high pass filter question

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davecg321

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I am attempting to e.q the stereo out on track i am working on.

I am using cubase 5 studio eq and want to use a high pass filter to remove bottom end below 35Hz.

I seem to have a problem as when i set the high pass there (35hz) it slowly starts rolling off from around 100Hz down to 20db at 0Hz

This is obviously a problem as i am still getting some lower end coming through. Is it not ideal to have a steeper slope to completely remove anything below 35Hz???

do i need a different e.q plugin?

many thanks
 
Most plugs will have a Q option which will adjust the slope of a HP/LPF, or the width of a notch.
Have a look for that.
 
Also bear in mind that HPF filters do not just cut off at that frequency. Even a steep filter like 18dB per octave isn't going to eliminate all sound below it.
I have a 12 dB per octave filter on my desk channels cornered at 100hz and at 35 hz it's reducing about 17 dB. And consider that really radical EQ/Filter operations will create a boost at the corner frequency which in your case could make things worse

What have you got going on below 35 Hz
 
nothing below 35. but when i set the slope to start at 35 (the little dot on 0db at 35 Hz) visually it shows roll off from 100hz
 
Well it looks like with Cubase you can drag the corner frequency until you can see in the EQ graph that roll off starts at 35hZ. With the nature of an HPF being an EQ curve though if you do this, even with a steep roll off filter, you'll be getting virtually no noticeable reduction of the signal until you get way below the the threshold of human hearing and your speakers ability to produce a sound with this method, but I guess it'll look the way you want

The reason is that with an HPF at a corner frequency you want a smooth cut rather than a drastic cut that will cause a frequency boost ahead of it. So as a consequence, the roll off goes higher but there's not much gain reduction happening until you get to that corner frequency. With the nature of frequencies, occtaves and the logarithmic nature of dB this can look confusing on an EQ graphic which is why listening to your audio is more important than looking at it

If you just want to completely eliminate everything below 35hz for whatever reason, then a spectral type editor may work better for you than an EQ filter but even then you may not hear any difference because most monitor speakers can't reliably produce much below 45hz anyway, unless you have some very expensive, large monitors and some serious sub woofers
 
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No offense meant, but are you looking at the graphic, or listening? So is there an actual problem here that you can hear or a perceived problem that you can see?

I HPF most things that sit in the frequency "midrange", and I start higher than 35Hz... getting partial reduction in the frequencies above the frequency I set and more in the lower range works for me, and I heavily multi track acoustic guitars, which tend to boominess...

I'd put your frequency higher, sharpen the bandwidth a bit and see how you go.
 
thanks for all the responses, much appreciated

i have only begun reading up on e.q and in most cases it says to cut from 35 down on the entire mix. Would i really want to start the roll at 100hz? on the entire mix?

instruments i get the impression that 100hz would be ideal to cut the "mud"

oxford e.q has a much steeper roll and can totally eliminate sounds below a certain point.... but if you guys reckon that it doesn't matter because then i'll go with that :)

i have listened to the sound after putting a high pass on some of my instruments. it does tend to clean things up in my opinion and give more presence to the higher frequencies

dave
 
I have read some mix books where they suggest this HPF technique since your speakers are unlikely to be able to produce the sounds below 45hz-60hz anyway and even if they could your room will probably not be treated adequately to cope with the very low end.And you can't mix what you can't hear or hear accurately so the logic is why have it there at all taking up headroom.

on many instruments except bass sounds, much of what happens below 100 hz is rumble and not useful anyway and will just get in the way of the instruments you actually want to be making noise down there

the HPF on my desk is cornered at 100hz but the roll off starts at almost 200hz. the roll off from 100hz - 200hz is from about 1 db down to zero however which is more or less unnoticeable

If you've removed the low end from instruments in the mix that don't need it and shaped the low end on those that do, there's really no need to HPF the whole mix.
 
