Digital audio equalization is used to enhance the listening experience introducing corrections in the auditory frequency response. The equalizer performance depends on its implementation which includes optimal filters with sharp transition bandwidth development and a low computational complexity. Starting from a previous FIR implementation based on multirate systems and filterbanks theory, an optimized digital audio equalizer is derived. The proposed approach employs an approximation of the FIR structure using IIR filters, in order to improve the filterbanks structure developed to avoid interferences between adjacent bands. The effectiveness of the optimized implementation is shown comparing it with the previous approaches of the state of the art. The experimental results confirms that the presented solution has several advantages increasing the equalization performance in terms of low computational complexity, low delay, and uniform frequency response.