high pass filter question

[davecg321]

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

[Steenamaroo]

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.

[Bristol Posse]

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

[davecg321]

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

[Bristol Posse]

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

[GONZO-X]

not all HPF's are made equal.

[Armistice]

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.

[davecg321]

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

[Bristol Posse]

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.

[RAMI]

i have only begun reading up on e.q and in most cases it says to cut from 35 down on the entire mix.

Who's "it"? If there really was a rule like that, it wouldn't exist.

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.