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feature photo of 8 inch 600 Series subwoofer showing two woofers one angled back and one angled front to show all cosmetic features

608 Subwoofer Gets Mean Mother “f” Revision

August 22, 2023

The 600 Series latest revision is a mean mother “f”. In the previous “e” revision they got bigger and better; and in this latest “f” revision they receive precision engineered, thermal cooling enhancements of major significance along with some design work that is literally cutting edge. DD is pushing the already highly efficient 600 subwoofers to meet our evolving performance standards to ensure longer periods of loud, continuous play.

The DD design philosophy is to prioritize the maximization of total efficiency: converting raw power to clean sound, while managing the intense heat created by this conversion. This was central to the industry changing Free Flow Cooling System: cross drilled cooling vents through the pole piece and top plates, along with vents in the voice coil gap, plus cooling holes in the voice coil. With this revolutionary suite of performance improvements, the harder DD speakers were being played, the more air was pumping through the motor; pushing the heated byproduct away from the subwoofers most vulnerable components.

subwoofer break-in free flow animation

While many new advancements in thermal transfer technology have been integrated since the introduction of the Free Flow Cooling System, the new 600 “f” revision incorporates what may be the most meaningful overall performance improvements to DD subwoofers in a generation.

The problem:

Amplifier power driven into the voice coil creates heat.
Much of this heat is absorbed by the cylindrical pole piece inside the voice coil.
This cylindrical low carbon steel heat sink will get hotter and hotter as the subwoofer plays.

The solution:

Aluminum. While low carbon steel is a good magnetic conductor, it’s not an optimal material for heat conductivity. With 5 times the thermal conductivity as steel, an aluminum tube, inserted inside the pole vent where the voice coil sits, will extract heat from the steel pole, and transfer that heat outside of the motor by two channels through one motion. The subwoofer dust cap and cone pumps air through the pole vent where the aluminum is radiating most of the heat it has conducted and this pushes the heated air out naturally as the subwoofer plays, while forcing the thermal conductivity to retreat down the tube where it is drawn into a thick, finned aluminum heat sink on the back of the motor. In addition to the aluminum tube, the heat sink also pulls heat from the backplate. Both the heatsink and the backplate feature vents to release pressure and facilitate air flow to the lower motor cavity, promoting overall motor cooling and thermal transfer.

It should also be noted that the cast frames used on the 600 series “f” revision subwoofers are tooled with bottom sections to be twice the thickness of normal cast frames, giving them heat sink properties of their own to extract heat build up from the voice coil gap, which is transferred out through the durable aluminum basket.

When you produce a subwoofer that plays louder and goes longer, you need to consider what else must adapt to the new demands that will be placed on it.

600 series subwoofer f revision close up side view slanted right of motor coil basket and surround

More power demands more Xmax and the new 600 series “f” revisions include the necessary enhanced excursion. With the top plate thickness increasing to 12mm, the voice coil winding lengths were increased proportionally to keep more coil wire in the gap. Increased Xmax and excursion also required refinements to surround and the spider to fully utilize the new motor design.

600 series subwoofer f revision slanted top view of surround and logo

The taller surrounds are double stitched to fiberglass loaded non-pressed cones. Double layer spiders continue the DD tradition of long term durability. The thermal efficiency improving heatsinks are adorned with polished aluminum DD logos, and the new motors are wrapped in a premium branded rubber boot, adding to the coolness in a way that is measured not in Fahrenheit, but HolySheit!

The new look of the 600 series “f” revisions pulls out all the stops to deliver a product that looks every bit as good as it sounds.

8 inch 600 series subwoofer angled back showing motor basket and cone


  • Taller Stitched EROM surround
  • High-Temp 2.5″ Voice Coil
  • Multi-Layer Deep Bass High Excursion Spiders
  • Non-pressed Fiberglass Loaded Pulp Cone
  • Cast Aluminum Heat Sink
  • Back Plate Magnet Cavity Venting
  • DD Cast Aluminum Basket
  • Embossed DDesign Magnet Boot

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