What 1" compression tweeter and crossover unit should I put in my cab?

[itu]

If you drive the elements with the same program (not in stereo) there's no need for the divider.

 

Hopefully both are in the same phase. It is easy to check that with a 9 V battery: if both elements move to the same direction when you connect the battery to the input, all's good. If there's a grille, put a pencil or chopstick (dull, not a sharp one) against the element and feel the direction. 

[stevie]

It looks like you've got a 120-litre box, which is twice the size you need. This will drastically reduce the power handling of the drivers. My software puts the tuning frequency at 39Hz. So, your two 300W drivers will handle about 20 watts at 40Hz. Time to get the saw out again, methinks.😀

[Bill Fitzmaurice]

Those dimensions give an approximate volume of 50L per driver with 55-60 Hz tuning, so the tuning is too high and the box is too big. A dividing shelf doesn't do anything other than to add bracing to the panels that it connects. You should have bracing, but as far as that's concerned a shelf is one of the least effective methods.

Edited 24 minutes ago by Bill Fitzmaurice