Controlling the velocity of the acoustic wave is critical for advancing time-domain signal processing. However, current slow acoustic configurations suffer from narrowband and backscattering loss. Here, we propose broadband topologically protected slow acoustic reciprocal systems via multiwinding modulation in the Brillouin zone (BZ). By coupling the resonance-induced nearly flat bands and the topological edge states (TESs), hybridized TESs with multiple windings across the BZ are formed, which result in broadband slow acoustic waves with controllable velocity. The relative bandwidth of $\sim 7\%$ and the velocity of $0.04c_0$ ($c_0$ is the acoustic wave velocity in air) are achieved, which greatly outperforms conventional methods. Our work paves the way for the development of high-performance acoustic devices.

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• Edge states
• Flat bands
• Phononic crystals
• Topological materials