[Mad Max]

A quick google search doesn't bring up comparisons, hopefully someone on here has heard both or you may have to look up Japanese reviews and improvise with Google Translate.

 

[HubaDavid]

They are not really in the same "ring" so I haven't find a comparison as well. Even the X3 is not the most popular AT heapphone, so there is not really a detailed review on it as well.. The M40X costs double compared to the X3IS. I just want to know,  is the sound quality as much better as that beside the built quiality of the M40X. But Still THX.

 

[Mad Max]

Winning combination: dynamat xtreme + polyester fiberfill
 

 

 
Tighter, fuller, better textured and detailed bass, more details all over now that they are no longer obscured by the cups' reverb, more detailed midrange, all around better soundstaging, cleaner, more detailed, and harshness-free treble.  There may still be a treble peak that might bother some folks a bit.  FR will vary slightly from one M40x to the next due to manufacturing variance.  Overall tonal balance is the same as before, though the improved bass may give an illusion of slightly increased bass.
 
I mentioned the dynamat before in a past post in this thread, but I didn't demonstrate, or take things farther with fiberfill.  Studio speakers have the same stuff inside to mitigate reverb in their cabinets.  Fiberfill won't be so simple to measure, unfortunately, so that part will take a good bit of trial and error to get just right equally in both cups.  Overdoing it with the fiberfill can lead to a muffled sound, and/or "overdampening" (sound will seem as if you wrapped a pillow around your head).
The depths of the cups facing directly the back of the drivers should never be loaded with dynamat, in my experience, or you will very likely get a sound which you probably won't like.

 

[Sp12er3]

I might tryto do that in the future... the improvements I sought for from the M70x is its smoothness and loss of Veil (that I noticed by doing A/B from M70x<->M40x) If it able to make the M40x's treble closer to what the M70x has, I'd be very glad

 

[Mad Max]

M40x has no veil post-mod to my ears, at least, not like what I've heard in DT440, HD6 MIX, and some random junk in the past.

 

[Sp12er3]

It's just something I detect only when I A/B test the two together... That the M70x is at a level above in clarity than the M40x

 

[Mad Max]

If it didn't, then M70x would certainly suck for the money, haha.

 

[Z3ph3r]

A close friend of mine owns the m40x, mrspeakers mad dog, hd650, shp9500, and beyerdynamic dt770. I am going to provide some input on his behalf in the form of some easy mods and my general opinion of these cans.
Stock: imo, these are as neutral as you can get for under 100, bar the srh440s.I imaging is slightly forward and more compressed soundstage-wise to the dt770. If I drew a line for the most neutral headphone in existence, the srh440 is a bit higher and the m40x is slightly lower.
(Just to give some perspective, I like bass quality. IMO, the m50x is a V shaped piece of *expletive)
Mods:
Alpha pads
Removed locking connector
Added 2.5 to 3.5 connector
Added vmoda boompro
Foam between drivers and pads (Mr speakers kit)
https://dbrand.com/shop/m40x added decals
Used o2/odac.
These now compete with the hd6xx, shp9500,t50rp, Talos, etc.
Full mods excluding boompro, connectors and o2/odac would cost 75 dollars.
The headphones were bought 60$ used.
New sound:
More bass, more soundstage, lower highs, better imaging.
Unfortunately, I do not think it beat the hd650 or the Mad Dog amped. They don't compete at all to the soundstage of the ship, but they do hold a candle to the dt770.
Thanks for reading,
Z3phyr

 

[Koskam]

M40xs are 80 dollars now on Amazon... Not sure if the price is going back up but that makes it more of a steal now.

