Instruction: Extract information from the supporting document to answer the given question.

Input:
Question: I see this has large drivers, but does it have adequate bass response?
Document: The cups are quite large, though for housing 70mm drivers, I expected, and have seen bigger. The color scheme is classic Sony black with silver Sony logos placed on the center of the outer cups with a thin silver accent separating the outer grill with the rest of the cups. The styling is pretty barebones overall. Not really what I'd call an aesthetic marvel, but they are inoffensive to the eyes, and won't bring attention to itself.
However, they are all a little to a lot more expensive, require more power, have frequency response bumps and dips (i.e. too much bass or treble), and may be more situational in use.
On the upside it depicts a very cohesive soundscape with absolutely stellar center-focus.MA900's tonal quality is a mixed bag for me. The moderately  forward  lower mids, along with the added bloom reminiscent of the mid-bass hump and the very polite treble response do hinder somewhat the sense clarity and refinement  of an otherwise a remarkably clean and grain-free sound.
It won't be the best at any one thing, but do all manner of things well. Tonally warm, well balanced, with some fantastic imaging, and a large, spacious soundstage. The MA900 in all honesty, shares a lot with the HD650 with some key differences, which I'll touch upon in the comparison section.Bass:The MA900's bass is actually quite impressive.
With the MDR-F1 Sony implemented a simple low-pass passive acoustic filter foam-like funnel  to enhance the bass impact (you can read about it here) and while it contributed to a rather acceptable mid-bass response the lower bass was still mostly MIA. For this reason probabley, the MA900 has gained a 40% increase in diaphragm size to a (presently) whopping category-leading 70mm (2 4/5"), With next largest AFAIK HD800's 56mm.
The MA900's warm, organic tonality is thanks mostly in part due to it's realistic voicing, and fleshed out mid section. Thankfully, the mids don't come out as shouty or over-emphasized due to the mid bass staying relatively on par with the mids, giving the MA900 a linear curve that doesn't particularly add emphasis to anything. The large, spacious soundstage places some distance between you and the vocals in the virtual space, so the MA900's mids aren't as intimate as something like the LCD2, HD650, and K702 Anniversary.
The MA900 was supposed to be an upgrade or perhaps even a replacement for the famed Sony F1. A marvelous headphone with a large cult following that has grown over the past few years. Personally, I find the MA-900 to be one of the most well rounded and useful headphones to come along in a very long time.
The Sony MDR-MA900. MA900 for short. Modeled after Sony's own F1 and SA5000, the MA900 (like the F1) stands out in that there is a huge opening between the drivers and the rear side of the pads. I can honestly say I have never seen any other headphone with such an obvious lack of seal/isolation outside of the AKG K1000.
I love a flat balanced headphone and got this after preferring the signature of the classic MDR-V6. I am using an iBasso DX-50 with these and needed phones that didn't require an amp. These are very sensitive and sound great with an portable player.The open (very open) design creates a wide soundstage and the larger drivers deliver great full range sound. Check out the extensive reviews on Head-Fi.com and you'll get all the info you need.
It is mid-bassy rather than plain-bassy, but in the context of it's design goal as described above it's is very good and I'd never describe it as an anemic response.
Answer: For open headphones, these are pretty bass heavy.I would say that they have more bass than the headphones I've listened to personally. (Grado Sr60/80/325i, AKG K271,Q701)Personally, I would consider them to have good bass response and that seems to be the shared opinion of other owners on Head-Fi.