Summary: The NHT is an exceptionally flat subwoofer in the near-field. The closed box may help here, especially when this subwoofer's sensitivity is considered. The DSP based filters also contribute to product constancy. The performance will stay constant over time thanks to the digital limiter that prevents damage should the woofer be overdriven. The B-10d measured as flat after all my distortion tests as it did out of the box.