[Ricci]

That's a lot of port. GL! I think that a slot vent may be easier. Actually how are your fabrication skills? You could try to use the power port design on it, to cut the vent length down.

 

[Ricci]

To give you an idea of what you'd have to build with a power port design here's a few pics from my 18" RE XXX design. What you have is a big port and imagine a rod going straight through the center all of the way to both ends of the port where it will meet up with 2 inverted flares (cones, think of a funnel) one on each end. the ports will also be heavily flared to match the curvature of the flow guides(cones), so that there is a constant distance all of the way through. There would be a lot more work involved with this and making the cones is the difficult part, but I have the calculator spread sheet for designing these if you are interested. You mentioned having a base with legs on your box and you need extremely long ports. This design cut me from needing a 63" port down to about 36.5" with the same tune.

 

[Ricci]

I looked at what you've got going on and you could get a 6" based power port to about a 41.5" straight length. You'd need a 2" center flow guide, 8" diameter flow cones and 2 " baffle spacings, with 1.25" roundovers on each end of the port. You'd still have to bend the port in the enclosure though.

You've got PM.

 

[Ricci]

Ricci... I have to ask, hows that XXX18 sound?

Deep...like the ocean . It's crazy when you feel the floor ripple and you get shoved by the pressure wave but it isn't accompanied by easily discernible sound because it's so low. :T Like when something heavy is dropped or set down and you feel the ground shake. It can actually pull off a pretty convincing reproduction of stuff like that. It also sounds very nice with music as well.
It's 25ft net, tuned to 11hz with a 10" based power port design. The power is from a bridged Crown CE4000. I use the 8hz DC filter in the amp for my highpass:whistling:. The full build log is here at the Shack.

http://www.hometheatershack.com/forums/funky-waves/10524-custom-re-xxx-subwoofer-build.html

 

[Ricci]

I have a question for the inputs for the AVR to the EP2500. What do I use! Do I wire up a TS/TSR 1/4" plug to a MONO-RCA and hook that up to the subwoofer pre-amp out on the Onkyo 805?

That should work, or you can even wire up an XLR to RCA cable. You can buy cables like this at various places also. I'm not sure about mounting the amp in the box. I don't see why it wouldn't work but it seems like a lot of work with adding extra fans and all.

Make sure to get some pics during the build and keep us updated. BTW you are going to need a SSF to protect the driver from over excursion below tune.