# The Poor Man's Multi-band Compressor



## 0bazooka_joe0 (Mar 22, 2010)

So, how many people don't have hundreds of dollars to spend on fancy Plug-ins? I am one of those people. However, I have come up with a work around to the multi-band compressor plug-in. For the purposes of this articles and its specific details I will be for the most part speaking relative to Pro Tools but these instructions can easily be applied to other DAWs.

*Bussing*

Create an aux track for every band of compression you wish to have. In this example I created 3 tracks - 3 band compressor. Set the output of all the tracks you wish send to your "Multi-band Compressor" to the inputs of your aux tracks. All of your tracks' output buses should match your aux input buses.

*EQ/Filters*

Basically a multi-band compressor simply uses filters to separate frequency bands so that is what we will do here. Just as a base we will use 120Hz and 4kHz as our cross-overs. On your first aux track (the low frequency band) put a HP filter on the first plug-in spot. Set the frequency to 120Hz and apply a 18dB/octave slope. It should be noted that in first experimenting with this I tried using a 24dB/octave slope but found it to change the sound of the track/mix (possibly acting as a slight notch due to the extreme slope). For the second aux track (the mid frequency band) I used the digirack EQIII 4-band eq. I made all of the eqs inactive just to be able to use the filters. I set the HP filter to 120Hz, the LP filter to 4kHz, and again both slopes were set to 18dB/octave. The last aux track (the high frequency band) i placed a LP filter at 4kHz at an 18dB/octave slope.

*Compression*

Simply add a compressor of your choice (ideally a less colouring compressor) to each track and you have your multi-band compressor. It should be noted that with multi-band compression, generally, very small ratios are used.

Note: You may find that your aux track meters clip slightly (particularly the mid-range band). This is a phenomena that I often encounter when using heavy filtering on tracks. I've researched and asked around but have never found an answer. If you do know the reason why this happens by all means post it, I'd love to hear it. A simple work around is to place a limiter on the tracks just as a precaution (a fast attack and release with a high threshold). I don't actually hear any distortion but better safe than sorry.

The images attached are an example to show you the bussing and EQ settings for each track. In the mix window, the EQs from top to bottom are low, mid, high. The duplicated tracks were for A/Bing to check if the "Multi-Band Compressor" bussing and EQ changed the way the track sounded. As far as I could tell, there was no change... until I rocked it with some compression :T

Any questions or comments post away or PM me.


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## spacedout (Dec 17, 2007)

Nice one :T



0bazooka_joe0 said:


> Note: You may find that your aux track meters clip slightly (particularly the mid-range band). This is a phenomena that I often encounter when using heavy filtering on tracks. I've researched and asked around but have never found an answer.


I do remember seeing an explanation for this fairly recently, but I can't remember where it was or what it was :rolleyesno: Hopefully it'll come back to me soon... onder:


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## ejbragg (Dec 13, 2009)

Obazooka_joe0, Great practical application, just using brains! I actually have a multiband compressor plug-in, but rarely use it because I think it's too colorful for most of my apps. This is a great idea. Thanks for sharing the info.

By the way, as for the peaks... may I take a shot at it?

I don't really know, but if the inputs are naturally set for full bandwidth, is it possible that the "full band compressor", working now in "single band mode" can't see that the levels at the band being used are high enough? Perhaps the single band is being poured into an averaging algorithm in the software that is sampling all the bands and averaging them. If the average comes up short, does the input level show lower than it really is?

I suspect my suggestion is off target, but is the nature of the suggestion heading down the right track?


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## 0bazooka_joe0 (Mar 22, 2010)

Actually the peaking phenomena happens even before the compressors are applied. I've had this happen before where I use an EQ for nothing but attenuated EQ or filtering and then the meter on that track (which wouldn't be peaking more than -4, -5dB before) is now going into the red. I'll admit that I don't actually hear distortion but its a bit concerning when your meters aren't reacting how they should be.


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## zacheus83 (Oct 31, 2009)

As far as the peaking phenomenon, it has been my experience that every time I perform an EQ cut on an audio track that is close to 0 it peaks instantly. I remember seeing the reason for this from another forum but it escapes me... 

This compression idea is very cool! I also thought about a way that it can be tweaked for parallel compression. Instead of sending the output of each track to the aux's, use the sends on each track (3 sends per track) and send each to the input of the 3 buses respectively. Now you will be able to mix the amount of signal between dry (on the original audio track, routed to the main outputs) and wet (the signal on the sends).


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## 0bazooka_joe0 (Mar 22, 2010)

Very Stylish idea zacheus :T


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## los153 (Nov 5, 2006)

This is a great tip, especially for anyone who likes to cobble together cool stuff by patching and routing!

