Alright, I got my HM5 Pleather Memory Foam Pads today. Let me just say, I do not suggest this for anyone who is afraid to tweak their equipment. I would definitely consider this to be an intermediate level mod. Changing these pads is a bit of a task, but the audio improvements are worth it. Just like the graph showed, the bass impact and extension is very much improved. The bass is now completely flat all the way down to 20hz with no roll off. Soundstage has widened noticeably. With the stock pads, the soundstage depth was better than my DT880, but was more narrow than the DT880. With the HM5 pads, soundstage depth is the same, but width is at least 20 percent wider. Obviously, this would be a result of the ears being a larger distance away from the drivers. The lower mids to midrange region is more forward. The entire 500hz-2Hz region is more pronounced. Vocals are a bit more forward, as are guitars. Guitars have more depth, energy, and warmth. Now, on to what I feel to be the real fault with this headphone with the stock pads, and that is the 7kHz-8kHz peak. I had to EQ this headphone, otherwise I would end up with ear fatigue. After the pad change, that peak is non-existent. There is improved clarity and extension from 10kHz to 16kHz as well. The upper treble roll off is definitely less. Now, there is something I should mention. With these pads removing that 7kHz peak, it will appear that the headphone sounds a bit less detailed, but after an hour of listening, you realize the treble now just sounds correct. You sacrifice that elevated mid treble energy, in exchange for an improvement in bass extension, soundstage width, and better upper treble extension.
To anyone who decides to do this, take your time. The HM5 pads need to be stretched out to get the rings to fit in in the back of them. You are probably looking at a solid 10-15 minutes of stretching for each pad. If it feels like the ring is not going to fit, then continue until the pad stretches a bit more. When you put the rings in, you will notice them bending. Go easy, and don't force it. They can bend somewhat, but within reason. If you are attempting to force them at a 90 degree angle, they will break. The pads are incredibly durable, and can handle the stretching just fine. For anyone wanting to improve the sound of this headphone, I highly recommend this pad change. IMO, it makes the headphone sound far better, and much more balanced.
This is the variant of HM5 pad to be used at the link, for those who decide to do this. Be aware that you have only two options. Number 1, you can sacrifice your Focus Pads, to get access to the rings they have glued on them. Number 2, you can buy another pair of rings direct from Hifiman. I ended up doing Number 1. I sacrificed the Focus Pads, and have no regrets.
https://www.amazon.com/Brainwavz-An...TF8&qid=1499227164&sr=8-1&keywords=hm5+angled