Many thanks to Audio-Technica Singapore for the demo set loan of ATH-R70x!
By the time i post this review, i have had it with me for more than a month.
http://www.audio-technica.com/cms/headphones/f39784ce643a82e6/index.html

Sound Quality, Amplifier Matching, & Comparisons
Features & Specifications
Updates and additional information
I was quite surprise of how light ATH-R70x was when I took it out of the box. Lighter than other headphones in my inventory. The matte black finish and the utilitarian design gives it a modern and professional look. A nice blend of form and function. ATH-R70x is designed in conjunction with Paris-based design company, ARRO Studio. When I listened to it for the first time, ATH-R70x gave me another surprise with its natural tonality. Not bright, not warm, it just sounds natural to my ears. From the beginning ATH-R70x feels, looks, and sounds professional.

When mentioning of professional open-back reference headphone, some of us might think of the well-known flagships, such as Sennheiser HD800, Beyerdynamic T1, or AKG K812. Is ATH-R70x competing with those flagships? Does ATH-R70x sound like any of those? The answer to both questions is simply, No. I have HD800 and T1 for years, and auditioned K812 a few times, and I'm glad ATH-R70x sound tuning has taken a different approach. In my opinion, it is complimenting those flagships rather than competing them. I will explain that later. Meanwhile for those who doesn't have much time to read the whole review, here is the summary, pros & cons, and some suggestions for improvement.

Detail and resolution are good, slightly better than HD650, but not yet at the level of HD800 or T1. ATH-R70x is rather a little forgiving when it comes to revealing detail, especially when compared to HD800 and T1. Dynamic is pretty good, but a little hard to drive. With 470 ohms impedance ATH-R70x need a good amplifier to sound lively. When compared to T1 & HD800, ATH-R70x is not as fast sounding as those flagships, and not the best choice for extremely fast pace & complex music. But regular pace music, pop and jazz, sounds gorgeous on ATH-R70x. I definitely enjoy vocal on ATH-R70x better than HD800 and T1. For example, ATH-R70x is my favourite headphone for albums from Stockfisch Records. ATH-R70x does classical as well, but performs better with small orchestra and chamber music. As an open-back headphone, ATH-R70x imaging size is around average, not very spacious, but also not congested. Imaging is accurate, but not as big and spacious as HD800.
I have burnt-in ATH-R70x for about 100 hours, no changes in sound quality. So, no burn-in is required for ATH-R70x, which is a good thing. Headphone that changes it sound after burn-in, to me is indicating inconsistency. As with DAC and amplifier, I didn't find ATH-R70x to have good chemistry with tube amp or warm & smooth sounding amp, and matches better with neutral to slightly analytic solid state amplifiers. With my ifi micro iDSD + iCAN, ATH-R70x is simply music. At 210 grams, ATH-R70x is feather-light and very comfortable. Headband pressure is pretty light, less pressure than T1, about the same as HD800. ATH-R70x fits really well on my head, always stays in place.
Some factors of ATH-R70x that in my opinion make it suitable for professional applications:
1. Very balanced, almost ruler flat tonality, makes ATH-R70x very useful for tonality observation & equalizer adjustment.
2. Light weight and comfortable for long sessions. Headband pressure is light, but it fits very well, and not easily moved from position even with lots of head movement.
I gave 5 stars for ATH-R70x, is that mean that ATH-R70x a perfect headphone? There is no such a thing as a perfect headphone. 5 stars are mainly for its performance, in comparison with other headphones within the price bracket that I've ever tried. Best achievements of ATH-R70x are the very natural tonality, almost ruler flat tonal balance, and the light weight and good fit of the headphones. ATH-R70x is probably not the one headphone that fits all music, but it really excels on what it does best, which are vocal, pop, and jazz. Generally modern recordings with closed miking sound wonderful on ATH-R70x. What I think can be improved further to match other open-back flagships mentioned above are the clarity, detail, speed and dynamic. Overall ATH-R70x is a very pleasing & comfortable headphone. Some headphone may sound technically right, but not necessarily emotionally involving. Not with ATH-R70x. With the right DAC and amplifier, ATH-R70x sounds gorgeous and emotionally involving. For under $500 bracket, in my opinion, ATH-R70x deserves 5 stars. An excellent sounding headphone for both professionals and audiophiles. Kudos to Audio-Technica!

