Prefiltering, or limiting the passband of a received signal, can be used to improve ordinary correlation threshold detector performance for an unknown source model. For the known source model, the cross‐correlation detector is equivalent to matched filtering, and intrinsically contains prefiltering. Prefiltering also improves higher‐order correlation threshold detector performance, but often with more advantage than seen in the ordinary correlation detector. This is true for both the unknown and known source models. Geometric interpretations are given to provide insight into the origin of potential higher‐order advantage. Eight energy signals, each with three different Fourier magnitude‐based filters, are used to test the cross‐correlation, bicorrelation, and tricorrelation detectors by Monte Carlo simulation and hypothesis testing. Significant signal‐to‐noise ratio (SNR) gains are evident for both the known and unknown source models with the tricorrelation exhibiting the largest gains. The tricorrelation...