M-Audio Studiophile Q40 Closed-back Dynamic Headphones

first review. yayyyyyyyyyy, so here we go.
I am no super expert in headphones, but heres what I think
the bass is very rumbling. I think that it wasn't as thumping or hard hitting as i would like it, but i really think that is because i am using the dt770 velour pads. when i put my hands on the outside of them, i can feel it hitting harder then it does on my ears.
 
the middle ranges sound good enough for me, definitely clear and smooth.
 
the highs sounded peerrrhhaps a bit hushed, but i haven't seen anyone else say that.
 
the sound really surrounds you and has a decent sound stage. it is really fun and i had a GREAT time moving and grooving. that being said i had plenty of room to get groovy BECAUSE OF THE LENGTH OF THE CORD. i got a replacement cord that is about a couple feet long.
 
the isolation is meh. it does a good job at keeping noise out, to be specific i am wearing these and listening to music and i cant hear my fingers on the keyboard even though it is usually very loud, but other people are able to hear what im rocking out to.
 
about the clamping force. it wasn't a problem for me. i didn't spend any time stretching it out and it fits nice, although i have a small head and like a tight fit.
 
another thing. although i haven't read much about other people who agree with me, i hear sibilance. and on some songs, its painful. just a warning
 
 any way guys thank you so much, just thought that i should put my opinion in!

q40>xb1000 in terms of sound and bass.
q40=m50 in terms of everything.
 
cable is very long, great for movement during sessions and can be used to mix clearly.The bass is big, but doesn't overpower the mids or highs due to the choice of fabric they used on the headphone cups.The clamping was bad at first, ears sore as doodoo after 35 minutes.

Full review here: 
http://www.head-fi.org/t/705731/m-audio-q40-full-review-ath-m50-comparison

I purchased these brand new for £49 and it was a good buy! They are very bass orientated so if that's not your sort of thing i doubt you will like these that much. The mids and highs sound great even though the bass is so strong. Comfort wise for me personally these are comfortable, but i don't have a large size head or large ears. I have seen some people saying these are uncomfortable and they have changed the pads to some Beyer ones. I could happily listen to these with the stock pads for a long period without them hurting my ears or the top of my head. The build quality doesn't seem brilliant, i own the Audio Technica ATH-PRO700MK2 and the build quality on them seems quite a bit stronger. The cable is removable and is actually pretty lengthy, the only downside to the cable is the fact that it is a thin cable and i prefer a coiled cable that stretches wherever i decide to use them. The jack is a 1/4 inch one but it screws off so you can use them with a portable media player or phone. They aren't heavy at all, in fact, they are actually very light. I used an Asus Xonar Essence STX and used the second gain option and they sounded fantastic. I did use them with my Samsung Galaxy S4 and they are 64ohms so they are pretty easy to drive, the volume from my phone was satisfactory using PowerAMP android player. I mainly listen to electronic music and i DJ for fun and these are a decent purchase. If like me you prefer headphones to be more bass orientated then these are great for listening to music with. They come with a carrying pouch which is of a leather material and the construction isn't bad. If you can grab them at a similar price to what i paid you are in for a treat! I would even say these are worth much more than what i paid for them. 
 


 
 
This is my first review on here so please be nice ha ha!

My audio chain is MP3@320 or FLAC > HiFimeDIY USB Isolator > HiFimeDIY Sabre U2 > Fiio 6" cable > Objective2 w/ 16v 400mA adapter > M-Audio Q40.
 
There isn't much I have to add to other reviews... They really aren't that great for anything other than bass and moderate detail levels elsewhere. At $60 they would be worth buying.
 
I advise buying a pair of Samson SR950s instead.

The M-Audio Q40 is the first high quality headphone I've owned, despite this I can still be honest and accurate about the qualities of this 'phone without overselling it.

