Well, I hate to spoil the fun..., but I have a different experience with changing pads of the Fostex TH-900. I first tried the Audeze LCD-3 leather pads. They are very comfortable, very soft, and they fit quite well on the Fostex TH-900. They greatly affected the sound of the headphones, it became more spacious, more 'you are there' compared to the more direct sound of the original pads. Better center image, but also less precise in terms of imaging (more fuzzy sounding). However, the major problem with these pads is that they accentuate the 'hole in the middle'. The midrange was more recessed, and sounded a bit cave like (e.g like from very far away) and hollow. I didn't even bother to listen to what extent the bass improved or its effect on treble. The hollow sound it created made it a definitive no-way. Maybe initially, you are impressed with the increase in spaciousness, it is more than I expected; pads do make a 'huge' difference. But do not get fooled, after a while you begin to notice that something is wrong in the picture......
Next, I tried the Stax-SR-002 pads. These are less angled and less deep than the Audeze pads. They are also very comfortable, although a bit less soft than the Audeze pads, they fit and look better on the Fostex TH-900 than the Audeze pads. I tried very hard to like them, but in the end I still much prefered the stock pads. Now they do not accentuate the 'hole in the middle' hollow sound of the Audeze, at least not to that extent. But, to me they do not improve anything either, but they do change things a bit for the worse in my opinion. First, treble is less pronounced, and bass has a bit less impact and is less defined. Next, airiness is reduced, and the midrange is less clear and dynamic. For some reason it seems to me that these pads make the sound a bit more 'classic tube sound'. Nice and cosy, but where is the fun.....For some these pads can be an improvement if you think the Fostex has too much treble or is too dynamic...
I will stick to the original pads. I am more and more convinced that the Fostex TH-900 is a very carefully designed and voiced headphone. Changing pads change their voicing more than I expected, and they lose a bit of their character. To me it is clear. I like their original voicing with the orginal pads best. And yes, compared to the Sennheiser HD-800 their soundstage is not as large. The Fostex still sound like a traditional headphone in that regard ( e.g. a bit left -right), and the soundstrage is not that deep (at least not compared to the Sennheiser HD-800). They are not directly voiced by the Fostex engineers to create that 'you are there' feeling (e.g. you are not in the audience of the recording venue with the Fostex), but they are more voiced to give you the impression that you are on the podium itself (e.g. the position of the conductor). The sound from a conductor's perspective is direct, immediate, present and dynamic. And that is how the Fostex sound. That is where they score big time. I am, and always was a 'front row' man. I still order front row tickets for classical concerts and opera's, because I like the impact from that position. It is easier to become immersed in music....
To conclude, different pads do change the sound of the Fostex more than I expected. You can increase soundstage depth and spaciousness by changing pads, but you lose impact, dynamics, clear imaging and midrange presence. All of this of course with my equipment ( see profile). But I still think it is good to offer an alternative perspective on changing pads of the Fostex Th-900
