2-15S cab and 1-15 cab with concert bass

[fatlizzard]

I have a 2-15S cab that I have used many times with my concert bass head, I just purchased a 1-40/C60 cab.
with the intent of using it with my "67" 200S when I get it restored. Could I use the 200S cab and 1-40/C60 cabs together with the concert head? The 200S has 2 16 ohm JBL D15S speakers wired for 8 ohms, the 1-40/C60 has an 8 ohm JBL D140, I'm sure I would have a 4 ohm load using both cabs which should be fine with the concert bass, but will all 3 speakers receive the same power as 2 are 16 ohm and the other is 8?

[JoeArthur]

will all 3 speakers receive the same power as 2 are 16 ohm and the other is 8?

No.  And you appear to already know the reason.

The 8 ohm speaker will receive 1/2 the total power.  The 2-16 ohm speakers will receive the other half - each receiving 1/4.

Used together, the cabs will be at the minimum 4 ohm impedance of the concert bass, so you could use them together.