Audio Technica ATH-M40FS Precision StudioPhones


New Head-Fier
Pros: 11-Foot Cable (Pretty Subjective), Quick Response, Resolute Sound, Clean High-end
Cons: Pads & Headband wear easily.
While the treble can be slightly "honky" (as another reviewer put it) at times, the high frequencies are very clear on this pair of headphones, and one can pick out different instruments.
These headphones (being studio monitors) are very clear, and one will have to a good bit of work in order to muddy the sound. They compete will with my Grado's in the category of "fast-response cans". I was able to listen to some swedish death opera with good clarity. I have no complaints whatsoever regarding bass, treble, or midrange - all of these are equally present.
In fact, my only complaint may be that they can can start sounding a bit muffled after a good while listening with open-back headphones.
- Acoustic Alchemy - Mr. Chow : A real treat. Crisp, resolute, discernible guitar and percussion.
- Diablo Swing Orchestra - Black Box Messiah : This piece is fast, and heavy with texture and a range of vocals; includes an electic violin. Sounded good, the cans were not at all taxed.
- Diablo Swing Orchestra - Guerrilla Laments : Also very fast, vocals were discernible, horns, bass, guitar, violin, drums, and whatnot could all be heard and were generally not muddy at all.
- Allan Holdsworth - The Things You See : Warm guitar was warm, so were vocals (this is the mastering). Everything was crisp -- matched my SR225is (with exception of sound-stage and some minor business with vocals).
- Bela Fleck (et al) - Blu-Bop : Piano could have been more present.
- Adrian Belew - Ampersand : Vocals seemed to be distant, but this may be the track (in some parts)
- Cake - Comanche : You can hear emotional cues in the intonation of lead singer. 
- Huey Lewis... - ... New Drug : Not muddy at all, echo was very discernible. 


500+ Head-Fier
Pros: Fairly straight frequency response, excellent dynamic range, quick dynamics.
Cons: A bit cold sound with serious headphone amps. Sometimes honky treble.
ATH-M50 prices have gone up (way up) and so the next logical choice was the ATH-M40, which was half the price. ATH-M40 has 40 mm. diaphragms unlike ATH-M50's 50 mm. Otherwise it's a fairly similar model; the accuracy is there too, although they're slightly colder (and faster). ATH-M40 have straight drivers, unlike ATH-M50, which have angled drivers. IMHO that is the only flaw with the ATH-M50: angled drivers bleed some soundstage and midrange power. Though the ATH-M50 drivers are engineered to compensate, they still have a few slight holes here and there in the frequency response. Angled drivers are a sales gimmick really, though A-T engineers did a good job with the ATH-M50. ATH-M40's straight drivers are therefore an advantage over the ATH-M50.
ATH-M40 is Audio-Technica's "straight frequency response" monitor model. Now in fairness, "straight response" for headphones is one that's adapted to your own HRTF frequency response. These are equalised to an average HRTF, but yes, they are quite "straight" in response. With one caveat...
ATH-M40 take a while to burn-in, and the burn-in transformation is the most obvious case. Out of the box, they were snowy-white in sound. Not even black-and-white, grays-on-white. No contrast or colour whatsoever. It even looked like AT made a blunder and equalised those to a "speaker-flat" frequency response. A special EQ profile had to be made to make their sound bearable (adjusted to HRTF with EQ band tones), and apparently this EQ profile helped, as after a week or so of playback they started warming up, and on the second week the EQ preset could be discarded.
Here's the original Foobar2000 EQ:

Now they play fine without it.
The design itself is curious, ATH-M40 boast clamp wire terminals. Unlike most headphones, the ATH-M40 are designed for cable replacement without soldering. Main cable terminals are of the screw clamp type, similar to speakers. Wires are inserted and then screws push down on the terminals (speakers usually have springs, but screws are more secure). The notion itself is a bit weird, as a screwdriver is required to disassemble the headphones, and anywhere headphones work where a cable might need replacement (like, say, straight cable swapped for a coiled one), there's electricity for a soldering iron. It's also highly likely that whoever's going to replace the cable will also be familiar with soldering. Still, it's nice, and safe in a way as plastic inside the cups is not threatened with a hot iron.
There's a capacitor buffer before each driver, giving the ATH-M40 a slight curious sound mellowness reminding a bit of older synthesisers (CS-80, Prophet VS...).
The headphones were modded, and well... They weren't a major reassembly trouble like the ATH-M50 (there's a thread describing the assembly somewhere over here, with photos). Still, pushing through the new headband cable through was difficult.

