The Noctua NH-D15 G2 LBC Cooler Review: Notoriously Big, Incredibly Good

Testing Results, Maximum Fan Speed

Starting things off, let's take a look at the NH-D15 G2 LBC performance with the fans at their full speed (12 V). The speed on our charts is the one of the slightly faster fan, with the secondary fan running at about 50 RPM less.

When the fans of the Noctua NH-D15 G2 run at maximum speed, the cooler shows outstanding performance, with an average thermal resistance of just 0.0849 °C/W. This makes it slightly better than the original NH-D15 and grants it the lowest thermal resistance of any air cooler we've tested to date. Impressively, its thermal resistance is comparable to that of many dual-fan liquid coolers. There are a few other implementations that do get very close in terms of raw thermal performance but their noise output is measurably higher.

Noctua's fan speed offset tweak also seems effective, as the noise output of the NH-D15 G2 is meaningfully  reduced compared to the first generation. This reduction occurs despite minimal differences in fan technology or speed between the two versions, suggesting that the tweak has shifted some of the cooler's noise to the lower frequency, less perceptible parts of the audio spectrum (as interpreted by A-weighting). Alternatively, it may be a sign that Noctua has reduced the number and/or magnitude of sound waves reflecting through the cooler.

Testing Results, Low Fan Speed

Using a PWM voltage regulator, we reduced the speed of the fans manually down to 950 RPM for the primary fan and 900 RPM for the second fan.

When its fans are running at 950 RPM, the Noctua NH-D15 G2's thermal performance sees a slight decline compared to the first-generation NH-D15, with an average thermal resistance of 0.115 °C/W. Despite this minor dip in cooling efficiency, the NH-D15 G2 still delivers exceptional thermal performance, rivaling many top-tier air coolers.

The slight reduction is offset by a significant drop in noise output, producing only 33.3 dB(A) and making it quieter than its predecessor. The NH-D15 G2 is also quieter than any other dual-tower air cooler that can even come close to it in terms of thermal performance, with only Be Quiet!’s Dark Rock Elite holding its ground against it.

Thermal Resistance VS Sound Pressure Level

During our thermal resistance vs. sound pressure level test, we maintain a steady 100W thermal load and assess the overall performance of the coolers by taking multiple temperature and sound pressure level readings within the operating range of the stock cooling fans. The result is a graph that depicts the absolute thermal resistance of the cooler in comparison to the noise generated. For both the sound pressure level and absolute thermal resistance readings, lower figures are better.

This chart reveals where the Noctua NH-D15 G2 stands when thermal performance is directly tied to noise output, with the cooler clearly leading the chart. It also reveals that the new version is significantly upgraded over the now aged NH-D15 – the NH-D15 does provide similar thermal performance when the fan speeds are low but the performance of the NH-D15 G2 significantly improves when the fan speeds increase. Albeit the differences are not major, no other air cooler manages to cross their lines with Noctua’s NH-D15 G2. Those that do reach the same figures of thermal resistance, they do so at significantly higher sound pressure levels.