 

[unknownrush]

If anyone's interested, I've achieved a more neutral sound (subjectively, mind you) via the following reversible mods using the stock pads:

Fixing the hot treble:
Since I don't have a source for the 2mm thick felt that Solderdude used in his guide, I fell back to another of the tried and true treble remedies: blocking the centermost area in front of the driver (the MDR-V6 does this, so do the newer Mad Dog and Alpha Dog via the 'BMD', and probably others); I cut a circle out of paxmate and stuck it blocking the innermost two circular rows of the driver, leaving only the outermost circular row of perforations free. This reduced the treble to an acceptable level for me without interfering with the mids too much. I reckon you could use other materials like foamie, variable layers of micropore, or even electrical tape.

Reducing the bass hump:
First, remove the grey foam padding under the earpads, this helps fill the dip around 450 Hz. The cups can be opened by removing the 4 screws visible once the pad is removed; remove the screws and gently separate the baffle from the cup, now inspect the driver assembly and note that one of the venting holes in the periphery of the driver has no paper in it. You can either block it for maximum bass reduction, or dampen the vent with some breathable material to adjust the magnitude of the hump; I used 3M micropore tape with good results. Clarification: This will NOT kill the bass, even blocking the vent completely leads to a slightly boosted bass response, try it for yourself

The results were 'verified' via sine sweeps and other test signals, then with music. I have no test equipment to show you the changes to the FR, so naturally take these results with a grain of salt. I've gone back and forth with these and other mods and settled with these two, sadly I haven't found a way to mechanically fix the dip around 4-6 KHz or reduce the hump at 1.5 KHz so I use EQ to alleviate it some.

Just want to say thanks for the this!

I purchased the M40x's based on reading numerous reviews, with everyone stating how neutral they are & that they have far less bass than the M50X (which I hated, but true), people were even stating there was no bass hump to be heard on them at all?! I was again really disappointed with them, on the verge of sending them back until I saw this post, that bass mod has helped massively reduce the hump. I have tinnitus & can't stand any bass rumble, no matter how slight it is.
So keeping them now.

Thanks.

 

[qAnAthemA]

So guys, a lot of confusion after reading this thread. Which pads will be better: velour or leather, angled or straight? I am looking for a bit more solid bass with good soundstage and overall sound quality. Also, I searched hm5 pads on Amazon and got only velour ones (https://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=hm5+pads&rh=i%3Aaps%2Ck%3Ahm5+pads). Are there only velour version of hm5 pads? If you can, just provide links to good earpads. 
 
PS Do you know if logo from dbrand for m50x (https://dbrand.com/shop/m50x) will fit for m40x? I am looking for some customization.
 
Thank you.

 

[Mad Max]

Those M50(x) decals should fit M40x as they are built very similarly.
 
You could even make your own black carbon fiber decals using 3M carbon fiber vinyl decal: http://www.ebay.com/itm/3M-1080-Black-Carbon-Fiber-Vinyl-Vehicle-Decal-Car-Wrap-Film-Sheet-Roll-/181915997497
That link is just an example.  It comes in a few other varieties, too.

 

[Madhur Shankar]

Velour pads will eat the bass, will leave you miserable. I use angled pads from Brainwavz, these are good. Angled pads elevates the bass slightly and gets rid off treble peaks. I personally prefer them for M40x. I also ordered ZMF cowhide pads, I will get them in couple of days. Will update on it once I get them...

 

[qAnAthemA]

[Mod: Link edited by Mod]
These (http://www.amazon.com/Brainwavz-Angled-Memory-Foam-Earpad/dp/B00ZY8PGJI/ref=sr_1_1?s=electronics&ie=UTF8&qid=1481078495&sr=1-1&keywords=Brainwavz+Angled+Memory+Foam+Earpad+-+Suitable+For+Large+Over+The+Ear+Headphones+-+AKG%2C+HifiMan%2C+ATH%2C+Philips%2C+Fostex)?

 

[The Krell]

I just ordered these from amazon to go with a DSS2 for gaming, I hope they sound good with battlefield 1.. I will post my impressions when they arrive..not that much bass normally means you can hear footsteps a lot clearer hopefully!