Why the Alfonso-class cruisers used gun shields

Why did the Alfonso-class cruisers use twin six-inch shielded mounts instead of turrets?

The shields saved weight and concentrated useful splinter protection toward the enemy instead of enclosing the crew in a very thin turret.

The Spanish Alfonso-class light cruisers mounted twin six-inch guns behind shields rather than inside conventional turrets. The arrangement saved weight. A stronger frontal shield could face the enemy, whereas a very lightly armored enclosure might admit or deflect fragments around the crew compartment. The choice resembles destroyer gun-house practice and trades all-round protection for economy and useful protection on the expected bearing of fire.