actual values the optimal nip line distances k 1 and k 2 are set principally based on the staple length of the processed fibers and may thus be preset in addition however properties such as fiber bulkiness sliver unity etc have an effect on the optimal nip line distances which may be optimized empirically such an optimization may then be transferred to the computer 26 which based on an inputted or on a continuously available program varies repeatedly the nip line distances k 1 and k 2 and after each new setting the irregularity of the drafted and doubled sliver 18 is measured by the measuring trumpet 17 and the signal generated by the measuring funnel 17 and converted by the transducer 28 is stored over a predetermined period and evaluated after performing such measurements and evaluation and storing the obtained data the computer 26 computes from these data the optimal nip line distances k 1 and k 2 and provides for an automatic adjustment the nip line distances k 1 and k 2 may also be continuously shown on display fields turning to fig7 the intake measuring organ 9 is connected by a transducer 50 and the outlet measuring organ 25 is connected by means of a transducer 51 with the computer 26 which in turn applies signals to two devices 52 53 for forming a respective spectrogram for the inputted sliver bundle 5 and for the discharged sliver bundle 18 respectively the devices 52 53 are connected to an evaluating device 54 in which the spectrograms generated in the two devices 52 and 53.