In this paper, customized series elastic actuator (SEA) force and position control solutions are proposed to achieve high performance while keeping the bandwidth low. In the context of active disturbance rejection, the higher the bandwidth of extended state observer, the more robust and accurate the closed‐loop performance. However, high bandwidth requires high sampling frequency and low measurement noise, leading to higher cost in practice. It is shown in this paper that the bandwidth can be lowered without sacrificing performance by incorporating additional information into the design, including not only the entire known SEA model information but also angle measurements of both the motor and the load. In addition, this allows both matched and mismatched disturbances, at the motor and the load side respectively, to be estimated and mitigated in real time, thus making the design more robust. Simulation results verify the effectiveness and robustness of the proposed approach.