Yes, a single speedlight can work with a 22-inch beauty dish, but whether it’s enough depends on your setup. The key factors are your flash’s power, how far the dish is from the subject, ambient light levels, and whether you’re using one flash or multiple.

A beauty dish is typically used close to the subject to create a focused, flattering portrait light with smooth falloff. When used close, you usually do not need an especially powerful strobe. In practice, some light is lost inside the dish, but not so much that a speedlight is automatically unsuitable.

If you move the dish farther away, you’ll need more power, and the effect becomes closer to using a bare flash. So for portraits in controlled light, a single speedlight can be sufficient; for brighter environments or greater working distances, a monolight may be a better choice.