Speaker driver efficiency, series vs. parallel etc

Okay Got a quick question...

Lets say you have 90 db 1w/1m drivers...

Now they are 8 ohm as well

You are to run lets say 2 of them in series and get a 16 ohm load, will the efficiency go up? I have heard anytime you double your driver that you will go up essentially 3 db..

So is this circuit now 93 db opposed to 90 db?

Next scenario--
Lets say we use the same drivers, 90 db, 8 ohm etc..

Now we use 4 of them in one speaker config so you are talking a total of 4 in one cabinet, and 4 other for the other channel..

We wire 2 of the drivers in series getting 16 ohm and than the other pair in that cabinet for another set at 16 ohm, than of course Parallel them together to come back to the full load being 8 ohm...

What is the efficiency on this? Will it go up to like 96 db, or higher?

Just curious..