Not the best photo, but there they are.
The new wiring is silver-plated copper, AWG 26, teflon-coated, with shielding (for the main cable anyway). The shielding is just aluminium foil. It all looks rather pretty inside the Techflex jacket, but foil isn't ideal as it tends to tear and deform over time, unless rolled fairly thick. A proper grounding copper braid would've been better, but it's heavier and it might be too thick to fit through the strain relief. Given a thinner braid though, it might also fit the headband cable (or better, two different diameter braids would have to be used).
The silver-plated copper cable cures the last stuck harmonics and veil the stock ATH-M40 have, and it makes them play full-speed, rather lively. The cable is terminated to a 3.5 mm. fat-barrel plug (the stock plug is 6.3 mm. full-size).
There's also Blu-tack on the driver assembly, helping stability a bit (the drivers are fairly stable as they are, attached to a platform assembly inside the cups), and Blu-tack, cotton and plastic fibre to improve isolation inside the cups. Isolation is important as these are street headphones and they're also used for monitoring next to loud drumkits and guitars. Studio/live work.
Impedance is 60-ohm, but the ATH-M40 are fairly easy to drive, an Apple Touch 4G player drives them to almost full noise isolation on the street. Not obnoxiously loud, but given the thing's low power, the ATH-M40 provide a stunning detail. They are a bit on the shouty/cold side when driven from proper headphone amps (and studio kit like mixers). What matters though is that they detect and show even very slight hiss and are suitable for track cleanup. As an example, in Nirvana's "Come As You Are" open reel tape noise can be heard even when playing on a weak player like the Touch 4G. Out of the sound interface, they show all the background noise in a microphone take.

Modified with silver-plated copper cable inside a heavy industrial copper braid shielding.
Sound-wise the ATH-M40 are transparent, they just put out what's there (tested against "straight-response" studio monitor speakers). Frequency response is not "perfect straight", of course, but they're just about right in that they show the picture. Response is fairly straight - compared to fairly straight monitor speakers (KRK RP6 G2 SE, they're mostly straight up to about 14 KHz), the ATH-M40 output is about the same, with more airiness and emphasis on higher midrange/treble (as is to be expected from monitor headphones, they're designed to pick out the dirt and show details). Electric guitars can be a bit light (and trebley) compared to what they'll sound like on speakers, but it's nowhere like the bodiless exaggeration of some other Asian makers (Pioneer SE-M290 - cold tint and bodiless guitars, Denon DJ DN-HP700 - too forward at 1.5 KHz, washing out electric guitars, etc.). Compared to speakers they're quicker (better dynamics and transients, though that's typical of any headphones) and they tend to be somewhat colder. As usual, it's not good practice to mix in headphones, so anything put together on the ATH-M40 will have to be tested and possibly rebuilt on monitor speakers.
The ATH-M40 were bought for monitoring next to loud sound, as the K-240 Studio are pretty much useless for that (being semi-open, they're like sieves when it comes to isolation onstage or even for studio tracking). Compared to the K-240 Studio, ATH-M40 are quicker, have a more "straight" frequency response (though this is not a flaw of the K-240 Studio, on the contrary, they're the best headphones for playing synthesisers and composing thanks to their tweaked frequency response) and have better isolation, though seriously, you ought to stick a few things like plied cotton inside the cups to improve isolation. Vibration killers like Blu-tack and Dynamat also help when used to pad the cups on the inside. Dynamics and overall painting finesse are better in the ATH-M40, but the K-240 Studio are still the synth tracking headphones that nothing can really beat, they're more musical (better note contrast) in spite of their being slower and darker.

