If I set up my pre-pro with all speakers on large, sub on, filter set to 60 Hz and enhanced bass on I get the following before the signal gets to the ICBM-Front L x R have full range output, sub out is low pass @ 60 Hz. So far all is OK. Now if I set the ICBM to 60 Hz for the front L x R I understand that the frequencies below 60 Hz will go to the sub out on the ICBM. The LFE dial will control how much of the sub signal comming from the pre-pro will be added to the signal derived from the front's via the ICBM. My question is this-isn't this a problem to have 2 seperate filtered signals added together in this manner? Am I to understand that they will add with such precision as to not cause any distortion?

If all speakers are set to large on your pre/pro, you shouldn't need to set any filter on the pre/pro -- the sub should only get the LFE signal. Large by definition means the pre/pro doesn't do any bass management to the speakers (so even if it offers the option of adjusting the crossover, there shouldn't be anything actually happening). I don't know what the enhanced bass is doing, so you may just have to try with and without it to see what you prefer. I'd probably start out with it off, but that's just me.

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gonk -- Saloon Links | Pre/Pro Comparison Chart | 950 Review

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.

You may want to give Outlaw a call and talk this over with Scott -- he should be able to answer all of your questions, but the Outlaws do not generally post here in the forum. I can offer some thoughts, but I may be misunderstanding some of what you're doing. Having said that...

Enhanced bass sounds like what folks around here have been calling "double bass" -- full range signal to the mains, but low freq information from the mains also sent to the sub. This does sound somewhat similar to the "L/R recombine" option on the ICBM, although that is primarily intended for use without a sub. I would tend to recommend using the enhanced bass only if you prefer the sound, but I'd start out with it disabled on the pre/pro -- the central idea behind the ICBM is shifting all bass management to it. The sub input on the ICBM is there because the ICBM needs to get the LFE signal (the separate ".1" track, independent of the five or more full-range speaker tracks). The ICBM does the rest. I don't know why there would be distortion or anything from using the enhanced bass in conjunction with the ICBM, if you chose to use it.

What pre/pro are you using? I'm wondering about the filter frequency option that appears when you have the sub on -- in some cases, a unit's setup will still have the option of setting a crossover frequency even when it is not actually used, such as when speakers are set to large. (For example, Outlaw's Model 950 has separate crossover points for the mains, center, and surrounds -- you can set these to anything you want, but if the associated speakers are set to large the crossover point is ignored.)

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gonk -- Saloon Links | Pre/Pro Comparison Chart | 950 Review