Por favor, please expand. Thought that the M19 box ('bout 9.4 ft3 I think) was still a little shy on volume for lowest bass extension and flat(ter)bass. Don't know that, just my thinking based upon unverified TS specs. A smaller box was used in the 846 but tuned way differently. May try to build some boxes some day and the difference between 6-7.0 and 9.4 ft3 is significant in my environment.
David F