Finally I had chance to complete my two, 365ltr 15hz sonosubs...
Ports arrived first ($62 each ColloPort-6" sourced from affordabledrivers.com.au [of course] - specifically tuned for the IXL18s at 15hz in 365ltrs). Truly beautiful to behold.
Then I got to work measuring and cutting the end caps (MDF 3x sheets from memory [check your measurements first!] of 18mm MDF sourced from Bunnings ~$100 total including lag bolts to attached the IXL18s to the enclosure and wood screws to attach the legs)
Don't try doing this (=bad!)
Next door neighbour kindly purchased a router and bits so I could borrow them! I whipped up an El cheapo jig out of some 4mm MDF
Then the sonotube arrived courtesy of neighbour's truck (~$210 sourced from Bowers & Lever). My daughter did not drive (it's illegal).
Tip - wait until the sonotube arrives before cutting endcaps - I used a dressmaker's tape to measure the endcaps and the tape was slightly out (1mm too small!). So I ended up having to cut a few more circles. Thankfully the glue I used expands (foams) to fill the gaps. Afterwards I used filler around the inside of the enclosure joints to seal any leaks.
I got to work gluing (Selleys Aquadhere from Bunnings - ~$25-$35 from memory)
Don't forget to remove the protection film before gluing in endcaps
Bottom on (IXL-18 from Affordable Drivers [naturally] - $304 including delivery)
Top on (MDF with floor vinyl stuck on with contact adhesive [Bunnings - $10 enough for vinyl for two subs. Repco for tin of adhesive - $16]). Port glued in with Araldite epoxy resin (Bunnings, ~$18 x 2 packs) and supported internally with small blocks of MDF glued between the edge of the end cap and the port (at the top near the opening).
Grill cover (Jaycar metal grills - $9 each, cut out to improve airflow, covered with speaker cloth, glued to plastic surround with contact cement adhesive) - not securely attached to endcap yet.
Splash of tyre black (it was sitting around here) at the top and bottom to blend with the black fur covering (fur sourced from Spotlight - $47 enough to cover two subs - just! Glued on with contact cement). Note, tube and endcaps were primed inside and out due to extremely humid environment here in Queensland - I want these babies to last forever!
The finished article (sorry for the blurry picture).
Closer up (note really cool fur effect top right - looks much better in real life - will try for better pictures)
Legs from Bunnings - $7 each (yes it has four, not three)
I'd post some REW response graphs but I'm at my limit for attachments - is there a way to post more photos/graphs? I haven't measured the pair anechoic but, after accounting for a huge room gain around 50hz (which I've EQed out - the acoustics are very average in the concrete bunker listening area I have here, unfortunately), they go pretty flat down to 16hz, then start to roll off slightly as they approach tuning. They sound fantastic, plenty of effortless grunt. Well worth the effort! Thank you everyone for all your help