Well, I finally bought a pair of NAD Viso HP50's the other day, burned them in for 50 hours with pink noise, and bass heavy music, and did comparisons with the HD650, HD600, and AKG Q701's with the bass mod.
The AKG and the 600 have stock cables, and the 650 has a Stefan Audio Art Equinox cable.
The amp is a HeadAmp GS-1, the sources are a Oppo BDP-95, and Marantz CD6004 optical disc players.
All genres of music were used for comparison.
The NAD's sound remarkably good even compared to these headphones, and they are comfortable. I do hate the short, flimsy cable a lot though.
I do think a better cable would improve the sound even further.
The NAD's are clean, clear, crisp, and relatively flat, with a warm tilt, with relatively responsive bass, and good low bass extension. They do have a very spacious sound for a closed headphone, and have a nice black background. They are more than competitive with any closed headphone I have heard.
They are very easy to drive, and go really loud with very little power.
They have more bass/midrange body, and a flatter midrange response than the AKG Q701. The HP50's don't sound peaky in the upper mids/low treble like the AKG either. The AKG's sound somewhat thinner, and can, at times, sound somewhat more shrill.
The sound seems closer and more forward than the AKG's as well...in a good way. The AKG's, oddly, can sound somewhat distant, and diffused, compared to the NAD's, or Sennheisers.
The sound on the NAD's is definitely warmer.
The treble extension seems surprisingly similar. The AKG's are slightly more spacious than the HP50, but the imaging can be less solid and less accurately placed than the NAD. The bass extension sounds slightly better on the NAD, but the AKG's is tighter and better textured.
The NAD's are much easier to drive, and don't distort on bass heavy music at higher volumes like the AKG's do. Overall, I prefer the NAD HP50.
Compared to the HD 650, the HP50 seems to have somewhat similar bass extension, and somewhat tighter bass with less mid/upper bass emphasis. The mids are comparable in neutrality, with the NAD's sounding slighltly more forward in the mids. The 650's do sound slightly more open, and spacious, with somewhat better detail resolution in the mids and highs. They both are great at giving body and some heft to voices and instruments.
They both sound somewhat dark, with the NAD's having a noticeable slight peak in the low/mid treble compared to the 650. The 650's as hard as it is to believe, seem to have slightly better treble extension in the top octave?! The NAD's do sound slightly more "closed in" than the 650. Vocals on the 650 seem to have a little more "air" than the NAD.
Overall its a toss-up, with a slight preference going to the 650. This is remarkable, considering the fact that the 650's cost almost double.
Compared to the HD 600, the NAD has better bass extension and bass tightness, with less emphasis in the mid/upper bass. At first the 600's, as well as the 650's, can sound alittle more impressive in the bass, due to the mid/upper bass hump, but the NAD's do go lower than the 600's without a doubt.
The HD600 does seem to have somewhat better detail resolution in the mids and highs, and the mids have more presence than the NAD, but is slightly grainy sounding compared to the NAD.
The NAD's do seem to give voices and instruments more body and heft than the 600's. The 600's seem to have a slightly more open and extended top-end than the NAD.
Imaging and spaciousness is comparable. The NAD does sound alittle more "closed in" or "canned" compared to the 600.
The NAD's are really, really great, especially for closed headphones, but if I had to choose, I would have to go with the 600 for overall neutrality, and overall treble response by a hair.
The NAD's are easier to drive than either the 600 or 650,
The only real weaknesses I could find with the NAD's sound would be just a touch too much warm tilt, for my tastes, a very slight dark sound, a slight peak somewhere in the low/mid treble, compared to the sennheisers, which can, or something else in their overall frequency response, at times give them a slight coloration or "canned" sound, and a slight roll-off on top, compared to the 600 or 650.
I'm still debating on whether or not to keep the NAD's, or send them back, since they do so many things really well.
Just thought I would share my experience.
Your thoughts or findings compared to these headphones would be appreciated.
