I wouldn’t. Any niche would restrict the sound coming from the speaker in unforeseen ways. If I were to install a subwoofer to that system, I’d place it out on the floor, even possibly on the other side of the room. 

Maybe a Sub Mini would be less intrusive?

Ciao Airgetlam, thanks for your suggestion. 

so it can not be installed from the front but from the side? is it better to be on the floor or can it be suspended?
thank you

The bass frequencies tend to be less directional, so often a subwoofer can be placed in different areas than the main speakers. For maximum effect, I’d keep it on the floor, but you could experiment with suspending it, and there are actually mounts that can be purchased that keep it off the floor. It all depends on how you think it’s sounding, not how we do. If you have an iOS device, TruePlay can help a little, but can’t ‘fix’ totally bad placement. In either case, you may need to try multiple positions in order to get the best sound from the subwoofer.