@lewm , transmission lines are arguably the hardest type of enclosure to design. Yes, you can effectively double the size/efficiency of the driver at some frequencies. The problem is that the front and rear waves are only exactly in phase at certain frequencies. Then there is the problem of the construct. The enclosure is composed of a number of dividers and pathways. It becomes much harder to control all the panel resonances that develop and to make sure every panel is locked down solid. Subwoofers, by nature shake the hell out of everything. It is what they do for a living. I lean towards small enclosures because it is much easier to make them stiff and solid (the soap bubble rule). The lower efficiency is now easily covered by the powerful amps we have and amplitude errors can be corrected in room digitally. Setting them up as a line array and placing them directly against a wall then minimizes room interaction.
@rauliruegas , Is less distortion in the woofer's frequency range going to make the rest of the loudspeaker sound better? Since the loudspeaker as a whole will sound better I suppose you could say that is true. It will in no any way effect the actual performance of the higher frequency drivers.
Raul, do you live in a bomb shelter? Put on a 20 Hz test tone, crank it to 90 dB and I absolutely guarantee you that your house will become a symphony of rattles.
When are the final versions of the subwoofers going to be ready? About two months after my wife stops handing me stuff to do. The prototype has been made and it works as advertised but it is nothing special to look at. It is used more or less to develop construction methods and procedures that will work and minimize waste.
