New guy, Odd shapes

So, what with a number of elements out of my way (stupid work), I am about to re-enter/ re-build my listening lab and start again with this project.
Before I begin, though I wonder if y'all might have some advice...
Months ago I ran a number of tests (using REW) with different drivers trying to optimise the various elements like Vb, port volume and XO values... My results, however were discouraging. Not that they sounded bad... but they sounded the same... Drastic changes in volume and port size, even sealing the port, produced what appear to be negligible changes in the response curve.:dontknow:

I'm running an ecm8000 on a Art USB preamp, via my MacBook. Doing nearfield measurements at 1m.

Now, I have yet to get deep enough into the software to know if there were any results of note in things like phase response, or the like, and subjective listening is still a ways off, but I was wondering if there is something I'm missing. Halving the volume of the box makes no real difference, doubling the port length has about the same effect as blocking the port. What gives?

I know I'm short on some details here, and I'll add graphs once the lab is restored, but if anybody can see through this haze and suggest whatever it is I might be missing, It should save me a bunch of time in this test phase.

Thanks in advance.
[ ]