Question about BobBrines' FT-1600MKII (Not seen before)

[OTMOPO3OK]

Hello Everyone,
I noticed (thru forums and other diff. sites) that throughout some time period (a year?) Bob changed the design dimensions little by little. Mainly the width and depth (i've seen all possible combinations from 8x8" to 10.5x9'' ID) and also the port length. Which is understandable if he is constantly improving the design. The newest picture i've seen in his web site is 9x9".

Now the question i have is that i've modeled almost all possible combinations (Thx to Martin!) of width/depth and port lengh/radius and Bob's recommendations look far from perfect (there are big ripples in freq.resp. and the graph falls about 6dBs below 150Hz). I can model a much flatter responce with higher Fs thou. For instance i still don't understand the magic behind using such big raduis port. From the knowledge i accuired from this forum the less diameter the port the better for MLTL since it smoothes out 5th harmonic and therefore one sees less ripple on the graph of responce. Since the driver does not move alot of air at all (1mm Xmax) why use such wide port?

Also i'm not sure if he accounts for the cement tiles in his drawings or not? (How thick are those 1/4" ,3/8"?)
I also modeled a center channel for myself but i was learning by re-modeling Bob's & Martin's designs, and it got me thinking maybe i'm doing something wrong. Maybe the graph's flatness is not that important? (i also know Martin mentioned that the peaks are not as evident in real life and he's correcting it in new sheets, but by how much?)

So can someone please enlighten me because i'm obviously missing something since Bob Brines himself worked on the design for many years and everything he did is probably for a reason. I know how accurately he tries to get the flattest responce so i cannot doubt his work for a second.
Thank you very much.

[OTMOPO3OK]

Hmm, no help? .....
well for some reason i can't edit my posts anymore
Anyway i figured out the deal with depth and the HardiBacker. the actual internal dimensions of the line were 8.5x8.5 for the latests designs with 1/4" HardiBacker used on walls. Just saw it today at Lowes - pretty cool stuff.

So now i need to know how does port's radius affects the 5th harmonics and why Bob made it 3" and not smaller? Please correct me.

Another thing i saw at Lowes/HomeDepot was thick marble plates and i thought why not use them as bottoms/stands.
I see that Bob used 2 MDFs on top and bottom and did not even line them with cement board. I'm gonna use 2 sheets of wood for the top too but for the bottom i thought of avoiding wood altogether and going with marble. Will it resonate? I haven't seen anyone use it so it bothers me.

Thanks for any comments.