Absorbers for airborne sound are usually tested at reverberated sound incidence in reverberation chambers at normal sound incidence. Wide-space installed absorbers for bass frequencies cannot be tested and compared on the basis of any standard measuring procedure. In order to estimate their acoustical efficiency in small rooms we will introduce a measuring technique here which will create the possibility to examine resonators at different orientations in room edges as practical use demands. An example calculation explains why the,,effective absorption space amounts to a multitude of the component surface at certain room modi below 100 Hz if the Sabine-formula is applied (only for the use of comparisons). An,,effective absorption degree, based on the mean value of different modi, however, as well amounts to values superior to 0,5 above 40 Hz and considerably superior to 1 above 63 Hz to 20 kHz, if new interconnected plate resonators are installed in layers in a room. Thus a measuring procedure for the design of compact bass absorbers for professional and private audio rooms is provided which can be used in any small quader-like rooms.