Thanks GM,
As usual,you are a golden mine!In our first attempt to measure the speakers we used a lower figure for the effective diameter(Actually 11.81 instead of 12.7).No doubt this has impacted the calculation of the TS .We will do next week a complete set of measures entering the right values and if i keep having problems with the added mass method,i will build an appropriate closed box(about 2.27 cubic feet) to end this exercise with decent data.I bought the very useful ,although difficult for an ex-economist,book of D'Appolito.I will keep you informed.