Well, this was supposed to be a full write up, but 4 tests will have to suffice. Sorry Seafish, I'll have to redo the whole thing later. One of the hurricane nuts backed out, and I'm going to have to tear apart the box to get it out.
So these are measurements of a completely empty box, a box with natural sheep skin wool, one inch thick ocf, and two inch thick egg crate ocf. The test box is about 0.99 cubic feet before driver displacement. The driver is a HAT L6SE. Nominal output was 114db at 0.125 meters. Bandwidth of test is 31.5hz-5000hz. I chose this as its really already past where a 7" midbass/midrange should be used on both ends.
I've included them all together as well as separate.
This is the empty box frequency response.
This is the sheepskin wool frequency response.
This is the 1 inch ocf frequency response.
This is the 2 inch egg crate frequency response.
Distortion plots are in the same order as above, I put them all together to make them easier to compare. Had testing gone smooth, I would have ended with a second empty box measurement just for consistency, but it didn't turn out. Notice the large uptick in 3rd order distortion around 188hz that almost hits 1% on each treated measurement. Also notice the reduction in distortion at 348hz and 700hz on each treated measurement. This corresponds with modes you'll notice in the waterfall plots.
Waterfall plots. Again, all together to make it easier to compare. Pay attention to 348hz and 700hz.