Final answer:
A transformer with the correct turns ratio is used to match an amplifier's output impedance with a speaker's input impedance in order to offset a transformer-coupled amplifier's poor frequency response.
Step-by-step explanation:
The poor frequency response of a transformer-coupled amplifier can be offset by employing a transformer with an appropriate turns ratio to match the impedance of the amplifier's output to the speaker's input. For example, to match an amplifier with an output impedance of 500 Ω to a low-impedance 8-16 Ω loudspeaker, you would need a transformer that reduces the impedance by a factor equal to the square of the turns ratio.
Since the speaker's impedance is much lower than the amplifier's output impedance, a transformer with a high primary to secondary turns ratio is required. The turns ratio can be calculated using the formula: turns ratio = √(Zspeaker/Zamp). Using this equation, the desired turns ratio would be √(8/500) or √(16/500) for an 8 Ω or 16 Ω speaker, respectively. This helps in minimizing losses and ensuring maximum power is transferred to the speaker, thus helping to alleviate the poor frequency response. The quality factor and resonant frequency also play a role in the frequency response of such a system.