Well, it's been a while since the last update, but it's finally here! I just got in a set of feet to finish off my subwoofers (for now). I was eyeing some nice satin nickel spikes, but instead opted for some much less expensive rubber feet since I was fairly certain the spikes would have absolutely no affect on the performance of the speakers. Below are the feet in their packaging.
To install the feet, I first marked the bottom of the cabinets. Instead of measuring every corner, I marked on a scrap of paper (making sure to denote the corner) as a template, and just used a screwdriver to make a divot in the cabinet after aligning the paper.
Next I drilled some pilot holes, and moved up to the full sized bit for the threaded inserts. Then I put a dab of glue on the insert and screwed them in. Finally I screwed in the feet, and I was done. I was surprised at what a difference it made in appearance. The floating look makes them look much more professional than before, and I'm very pleased.
Since I was curious to see if the feet made any difference in the frequency response of the speakers I went ahead and measured before and after. As expected, there was almost no difference in terms of the performance. However, lifting the bottom of the cabinet off the ground did help prevent some of the vibrations from carrying through into the room, which I consider an improvement.