Let's start with the build quality and design. The plastic that this headphone is mostly constructed out of is rigorous and it'd take quite a bit of effort to break and in no way feels cheap, brittle or flimsy. The headband is malleable to a degree, but I'd be careful and not overestimate it's flexibility or test it's limits because it's definitely capable of being bent or stretched to any head shape, --- which I've actually gotten it to do for me, despite my larger than average head. The headphone cups are good too, but honestly the additional pseudo-grills they added onto it are loose and can creek and cling sometimes when you're adjusting the headphone on your head or touch them, but for the most part aren't really noticeable or problematic in anyway. Now, here's what really urks me about these headphones; on BOTH sides of this headphone about 3.5 inchs of wire is exposed and for me I can't help but worry that one day this'll be the thing that does these headphones in. Other than that, construction is top-notch and I wouldn't expect it to break unreasonably.

Comfort is mediocre in these but not as terrible as some would like to state. Once you stretch them out a bit they actually can be worn quite easily for a few hours at a time. The pads are pretty thin and look/feel like a cheaper type of pleather but are still pleasantly soft despite being thin and aren't too bad. I'll honestly say the first time I put these headphones on I couldn't wear them for more than a few minutes without having a discomfort-caused headache, but at this point I'm accustomed to a strong clamp and they've loosened up a bit so I can't really complain.
 
Now on to my favorite part: The sound of these headphones.
For this part of the review I'll explain how this headphones fares in certain situations and what it's like.
 
So without any equalizing, the Q40 is a slightly bass-emphasized headphone with good, clean mids that are a bit less than what you'd say it 'forward' sounding, so vocals on some tracks are a bit softer sounding than the instruments but still quite clear and good sounding -- to elaborate on that, they sound very natural to me and are very pleasant. (which is unusual for bassy headphones) -- the highs are good, but there's a small 10k spike and a pretty big roll-off thereafter. I personally could do without the 10k spike (and usually do when I apply an EQ) but the rolloff for me is a big plus, because I can't stand fatiguing treble and my ears are unusually sensitive to higher frequencies. The lows are probably what most people are interested in, so I'll get right into detail with those. These headphones aren't all about mid-bass, which is probably the bass 'bassheads' per say, would be looking for. I am a self-acclaimed basshead and I know a lot of bassheads originate from a listening experience with the Sony XB-500 or Dre Beats, (I know I did --- XB-500s, not Beats, I don't even need to elaborate the silliness of the latter) which is very mid-bass heavy. The Q40s have really good sub bass, a type of bass most headphones don't even touch. Every frequency from 20 - 300 hz is at least at and/or above neutral and 50 - 100 hz is the most elevated frequencies (100 hz being the peak). 50 hz going towards 20 hz is like a slope, but it's still elevated, audible and present. Now, going past the quantities aspect, I'll start off by saying the Q40s bass is tight, very fast and well-textured. This is highly evident when listening to metal with fast, low, hard-hitting drums and these headphones really don't miss a beat. Despite the lows being highly present in this 'phone, they're very proper and not intrusive to the mids or highs and don't make a big mess of everything. Quality over quantity, a lot of people would say and prefer --- HOWEVER, the bass quantity in these headphones to me is unrivaled by most headphones and just a bit below XB-500 level, DISCLAIMER; with a bit more power than an onboard sound card or normal iPod offers they are really on-par with the XB500 (un-equalized) and with a bit of bass boost can easily rival the XB-500, not that it's necessary cause the sound of this headphone as a whole presents it's self in such a lovely fashion that much alteration isn't necessary to be satisfied. 

All in all, I'd sum the sound to say they're a warm, clear, well-defined sound headphone with excellently present sub-bass and decent mid-bass. The midrange is perfect, for me, and if you get rid of the 10k spike there isn't a thing wrong with the sound of these headphones, unless you really like far-extended highs and overly bright headphones, then I guess these would feel a bit lacking in that aspect. For casual listening at home and in quieter place, there's no headphone I'd choose over these. For portable headphones and in loud places, these do work for portable headphones, but with the exposed wires and need to turn them up really loud I really find it more on the inconvenient and worrisome side.

