HD9
headphones
$95
Used market: $75*
Specifications
3 of 7 values have a recorded sourceExpert Audio Engineering Commentary
Tonal Profile
Closed 45 mm drivers at 40 Ohms, aimed at tracking where headphone bleed reaches the microphone. Sensitivity and impedance are both stated with their reference, which makes the amplifier question easy: 100 dB needs 1.6 mW, or 0.25 V. The power-handling line on the same page is less consistent — see the spec claim below.
What the datasheet actually says
Quoted verbatim from the manufacturer’s own page, with the date we checked it. We state what is printed, not what anyone intended by it.
«The HD9 offers high power handling (900 mW per channel into 40 ohms) ... Headphone Maximum Power 1800 mW»
The prose and the specification table on the same page give two different numbers for the same quantity. 1800 mW is exactly twice 900 mW, so the table appears to state the sum of both channels while the prose states one channel. Anyone comparing the headline 1800 mW against another maker's per-channel figure compares a pair against a single driver and overstates this model by 3 dB. The per-channel figure, 900 mW into 40 Ohms, is the one to use — and it is a durability limit, not a demand on the amplifier: normal listening needs under 2 mW.
checked 8/5/2026* Estimated with the depreciation fallback (~79% retained value). · checked on 8/5/2026