First T-Line box build, a little help required

[Jama]

Hello all.

I am helping my brother with his first box build.

He has an MA Audio EHO154 subwoofer with the following parameters

MECHANICAL PARAMETERS •
FS = 39.25HZ • 
QMS = 5.918 • 
VAS = 46.03 = 50.65 • CMS • MMS = 324.6 g • 
RMS = 29.82 kg / s • 
P-DAY = 12:56 in • 
SD = 0:08 sq.m •
ELECTRICAL PARAMETERS •
QES = 0.579 RE = 1.3 ohms • •
Z = 1.3 ohms
BL = 21.74 Tm • • 
ELECTROMECH. PARAMETERS • 
Qts = 0.528 • 
In = 0:47% • 
1-W SPL = 89.04 Db • 
2.83 - V = 92.5 Db SPL 
ENCLOSURE RECOMMENDATIONS • • 
VENTED: 5 ft3 5 ft3 • 
ROUND: (2) 5 X ROUND 9: (2) 6 X 7 • 
SQUARE: 12 X 3 X 7 SQUARE: 15.5 X 3 X 7 • 
TUNING: 40Hz TUNING: 50 Hz

His available boot space is 36" x 18" x 17"

We are looking to make a 1/4 wavelength T-Line as per the guide here.

The resonant frequency is 39.25Hz so the length needs to be 7.1'

It is a 15" cone so the port area needs to be 175²in

He has had a rough go with SketchUp.

He has come up with a feasible design.
There are no 45 angles yet.

I was just wondering if someone with a bit more experience could take a quick look over before we go and spend out on the MDF.

On that note, is 18mm MDF suitable, with a single layer for the majority of the box and a double layer on the sub face.

The .skp and .skb are here http://www.sendspace.com/filegroup/MBMaYJ5A0NeKeD4lhn1xCQ

Any help would be greatly appreciated.

[john253a]

I find it better to measure cone area and not the surround

The mounting diameter is normally pretty to the cone size

I haven't seen the pics as I'm moble and can't bring them up

But you want the port to exit next to the sub in the same direction, or as close to it as you can

And power wise idd be looking 500rms tops