After several hours of listening last night, some initial impressions of the k812, compared to the hd700, driven by the dx90. One caveat is that none of these are burned-in, for those who believe in burn-in. Burn-in seems to have pretty widespread credibility in the dx90 thread, so I wanted to specify that. Even with these conditions there are a couple of observations i've made, and a conclusion i've drawn.
The k812 was spacious, airy and clearly detailed. The was no soundstage for me, though, just a headstage. I'm not sure if this is one of the things that is supposed to change with burn-in.
I was especially aware of the trebles when listening to the second movement of schubert's quartet, “death and the maiden,” in which there are passages climaxed with sustained very high violin notes. Those notes were unutterably sweet, rich and textured. Of course much of the sweetness is owed to schubert, but also to the headphones and the dx90 driving them. The bass was highlighted when I listened to charlie hayden and pat metheny playing “first song (for ruth),” which contains a long solo on stringed bass, in which hayden really digs deep into the instrument and deep down the scale. Again those notes were full, rich and resonant, and I could feel the sub-bass a bit in my chest.
At this level of performance, I already want to thank those members who've espoused the virtues of both the dx90 and the k812. From what i've read about their sound signatures, they are natural complements – one strong in in just those ranges where the other is weak. But theory aside, it doesn't have to get any better for me to be pleased. If this improves with burn-in, it will be the icing on the cake.
In comparison, the hd700 driven by the dx90 felt dull and numb. It also produced just a headstage, but the music was a bit recessed compared to the k812, and both the highs and lows were MUCH thinner than those produced by the k812.
But the hd700 produces a broad soundstage and much better sound quality when driven by the headphone out of my nad c375bee integrated amp. Evan so, the k812 driven by the dx90 was more soulful and immersive, more musical and engaging than the hd700 even when the latter is driven by a full amp.
One conclusion I have is that those people who say they are driving an e.g. hd800 with their dx90 are kidding themselves. They say they get full volume. So what? I got full volume on my hd700, and I played with various gain settings as well and it didn't make much difference. The music could get loud, what it couldn't get was good - detailed, rich and textured. And the hd700 has an input impedance of only 150ohms, and is reputed to be much easier to drive than the hd800.
I also have a question for any of you tech experts- is there any risk to my k812 to try it out of my nad amp. The headphone out is 68ohm, almost double the input impedance of the k812. I know this would make the setup more subject to distortion, but could I damage the k812? The nad headphone out, as I said, is 68ohms, I have not been able to find any more information about it, e.g. what power or current does it create? I read in some thread here, maybe even this one, that the k812 has a maximum recommended of input of [iirc] 300mW. So any advice or information on this would be appreciated.
