Catalyzes the oxidation of 3-hydroxyadipyl-CoA to yield 3-oxoadipyl-CoA. (3S)-3-hydroxyadipyl-CoA + NAD(+) = 3-oxoadipyl-CoA + H(+) + NADH Aromatic compound metabolism; phenylacetate degradation. Homotrimer. Activated by cAMP receptor protein (CRP), integration host factor (IHF) and by phenylacetyl-coenzyme A (PA-CoA) that prevents PaaX from binding its target sequences. Inhibited by PaaX. Mutants accumulate 3-hydroxyadipate and are unable to use phenylacetate as a carbon source. Belongs to the 3-hydroxyacyl-CoA dehydrogenase family.