Thanks for all the suggestions. I am using the Rives CD with 1/3 octave tones calibrated for the RS Meter. I am going to check out the realtraps site. Using this, I was also able to find a wire vibrating inside the speaker at mid-range frequencies. A little Blu-tak and voila! No more vibration.
PDN - Measure test tones with the meter in dB then graph the test tones and you will determine what your response is in a given frequency range.
I took readings with and without the sub and with the subwoofer by itself. This really helped clarify what was going on (thanks Dave). I was clearly having phase cancellation. After tweaking the settings on the sub and taking readings at various settings, I was able to eliminate the dropout at 50 hz and get a fairly flat response. The exception is at 35 to 40 hz where I have about a 10 dB increase. This seems typical of many subs and may also be the room.
Would this be eliminated by stuffing more material into the sub or external bass traps.
PDN - Measure test tones with the meter in dB then graph the test tones and you will determine what your response is in a given frequency range.
I took readings with and without the sub and with the subwoofer by itself. This really helped clarify what was going on (thanks Dave). I was clearly having phase cancellation. After tweaking the settings on the sub and taking readings at various settings, I was able to eliminate the dropout at 50 hz and get a fairly flat response. The exception is at 35 to 40 hz where I have about a 10 dB increase. This seems typical of many subs and may also be the room.
Would this be eliminated by stuffing more material into the sub or external bass traps.