What I basically did was purchase some Beyerdynamic "EDT 990 S" pads from their website for 39 dollars shipped. Took them and applied Krazy glue to the bottom of the pads and attached them to the stock versions. I had also attached a spare M50 ear cushion to the headband, known to me, as I'm the creator, as the "Headband Cush-Relief" mod :)
Comfort - since I wear glasses the stock M50's would press on the arms of my glasses to my head after about an hour. The pain would quickly intensify after that necessitating the need for taking a break from them. With the "Cush x2" mod, they're seriously as comfortable as ANY Beyerdynamic or ADxxx series from Audio Technica! Plus since the Beyer softskins are round and not oval like the stock M50 pads, if there is any pressure, it is spread out evenly over the ears. Nevertheless, there is no squeeze or pressure I can feel, just pure comfort. I did stretch mine over the retail box for 16hrs also.
Sound - The most noticeable thing that is changed is the bass quantity. It literally doubles! Before I go any further, I must point out that this pair of M50 (straight cable) are the newer version that currently comes in a mostly white box with a very light blue top flap on the box. This version has less bass and more bottom mids than previous versions that came in a mostly black/blue box. I was worried that the bass would become sloppy and not have those crunchy sub-sonic lows pulling through. I'm so glad that this wasn't the case! It still maintains the crisp, defining, and authoritative lows that the M50's have stock, yet now there is twice as much! Just awesome!
The mids might seem to be a touch more recessed but I think it's because there is extra distance between the driver and your ears. No big deal for me, I just turn up the volume a little more and the sound is immediate like before. The highs seem to remain the same to me, crisp and smooth with just the right amount of sharpness that I love so much about the M50's.
The soundstage also increases substantially! It is larger in every way; front, back, and with additional depth. Also it is more 3D, like the DT990's or AD700's. In fact, the soundstage is literally just as large as the 990's! These have replaced my DT990's for movies due to the fact that the bass has tons more impact, the M50's can get much louder than the 990's without it distorting the heavy action scenes at the very loud volume that I like, and there is more mids detail in movie soundtracks compared to the 990's. The minor difference though is that the sound has more air in the 990's due to it being open in design whereas in the M50's there is a very large space (bigger than the Denon AHD 2000's and the DT770 series), yet you can feel where the soundstage ends in the M50's. Nevertheless those limits are absolutely jaw-dropping with the mod, making the M50's seem more like an open headphone.
The only con I can see with the sound is that it may need a little more volume from your source, otherwise I personally couldn't detect any abnormalities with the sound unless you already think that the M50's were too bass-heavy. Me, I'm a basshead and love headphones that can produce it with authority. In addition, you can mod these to try without it being permanent as in my case. Just purchase and additional set of M50 pads or Beyer pads, place them over the stock ones and have a listen. You might be blown away with the comfort and sound of these! (sorry if I was a little sloppy with the glue, wasn't expecting it to be so runny :)
I will also have within a week from this entry the ATH PROMK2's. I will test those both stock and with the mods.
Edited by GN3RAL KARL - 5/9/11 at 8:54pm