Changing transducers

As your discuss about horn making, I have a question.

I wanted my generator supplier to give me variable power. He modified the standard 1500W generator to give 4 outputs like, 200 to 400W, 600W to 800W, 800 to 1200W and 1200 to 1400W.

Here I am using 12 x 50W transducers = 600W, when I measure the voltage across a transducer it varies from 650V to 950V with varying frequency from 16 to 23kHz.

In this situation if I replace 12 pc x 50W transducers to single 600W tranducer and get a booster, how to make a horn for this varying frequency?

Thanks