[DanDan]

The lowest frequency tested should not be lower than 125 x the cubic root of (180/Volume) Hz. So there!
British Standards say that for lab testing of partitions etc. the minimum size of a rev room is 100Cubic Metres.
For Absorption testing in a Rev room the minimum size is 200 Cubic Metres.
These Semi and Reverbrant Rooms are good for tests down to 100Hz only. To work below that frequency would need much larger rooms. Most Labs won't even attempt measurements below 100. I wouldn't sweat this 'not defined' etc. My real point there is that the Maths will not be applicable because it was written for large room conditions. Even in large spaces, the mathematical predictions are rarely close to the measured reality. I am suggesting that these weakness in the Maths may be the reason why several serious attempts at software to measure EDT are not very convincing, i.e. ETF and FuzzMeasure. (Note I don't have FM3) Even Bruel and Kjaer with their twenty times the price product, take extreme care to get useful results. It is looking like John has combined various elements of classical Maths with some innovative techniques of his own, to come up with a reliable way of measuring small room decay times over a useful spectrum. In that case we really do have a breakthrough here.
DD