I received my Pioneer SEM1's earlier this week, and after a few days of listening from my Questyle CMA800i my brief listening impressions are that these cans sound amazingly full bodied, smooth, and display a very rich tonal balance with certain recordings (best audiophile vocals series, demo discs, etc.). The level of transparency, realism, and "singer in the room" feel in my opinion also greatly exceeds that of the Sennheiser HD800S I have here, and is roughly similar to that of my speaker setup (Marten Duke + ARC VSI 75), but without a better source and amp it is difficult to say how much better these cans can be... they are also much easier to drive than the HD800S. Listening to EDM, bass clearly has more impact and overall excitement, while retaining similar levels of detail and tone. I find the tonal balance in the bass region to be perfect and not overly done whatsoever, even if not measuring flat. I knew from first listen though, that this is exactly the "type" of sound I am looking for, which is a replacement for my loudspeaker setup. Comfort, build quality, soundstage, etc. echo what others have already posted here. If you are used to what is IMO, the leaner presentation of electrostats, HD800S, loudspeakers without baffle step compensation, switching amplifiers, etc., you would probably find the SEM1's to be a bit heavy or ripe in the lower midrange (not muddy however), but for those used to the sound of SET amplification, I think you will feel right at home with the SEM1's out of the box tonal balance. Interestingly, I also once owned the Pioneer S-1EX loudspeakers, which are essentially mini versions of the TAD Evolutions, and the tonal balance, presentation, and overall sound is also very very similar to the SEM1's in many ways.
I will say that I am not a fan of soft diaphragm materials, and the plastics/mylar/paper/silk diaphragms found in many loudspeaker/headphone drivers have never provided for me that sense of realism and the full tonal palette that I hear with well executed stiff diaphragm materials. Typically, if a stiff diaphragm doesn't sound good (harsh, colored, zingy), it's not because it's stiff, but rather, because it's NOT stiff enough and the breakup modes are not pushed high enough in frequency to be inaudible. Unfortunately, such is the case here with the Pioneers... and for the $2,500+ these are selling for I am hugely disappointed that they did not choose to use a beryllium or pure ceramic diaphragm, but rather a cheap anodized aluminum diaphragm that can be found on any $100 tweeter. On less than ideal recordings or hot recordings that are too close mic'd or sibilant, there is a clearly audible sense of harshness/ringing in the upper frequencies that can be quite painful to listen to. Fortunately, I did not detect any overt coloration of the sound overall, that is, no metallic, cold, sterile, etc. sound typical of cheap stiff cone drivers from the past... Pioneer at least did an excellent job of dampening resonances throughout most of the audible frequency range. However, I will say that this is not an uncommon problem with loudspeaker design and typically passive circuits are designed to filter any audible diaphragm breakup or frequency response deviations. While a passive solution is not practical for headphones, using an active circuit should be quite simple to implement. I'll need some time to measure the SEM1's and play with different filters, but I'm confident based on past experience with loudspeakers, that the breakup on these cans can be effectively dealt with something as simple as an ASIO plugin to Foobar.
I will post more as these break-in and I get more time with them.
