The Sony MDR-MA900 is certainly an interesting headphone. It is the spiritual successor to the MDR-F1, just sexier, sleeker, blacker, and with a bigger D(river). I believe it shares the same or a similar type of 70mm driver as seen in the Z7. Like the MDR-F1, this is an open-back headphone with an angled driver that is vented on the front-rear side of the driver. As Marv put it, this is similar to having a driver suspended in air in front of you. That said, the pads are relatively thin and seem to be made entirely of cloth + interior padding, so not only are your ears close to the driver, there's not much between you and the open drivers. Note: This headphone is discontinued, at least in the USA. You can still find used pairs and international pairs on various forums and eBay. Picture Time! (And Some Thoughts on Comfort) Let's look at some pretty pictures to make it easier to visualize. (These are random internet images, and I do not take credit for them. Just saving you time from having to Google them yourself.) Below we see the MDR-MA900 in its full glory. It looks nicer in person. Pictures make it look like a cheap, flimsy $30 headphone with huge drivers, if you understand how big they are to begin with. However, I've been told these use some sort of lightweight, yet strong, metal material in many parts of the headphone. Don't get me wrong, the headphone is flimsy and flexible, yet also feels like it won't break unless you purposely step on it with the sole purpose of trying to break it. Think of it as solidly flimsy. This isn't something you want to toss in a backpack full of crap, but it should last you a good long while if you treat it nicely at home. It's very comfortable to wear due to it being so slim and light, though the top portion of the headband could use a bit more cushion to help prevent any uncomfortable hot spots. If you bend the top part of the headband to better fit the bumpy, ugly curvature of your skull, it's mostly a non-issue. Here we see that vent I was talking about at the rear end of the angled driver. There's no real baffle that the driver is mounted in or on...it's just all driver on the front side. Plenty of space for even the largest ears. As you can see, the entire purpose of the rear-side vent is to push all sound through the rear of the headphone, bypass your ears, and send it towards the back of your head, where your hairs are most sensitive to sound. This makes for an interesting listening experience unlike any you've heard before. (In reality, this is what makes it like having a driver suspended in free air.) Subjective Impressions The MDR-MA900 is rolled off on the low end, usable only to about 50-60Hz, has a touch of an emphasis in the mid-bass through lower-mid area, and is slightly bright. I'm not talking HD650 level of mid-bass emphasis, nor am I talking HD800 or, say, AKG K7XX levels of bright. It's just as I said; It's slightly warm and slightly bright, yet close enough to a fairly neutral curve to still sound good. Staging is wider, a bit more curved, and sits more in front of you than the HD6X0 family. Naturally, if you're doing any listening tests or comparisons for staging and imaging, or if you get too turned off by the HD6X0s staging characteristics and abilities, the MDR-MA900 will serve you better. It's not the widest, largest, or airiest headphone I've heard, but it does well enough and makes for an engaging listen if staging is what you're after. In those aspects alone, I think Marv put it best when he said, "Think of it as an HD600 lite with [a] deeper and more open sound." In many ways, it does sound similar to the HD600. The most noticeable differences are the lack of bass extension on the MDR-MA900 and the leaner midrange. If you're like me, you'll notice the MDR-MA900 is not as emphasized in the upper-mids and lower-treble as the HD600. The MDR-MA900 does share a bit of the HD600's upper-mid/lower-treble bump, but whereas I find the HD600 too "hot" to listen to, the MDR-MA900 seems to push this emphasis up a bit further in the spectrum and with a less aggressive presentation. So, instead of "hot," it just adds to a sense of clarity and attack with the downside being it can make the MDR-MA900 sound a bit steely or splashy at times. When compared to the HD650, the HD650 sounds fuller and has a much smoother and slightly more neutral midrange and treble. The MDR-MA900 is thinner, cooler, and sounds a bit more like steel, but it does have this nice sense of transient speed and clarity, on top of surprisingly similar resolving capabilities, that still make the MDR-MA900 an engaging listen. Going back-to-back almost makes the HD650 sound a bit slow and veiled until you readjust to its sound (and it is still a better sound overall, the HD650 that is). Thankfully, the staging abilities of the MDR-MA900 give it something that make it worth picking up over the HD650 depending on your mood. It's not a shock to go back and forth between the HD650 and MDR-MA900. Both are engaging to listen to, sometimes for the same reasons, and sometimes for different reasons. I do want to reiterate that I find this driver to sound surprisingly snappy, fast, and tight. You might be surprised how well it keeps up with the HD6X0 on detail retrieval, even if it's possible it's just the brighter sound making it seem a bit sharper sounding. On Channel Balance, How Placement Affects Sound, and Amp Pairings I have found the MDR-MA900 to be very picky about where you put it on your head. You can noticeably change the sound by shifting it forward and backward, much