Well maybe not free but attaching free range egg boxes to the sides of the walls up front has made a little difference with some frequencies. At the moment this is only an experiment. Given the shape and surface it sees to help with some directional high frequencies.
So with a little saving of the good ole egg box from each purchase seems to work ok, it may not look appealing but with a little Blu tack stuck to the front of the egg box and stuck to walls surface what harm can it curse.
I'll be trying out kitchen roles next to see what I can solve on the affordable means that is.