individual sections of a headbox as will be apparent below there may be an individual one of the control apparatus shown in fig1 a for each of the individual sections of the headbox across the machine width and each of those individual control apparatus shown in fig1 a can be operated independently during a periodic quality control check of the paper web being produced or of the pulp suspension being dispensed by the headbox it may be found that the weight per unit area profile basis weight at the individual section across the width of the web of the mixed pulp suspension which is supplied through mixer 20 in fig1 a and controlled by the control devices shown in fig1 a differs beyond an acceptable level from a desired value either in flow volume q m or pulp suspension concentration c m therefore the pulp density of the suspension in the headbox must be suitably corrected at this section across the width of the headbox according to the invention the adjustment can be made by varying the concentration c m of the individual section stream 22 that is controlled by the control apparatus shown in fig1 a the necessary change in c m that is dc m can be determined from a previously prepared weight balance sheet the resulting corrected concentration c m is dependent exclusively upon the ratio of the control streams q h q l the total flow through 22 of these two streams 24 and 26 may be halted while the ratio adjustment is made the corrected value of the basis weight is used as a basis for ratio control to establish the desired value setting the ratio control sets the new flow ratio q h.