I think that I can offer a suggestion for the peaks going into the red on the mid-band. If it's a bandpass (or the equivalent lowpass and highpass cascade), then it will tend to "ring" in the time domain, even if it's at a relatively low Q. (The Q of a bandpass filter is the ratio of its center frequency to its bandwidth. The center frequency is the average of the upper and lower corner frequencies, and the bandwidth is their difference. The higher the Q, the more resonant the filter.) The effect of the ringing is an "overshoot" in the output in response to transients at the input. The overshoot has a high peak-to-average ratio. So even though the sound level of the band isn't high, the peak level still can be.


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## 0bazooka_joe0 (Mar 22, 2010)

Ahhhh very interesting. That makes a lot of sense. So if a band-pass filter causes ringing at its centre frequency than there is a bit more EQing that needs to be done in order to make a (near)perfect replica of the i.e. 120-4000kHz band of the original track. I'm going to go tool around with the masterX in studio today and see if I can't figure out how to replicate how a multi-band compressor keeps its mid-bands from ringing.


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## SteveHi (Nov 19, 2009)

I don't believe there will be much peaking in the center of the filter passband. I think what you are experiencing is a small amount of unwanted boost around the filter transition frequency (band edges). An increasing peak is introduced in the response curve around the transition frequency, with a steeper filter slope (rolloff) making the problem worse, as was noticed. To offset this effect, you could add some attenuation specifically at the band edges, such as subtracting 3 to 6 dB at precisely, or as close as you can get, at the low end and also at the high end of the filter passband. A steeper filter slope (rolloff) will make the problem worse, as was mentioned. I have experienced this problem, also, and have noticed far worse peaking effects from using low frequency "shelving" filters.


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## 0bazooka_joe0 (Mar 22, 2010)

Hm maybe I'll try it out with a less steep rolloff...or a differently shaped rolloff. Like a kind of S curve.


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## 0bazooka_joe0 (Mar 22, 2010)

Tweaking the slopes changes the sound too much. the 18dB/oct slope is the best one and as far as that mid range peaking, looking more closely it is barely boosted. Either putting a limiter on the track or turning down the source .5-1 dB would alleviate the problem. It SOUNDS the same to me which is ultimately the most important thing.


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## Kirill (Apr 14, 2010)

Hi 0bazooka_joe0 once again. Hmmm very interesting issue you got here. Let me give you an opinion on it. 



0bazooka_joe0 said:


> You may find that your aux track meters clip slightly (*particularly the mid-range band*). This is a phenomena that I often encounter when using heavy filtering on tracks.


I think that the bandwidth on that particular Mid-range that you got on a picture is way to wide for just a mid range. It also grabbed a LHF and MHF as well. So by having that you perhaps overwhelming you Thresholds on a Compressor. Thinking just about HF peaks alone they are usually appear to be stronger 
on a meters and to ears as well. So just from that point alone I'd create one more band thus preventing that issue. At least I think that should fix it. I gotta have to try your way. I see where you coming from but to confirm my own thoughts, I'll have to try it. I'd create one more band, let's say from 2kHz-10kHz. I think that could fix your problem and of course create another Compressor as well.
Well once I try it I'll post another reply here. I'm interested to try it myself and test the theory :heehee:
Interesting Technique, that is good for a person who doesn't have an actual Multiband Compressor...

Kirill :T


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## Kirill (Apr 14, 2010)

Just looked at your images once more. I think I see 2 issues in your routing. 

All of you AUX channels have same i/p BUSS 3/4. Thus by applying all the levels at the same time as well as thinking about the width of your Mid-Band it's quite a lot of frequencies over there man. So these volumes all together pushes the AUX i/p to the max. I think you should break your BUSSes into more, say LwCm with i/p on BUSS 3/4, MdCm respectively 5/6 and HighCm at 7/8.
Af course that will only work if you PT have more then say 16 BUSSes. This way you'll separate all you gains and strong levels into parts. Well at least that's what I think about it. Without trying. I'll though. So expect at the least one more post regarding your issue.

Kirill

p.s.: Question. Do you BUSS 2 absolutely different tracks to those AUXs?


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## SteveHi (Nov 19, 2009)

That is exactly what I have had to do - turn down the source 0.5 to 1 dB. Sometimes a bit more, depending on the EQ, which I still believe is the root cause of the issue you were describing. Also, I agree that another compression band might help you out, as most of the time I use four-band compression. 2 to 10 kHz was a good suggestion, depending on the type of music you are processing.


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## los153 (Nov 5, 2006)

Slightly OT but related idea... maybe the OP or someone may be interested in pursuing:

Replace the compressors in each band with a distortion. Now it's multi-band fuzz.

Or replace the FX in each band with a different delay, or a different chorus... you get the idea. You can get some crazy modulations and FX going on in multi-band.

One application is a chorus for bass, where only the higher bands are chorused. Using light (or no) chorus on the lower bands maintains the "body" of the bass, and reduces "pumping" of the fundamentals.

Just some thoughts...


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## 0bazooka_joe0 (Mar 22, 2010)

Kirill said:


> