It would need two 1.5A secondaries. If you could find 3V secondaries then a 9VA transformer would do, but 6V is going to be more common, so would require a 18VA transformer.
It would need a drive circuit that could drive 2Ω, identical the the circuit that would be required without the transformer.
It would need a drive circuit that could drive 2Ω, identical the the circuit that would be required without the transformer.