I finally had a chance over the weekend to do some semi-serious measurements of the sub I built. I connected my multimeter and set the drive level at 3.02 volts @ 60hz. I wanted to get close to the 2.86 that is normally used. I could have fiddled with the sub amp and set it even closer but this should give you a good reference. This first set of measurements is with the SPL meter laying on the floor one meter from the edge of the cone. My 281s were also on, so you will see the hand off at 80Hz via the internal bass management of the receiver. I suspect I have some phase cancellation and will try reversing the input on the sub in the near future to see if things improve. I only have 180 degree options not variable phase. FrequencyCorrected Reading 18Hz.104.29 19Hz.105.35 20Hz.104.50 21Hz.102.92 22Hz.102.38 23Hz.102.88 24Hz.102.42 25Hz.103.00 26Hz.104.62 27Hz.104.27 28Hz.102.95 29Hz.101.65 30Hz.101.38 31Hz.101.12 31.5Hz.101.00 32Hz.100.97 33Hz.100.91 34Hz.101.84 35Hz.101.78 36Hz.102.72 37Hz.102.67 38Hz.102.11 39Hz.101.55 40Hz.101.50 41Hz.102.26 42Hz.103.18 43Hz.103.09 44Hz.102.99 45Hz.103.90 46Hz.103.81 47Hz.103.73 48Hz.103.66 49Hz.103.58 50Hz.103.50 51Hz.103.50 52Hz.104.00 53Hz.104.50 54Hz.104.00 55Hz.104.50 56Hz.104.50 57Hz.104.00 58Hz.104.00 59Hz.104.00 60Hz.104.00 61Hz.104.00 62Hz.103.50 63Hz.103.50 63Hz.103.50 64Hz.103.00 65Hz.102.50 66Hz.102.50 67Hz.101.50 68Hz.101.50 69Hz.101.00 70Hz.100.50 71Hz.100.50 72Hz.100.50 73Hz.100.00 74Hz.100.00 75Hz.100.00 76Hz.100.00 77Hz.99.50 78Hz.99.00 79Hz.98.50 80Hz.98.50 81Hz.98.52 82Hz.98.54 83Hz.98.57 84Hz.98.59 85Hz.98.61 86Hz.99.14 87Hz.99.66 88Hz.99.68 89Hz.99.71 90Hz.99.73 91Hz.100.26 92Hz.100.78 93Hz.100.81 94Hz.100.33 95Hz.100.36 96Hz.99.89 97Hz.99.92 98Hz.99.94 99Hz.99.97 100Hz.99.50 And here is the results at the listening position with a slightly higher drive output. Even this was indicated at less than 2 watts using the level meters on my amp. Also, my room is about 8000 cubic feet. This listening position is 15-16 feet from the sub/corner. FrequencyCorrected Reading 18Hz.83.29 19Hz.84.35 20Hz.84.50 21Hz.85.92 22Hz.84.88 23Hz.83.88 24Hz.84.42 25Hz.85.00 26Hz.85.62 27Hz.85.27 28Hz.85.45 29Hz.84.65 30Hz.83.38 31Hz.82.12 31.5Hz.82.00 32Hz.80.97 33Hz.78.91 34Hz.77.84 35Hz.78.78 36Hz.79.72 37Hz.80.67 38Hz.79.61 39Hz.79.55 40Hz.78.50 41Hz.78.26 42Hz.79.18 43Hz.79.09 44Hz.79.99 45Hz.80.90 46Hz.82.31 47Hz.82.73 48Hz.82.66 49Hz.83.08 50Hz.83.00 51Hz.83.50 52Hz.83.50 53Hz.84.00 54Hz.85.00 55Hz.85.50 56Hz.85.50 57Hz.86.00 58Hz.86.50 59Hz.86.50 60Hz.87.50 61Hz.86.50 62Hz.86.50 63Hz.87.50 63Hz.87.50 64Hz.87.50 65Hz.87.50 66Hz.87.50 67Hz.87.50 68Hz.87.50 69Hz.87.50 70Hz.86.50 71Hz.85.50 72Hz.84.50 73Hz.83.50 74Hz.82.50 75Hz.81.50 76Hz.81.00 77Hz.80.50 78Hz.80.00 79Hz.79.50 80Hz.78.50 81Hz.78.52 82Hz.77.54 83Hz.77.57 84Hz.77.59 85Hz.77.61 86Hz.77.64 87Hz.77.66 88Hz.77.68 89Hz.78.71 90Hz.79.73 91Hz.80.76 92Hz.81.78 93Hz.81.81 94Hz.81.83 95Hz.81.86 96Hz.80.89 97Hz.79.92 98Hz.78.94 99Hz.76.97 100Hz.74.50 I seem to have a very broad hump from about 41 to 80 hz and another spike down low. Phase experiments may cure part of it. Otherwise a BFD will take care of everything. I am very satisfied overall. I don't think I could have purchased a completed sub for anywhere near my investment on this.