To get to the soundstage level you really have to push the boat out with patience, cash, and careful audio route planning. It's not all about the headphone. If things were only that simple.
First of all, the musical detail has to be present in the music track that would allow for a realistic soundstage. Don't expect anything from mp3. FLAC, WAV, APE are the kind of formats you need to look at.
Next you need a DAC that can dig down to the soundstage bit level and reproduce it without any artefacts that could misalign the soundstage.
And then you need a low distortion headamp that can produce the rms voltage that the impedance of your headphothne would need in order to cover the full audio frequency and signal dynamic range.
Finally, you need a headphone that can produce a soundstage. Only then can you really enter the soundstage domain with your cans.
It is often assumed that just about any headphone design concept can produce a good soundstage, as long a the above criteria are met. Not true. Some designs are better suited than others. Electrostatics are almost guaranteed a place at the top, but conventional drivers set in an unconventional design can now also be considered. I am thinking of trend setters like the MDR-F1 and SA5000, and the more recent HD800. But there are also exceptions that transcend the rule. One of them is the D7000, which has a closed design that is not normally associated with a realistic soundstage. But such odd technical marvels come at a price.
Look, the HD650 is a good set of cans, but it has a couple of shortcomings that hinders its true potential. Mods galore to try to overcome that. The basic sloppy bass and recessed tops impair of a sizeable portion of the soundstage experience. To get round that you need to read up and then try a headamp that is more or less mapped to correct the anomalies with the HD650. Don't get me wrong. I am not singling out the HD650. I own one and wouldn't part with it. I still put it back in its original box after use. But I had to knock up a TPA6120 headamp with a +/-15V supply rail and incorporate a filter network to take down the bass lift and raise the tops before I could get the HD650 to transform from sleeping beauty to fiery vixen. The dryness from the TPA6120 counteracted the woolly feeling of the overall HD650 sound.
So expectations should be tempered. The journey has only just begun in your search for headphone soundstage. I would advise you to go through the archives and threads about the HD650, such as the HD650 appreciation thread. Some outstanding advice and information can be found there on how to get the best soundstage out of the HD650.
Of course you could go and buy headphones till you find what you are looking for. Many of us have, and are a few $$$grands poorer from it. So headphone users like me know the rough edges and pitfalls along the way that should be avoided when in the persuit of soudstage.
Edited by Baxide - 2/28/13 at 5:11pm