@Superfrg: The diffusers are from Vicoustic. Similar to those from others but considerably less costly. I mounted them on artist's canvas stretcher frames and added Dynamat to the back to damp them (which would not be necessary if they were glued to the wall directly).
Link to Vicoustic
@Rojet2015: The floor is pre-finished cork planking over an underlayment, that over the concrete. The underlayment is wool with a plastic moisture barrier, supplied by the flooring manufacturer.
Link to Ebro cork