Someone asked me for a comparison between the MSR-7 and the A990Z, thought I would post it here. I also threw the A1000Z in there as well, which I ended up getting. I used Pink Floyd's The Wall as the test album, mostly CD2 - first 3 tracks & Comfortably Numb, which I am very familiar with. Used a Cavalli EHHA rev 1 (DIY) and Rudistor RPX-33 MK2 for amplification, and a Soekris dam1021 R2R DAC.
MSR-7 – All the sound is there, not as filled out as the others (might be described as lean). Crisp, clean, PRaT is well executed, attack and decay can be well observed. Highly resolving, but not overly analytical or sterile. Bottom end does not have as much quantity as the others, not as big, but it fits well with the rest of the spectrum due to the headphones relatively lean nature overall. The other side of this is Instrument separation, which is excellent. Lots of room to breathe from top to bottom; This is at the core of the sound profile of this headphone, I feel.
A990Z – Vocals come through with more emotion, compared to the MSR-7. More musical overall, but a bit "soft". Presentation is more forward and up-front than the MSR-7. The instruments have a bit more weight, but compared to the MSR-7 there is less perceived space between them. Bottom end is bigger, perceived texturing is not as well done as the MSR-7, especially during complex passages. Bottom end leaves you wanting a bit more separation from rest of the spectrum. Midrange is slightly recessed. Great sense of room dynamics / reverb, edges out even the A1000Z in this regard.
Switching from A990Z to MSR-7 has you turning the volume up. Not as easy to listen to, edges are harder compared to the A990Z. One can see how the MSR-7’s might be a better fit in a studio vs the A990Z which might be better suited for home listening. Though if you aren’t switching back and forth between it and a more “musical” headphone, you would not jump to this conclusion all too quickly, I know I didn’t!
A1000Z – Instruments separation is noticeably better, compared to the A990Z. Allowing them to be better resolved and display texture without as much difficulty. Instruments have more dimensions than the A990Z. The other side of this is that sound is perceived to be just a bit further from listener. While the A1000Z is not as upfront sounding as the A990Z, it retains most of the emotional expression of its younger sibling. Sound profile is not as “soft” as the A990Z, but still a great contrast to the MSR-7.
The A990Z is great if you like a very upfront sound, but you will sacrifice instrument separation for it. It’s also a bit softer approach to an upfront sound than say a Grado headphone. I will say that if you keep this on your head without switching to its bigger brother you will be very happy with it.
The A1000Z is very well put together, the changes between it and the A990Z are enough that the it has a different sound profile altogether. It puts the listener a further from front row, has better instrument separation which yields quite a few technical advantages sonically. It also comes equipped with nice earpads, a stiffer suspension on the wing system (headphone does not slide down as far compared to the 990). It's also a bit better detailed aesthetically, as one would expect, the red cups are pretty cool.
The MSR-7 is more a cousin to the other two than a sibling, and will perform well in studio / monitoring environments. Though many, including myself, have found it a pleasure to listen to at home.
I would recommend using an amp best suited for low impedance headphones for all three. A tube/hybrid might have better synergy with the A1000Z or the MSR-7 than solid state.
I will probably end up selling the A990Z, as it was really purchased as a backup in-case I could not acquire the A1000Z. Even though the upgrade was not completely vertical, currently I'm trying my best to keep my headphone collection low ..ish.