High precision x ray spectroscopy of highly charged heavy ions In the present thesis the advantages of two new and complementary detector concepts for x ray spectroscopy of highly charged ions over conventional semiconductor detectors have been worked out. These two detectors are the twin crystal spectrometer FOCAL and the metallic magnetic microcalorimeter maXs. Although the maXs microcalorimeter is still under development first very promising x ray spectra could be recorded at the ESR storage ring at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt. With the crystal spectrometer FOCAL which was fully equipped for the first time a dedicated beam time at the ESR aiming for the precise determination of the 1s Lamb shift of hydrogen like gold (Au78+) could be conducted. The obtained result for the Lyman a1 transition energy is afflicted with a small statistical uncertainty however the encountered systematic effects are still posing a challenge to overcome. In the outlook it will be discussed in detail how the accuracy of a future measurement could be improved and in which way both detector concepts could support each other optimally.