"no coffee yet, so here's my fav lately.....Keith Miller 2:1 bandpass, 166.5dB"
after you have your coffee, sharpen up your pencil and you'll see that what this shows and what electrodynamic is referring to is the significant effect of the third term in the pressure equation for a subwoofer inside of a sealed enclosure (car).
-20log(v) means that each time that you reduce the enclosure volume by half, spl will increase by 6db, which is the same effect as doubling the xmax of each driver or doubling the number of drivers or using four times the power.
the video also shows quite a bit of flex in the structure of the vehicle, so he is losing spl there.
sadly, popalocks room is larger than a car, which is why so many woofers are required. i don't know the exact dimensions, but at 8'x12'x20', total volume would be ~54k liters. using the linkwitz equation, and assuming sufficient power, spl below 23hz will be around 133db, less room losses of course.
the same could be predicted using winisd taking a 12db/oct gain from the long dimension 1/2 wavelength down.Edited by LTD02 - 3/14/13 at 2:08am