Howdy!
Just wondering how yall go about removing inaudible frequencies from your tracks in Renoise? Unless I am using them wrong, the standard filters don’t seem to be able to remove freq below 20 and above 20k with pin point precision all that well?
Or I am doing it wrong! 
Advice, tips, freeware effects and tools that might help are welcome!
I’m sure somebody is going to come along with a more technical and in depth answer for you… but till then… The filter cutoff is where you begin to filter out the frequencies, based on the type of filter you are using… so, if you are using a HP Filter, and you have your cuttoff at 5500 htz, than freqeuncies below 5500 are going to be filtered.
Hi-pass filters low, low pass filters highs…
but than, you are dealing with a slope… the only thing, “pin point,” is where your cutoff is… you wont get a vertical slope! ( That somebody else can explain, as that is way beyond my technical knowledge of signal processing. )
As far as mixing music goes… I know how to do that, and you don’t need to worry about removing all the frequencies above and below 20 and 20k. If you are having something put on a vinyl record, you might put a lp filter around 15,000 htz… and a mastering engineer might put a hp filter around 27 or so… but um… with digital and mp3, and making tracks in the home studio… I wouldn’t even worry about this stuff.
Also, I think you can type in the values, it’s just that Renoise won’t show them any more precisely than 0.02 KHz for instance. So set it to 0.02 KHz with the mouse, then double click on the field where it says 0.02 KHz and type in ‘0.015’ and press Enter. Now see if you hear any difference (probably not because it’s not in most human ears’ spectrum).
I think this works in every value-field so it’s just a difference between how precise you are willing to type it in and how precise will eventually be on display (it’s not always that the same exact value is used you see?)
One other method of getting more precision than the 100 pixels the mouse usually offers (the number of a hundred is totally unprovable it just fell out of the sky so I took it) - is connecting a Hydra to a certain parameter. So add a Hydra in the chain, before connecting it to the Filter’s Cutoff param, you set the ‘Out1 Max’ to 5% instead of 100%. Now select Current Track/Filter/Cutoff and swipe away a little bit with the Hydra. It’s fun really! And one of the reasons why Hydra is so useful.
The maximum slope in the Renoise filter is 48dB, also known as the “Butterworth 8n” mode, so a good choice if you want to completely cut of those low frequencies.
Here is some more in-depth info from dblue about those filters: A Quick Analysis Of Renoise Filter3 Modes
Awesome info, thanks guys 
This is an awesome question to ask and his something that has been in the back of my mind for quite some time. Thanks for the useful info guys!