There is surprising variety in spiraeas. There is plant in one of my flower beds (which I would like to be rid of, 'cos it is a bit invasive, but would require me to dig up the whole bed to get rid of the roots - I successfully got rid of it in another part of the garden that way) which sends up individual canes (raspberry fashion) each topped mid-summer with a single pink pyramidal feather-duster of a group of flowers, and spreads underground (raspberry fashion). Took me several years to work out it is a spiraea, this one http://en.wikipedia.org/wiki/Spiraea_douglasii I think.

Yes, S nipponica has white tennis-ball groups of flowers on long bending stems. But the one you have photographed is rather disappointingly thinly covered in flowers in comparison to the ones I've seen. But there are also loads of hybrids which probably makes positive identification difficult in some of these cases.