HPF EQ question - prochannel or not :/

I'm doing some EQ tweaks, and throwing a HPF on the prochannel band of a bus, cutting off at about 80hz. I open up CW Analyzer in the FX chain, and a third-party analyzer (who will remain nameless) and I am seeing movement down below 80 and even 20hz still. What am i missing here??? I want a total cut of all activity below 70-80. Is there any way to do this with eq or is the 24db/octave what gets in the way?

Thanks Danny.  I think I'm just looking for a deeper cut.  I've tried prochannel eq, using post and running the analyzer in an output bus (because an analyzer won't reflect pceq in post position changes on a track) and also plopping the analyzer into an fx bin in the prochannel. I guess I just need to look around for a filter that gets the results I want.

edit to add: I was practicing posting with my android.

The smile is all I could do... I can't type on it.

Slope is what it is all about. For instance in Studio One the filters that are on the extremes of the spectrum can be set to a whopping 48 dB/octave slope and that is steep and I mean steep.

But even for a slope of say 24 dB /octave if you set that to say even 100 Hz it means at 80 Hz you are still almost flat but at 50 Hz you are 24 dB down in level. Do you have any idea how soft a signal is that is 24 dB below the nominal level and at 25 Hz you are 48 dB down!

I would not be concerned too much about what activity you may be seeing on a spectrum analyser as it is much more important as to how it sounds. I have found from experience that actually less steep slopes can be very useful in taming an otherwise bass heavy track. Don't be in  hurry to necessarily use the steepest slope as it may end up sounding a little too thin. A more gradual slope however can often sound just right to my ears. That is what the slopes are there for.

I have found however where the steep slopes can be very helpful is in a mastering situation where sometimes you do want to take out the bass rather quickly. Danny will agree with this in that the LP64 is also very good for setting up good filter responses. Nothing to stop you either from setting up several nodes all around the same point and choosing a high Q for say 2 or 3 points and together they can make an almost brick wall slope between them. Be prepared to play around with that. You can also do that with the Sonitus too.

I don't know EQ math very well, I would definitely defer to Bitflipper or a handful of other folks that are members here for that sort of info.

I've asked Cakewalk several times to identify the filters they use but I've never gotten an answer.

I think it's really cool to learn that someone at Logic thought it would helpful for you to be able to learn about that.

From what I can gather, very few hi pass filters actually use a "Q" parameter and I have read speculations that the "Q" in Sonnitus may actually be some other parameter sitting in a box that has the "Q" label for use with the other types of filters. How ever, I did once find a vague reference to a hi pass filter, in an article some where, that did have a Q factor but I can't recall its name. I asked Cakewalk about it, but it will not answer the question... I have been told repeatedly to just listen with my ears.

Traditionally "Q" has a specific definition throughout engineering and it is applied to the width of a sinusoidal signal and describes the width of the sine wave at the RMS level, which is 3dB from the peak. It seems like a lot of dsp guis don't match the Q labels with the actual "Q". It can get really confusing because you hear descriptions like modern or vintage etc. which really just refer to the fact that it was very hard to make an analog circuit that didn't deviate from the math a bit and so the labeling on old analog gear wasn't 100% accurate. Now with digital it seems like designers mis label the Q on purpose when they are emulating the old analog gear. It's not easy to keep track of and it would be helpful to know what actual filters are being emulated.




In the mean time here is one way to look at it.

If you use Sonitus or any other EQ to set up a multi-order or multi-pole example of what ever filter it has... you can have some extra control over the slope. Many filter names are associated with multi-order math and it is simply implicit in the naming.

Take a look at this as an example:





I wish I knew more about EQ filters and the math but it requires specific study and a real good teacher.

I'm still looking for that teacher. :-) Hopefully someday I'll get there.


all the best,
mike

bapu


swamptooth,

Notice how Sonitus HPF @ 80Hz and Q=1.0 slopes differently than FabFilter-Q Low Cut @ 80Hz and Q=1.0.

If you look at the actual numbers, these aren't actually THAT different. The graph scales are the biggest difference. Notice Sonitus goes down to -18dB and FabFilter goes to -12dB? Check crossover points. FabFilter is definitely still steeper, without a doubt, but this goes to show how it's important to not rely on graphs as well! The difference is not as great as one might first assume from just a quick glance. And who says those graphs are even accurate to what's happening in the first place?!