Bass Routing is another new feature in SPEC 4.4.
Here some info on what that is and how it is different than "Bass Management" in an HT:
This is what your HT should do (if you have a satellite/sub system):
It does two things:
1) It has a highpass filter (one half of the crossover) between the 5.0 channels and your satellites.
2) It sums the 5.0 channels with the LFE (LFE at +10db to make the LFE the same volume as the 5 other channels added together) and sends it through a lowpass filter (the other half of the crossover) on to your subwoofer.
ArcTan and SLICE are 5.0. They don't do anything with LFE. LFE happens in the Time Domain, connected between SPECs LI RI ins and the LFE out.
Now, inside ArcTan and SLICE, we are doing something sort of like bass management, except instead of routing the stuff from the low pass filter to the sub or LFE we route it to some of the other speakers.
Bass routing settings (spectral domain):
5.0 No bass routing
4.0 The frequencies below the XOver point is removed from the center channel and half of it (volume wise) is added to LF and half to RF.
3.0 The frequencies below the XOver point are removed from LS and added to LF, and from RS and added to RF. No change to C.
2.0 The frequencies below the XOver point are removed from all channels. The frequencies below the XOver from LI and RI are added to LF and RF respectively.
1.0 The frequencies below the XOver point are removed from LS, RS, LF, and RF, and added to C.
Now if the bass routing XOver freq is set less than or equal to the crossover freq. of your bass management rig bass routing won't do anything because you bass management will be putting everything in you subwoofer at that point.
The idea of bass routing is that if sounds below 200 hz don't add directionality (i.e. separation) then let's not send them to the 5.0 speakers at all. This idea came from a "dolby of video" post, where thy removed signals that didn't have "depth" information.
Another part of the theory is that if we take all that sound that doesn't add to directionality, and put it in the subwoofer, we have less chance of cancellation in the room and should end up with tighter bass.
So, why not just raise your bass management crossover point to 200 Hz? Well I guess you could, but a) your subwoofer may not be designed for that b) if your satellites can produce lower freq. than 200 Hz my guess is that for stereo, movies, etc. you're going to want a lower crossover point. Somewhere between 80 and 120 Hz.
So this Spectral Bass Routing is really only has a working range between 200 Hz and your HT Bass Management Crossover freq.
Hmm, maybe I should add a control that cuts out the highs, so you can hear only the low freq. stuff so you know what you are routing and it be easier to tell if it's going to help with separation or not?
Anyway, let's come back to LFE. The LFE in SPEC 4.2 and above is as you know three filters, connected in series between the sum of the LI RI inputs and the LFE output of SPEC. Lowpass filter, peaking or bandpass filter, and highpass or subsonic filter. If you use LFE in SPEC that signal gets passed along to your bass management in your HT and sent on to the sub as described above.