Hi Three
Yes you are correct it is very heavy 18mm birch ply this was made by Sai chorley they built mainly band equipment 4x12s etc but when disco took off they had a go at that as well top quailty gear without a doubt.still use mine.
plus amp heads bass ,bass/treble
But this is different because its orange and everything else they did was black or dark grey but all their cabinets were ply and heavy and sound fantastic and very punchy, for a 200w cab this rattles things.
And the pictures are of my 4 Sai ported bins which are 1000w RMS each
regards John