Frequency Response：20 to 20,000Hz
Rated Impedance：16Ω @ 1KHZ, copper-coated aluminum wire
Sensitivity：103dB SPL, 1mW
Total Harmonic Distortion：˂0.25% at 1KHz/1V
Cable：0.6 m (8.2 ft) 'Y' cable + 0.65 m extension
Connectors：Φ3.5mm adaptor, gold-plated connections
Net Weight：12g (9.75 oz)
HD381B (grey) has a very sparkling high and bright mids, but not excessively bright. While bass amount is less from HD381F, the bass is still nice, extended very well to very low bass. The mids and high are more dominant than the bass, but the bass harmonic is still very much present & rich. The HD381B sound has good sense of space and atmosphere. Tuned for mids and highs clarity.
As for imaging, overall, HD381 series have good imaging, slightly wider, less 'in your head' kind of imaging, than other fully sealed IEMs. Pretty good instruments separation and sense of space (especially HD381F and HD381B), although not as good as full size headphones. Detail and clarity is very good, especially considering this is a normal dynamic driver, not balance armature, on my ears, details can be as good as those IEM with BA drivers.