*update, over a year later*

I've long since sold my original Q40 and bought a new one. I modded the new one with a decent amount of fiberglass and cotton, as well as replacing the stock earpads with 840 pads. Stock earpads sound best, but comfort is important too. The clamp on these headphones is a bit much for extended listening. I usually don't listen to these without equalizing down 100 - 200 hz by about 3 decibels. When equalized they're a really good sounding headphone for 100$ (what I paid the second time). They have a smallish soundstage, but when equalized like I do they have a very nice, textured sound that makes them a very fun listen, preferable sometimes to my MA900 and T50rp II. Build quality is questionable, I know the wiring is ****ty but I don't think the headphones will fall apart anytime soon. Stock cable is mediocre, it wines when plugged into my Magni. I'd say you can't go wrong at 100$, but as you get closer to 200$ there's many more options, most of which are objectively better -- though, not as much competition for a good basshead 'phone. I'd say these are clear sounding without equalization, the upper bass makes them seem muddy, though they aren't. After extensive research, I re-purchased these instead of the DT770 and I'm glad I did, aside from the comfort issues.

 

 
M-Audio "Studiophile" Q40  A smooth bassy treat on a dime.
 
Always on the prowl for a new headphone to try, I do at least have a taste that steers me towards one versus another, and that's bass capability. I tend to think a headphone that is to be used for casual music listening should be bass capable, ie, neutral at a minimum, and slightly enhanced if wanting a bit more fun regardless of it being "audiophile" worth or not to like a colored sound. That said, a headphone came to my attention on the recommendation of RPGWizard (thanks!) here on Head-Fi: The M-Audio Q40. So naturally I had to try it, as it was supposed to be a bassy headphone with a great over all sound.  I found some flaws, found a lot of great things, and have spent enough head time to feel like an opinion can finally be put down in words. So let's talk about the Q40.
 

 

 
Quick reference for the impatient:
 
·         Closed back full size headphone.
·         Entry mid-tier price range ($120ish USD); with suggested upgrades ($160ish USD).
·         Quality bass (emphasis on bass), warm, full, smooth, clear, organic and musical sound.
·         Relatively easy to drive (64ohm, 116 dB/mW).
·         Collapsable frame; detachable cable, sturdy build. Portable friendly.
·         Tight clamping force; relatively shallow cups (this is the upgrade path).
·         Did I mention bass? Basshead worthy headphones.
 
Just to give a quick summary of what this headphone is all about, imagine a very bassy headphone that doesn't bleed out of the mids and treble that isn't overly enhanced so you result with a smooth sound instead of something too bright. That's the Q40. My first reactionw as that it was like a bassier DT770 with less bright treble. So much so that I transplated the ear pads from a DT770 to the Q40 and found it to be absolutely necessary for an upgrade because the Q40 isn't without flaw--it needs deeper cups and the vise-like clamp force it has needs to be loosened (both correctable). Also this headphone can be for home use or portable use. It has a collapsable folding frame and is built like a tank.
 

 
Necessary information; Upgrade suggestion; Warning:
 
Attenion: Mandatory ear pad upgrade: Beyer Dynamic DT770 Velour Pads
 
Right away, I will warn you that the Q40 has a very tight clamp force, so if you're senstive to this kind of pressure this headphone may not be for you. Also, the ear cups are shallow, so your ears will touch a little; and if you're sensitive to that, this headphone may not be for you. That said, if you're still interested, both of these issues are correctable. I loosened the grip by simply stretching them over a speaker for a few days in between use. And I replaced the ear pads with some Beyer DT770 Velour pads (black color or grey color, your choice, I went black) to make it more comfortable, seal better, and deepen the cups. The result of loosening the clamp and changing the pads resulted in what felt and sounded like an absolute wonderful headphone. I consider these upgrades mandatory. If you're not willing to buy the $29+shipping DT770 velour pads, then you may want to hold off buying the headphone all together. From this point foward, everything is based on using DT770 velour pads and not the stock pads!
 
Buy those pads. Again, everything here is based on using those velour pads, not stock. It's absolutely worth it. It's mandatory in my mind. Buying the Q40 means buying these pads too as far as I'm concerned.
 
Pad Swap:
 

 

 

 

 

 

 

 
Stretching the headband, loosening:
 

 
What Comes in the Box:
 
·         The headphone itself.
·         6.3mm gold adapter that screws onto the 3.5mm terminated cable.
·         Detachable cable (3 meters). Note, there are two cable types (coiled & straight).
·         Carry bag.
·         Some wasteful paper goods, registration, warranty, etc.
 