Feather-light weight (approx. 210 g w/o cable).
Only one long (3 meters) stock cable is included.
Headband size might be a little short for extra-large size head.
Larger & thicker earpad for greater comfort.
Shorter cable (approximately 1.5 m - 1.7 m) to be included.
Semi-hard case protective carrying case.
By the time i post this review, i have had it with me for more than a month.
http://www.audio-technica.com/cms/headphones/f39784ce643a82e6/index.html
Sections:
Summary & HighlightsSound Quality, Amplifier Matching, & Comparisons
Features & Specifications
Updates and additional information
I was quite surprise of how light ATH-R70x was when I took it out of the box. Lighter than other headphones in my inventory. The matte black finish and the utilitarian design gives it a modern and professional look. A nice blend of form and function. ATH-R70x is designed in conjunction with Paris-based design company, ARRO Studio. When I listened to it for the first time, ATH-R70x gave me another surprise with its natural tonality. Not bright, not warm, it just sounds natural to my ears. From the beginning ATH-R70x feels, looks, and sounds professional.
When mentioning of professional open-back reference headphone, some of us might think of the well-known flagships, such as Sennheiser HD800, Beyerdynamic T1, or AKG K812. Is ATH-R70x competing with those flagships? Does ATH-R70x sound like any of those? The answer to both questions is simply, No. I have HD800 and T1 for years, and auditioned K812 a few times, and I'm glad ATH-R70x sound tuning has taken a different approach. In my opinion, it is complimenting those flagships rather than competing them. I will explain that later. Meanwhile for those who doesn't have much time to read the whole review, here is the summary, pros & cons, and some suggestions for improvement.
Summary:
ATH-R70x has a very smooth, polite, and balanced sound signature. Tonality sounds natural and very pleasing without any annoying peaks or dips on the frequency spectrum. Sometime may sound a little too smooth, depending on recording. Tonality leans a little, to the warm side, just a little, not as warm as HD650. Bass and mids are balanced, with good bass presence & low bass extension, but it doesn't sound bassy. It has more bass than Beyerdynamic T1, but less bass than Philips Fidelio X1. Treble is only a tad softer than the midrange, but not lacking and overall still quite balance. I do prefer to hear a little more clarity, especially for my music. If HD800 brightness is North Pole, and HD650 warmness is South Pole, ATH-R70x tonality is probably Australia. ATH-R70x is not for basshead, and also not for those looking for HD800 or T1 transparency, but an excellent choice for those looking for natural and balanced sounding headphone for long period of music listening. ATH-R70x is especially good on vocal. Vocal sounds smooth, natural, and full bodied.Detail and resolution are good, slightly better than HD650, but not yet at the level of HD800 or T1. ATH-R70x is rather a little forgiving when it comes to revealing detail, especially when compared to HD800 and T1. Dynamic is pretty good, but a little hard to drive. With 470 ohms impedance ATH-R70x need a good amplifier to sound lively. When compared to T1 & HD800, ATH-R70x is not as fast sounding as those flagships, and not the best choice for extremely fast pace & complex music. But regular pace music, pop and jazz, sounds gorgeous on ATH-R70x. I definitely enjoy vocal on ATH-R70x better than HD800 and T1. For example, ATH-R70x is my favourite headphone for albums from Stockfisch Records. ATH-R70x does classical as well, but performs better with small orchestra and chamber music. As an open-back headphone, ATH-R70x imaging size is around average, not very spacious, but also not congested. Imaging is accurate, but not as big and spacious as HD800.
I have burnt-in ATH-R70x for about 100 hours, no changes in sound quality. So, no burn-in is required for ATH-R70x, which is a good thing. Headphone that changes it sound after burn-in, to me is indicating inconsistency. As with DAC and amplifier, I didn't find ATH-R70x to have good chemistry with tube amp or warm & smooth sounding amp, and matches better with neutral to slightly analytic solid state amplifiers. With my ifi micro iDSD + iCAN, ATH-R70x is simply music. At 210 grams, ATH-R70x is feather-light and very comfortable. Headband pressure is pretty light, less pressure than T1, about the same as HD800. ATH-R70x fits really well on my head, always stays in place.
Some factors of ATH-R70x that in my opinion make it suitable for professional applications:
1. Very balanced, almost ruler flat tonality, makes ATH-R70x very useful for tonality observation & equalizer adjustment.
2. Light weight and comfortable for long sessions. Headband pressure is light, but it fits very well, and not easily moved from position even with lots of head movement.
I gave 5 stars for ATH-R70x, is that mean that ATH-R70x a perfect headphone? There is no such a thing as a perfect headphone. 5 stars are mainly for its performance, in comparison with other headphones within the price bracket that I've ever tried. Best achievements of ATH-R70x are the very natural tonality, almost ruler flat tonal balance, and the light weight and good fit of the headphones. ATH-R70x is probably not the one headphone that fits all music, but it really excels on what it does best, which are vocal, pop, and jazz. Generally modern recordings with closed miking sound wonderful on ATH-R70x. What I think can be improved further to match other open-back flagships mentioned above are the clarity, detail, speed and dynamic. Overall ATH-R70x is a very pleasing & comfortable headphone. Some headphone may sound technically right, but not necessarily emotionally involving. Not with ATH-R70x. With the right DAC and amplifier, ATH-R70x sounds gorgeous and emotionally involving. For under $500 bracket, in my opinion, ATH-R70x deserves 5 stars. An excellent sounding headphone for both professionals and audiophiles. Kudos to Audio-Technica!
Pros:
Almost 'perfectly natural' tonal balance.Feather-light weight (approx. 210 g w/o cable).
Cons:
Obscured Left and Right markings.Only one long (3 meters) stock cable is included.
Headband size might be a little short for extra-large size head.
Suggestions For Improvement:
Clearer Left and Right markings.Larger & thicker earpad for greater comfort.
Shorter cable (approximately 1.5 m - 1.7 m) to be included.
Semi-hard case protective carrying case.