Sennheiser HD650 has been known for its deep bass and neutral tonal balance ever since its release. After 12-consecutive-years of dominance, does this headphone still have a chance against new-bloods?
PRO: While the driver is tightly damped, HD650's frequency response is accurately diffuse-field equalized with a slight downward tilt. This yields a very neutral tonal balance. In addition, there's a high level of second-order harmonic distortion in the sub-bass range, which may contribute to the enhancement of perceptual bass quality.
CON: Since the diameter of the transducer is only 38 mm, the headphone's sweet-spot is very small. My recommendation is to place the driver to the rear portion of the pinna, so that the harsh peaks in the high frequency range are settled. Meanwhile Mr. Jan Meier of Meir Audio recommends the exact opposite. His method yields a sharp null in the treble, which creates a 'veil' like sound quality.
ON SECOND THOUGHT #1: Even Sennheiser HD650 doesn't quite suit the Harman International's new headphone reference.
ON SECOND THOUGHT #2: Here's a simple peer-review on EURI's HD650 measurements(Blue/Orange) compared to other simulator data. While the red graph is of GRAS 43AG of Stereophile, the cyan plot is of B&K 4128C of Samsung Electronics. And as expected, Innerfidelity's Head-acoustics HMS.II data (light gray) don't quite add up here somehow.
ON SECOND THOUGHT #2: I might be able to provide a simple modification guide on Sennheiser HD650. Stay tuned!