No fancy carry case or anything, but it at least comes with a nice little carry bag. The headphone folds up and is built like a tank so it can be tossed into your bag or left around your neck if you're out and about, it can be a nice portable (note: the cups do not swivel though). But it can survive a backpack or messanger bag. The cable is of average quality and quite long (replaceable). The cable & 6.3mm // 3.5mm adapter all screw on, so there's no "pulling" of things. Nice and tight.
 

 
Specifics of the Headphone & Accessories:
 
·         Cord length, 3 meters (detachable), 6.3mm adapter. Cable terminates to 3.5mm.
·         Note, there are two cable types: coiled & straight.
·         64ohm resistance, 116dB/mW sensitivity (easy to drive; some benefit from an amplifier).
·         40mm drivers, not angled.
·         250 grams without the cable.
·         Pads are a memory foam type material, comfortable, circular and replaceable.
·         Height adjustment is done with notches that are numbered.
·         Closed back design, with vents.
·         Isolation is good, but not the best (ie, leaks less than an open-air, but isn't dead silent).
·         Both cups do not swivel. Both cups do collaplse and fold.
·         Carry bag is a pleather substance, with draw strings. Headphone only fits in it while folded.
 

 

 
Construction, Materials & Comfort:
 
The Q40 is actually built pretty well, it's very sturdy and feels good in your hands, it has a weight to it, even though it's pretty light weight (250grams). It doesn't feel like an inexpensive toy. I contorted it and bent it around to see if it would break right away and it did not (thankfully). Housing material is plastic with what may or may not be aluminum or magnesium venting plates and what looks like aluminum height adjustment arms. It's pretty tank like and feels like something that will survive your bag.
Comfort was the first flaw that struck me. The memory foam pads on the headband and ear cups are fine, they're very soft, the problem was two things: very strong clamping force (which comes from the headband and arms), and shallow cups (comes from the pads being relatively thin and there being a foam insert that sticks out from the driver). These are unforgivable flaws in my book. But instead of immediately returning the headphone, I simply tried two simple fixes: stretch the headband over a few days to loosen it, which worked; and replace the ear pads with something deeper, thicker, and of course in my case, made of velour, which also worked. After a few days of loosening up stradled over a speaker, and with the new Beyer DT770 black velour pads installed, the headphone is very comfortable to wear, the cups are deeper and I feel like it seals better even. It's still what can be considered a tight fit, it's not a loose headphone (eg, Denon) by any means. It will grip you. But it at least look that vice grip pressure off and feels much better. I consider these mandatory. Again, please note that this entire review is based on using the Beyer DT770 velour pads instead of stock!
 

 

 

 

 
The headphone can be disassembled, it is held together with screws, so it may be mod-friendly to those that like to tinker with things.
 
Cable Swap / Replacement:
 
You can change the cable to something shorter. There's a thread dedicated to this with example photos and a link to the cable used which is very useful if you want to use it as a portable or simply want to shorten the cable without buying something expensive. Also note, you can order the replacement cable from M-Audio, just email them for the part number. See this thread for more information on an easy cable swap that works.
 
Sound Characteristics:
 
Right away, I put on the Q40 with stock pads and noticed all the above information, but the first thing that slammed me was of course the bass. I bought them for that reason, so naturally, I started with some dub tracks to see how it handled sub-bass and mid-bass tones. I was impressed right away, so started going from there to the further testing songs and of course Audiacity to really play around with test tones to see what the headphone was capable of in a very critical setting instead of relying on a music track to deliver the tones I'm testing.
 
Initial impressions were that the bass was emphasized, big, full bodied, thick, warm, impactful, seriously satisfying for a basshead, extended low... very low, down past 15hz tested and very audible, low. This is an impressive bass oriented headphone. You can call it an earthquake generator. It does it. It instantly made me think of the PRO900, XB500, HTF600, D5000, etc, in terms of quality bass, big bass, and siezmic sub-bass capability, more on those comparisons later though. The mids were actually great, I expected them to be leached out due to the monstrous bass, but they were not. This was a big surprise and was spot on with the recommendation given to me when I initially was introduced to this headphone. The vocals are handled very well, they don't sound in your face like the SRH940, but they're not under water either like something with very dimmed out, bled in, mids. Treble was very smooth, it doesn' t have that sparkle that some headphones tend to have, so I would say this is not a bright headphone, but it's not dim like the XB500 or HD650, it's right in the middle, which is a good place to be--smooth, not sibilant, but you still feel like you're hearing what you're supposed to without the fatigue.
 
