the reflected load on the primary of an output transformer is the load (say an 8 ohm nominal speaker load) put across the secondary terminals multiplied by the turns ratio squared.

so if you have a turns ratio of 20:1 step down and you put an eight ohm load across the secondary you will reflect back to the primary an impedance of 3200 ohms.

generally when we "spec" or use "specs" for a power trans... we don't use the impedance language but instead talk the "voltage" and "current" language.

so that a 20 to 1 step down trans with say 120 volts across the primary will have 6 volts across the secondary. On power tranneys the moreso relevant and useful "numbers" are voltage and current.

cheers,

msl