506d: 150w to 400w - 6 Inch Power Tuned Subwoofer - DD Audio
DD Audo 6.5" 1500 Series Subwoofer
DD Audio - Six DD REDLINE 506 subs in an under the seat... | Facebook
DD Audio - Six DD REDLINE 506 Subwoofers in a Chevy... | Facebook
DD Audio 8" 600f Series Power Tuned Subwoofer
DD Audio - Many of you are familiar with the 500W, 6.5" #DD506 Subwoofer. Well, it's back as the #DD606. The name is different, but the power and reliability is the same!
606d: 250w to 500w - 6 Inch Power Tuned Subwoofer - DD Audio