Headphones

As mentioned in the review text, the 3.2 is a low-sensitivity headphone. Nothing like as low-sensitivity as the recently tested 91.5dB Hifiman Susvara [HFN Dec '19] but at 102.7dB for 1V input at 1kHz, the 3.2 is still about 12dB shy of what we typically measure from a modern moving-coil headphone. This measurement, like the frequency responses, was taken with the 3.2's sound frames (capsules) angled half-way forwards, at about 18o through their 36o range of articulation. Uncorrected frequency responses in the same position illustrate the following features [see Graph 1, below]: an early low frequency roll-off; an early peaking at about 2kHz (3kHz is more normal to achieve a neutral tonal balance); and lack of high treble output. Of course, the response changes somewhat as the capsules are swung in or out but these general features are retained.

The outcome for the corrected traces [see Graph 2] is predictable: while the diffuse-field corrected trace [green] has an unusually flat trend from 100Hz to 4kHz, output falls away either side of this passband and there is a prominent peak in the third-octave centred on 2kHz. This coincides with the narrow peak in the uncorrected response and with a ridge in the cumulative spectral decay waterfall (not shown here), which identifies the cause as a resonance. Elsewhere in the audible spectrum, though, the 3.2 is free of obvious resonance modes. Heinz Renner supplied me with LB-acoustics' own target curve but this places the presence band peak at 5.5kHz, even further from the 3.2's. Impedance ranges from a minimum of 93.6 to a maximum of 414ohm, enough to cause a 0.67dB modification in frequency response with a headphone amp having a 10ohm source impedance and 1.81dB with 30ohm. Total harmonic distortion is high (for a headphone) at 1.5% for 90dB SPL at 100Hz, for reasons explained in the boxout. This suggests that EQ of the bass roll-off is inadvisable. KH