Can't figure out what kind of transformer I need
ZL1/ZL2= 20

On your previous question the small AC per transformer will work using the centre tap and one side only like this schematic.

240V/12V means Z1/Z2= 20:1 inductance ratio.  To lower the source impedance of caps to speaker and thus drive more current force on cone.

The voltage ratios are the same except your source 9Vdc with limited current