A note on burn in. I listened right away, and several days later after over 200 hours of continuous playback rant through the headphones and it sounded the same to me each time. I do not subscribe to burn-in, however, I will at least note it since it always comes up. You will not experience a new addition of "insert something here" or an expanded "insert something here" after "XXX" hours. Just put on the headphones and go.
 
Quick break down:
 
·         Earthquake level bass, basshead approved.
·         Mids are not bled out or missing, they're actually great.
·         Treble is smooth, not dim, not sibilant, just right.
·         Sound stage is adequate for a closed headphone, improved with the pads upgrade.
·         Isolation is average for a closed headphone.
·         Signature: warm, organic, rich, thick, full, detailed, crisp, fatigue-free.
 
I used several pieces of equipment to test differences to see how it drives from different sources and how it behaves and sounds. I'll list them briefly merely for reference purposes to know whether or not you can run a setup similar and have similar experiences.
 
Sansa Fuze - Ran fine without any additional equipment, volume was fine, I even had to turn it down from maxmium on some tracks, and it was never too soft on tracks that I have that are notoriously quiet. So it's an efficient enough headphone to run from modern portable players.
 
Fiio E11 - Using LOD from the Sansa to my E11, the headphone does have a noticeable change that feels more impactful and controlled, and requires minimal volume increase from the E11. Most importantly though is that the EQ setting on the E11 is much better than using the built-in EQ of a portable player. The EQ setting of 2 (bass) on the E11 makes the Q40 rumble and slam you. Fantastic. I would say you're safe without an amplifier, but you can definitely get some benefit from an amplifier.
 
Hifiman HM101 - Pluggint the HM101 via USB to my Netbook, the Q40 sounded great right away, definitely drives it adequately and it gets you off the noisey netbook port and gives you a much improved DAC and a little amplification, allowing you to play the Q40 very loud if you want and very well controlled. Great solution for an inexpensive cost.
 
Droid Incredible - I tested on a phone just to see if it would work out, and it plays fine on maximum volume from my phone (which I do not use much, because it's output for headphones is awful). But the Q40 is efficient enough to run from this phone, so it definitely will run from your iPhone, iPod and iPad. I did feel like the bass was a little less prominent but that is likely a power issue and more the fault of my Droid since it has very weak output on its headphone output.
 
iPad - I plugged into my iPad and it immediately sounded great, full volume, no extra equipment needed, was clean and sounded like it should. So it will certainly play from your apple devices without an amplifier. I still like the sound of the amplifier added, simply because the extra EQ and bass was more basshead satisfying. But it's not necessary.
 
Schiit Bifrost & Asgard - Nothing to say here other than it was dead silent, clean, crisp, and well driven and way over kill for this headphone in every way. But that's how I roll and it's my primary listening setup.
 
Asus Xonar DG - Plugged directly into the DG just to test on a sound card with an amplifier, it was just like any other device used above and worked great without any weird jitter or noise and the DG is a great way to get off the onboard solution of a PC for an inexpensive cost with a good software suite for playing with power output.
 
Verdict: It will play from anything quite well. I feel like it benefits from an amplifier, but it's not necessary.
 
Treble:
 
The treble is not spiked, there's no noticeable spike at 10khz like most bassy headphones tend to try to have to make up for the bleed from being overly bassy. Not the case here. I cranked up the 10khz in an equalizer to see the effect, and it added a bit of a hiss and more edge to vocals and cymbal taps. Left flat line, the treble is very smooth, there's no sibilance at all unless it's inherent to the track and super emphasized, but I didn't experience any on my tracks. I played a 10khz tone in Audiacity to see if it would cut me in half, and it did not, it sounded like a cricket and was tolerable. So this is a smooth treble experience, not something that will fatigue you right away (unless you're super sensitive, in which case, there's no hope for you anyways). 7khz was noticeably a touch louder than 10khz, to me, but this may be due to my hearing (or hearing loss), so keep that in mind. I did the same thing with 2khz, 3khz, 4khz, 5khz, etc, and the result was that it sounded more and more prominent and loud as I came down. Again, this may be due to my hearing. But if not, it means the treble is rolled off as it spikes up, which makes sense, since the headphone sounds smooth and is not overly bright or sibilant.
 
