A flexible Block Recursive Least Squares frequency domain (FBRLS) using the multidelay filter (MDF) is presented throughout this paper. The choice of implanting the FBRLS algorithm using MDF adaptive filter, allows one to choose the size of an FFT consecrated to use efficiently the hardware, rather than the requirement of a specific application. In term of performances, the MDF-FBRLS adaptive filter introduces smaller block delay and is usually faster, ideal for a time-varying system, such as modelling an acoustic path in a teleconference room. These good performances are achieved by using smaller block size, updating frequently the weight vectors. Those issues, will reduce the total execution time of the adaptive process. The comparison between MDF-FBRLS and FBRLS algorithms, proved the advantages of the first one, in term of the total execution time, and the efficiency of the computational complexity of the adaptive filter.