I'd like to share my impressions on MA750 with you guys.
First of all, some pics:

(Disclaimer: I've been listening to modded 3DD and my modded MH1 recently)
RHA MA750's sound has a strong emphasis in the bass and the treble; thus it is V-shaped.
Right out of the box, what struck me greatly was its deep, dark signature. There were bulk and airiness, which are critical for reproducing a well-balanced vocal, but certainly MA750's mid was lacking definition, which contributes to the overall punchiness and dynamicity of the music. Although I believe lacking is still better than shrieking, the manufacturer could've easily overcome this issue by simply shifting the mid resonances to the lower frequency range by further optimizing the IEM's bore design. On the other hand, bass is sufficiently thumping & rich with overtones. But its overwhelming emphasis clouds the upper frequency range resolution, and further inhibits the presence of mid-range notes.. Is MA750 really full of disappointment then?
Well, my overall impression on MA750 is still quite positive; With the help of RHA's proprietary Aerophonic™ Design & the hand-crafted driver, its treble extends all the way up to 20 kHz, and secures miniscule details that can easily be overlooked with most of conventional IEMs. As such feat is extremely critical for reproducing the sound of instruments with rich harmonic components, such as a violin and a clarinet, MA750 finds its glory when an accurate treble is essential.
For more information, please refer to my blog.