Spectral montage for models in which the CDS is composed of the material from the helium-star explosion models of Ertl et al. (2020), increasing in initial mass (he2p9 to he12p0) from top to bottom (thick line). The sequence corresponds to a decreasing fractional helium mass (M(He)/M_ej varies from 83% down to 4%, in the same order). The CDS is at a radius of 3 × 10¹⁵ cm, has a velocity of 2000 km s⁻¹, and is powered at a rate of 2 × 10⁴² erg s⁻¹. For each model, we include the spectrum corresponding to continuum processes and He I bound-bound processes (thin line). He I lines weaken as the helium-star initial mass is increased and the mass of helium reduced due to wind mass loss and burning to heavier elements.