Need tips: How to split a signal in different bands correctly

Erkan

mr-walker.bandcamp
Jun 16, 2008
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Uppsala, Sweden
mr-walker.bandcamp.com
Hey!

Today while I was at work, I started thinking about a way to make a kick drum tighter. After some thinking, I arrived at the conclusion that a lot of the tightness in a kick drum is determined by the length of the bass frequencies in the kick drum itself, or perhaps known as "sustain". So what I thought I needed to do to gain full freedom over the bass frequencies was to split kick signal into 2 tracks where one track would contain the bass ( 0-100 hz or so) and the second track would contain everything else, so that I could then mix the tracks back together once I was done processing the bass freqs.

So why do I need to split the signal? Well, I thought about using a transient designer like Dominion to simply pull the sustain down, and maybe increase a little attack while I'm at it.. whatever works. Maybe you could achieve a little of this effect with a multiband compressor but I always find a real transient designer to work much better and Dominion is pure love for drums. Since Dominion doesn't let you select what frequencies to process, I would have to make my own "crossover" so Dominion can process that part of the signal.

The question then is... how do make a proper crossover? I can't imagine it being as easy as just slapping a hi-pass on the bass track and a lo-pass at the "everything else" track and expect it to sound good. There surely must be a ton of things to take into account when doing this? Hence, why I'm asking... just want a way to control what goes into Dominion and not (and to make sure it still sounds good and correct/no phase issues when the signal is combined again) :)
 
Instead of relying on one mic to capture a great low end and a great attack, pick two mics that are better suited to each range and then blend to taste. The SM91 is hard to beat for the attack, and then a Beta 52, Yamaha Subkick, Audix D6, etc. will work well for the low end.
 
Instead of relying on one mic to capture a great low end and a great attack, pick two mics that are better suited to each range and then blend to taste. The SM91 is hard to beat for the attack, and then a Beta 52, Yamaha Subkick, Audix D6, etc. will work well for the low end.

Yes well, that is true of course but for someone like me who only has 8 channels to record through (still waiting for the Profire 2626), and who doesn't have a wide selection of mics, it's kind of hard. I've got a pretty cheap drum mic kit and an SM57 and SM58 and that's about it.

I can absolutely not get a good kick drum sound out of the kick mic I currently have so I rely quite heavily on blending in samples. So I still need to split the signal and process the low end for tightness, since it's mostly samples I'm using on the kick.

I wonder how certain plugins succeed in splitting the signal, like multiband compressors etc. It's gotta be reproducible "manually" or so to speak by a combination of filters..
 
simply by doubling the track, and putting some HP/LP at the same frequency ? You put a LP at 100Hz for the low track, and an HP at 100Hz for the HP. Because of the 3dB loss at 100Hz of these tracks, the addition of these two tracks is mathematically the original track, and you're done.
 
Interesting stuff, Erkan. As you probably know EQs can't get that accurate, at least the digital ones. What I thought about is using something that would help you solo certain bands, just like multibands do. So, for example, you duplicate the track, put a multiband comp on each with the same settings (crossovers!), and solo the low end in one and the other stuff in the other track :p Make sure the multiband isn't 'working', except for the 'solo' part, and work on with dominion that way.

I obviously don't know the technical aspects of how digital plugs work, dsp is like latin to me so I'm not sure if what I mentioned up there is the best solution.
 
Interesting stuff, Erkan. As you probably know EQs can't get that accurate, at least the digital ones. What I thought about is using something that would help you solo certain bands, just like multibands do. So, for example, you duplicate the track, put a multiband comp on each with the same settings (crossovers!), and solo the low end in one and the other stuff in the other track :p Make sure the multiband isn't 'working', except for the 'solo' part, and work on with dominion that way.

I obviously don't know the technical aspects of how digital plugs work, dsp is like latin to me so I'm not sure if what I mentioned up there is the best solution.

This is EXACTLY what I thought of today just after logging off from the computer to get to work :) I guess this technique should work correctly without any loss... I hope!

What I'm worried about with LPing and HPing 2 tracks is that there might be some loss of audio somewhere inbetween those filters with normal EQs.. but I'm not really sure.
 
simply by doubling the track, and putting some HP/LP at the same frequency ? You put a LP at 100Hz for the low track, and an HP at 100Hz for the HP. Because of the 3dB loss at 100Hz of these tracks, the addition of these two tracks is mathematically the original track, and you're done.

Hmm is that how it works? If you put a LP and HP at the same frequency on 2 tracks, they will sum up and become identical to the original track?
 
I would have to say your best bet is to save and get some better mics. besides the source, they will have the biggest impact on how good the kick sounds!

Already invested 1300€ in new gear and that didn't include any mics haha :O Wish I could do that but I have a damn driver's license to spend money on as well... so I'm still heavily dependant on blending samples (a lot) with my own kick track. The problem is that many samples sound good but they could use some shaping in the bass frequencies... or atleast I'd like to try!
 
How on earth does your CPU cope with linear phase eq's on everything? I know mine sure as hell can't cope.

Joe
 
Hmm is that how it works? If you put a LP and HP at the same frequency on 2 tracks, they will sum up and become identical to the original track?

Yes, if you do calculus with an capacity (C) and a resistor (R) put in a filter way, it shows that at the proper frequency (1/RC) the gain is exactly -3dB (power divided by 2).

And I'm quite sure the sum of both LP and HP with the same f is supposed to be equal to the original signal, even if the loss is -24dB/decade etc (assuming it's the same for both).

I'm thinking that mathematically it may be only true if the EQ is not linear. Because a filter adds a phase delta of -90° (or Pi/2) on the extreme altered frequencies. So maybe mathematically it's only true if linear phase EQ are used (I don't know what mathematically is a linear phase EQ and if it would delete the phase for a LP because it seems impossible to me, but there I'm not sure)
 
This also makes me wonder. I'm more interested in how this applies to bass, but it's the same concept. I currently use GHi and GLow to split the bass track at the same frequency.

You could throw the HI and LOW filters on the there and then render the bussed track and see how close it matches up with the original track.