I have tried this setup and it has worked OK, with a good sound level output from the speakers.

However, I wonder if doing this is unsafe, because the Apple charger puts out more watts (5 W) than the rating of the speakers (3 W), and if it could result in an electrical hazard.

I suppose that the 3-watt output rating of the speakers could be derived from any of three permutations of voltage and amperage:

3 V x 1 ampere

1 V x 3 amperes

or

(square root of 3) V x (square root of 3) amperes

In each of these three scenarios, could the 3-watt speakers (1.5 W + 1.5 W) safely handle the 5-watt output of the Apple charger?

Maybe the speakers might pull only as many watts as needed. On the other hand, the 3 volts the speakers consume together would be less than the 5 volts the charger is pushing out, and perhaps the speakers would not be able to safely dissipate the excess voltage.

Many thanks for any feedback on this question.