Mids:
 
The mids are not bled out in a way that is very noticeable, unlike most headphones that are bassy, where this is the first place you notice a problem. This wasn't the case here. Vocals and instruments sounded right to me. They were not dimmed out, or overly forward. Vocals specifically sounded great. There may be a very small touch of recession, but it's not drastic and not something I would wave a finger at since this is not a high-end linear headphone and is a bassy headphone for fun. Instruments like guitar and piano sounded great, good textured feel, good detail, a touch of crispness, not dull. The strum of guitar, the key press of a piano, and the intricacies of vocal changes all sounded appropriate to me. The mids are definitely not forward, but they're not in a big trough either. Tones in audiacity were well controlled, I didn't hear a waving wobble or any lack of control and they were more prominent sounding than the top end treble that I played (again, maybe due to my hearing possibly, so keep that in mind).
 
Bass:
 
Oh the bass, here's the subject anyone interested in the Q40 is probably quite curious about. The Q40 is definitely bassy right away, you'll notice that. It's not just mid-bass though. It's sub-bass is earthquake worthy. In Audiacity, I tested 10hz and I could hear it, it was dim, but I could hear it. 15hz was definitely audible, but had a wobble to it. 20hz hit with authority, a slight wobble to it, but very prominent. So this headphone drops to 20hz before it really falls off. It can do serious sub-bass. Naturally, most music is not this low. 30hz was serious. Very satisfying and rich. Put to the test on real music, it was very authoritative and impactful with some dance music, trance, dub and the like. The slam was great, the drops were serious, they were gut busting. This is defintiely a basshead worth headphone. The bass is not muddy and cruddy though. It's not perfectly tight, but it's not a loose cannon either. The mid-bass is a touch more than the sub-bass, but not in a way that kills the mids (which is why the mids are preserved probably). Without amplification, it drops this low, but I feel it is a little better and decay is better and recovery is better with a little amplification behind it, but this is my subjective opinion on that.
 
Soundstage:
 
Separation is great, it doesn't feel like a distinctly stereo image. It sounds like an atmosphere, so the sound stage is a little better than your average closed headphone. However note, again, as warned, this is with the DT770 velour pads upgrade which I consider mandatory. Stock pads, it was different. The deeper cups and placement with the pad upgrade was quite a change here both in comfort and sound stage, so it's a two-for-one upgrade. Testing some binaural recordings, the placement was spooky good, so the imaging ability with soundstage is great. This can be used for gaming and movies for sure. And for music it is fantastic. It's not a sweeping sound scape like some headphones with huge stages that are almost artificial sounding, but it's not a tight closed in space with no stage (eg M50).
 
Isolation:
 
Isolation of the Q40 is normal, it didn't feel like it was absolutely perfectly isolated, so it's less than optimal (the FA-003 is one of the most passively isolating headphones I've listened to). But it's not a leaking seive like some closed designs with ports/vents that allow a lot of leaking. It definitely is better at isolating inside than out. When wearing them, I can hear myself breath in my head, so it's definitely shutting out at least 15db~18db of sound from the environment. When I take them off and seal them, you can hear them at moderate to moderate-high volume if you get close. I would say someone next to you on the buss/train/plane will hear you a little bit, but not like a leak-cannon (eg Grado). Good passive isolation, but not the best, but it doesn't leak as much as some other closed designs that tend to leak a little more than average (eg, HTF600 and Denons).
 
Changing the Pads:
 
So as mentioned, the DT770 velour pads are what I'm using. The difference, other than sound stage and comfort, is that not much changed, and that's great. I don't feel like it really took away from anything. Bass is still awesome. Mids are where they were. Treble sounds smooth like it did. If anything changed, it may have taken a slight edge off the already smooth treble. But it didn't do it in a way that made me want to equalize. But your mileage may vary there, so keep that in mind. I still definitely consider the DT770 velour pads a mandatory purhcase along with the Q40 as one. That said, the pads fit over perfectly, and are easy to change. You can get the pads in grey or black, I obviously went with black.
 
