Gonk, the "enhanced bass" gives me the following; front speakers set to large-all pass to the ICBM. Sub on with the low pass frequencies derived from the fron but not removed. This is similar to the option of "recombine" on the ICBM. With this setup I have a full range signal going to the ICBM from the front speakers and a sub output from the pre-pro also going to the ICBM. This could not be a wrong setup since the ICBM is equipted to accept this via the control for the "LFE" signal from the pre-pro as well as the bass signal derived from the fronts, center etc.Leaving the sub on via the pre-pro leaves no choice but to choose a filter frequency! If it is set to off then there will be no low frequency output from any source at all via the pre-pro, including the LFE.I wish some one from Outlaw would comment on the possible interaction of the 2 unique low pass signals and their combination/interaction inside the ICBM.