler with a thin metal membrane and polymer film to create lifelike vivid high frequencies. This provides a clear and dynamic high frequency response.