Compared to Other Popular Known Bassy/Capable Headphones:
 
Comparison is all we can do when you've not heard something, and I have a lot of things to compare them to. So I won't go into painful detail on it, but I will basically give a summary of similarities or differences based on other well known bassy headphones. All comments are based on the Q40 compared to the headphone listed.
 
Ultrasone PRO900 - Q40 is less bright, better mids, just as bassy. This was my first thought, was that the Q40 sounded like a PRO900 with the treble equalized down heavily. So if you're looking to save money and get what sounds very similar, this would be the way to go. PRO900 had a slight edge on sound stage.
 
Beyer DT770 PRO - Q40 is a touch less bright, but the DT770 isn't overly bright either to me. Otherwise, the Q40 had more prominent bass and mids were similar. So the Q40 is a bassier DT770, with a touch less treble, for a bit less cash.
 
Beyer DT990 600ohm - Q40 has much less treble, similar mids, and more prominent bass, but less sound stage and less comfort, but naturally much more isolation.
 
Fischer Audio FA-011 - Q40 has less treble brightness, similar mids, and more prominent bass with a similar sound stage and to me better comfort (with pads upgrade) and of course more isolation.
 
Fischer Audio FA-003 (or Brainwavz HM5) - Q40 has less isolation, similar sound stage, a touch less mids perhaps, smoother treble, and much more prominent bass; similar comfort with similar clamp.
 
Denon D2000 / D5000 - Q40 has less bright treble, less sparkle, but otherwise quite similar. The Q40 has more prominent mid-bass, but quite similar in sub-bass.  Sound stage is better on the Denons, comfort is definitely better on the Denons.
 
AudioTechnica M50 - Q40 has less harsh treble, similar mids, if not a bit better, more fun bass, more prominent mid-bass, much improved sound stage, and more comfortable to me (subjective though); virtually better in all ways to me for the same cost (including the upgraded pads).
 
AudioTechnica A900X - The Q40 is less bright, less forward mids, but way more bass in all areas, with a similar sound stage and to me better comfort (with pads upgrade).
 
Panasonic HTF600 - Q40 has similar treble, both are smooth, similar mids, both have good mids, but the Q40 may have better mids of the two. The bass is similar, but I'll give an edge to the Q40 simply because felt a little better controlled. Isolation is definitely better on the Q40. Soundstage is about the same (again, with the upgraded pads). Overall detail and refinement and build quality just feel/sound better on the Q40.
 
Sennheiser HD650 - Q40 has more sub-bass and mid-bass, a bit more treble, a bit less mids, less sound stage, less comfort. Only compared due to bass & smooth treble similarity.
 
Sony XB500 - Q40 has more treble and more mids right out of the box, in a much better way, better sound stage, and very similar bass capability. Obvious upgrade path for a basshead to me.
 
Closing Thoughts:
 
The Q40 does nothing but impress me for it's cost and coming from a manufacturer that is not typical in the headphone world, M-Audio. It's not a perfect headphone, it has it's flaws, which are mainly construction based (clamp & pads), but both were correctable which leaves you with a great audio experience without tampering with it. I didn't feel the need to equalize anything and it was great right out of the box and runs without an amplifier, though I feel it does gain a little benefit from one. It reminded me very much of a bassier Beyer DT770 with smoother treble, which could be thought of as a less fatiguing Ultrasone PRO900. Those are the two that it most reminded me of. Yet it costs less than both. The bass quality and quantity are where it's at for a basshead, yet the mids & treble are fantastic, so it's good for all genres and not just for bass oriented music. Acoustic and jazz sounded great without feeling like it was overly enhanced with bass or that it was degraded from a bleed in. Classical had a body to it that was great and a sweeping feel on the sound stage. Even rock had the texture and mids needed for a good time. Bassy music just rumbled and impacted like it should and was amazing. Overall, it's great for everything from gaming to movies to listening to all genres of music.  If you're on the market for something in the $150ish range, this is a serious headphone to consider if you're looking for something closed back, bassy, but not fatiguing that will run off any device and that can be used as a portable with a good sturdy tank-like build.
 

 

 
Some size comparisons and how they look on your head for those interested in size/style:
 

 

 

 

 
Very best,