Look, we are talking about a DAB alarm radio, aren't we? If so, there's probably no need for all this FUD. A few extra ohms in series with the speaker isn't going to hurt anything.
If this was a hi-fi system, at worst you might be worrying about the reduction of damping of the loudspeaker (which would show up its natural resonance and therefore affect its frequency response). But even a high power audio amplifier should not suffer any damage whatsoever when driving into higher-than-normal impedances (including a complete open circuit).