Many axion dark matter experiments search for an axion signal with a Maxwell Boltzmann distribution, predicted by the isothermal halo model. However, recent work has shown that the dark matter distribution may be more exotic, such as containing caustics or being entirely composed of miniclusters. A key feature of these models is the signal becomes much narrower. This chapter introduces the effect of narrow signals on detection and describes the analysis of ADMX run 1c data, placing limits on exotic halo structure. Ultimately, this analysis rules out narrow halo structures with \(\rho _a \gtrsim 0.03\,\mathrm {GeV/cm^3}\) , over the mass range \(3.3-4.2\,\mu \text {eV}\) .