Just received my GR07 today. I have been listening most of the day. At first, I was not impressed. I was at work, and didn't have an oppotunity to echange tips to find a great seal. I did try the tips that came on them, and one of the pairs of foam hybrid types. They just seemed really low energy, and no low end. I am no bass head either.
So, I got home a couple of hours ago. I tried a few different tips. Once I stuck the blue hybrid style, without foam, and tried them on, they came to life.
I was a little suprised, because the other tips I had tried didn't feel like a poor seal. But once I found the right tip, I find these to be very high energy IEMs. The low end is very present and punchy, but never bloated at all. The mids, while not forward, are really smooth. The highs are crisp and detailed, and not recessed. I really like these a lot. I have limited experience and am a bit of a noob, but to me, the energetic presentation of these compare very closely to my Grados. Not the signature so much, just the toe tapping, head bobbing presentation. With my limited inventory of Grado 325is, Beyerdynamic DT880 250, and RE-262, these are closer to the Grado, with a better low end, than any of the others. The Beyer being a very low energy, laid back presentation, and the 262 being a mid-forward sound.
This was a really good purchase