I think your misunderstanding. I don't quite understand it either but a regular EQ smears the frequencies when you shape them the way you want. The LPEQ does not do this which is why it is so CPU intensive.

I watched again. There's some cool stuff in there!
 
If you have a mono track that isn't correlated with another track, do you care much about the phase issues? I suppose you would usually prefer a post ring in an uncorrelated signal.
 
I suppose that if you record a vocal and guitar together, the tracks are correlated in so much as there is bleed in the mics.
 

I just watched it as well. I wish X3 had that analyzer in the EQ. That would be cool!

X3 does have Frequency Analyzer in the PC EQs, but it doesn't have the before and after view of the signal.

Equalizers, by nature, shift phase. However, it's rarely an issue because under normal conditions the effect is simply not audible.
 
The truth is that we cannot hear phase shift. We can only hear the side-effects of phase shift when we add two versions of the same (or very similar) signal that are not in phase with one another.
 
For example, if you record one source with two microphones, it's possible that by using different (and extreme) EQ settings for each microphone you could conceivably hear comb filtering at some frequencies. More likely, just the fact that you used two microphones is going to be a far greater concern. Presumably, the OP is singing into just one microphone.
 
So-called "linear-phase" equalizers shift phase, too. They just shift all frequencies by the same amount so they remain in sync with one another across the spectrum. It's one of the reasons linear-phase EQs are primarily used on the master bus, because the delay doesn't matter when filtering the entire mix. A linear-phase equalizer would still cause comb filtering under the conditions described above, except that it might be even more noticeable because it'd be across the board, not limited to a particular frequency range.
 
Extremely narrow notches (and boosts) can cause another problem - not related to phase shift - called ringing. This is what happens when the Q is so narrow that the filter is on the edge of being an oscillator. It's usually something to be avoided, but it applies to all equalizers, uh, equally. You can't avoid it by choosing a different EQ.

Guitarpima
I think your misunderstanding. I don't quite understand it either but a regular EQ smears the frequencies when you shape them the way you want. The LPEQ does not do this which is why it is so CPU intensive.

It is CPU intensive because it uses a less efficient process to do its work. One should take care not to confuse "less efficient" with "better". 
 
All EQ's shift phase (that's how they work). With linear phase EQ's, the phase shift is such that the time delay is the same at all frequencies. 

Just to clear something up; Sonar's PDC takes care of the LP EQ if you put in on a track, so you really shouldn't get phase issues by using it on a regular audio track instead of the master bus.

bitflipper
 
Extremely narrow notches (and boosts) can cause another problem - not related to phase shift - called ringing. This is what happens when the Q is so narrow that the filter is on the edge of being an oscillator. It's usually something to be avoided, but it applies to all equalizers, uh, equally. You can't avoid it by choosing a different EQ.

Oh no................ALL I use is narrow (20+ Q) notches to get rid of the nasties...anywhere between 3-10db...thought that's what I was "supposed to" do.  I could be creating MORE problems while attempting to fix others????  Lord.......

That's why I suggested treating the problem at the source, acoustically. It'll preclude the need for extreme corrections later.

Even though I used to fall victim to the temptation to use EQ to try and fix general crappiness, I've learned the hard way (by having stuff rejected by pros) to keep things simple and honest.  I have some truly great performances I have recorded and have totally and irretrievably (!!) ruined with EQ.  If you are having to apply a lot of EQ to various things, I suggest you deeply ponder the "Why".  Bitflipper suggests it may be your room; download REW5 and buy a reference mic and see what you are dealing with.  A hundred bucks worth of Roxul stuck about in frames can make a world of difference.  The objective of recording is to capture a great sound, not create a modified sound that sorta sounds sorta ok sorta.