There is a high demand for portable audio on the market. Hence, manufactures of headphones and hearing aids have to deal with miniaturization of electroacoustic transducers (micro speakers) but maintain sound quality and energy efficiency (battery life time) at the same time. Different techniques are known for downsizing transducers. A very successful method is provided by the semiconductor industry. The use of the so-called MEMS technology (Micro- Electro-Mechanical-System) has already led to great success in microelectronics and MEMS applications such as microphones and accelerometers. This success has triggered a high interest in implementing MEMS technology also for speaker manufacturing. Based on patents, the initial approaches of MEMS loudspeakers will be presented. An outlook of the arising new potentials for portable spatial audio with MEMS based speakers will be given.