TranceAddict Forums (www.tranceaddict.com/forums)
- Production Studio
-- Low/High Cut Filter Question

Low/High Cut Filter Question

Why do filters roll off at a certain DB/Octave instead of cutting out every frequency below/above the specified level completely? The exception to this was on an Andy Vax mixing video I recently came across. I can't remember the name of the filters he used, but the slope was almost straight up and down (an extremely high DB/Octave). If you want to cut ALL frequencies below a specified value shouldn't it let you? Or does this have some kind of nasty effect?

Actually this interests me as well. I would like a filter than cuts to 0db straight away.

He was using the Cambridge EQ plugin that can be purchased if you have a UAD-1 card. This EQ has an Eliptical 6 filter, which does like a 96db/oct cut which is almost straight down.

To be honest, I really dont like this extreme type of a cut. It can be good for a surgical EQ type of situation, but it doesn't sound nearly as "musical" as a 12 or 24db/oct cut. Your ears are not attuned to such extreme cuts and it really adds quite an "unpleasant" quality to the sound. I'd stick with the less-steep cuts.

Take a look at circuit diagram for a high-pass filter and you will see that it involves a capacitor inline with the input and a resistor in parallel to a speaker. Since the current alternates rapidly the capacitor sees changes in the potential difference. Capacitors have a charge/discharge rate and are therefore subject to the rate-of-change of the applied signal. The values of the resistor and capacitor determine where the cutoff is. That's a first order filter, and puts the output 90* out of phase of the input. (that's a slope as well)

In terms of software, the steeper the slope, the more calculations, the more processor taken up.

Waves has a low cut filter that is pretty steep.

Thats a very good answer. The other thing is that the steeper the roll off rate of a filter, the more artifacting you will get. Many instruments will not sound natural when you roll off audible parts of the signal with a 36dB/Octave LP filter and they would sound flat out fucked if the cutoff was instantaneous.

If you are rolling off a range which is almost wholley inaudible or imperceptible then you should probably ask yourself why are you doing it if you can't hear it anyway?

There are about 15 filter types on the Cambridge, you have to be weary of using severe slopes though, can sound too unnatural

A very nice eq none the less

any other filters that are like that?

What I do (that helps a little) is run two filters. For example I'll put on a high pass filter and then also cut out the low end on the EQ. So that way there's two different effects working together....I hope.

Cambridge is a very nice eq.. wish I had it.

google RubberFilter. 384dB butterworth filters.

it comes down to math. WIthout a supercomputer , you ain't getting a complete brickwall filter. Besides , why on earth would you want one. As far as the nasty effect ? ya it soudns like shit.

I want a notch filter that has an incredibly steep slope. A? Forget A! There'll be no 440hz in MY beats! 439 and 441 can stay, but 440 is OUT!

Wave Arts TrackPlug has brickwall filters.

Thanks for the topic, was an interesting read.
I may save this info into a word document .

Kopi =o.

quote:

Originally posted by strathos Wave Arts TrackPlug has brickwall filters.

no it doesn't

quote:

Originally posted by RichieV no it doesn't

According to that link he posted, it does. Both high pass and low pass cut 60db per octave, again, according to the reviewing website.

Powered by: vBulletin
Copyright © 2000-2021, Jelsoft Enterprises Ltd.