like the HD800. Getting the best channel balance might require some placement fiddling to get it just right. However, I have noticed that if you always hear some inherent channel imbalances, it could be the amp you're using. From my DIY Butte, which doesn't have great channel matching to begin with, the MDR-MA900 always seems to be a tad bit imbalanced. I have to crank the volume quite high to get it where it needs to be. From the Eddie Current Super 7, I have zero channel balance issues, save for when the volume pot is set very low, as is the case with any headphone. I am not sure why the imbalances goes away with the S7. I've also found the MDR-MA900 pairs better with the Super 7 in general, especially with some warmer sounding tubes. It helps it sound a bit fuller and less bright in a good way. From the Butte and my phone, even though it gets plenty loud, it sounds thinner, brighter, and generally just harder or more metallic. Still not too bad, but I much prefer it from the Super 7. Built-In Crossfeed? I have noticed that the MDR-MA900 plays the opposite channel, very softly, in the main/other driver (so, a bit of left plays in right, and vice versa). I tried this from all of my sources and amps and made absolutely sure I was hearing this correctly. I think a few others have noticed this before based on a quick Google search. There's a possibility this contributes to the MDR-MA900's strong staging capabilities and how, despite being a bit bright, it remains fairly easy to listen to. That is, I've read crossfeed can make headphones sound more natural and less fatiguing, though I've never experimented with that myself to verify. I am wondering if it's possible to bypass this. I know you can bypass the resistors on the wiring PCBs, so perhaps through different PCB contact points, which I believe exist, and new wiring to each driver directly, one could circumvent the crossfeed. On the other hand, it might not be such a bad thing to leave in there. I might try the resistor mod for shits and giggles. Measurements Due to the angled nature of the drivers and my in-ear mic, which my right ear doesn't seem to like anymore (won't stay in), I'm stuck with left channel measurements. Frequency response results show a slightly U-shaped or M-shaped response, with the emphasis points being around 90Hz and 3.5KHz-5.5KHz. The bass drops off severely around 50Hz, but the treble remains fairly well extended overall with some drop-off above 9-10KHz. The brightness is likely caused by that lower-treble emphasis. Still, these sound somewhat neutral, if both a bit warm and bright, and are more engaging sounding that the response alone might indicate. Distortion results look good until you get to below 100Hz. These results show more distortion than the HD650 with bass, though it's probably less of an issue than you'd think. It's common to see distortion climb like this when the bass rolls off on these types of headphones, at least based on many measurements I've seen. CSDs look fairly good. They are not as clean or fast as the HD650, but there is no major ringing or other nastiness. Assuming a fairly centered position with a bit of variation here and there, the MDR-MA900 has a surprisingly consistent response. It's not until you start shifting if very far back and forward that things really change. Here is what happens when you push the MDR-MA900 very far back, that is, with the front (non-vented) portion of the headphones essentially touching the front of your ears. This is the opposite, where I've pushed it far forward. My ears were close to touching the back rim of the headphone. Here's what happens when you push it far enough forward, and downward as well, that your ears do touch the back rim. This is not comfortable for long-term listening, but the subjective effects are interesting. What about if you wear it normally but cover up most of the back of the cups with your hand? What about if you block off most of the front/rear-side vent? I used a layer of a bath mat for this, which was large enough to not only fill most of the vent but also fit up against the open rim on the rear of the headphone. I thought this might reduce reflections off that plastic. This makes them bassier, more extended, less bright, but does make the midrange dip stronger. Here is a rough look at how the MDR-MA900 compares if you used a modded HD650 as the reference (flat) point. I believe this compensation curve was used when my HD650 had more compressed ear pads, which boosted the bass a bit on the HD650. Still, the MDR-MA900 is a leaner, less extended below, and somewhat brighter headphone than the HD650. Conclusion, in Bullet Points - Slightly warm, slightly bright sound signature with a noticeable low end roll-off. Usable to about 55Hz. Still fairly decent sounding response, though, but can be a bit steely sounding. - Sort of like an HD600 with less bass, less thickness, less "hot" sounding. Wider and more engaging stage than HD600. - HD650 is smoother and much fuller sounding. - MA900 surprisingly snappy and resolving. Since it is still neutral-ish and has that nice staging ability, it makes for an interesting and engaging listen. - Very dependent on placement. - Pairs best with warmer, lusher amps. Some amps might make the MDR-MA900 sound like it has a channel balance problem. - MDR-MA900 seems to have built-in crossfeed. - Not as well rounded as the HD6X0 family, but worth as an alternative for something slightly different OR for very lightweight, comfortable listening if you can snag a pair for around $200 or less.