Alright, I have had my K712 Pro for a couple days now. As I do with every headphone, I have gone through my usual critical listening stage for the first 10-15 hours. I will put my EQ up at the end of my description down below as well. Oh man, does this puppy ever respond well to EQ. This is a fantastic headphone. It is a full step up from my DT880 in every way. It is also beating my HE400i, which I modded with the HM5 pads. Of these 3 headphones I own, the K712 Pro is definitely my favorite. In terms of build quality, I wish there was a little less plastic used, and the use of more metal. It certainly makes me wonder how these headphones will hold up over time. I baby all of my electronics, but a better build quality would have been nice to see. In terms of comfort, these are the most comfortable headphones I have ever worn to date. I thought my DT880 was comfortable, but this is even better. The clamping force is perfect, and I get no hot spots on the head at all. The pads are like pillows around the ears. I imagine I could use these for a full 12 hours straight, and would not feel the need to take them off.
Now, lets get on to the sound. This headphone has really surprised me. Right out of the box, it has better bass extension and quantity than I expected. I am right into hard rock and heavy metal, and the K712 Pro totally excels at these genres. In terms of bass, It fully extends down right to 30Hz. In fact, the bass on this headphone actually reminds me of the bass on a closed back headphone. It is fast, tight, and detailed. In the sub to mid bass range, there is nothing I would change. The lower bass sounds perfect to my ears. This is such a grooving headphone for heavy music. The bass on the K712 is deeper, more extended, and more impactful than the DT880, no question. With that said, however, I find the bass to be a bit too forward in the upper bass range of 160Hz to 300Hz. This upper bass increase is not present at all on the DT880. It results in a bit of muddiness and bloat. With a slight EQ of that region, things are much more balanced now. Be aware, that as an added bonus, by reducing the elevated upper bass, the soundstage, separation, and imaging on the headphone will improve. I have actually seen a couple people claim this headphone lacks bass. I am totally shocked. The only way someone could find this headphone to lack bass is if they are a complete bass head. Either this, or they are using a weak amp/no amp. I did not expect this headphone to actually have the low end frequency capability that it does.
Now, regarding the mids, the K712 Pro has a strange tuning. There is that classic 2kHz to 2.5kHz peak that is often present on AKG headphones. However, then there is a sudden drastic dip right at 3kHz, which continues on to disrupt 4kHz as well. Without any EQ, it gives me a bit of that "I put my hands over the back of the headphone cups" type of sound. Once I put EQ to this area, I was able to flatten the entire midrange. Regarding the mids on this headphone, just wow. Guitars on this headphone sound fantastic. They are detailed, thick, and full of body. There is nothing harsh about the presentation. Guitars sound exactly like they should. The vocals on this headphone actually have a similar presentation to the DT880, however, they are certainly more forward in the mix on the K712 Pro. Vocals are clean, smooth, and realistic. This headphone has a character to it which is very similar to a quality "speakers in a room" type of sound. The soundstage on the K712 is also wider than the DT880, and with increased depth. There is more space between the instruments. This is also a warmer sounding headphone. I actually did not expect this headphone to have the warm presentation that it does. I usually go for a more neutral headphone, but this puppy really makes things sound good. I remember when I had the K612 Pro, and I ended up selling it. It had flaws in its sound that I just could not tolerate. The 2kHz peak on the K612 Pro had a grain to it that actually ended up giving me a headache. After it happened over and over again, I ended up selling it. Interesting enough, the K712 Pro also has a 2kHz peak, but there is no harshness or grain to that peak. It is MUCH SMOOTHER. In fact, there is a smoothness to the entire presentation on this headphone, at least on my pair. It is amazing that it seems to do this, yet offers so much detail. These headphones love pulling details out of music. You can hear things that other headphones at this price level just can't produce.
I have seen a couple people say that this headphone has a monster 6kHz peak, which causes fatigue. On my headphone, this supposed issue completely does not exist. I am not sure if this is a result of driver variance, but the entire mid treble on my headphone has no harshness at all. In fact, everything sounds as it should all the way up to around 9kHz, and from there, I can hear a bit of roll off all the way up to 16kHz. Yes, there is an upper treble veil, but it is not huge. It gives a sound that that is a bit relaxed. The treble is quick, accurate, and defined. Everything is smooth, and without any grain or harshness. Everything in the upper frequencies is articulate. The drivers in this headphone are very fast. I have seen some claim this headphone is actually too bright. To me, there is just no way. I do not find that to be the case at all. I do not detect any fizz, sssssss, or other ear fatigue causing aspects. I say once again, this headphone responds better to equalization than most headphones I have tested.
Edit: On further critical listening, I have detected a small spike right at 12.5kHz. This is interesting, as the rest of the upper treble is actually slightly rolled off. I ended up lowering that by - 0.5.
In terms of power, of course this headphone needs an amp. With my M-Stage, the K712 requires the least on the dial of my three headphones. My DT880 Premium 250 Ohm requires more than the K712, and the HE400i requires the most out of three. I was expecting the K712 Pro to require the same amount, if not a little more, than the DT880. Turns out, it is about 10 percent less on the dial to reach the same volume.
In terms of EQ, I highly recommend anyone to try this set. Granted, we all hear things differently. I would bet that at least a few people here will like this EQ though. This is it for me for headphones for quite a while. I don't see any point in looking elsewhere. This is a fantastic piece of audio hardware.
Pre-Amplifying: - 2
63Hz: + 0.5
80Hz: + 0.5
160Hz: - 0.5
200Hz: - 1
250Hz: - 1
315Hz: - 1
1.25kHz: + 0.5
2kHz: - 1
3.15kHz: + 2
4kHz: + 1
6.3kHz: - 0.5
8kHz: - 0.5
10kHz: + 0.5
12.5kHz: - 0.5
16kHz: + 0.5
Edit: I am sure someone will ask. Mine is a Slovakia version..
Edit 2: I am probably at around 35 hours use now. Wow, this is an amazing headphone !!!!! The sound is even smoother now than it was out of the box. I am so impressed. This headphone is a must buy for people who enjoy hard rock and heavy metal music. The smoothness, combined with the imaging and detail retrieval, is just fantastic.