I started collecting data for stringbed density. I was curious about this because I had discovered recently that my O3 Red seems to have a ridiculously open pattern, requiring very high tensions if I want to volley decently.
I used the distance between the 8 center mains (call it "ESDV"), because I discovered that the 12-string distance could be misleading (for example, the Diablo mid is dense in the center and plays with a lot of control, but it's not very dense beyond the 8 center mains.
To take measurements on few models of interest for comparison, I simply pulled up the "Plan View" of a racquet model on the TW site, and measured the ESDV in cm with a ruler on my computer screen, then also measured the length in cm on the screen. I then used the specified length to scale the result into an ESDV in mm. I also included a column for "Stringbed Control Factor", which is simply 100000/[(ESDV)^2], since the square of the linear density should give a better indicator of relative stringbed control. So ignore the columns with cm units - the last 2 columns are the important ones to compare.
Here is the data I've collected so far. One interesting thing - TW fudges their Plan View photos by photoshopping the stringbed most of the time. I've updated the table since my original post to include only racquets where I could measure the actual stringbed photo.
Edit: After further review, I've come to the conclusion that measuring only the mains spacing is insufficient to define string spacing.
I came home and measured my ESDV on my Diablo Tour mid (great control on volleys) and my RDS001mp (relatively ball-spraying feel on volleys). They both had ESDV of 78mm.
Then I compared the distance between the 8 center crosses: Diablo was 79mm, and RDS was 88mm. I think this might account for the more control feel.
So given this finding, I think a measure of the product of the distances between 8 center mains and 8 center crosses might be a good reference number.