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davecg321 said:
i have only begun reading up on e.q and in most cases it says to cut from 35 down on the entire mix.
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Who's "it"? If there really was a rule like that, it wouldn't exist. :eek:

Every decision you make during mixing should be based on what you hear and what you want to hear. A good example of not doing this is what Armistice was touching on. Unless you recorded tracks with an obscene amount of mud in them, I'm pretty sure you don't hear a difference when you HP at 35hz. There's no hard and fast rule that says you should HP your entire mix, or even individual tracks. If you feel you need to do it, then do it. But don't feel that you SHOULD do it just because.
 
RAMI said:
...I'm pretty sure you don't hear a difference when you HP at 35hz. There's no hard and fast rule that says you should HP your entire mix, or even individual tracks. If you feel you need to do it, then do it. But don't feel that you SHOULD do it just because.
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Well I hear... or more correct would be - I feel it. I do it mainly because it frees up some extra space for making the song louder, but I also feel that there isn't any need for frequencies so low.
 
Seidy said:
Well I hear... or more correct would be - I feel it. I do it mainly because it frees up some extra space for making the song louder, but I also feel that there isn't any need for frequencies so low.
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Exactly what are you using as monitors that allow you to hear/feel sounds down to 35Hz? In most studios it takes a pretty special monitor to give much information below 50Hz and most monitors of the type you can afford for home use fizzle out much higher than that.

In the live sound market, my personal favourite subs (d&b Audiotechnik Q series) are already down by 5dB at 40Hz and are rolling off rapidly by that point--and they're subs designs for the "kick in the gut" sensation. Also, each box costs several times the price of a typical home studio setup.

If I'm going to use a HPF, I'll choose my settings by ear (using large monitors that DO go down to 50Hz) and pick the frequency and filter slope that way rather than according to any "rule".
 
Bobbsy said:
Exactly what are you using as monitors that allow you to hear/feel sounds down to 35Hz? In most studios it takes a pretty special monitor to give much information below 50Hz and most monitors of the type you can afford for home use fizzle out much higher than that.
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Genelec 8030 for upper end and mids and low end is covered with Behringer (sorry about the B- word :D) Truth B2092A. On the home page it says it runs linear down to 32hz, but really you can hear-feel below it. I don't remember exactly the results, but I did a test few years ago with signal generator to see how low does the signal dissapear. I can do a test again if you like. :eatpopcorn:
 
So just for update.
Did a quick test using SweepGen generator. Belive it or not I can still hear/feel 20Hz (come and check yourself if you don't belive me.). Now that said, the volume drops drastically under 28hz (could be my room), but it's still there.
 
davecg321 said:
I am attempting to e.q the stereo out on track i am working on.

I am using cubase 5 studio eq and want to use a high pass filter to remove bottom end below 35Hz.

I seem to have a problem as when i set the high pass there (35hz) it slowly starts rolling off from around 100Hz down to 20db at 0Hz

This is obviously a problem as i am still getting some lower end coming through. Is it not ideal to have a steeper slope to completely remove anything below 35Hz???

do i need a different e.q plugin?

many thanks
Click to expand...

If a steep filter is what your looking for, try using RubberFilter (KVR: Rubberfilter by Christian Budde - Details) which goes up to 384 dB/oct. Just watch out, having a filter this steep will most likely cause artifacts especially in the low end. What I mean when I say artifacts is this:

For example let's say you have a kick drum and you want to cut out anything below 50Hz so you set a really steep filter such as the one above^ you will start to hear a lot of ringing going on, especially in the low end. This is very bad and the steeper the filter, the worst the ringing gets, so make sure to watch out for that. Try that out and you will see what I mean. That's basically what Bristol Posse was explaining before.

I Hope this helps. :)
-Jeff


EDIT: 384 dB/oct is an EXTREMELY steep filter and is REALLY not recommended.
 
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Was going to reply to this thread, then I looked at the date.
 
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