SSD Series: Available options and what they do: Flatwound coil (+$20) – The flatwire coil option simply helps the power handling of the sub. The coil has more surface area to dissipate heat and will take more power then the regular round wire coil that comes in the ‘stock’ version of the sub. This option will also make the sub tend to be more prone to ‘peaking’ for a budget daily driving sub where you don’t have to use a ton of power to get maximum output and sacrifice sound quality a little bi