I read a thread here recently about speaker alignment and the pros' and cons' of stands v floormounts v shelf standing v hanging, in which Marco (I think, forgive me if I'm wrong) suggested that tilting speakers up slightly at the front could improve things. I have been frustrated by what I can only presume has been a standing wave effect in that the bass response is much better off-axis than if I sit in the centre between the two stand-mounted Wharfdale Diamond 9.1's. So, I angled the front of the speakers slightly upwards by placing a small wooden block about 25mm high (1 inch in old money) just under the front of the cabinets. See photo.

The result is astonishing. All of the "missing" low down bass is now there. I'm still chuckling.