The completely redesigned Redline 500 series subwoofers have many things that make them better than their predecessors. The redesigned frames and suspension geometry allow for a lower Fs value as well as a larger trajectory. These two things will give you MORE LOW BASS.
The redesigned voice coils have higher heat resistance, reduced inductance and better efficiency. These things give you more balanced playback, more sound on the same amplifier, and more power endurance.
Previously, the red double stitching characteristic of DD Redline no longer exists, it is replaced by a red stripe or redline at the junction of the cone and the thermally cast multilayer top suspension. The dust cup logo is made of a reflective metal foil. All cones and dust cups have a matte black finish. The frames have DD logos either stamped or cast.
Triple voice coil ventilation, wires braided into double under-suspension, laminated under-suspensions, and extended pole pieces that have always made DD subwoofers work so well can still be found in new models. The cone is a mixture of fiberglass and paper fiber and coated with a moisture-resistant coating. This creates a light and strong cone that withstands the conditions of the car very well.