HypetheSonics’ headphone database is a self-consistent set of measurements for some of today’s higher-quality in-ear monitors and earbuds. All measurements on this database are produced using the GRAS RA0045 coupler. If needed (i.e., for shallow-insert earbuds), this coupler is also connected to a GRAS KB5010 artificial pinna. Unless otherwise noted, all IEMs are measured with medium silicone stock tips. Where noted, some measurements are also given using SpinFit silicone Cp100 or Cp800 eartips (depending on nozzle diameter) as these eartips usually improve the treble response and allow for a more consistent insertion in the coupler. Insertion depth is determined by what arises naturally with the given headphone and eartip. The database includes information such as sound pressure level versus frequency, distortion (at 80 dB and 94 dB @ 500 Hz), impedance (where relevant), impulse response, external noise attenuation (with active noise cancellation on, where relevant), and total non-tonal error. In addition to the measurement data, various tools are available to help compare headphones against one another and against given target functions. These tools are explained in detail in the main ‘How To’ section (top right menu).

All measurement modes have a search feature that allows users to rank the various headphones according to the relevant metric(s). For example, headphones can be ranked in order of closeness to a chosen frequency-response target (which could be another headphone’s frequency response, a frequency response uploaded by the user, or any arbitrary modification to these curves). Headphones can also be ranked in order of integrated total harmonic distortion, minimized FR drift due to a given output impedance, closeness to a theoretically-perfect impulse response, total noise attenuation, and median or 95th-percentile total non-tonal error.

While the search and rank feature is useful for research and guidance, please note that the headphone at the top of any particular rank search is not necessarily the ‘best’. Life is more nuanced than that. Given the variances in human hearing, sensitivity of FR perception to loudness, and potential variation in spectral content in any specific recording, there isn’t one frequency response that is optimal in all situations. We generally like the Harman target but prefer it adjusted to account for a lower-listening volume. While harmonic distortion usually isn’t a major concern, it is worth keeping an eye on distortion from balanced-armature-based IEMs. Impulse and/or phase response can be quite poor (as a result of resonances, driver circuitry or DSP), and the headphone can still sound quite reasonable, however these effects can change spatial perception. Unless you have a very low output-impedance source, you should generally favor a headphone that has a flat impedance curve, however, even this has exceptions as somebody might prefer some altered frequency response as a result of a high output-impedance source. External noise attenuation can be important for both safety and listening enjoyment in noisy environments, but having very poor sound isolation can actually be helpful in situations where you want to avoid occlusion effects, minimize the ‘closed-in’ feeling you can get with plugged ear canals, or simply be aware of your surroundings. The goal should be to find the optimal headphone for you and your specific situation.