High-order Ambisonics (HOA) presents spatial sound by controlling the sound field inside a compact region. Interactive applications require the listener to move freely; therefore, the listening zone must be shifted accordingly. Dynamic HOA systems face two challenges. First, the angular distribution of the loudspeakers depends on the listener's viewpoint, requiring different decoders as they move. Second, the presented sound field must gradually change, matching what would be heard in the actual world. This research tackles both problems with a modified HOA decoder that makes use of spherical harmonic shift operations. The proposal is evaluated by considering a 157-loudspeaker array. Results show no significant degradation in reproduction accuracy as the listening region is shifted, compared with the accuracy of conventional HOA.