When it comes to the ?Big Boy's? of air cooling cooling there are a few names that come to mind, but one that always comes up in discussions is Noctua. There are known for their massive air coolers and their distinctive brown fans. It seems every time we review a Noctua product we are impressed and each product is designed for a specific scenario. This time we have the new NH-D15S, which is much like the NH-D15 that we reviewed about a year ago. The main difference between the two is the NH-D15S has a new offset asymmetrical design that makes more room for memory and PCI-Express card compatibility. Noctua has also removed one of the two fans so you have a center-mounted 140mm cooling fan. The fact that you don't have a fan on the front or back also helps with compatibility with memory modules. Will these changes affect performance or do we have another winner from Noctua? Read on as we take a look!