Modded ATH-M40 and ATH-M2X (furry).
They're fairly comfortable, though the headband likes to slide around, at least the first couple weeks before it moulds and adapts to the head. ATH-M50 can start feeling crammed, especially for those with bigger/pointier ears, the ATH-M40 have more space inside the cups and give a nice, spacey soundstage as a result, though the drivers could sit closer to ears (SIGH, one of these days one ought to get custom-made and measured headphone cups 

Overall, they're a good buy, basically what you get is a headphone equivalent to straight-response monitor speakers for not as much (ATH-M40 sell for as little as $75 or so online). There're much worse headphones out there for twice the price, that's for sure. They work fine with anything, even weak cell phone outputs (just don't expect miraculous loudness there), so they're an automatic choice for all-purpose headphones. They're also fairly straightforward to mod, thanks to the wire screw-clamp terminals (the right cup has screw terminals for the headband cable as well).


Headphoneus Supremus
Pros: Very comfortable, earpieces both swivel 180 degrees, rugged construction
Cons: Underwhelming bass, very forward mids, thin earpads
(Review edited 6/6/13 to add comparison to Sony MDR 7506, additions in bold text).
Disclaimer: My only other good cans to compare these to are Beyerdynamics DT770 (250) and Sony MDR 7506's. I fully realize this review will be biased because of that. So please keep that in mind. This review is my purely subjective opinion.
I bought these because of the nearly 400 gushing reviews on Amazon. Also, because they were cheap. I use them at work, and leave them on my desk when I go home. If someone walks off with them, I won't be heartbroken. They are powered by a stock Bravo Audio V2, driven by an ipod. Can't plug into the computer at work, so the setup has to be standalone.
The Pro's:
They are indeed comfortable. I wear them all day long, and have been doing so for a couple months. They are loose fitting, and will definitely come off if you move around a lot. However, if you are going to leave your behind parked in a chair all day, you will love how comfy these are. They are more comfy than my Beyers (which kind of feel tight after an hour or two). They are about twice as heavy as the Sony MDR 7506 (which are equally comfortable).
I suppose if you're a recording engineer and you need to keep one ear open, and the other covered with a headset, you will also like these. The construction seems very solid. Both head pieces swivel, and it seems like you can hold one on an ear and it'll support the entire weight of the device with no concern something will break. I do not use mine that way.
Compared to the headphones I broke (Sony MDR NC-40's), these are a world apart. But they need to be amped to sound good. I am not impressed at all, when driving them with my ipod and no amp. I'd sooner go buy another pair of the Sony's, if I could not run these with an amp. They are decent if you're going to plug them into a computer (which is an amp), and use Windows media player (which has the necessary EQ).
Sound isolation is excellent. No leaks, and I can't hear the phone ringing next to me when they're on.
The Con's:
I power these with a Bravo Audio V2 (also purchased because it's cheap, and I leave it on my desk at work). With all EQ off, the bass is there, but its overwhelmed by the really forward midrange of these cans. I honestly would not call these flat (though my caveat about comparing to the Beyer DT770s may make some of you giggle). I know, my Beyer's have recessed midrange, so switching back and forth between these two cans really shocks me with midrange. One set of cans has disappearing mids, the other is nothing but mids.
Now, about bass. With my ipod EQ off, the bass is there, but it's well hidden. If I cheat and hit the "Rock" EQ setting, this all changes. Suddenly, these cans aren't so bad. Take a look at iTunes and you'll see the Rock EQ setting boosts bass and treble, and cuts out about 5dB of the midrange. Brilliant! That's exactly what these cans need. Now I can go home to my Beyers and not feel so bad. LOL. More importantly, this bit of EQ allows the bass that these cans do have to come through (as well as some decent high end). So, pull my audiophile card. LOL. That EQ switch is making up for a poor purchasing decision on my part.
The earpads seem a bit thin. My ears are already starting to press into the cloth covering the transducer, so I can see it under the cloth. And I don't use mine like a recording engineer would. I might speculate that the thin earpads would become annoying to a recording engineer using them as I described above, because it won't be long before you're pressing the transducer right into your ear. This has not become an issue for me yet. I just notice the impression inside the ear cup when I take them off. Two months of use. This might become an issue soon.
In comparison to the Sony MDR 7506, the midrange sounds really bad. Artificial. Cheap. I can't really think of a better way to describe it. I would really not recommend using these for studio work, they simply aren't good enough. For under $90 USD, the Sony's are far better. The bass response of the Sony's is slightly better, and the high end is clearer. I can turn off the EQ on my iPod with the Sony's, and run it flat. I'm really astounded at the difference.
There are a lot of reviews on Amazon that indicate people are happy with these cans, but I only found one lone review here. I find that very interesting. I suppose many people rely on Amazon reviews (without coming here). Then again, I'm not sure how much patience people have when trying to take in the sheer volume of information on this website. Reading three old reviews on an Amazon webpage is enough if you're like me and you initially decide to spend 50 bucks or less on some replacement headphones. It only took a few minutes, not a few weeks. Once you realize you didn't get all you wanted, you spend more time.
And after spending a few weeks reading Head-fi, you start spending more money on better gear. Then you want more. You wonder how many upgrade paths there are. Tubes or solid state. Open back or closed. Should I really drop 35 bucks on a cable? Should I spend 50 bucks on a tube? Soon, the unofficial slogan of this website finally sinks in and takes on meaning:
"Welcome to Head-fi! Sorry about your wallet!"
So. Yeah. Ignorance is bliss. It is also cheaper. These cans were nice for me for a short while. Those days are gone. I suppose I will keep using them at work until they become uncomfortable, or something else happens. Then again, maybe not. I keep wondering if there are some nice 100 dollar cans I can use for work, and if I won't mind if someone walks off with those...
Epilogue: These are no longer my work cans. I've replaced them with the Sony MDR 7506's, which sound superior, are just as comfy, and lighter. I'm not sure what I'll do with them. Maybe I'll use them for a computer in my garage.
Read my own review for the details, here's a photo of the current setup:
In brief: silver-plated copper shielded wiring, Blu-tack driver stabilisation, Blu-tack, cotton, soft plastic fibre padding inside the cups (isolation++), 3.5 mm. fat barrel plug.
The burn-in was simply Foobar2000 playing a few punchy tracks (playlist on repeat all/random) several nights, with an EQ calibrated with my own equal loudness tone test.
Also: the shielding now is copper braid, originally it was aluminium foil, which is worse.
BTW, it might be a different production batch, but the ones here are anything but bass-shy. They're accurate though, no exaggerations. Frequency response is close to straight-response monitor speakers. The MDR-V6, last time tried, were quite fatiguing and shouty in the treble.


