The HD650 is the evolution of the HD580 and HD600, but I would call it a simple side grade, with slightly different tonality. The Massdrop HD6XX is exactly the same headphone as the original HD650, with a different painting.
○ Release : 2003
○ Current status : In production
○ Type : Over-ear / Open-back
○ Measured weight : 268g
○ Impedance : 300 Ohms
○ Sensitivity : ~98dB/mW
○ Average used price : $150-200
The HD650/HD6XX is basically a warmer HD600. Judging by ears and measurements : slightly more bass and midbass (1-2dB), a bit less upper-mids/lower-treble (2dB less around 3-5khz), and less mid-treble (3-4dB around 8-10khz). As a result, the HD650 is definitely a warm headphone that retains the fantastic midrange timbre of its older brothers. My preference is still for the HD600/580.
I have owned both headphones for many years, and compared them for hours and hours, in the same conditions, with brand new pads (as pad condition affect the mids and treble a lot). The HD600 is leaner but a bit more natural sounding to me. My main issue with the HD650 is the general lack of treble energy between 6 and 10khz, even with new pads. It’s a bit too recessed for my tastes. The midrange is excellent, and I prefer it to the HD600.
The difference in bass/low-mids body next to the HD600 is easily noticeable, and in my opinion, more discernible than what the graphs and measurements can suggest. The HD650 can sound a bit bloated at times, or congested, while the HD600 gives a little better sense of clarity and openness (same for the HD580). Both don’t have a great low-end extension below 60-70hz.
The HD650 is still one of the mid-fi kings with the HD580 & HD600, 15-25 years after their release. By far the best warm sounding headphone under $300 (thanks to the HD6XX existence) or even $500.
Measurements & Resources