Determining a "good" frequency response involves both objective and subjective factors. Trust your ears: if your headphones reproduce music naturally and enjoyably, that's a good sign. Look for professional measurements showing a relatively smooth response without dramatic peaks or dips. Read reviews from trusted sources, paying attention to descriptions of tonal balance. Develop a set of familiar test tracks and listen critically for elements like bass extension, vocal clarity, and high-frequency detail. Remember, a good frequency response is subjective and should align with your preferences and the headphones' intended use.