New Head-Fier
Pros: Ideal for use in recording music
Cons: Not ideal for music playback. Terminated with 1/4" connection only
I do not know much about headphones, but figured I'd fill the void and give me basic, Layman's experience. I got these headphones because they were reasonably priced, were well reviewed, and meant for the studio. At the time, I was getting into basic guitar recording--just through my laptop, but I owned a Boss GT-8 digital processor board, and a M-Audio FireWire Solo. Each had 1/4" connections, so at the time, headphones terminated with only 1/4" jack weren't an issue. They work well for guitar playback--their description of having a flat response is accurate; you hear what you're supposed to hear. So when tracking guitar, or adjusting amp models, you don't want headphones that have huge bass boost, or emphasized highs--you want accurate feedback so when you lay the track down, or go to plug into a speaker cabinet, you don't have to many further adjustments.
That being said, lately I've been desiring headphones for music playback. I have Shure SE-310s which are great for commuting, but while at work and home, I don't mind a larger, heavier headphone--I'm looking for a great music listening experience. Aside from no speaker dynamics, the lack of a 1/8" terminal makes iPod or laptop playback difficult. I picked up a 1/4" female to 1/8" male adapter, but that creates an awkward weight to the jack on the source, putting potential stress on the components. But, these were designed for the studio, so minijack adapters are not necessary in that environment.
Also, over time, the vinyl/leather pads do get hot, causing my ears to sweat with some extended use. They fit over my ears well though, so I do not recall any discomfort  to my ears, head, temple -- just some undesired moisture.
I had these and you are right, is a very flat response. they are very comfortable too. and yes, not the most musical headphones for listening.