usuly when you build with 2x4's you "crown" them so the inevitable bow's all go in the same direction to avoid some wobbly walls and crown them up os roof joists to keep the sag out. In this case you would want the crowns to alternate for rigidity.
But I have built butcher blocks out of pine and I tell you, there is no way they would ever leak. With access to a planer if you build them long sides touching, a jointer if they are joined short side, but this wouldn't be as strong.
The prep work wouldn't be too long and it would look like a big bassy fucking counter top, I want to do it now!
How I would do it;
Plane the long sides, all of them before you get joining them like when you build a table. Join them in sections small enough to go into the planer so you can plane the sections before you join them for aesthetic reasons. Dowels and large clamps with a good amount of glue would prevent them from leaking if done right provided you use a good glue like Tightbond II. All you would need is a big ass blade to cut the holes for the subs. This would be a tank of a sub enclosure!