This article is a part 2 of this article on target curves.
Let’s start by answering a simple (but not too simple, actually) question: what are the headphones sound parameters that can be measured at all? Or, more precisely, the sound parameters that are usually measured. I’ve divided those into two categories: the main ones – the most significant and frequently cited, and the additional ones – less significant, but also important.
- The frequency response is the dependency of the sound pressure level on the frequency of the reproduced harmonic signal at the headphones output. The frequency response is a reflection of the played sound volume at different frequencies. In the audiophile universe, it’s called tonal balance. The frequency response is the most significant characteristic of the headphones sound delivery. This is what we most often pay attention to when describing the sound.
- The cumulative spectrum (waterfall) reflects resonances and reverberations at different frequencies after the headphones stop playing the signal. Each resonance adds a certain emphasis to its corresponding frequency. If the amplifier also introduces some distortion, such a distortion is going to be amplified at the resonant frequencies. At some point, the resonances can be considered as a qualitative parameter, where less is better. However, it’s still more correct to address it as a versatility indicator, like less resonances mean less glitches visibility on the amplifier side.
- The impulse response — a response to a single shortest possible impulse. The pulse response wave form primarily depends on the frequency response, the attenuated resonances and reverberation of the headphones themselves, as well as on the acoustic test chamber stand. The total length of the impulse is about 5 seconds, while visually it’s somewhere around 2-4 milliseconds long.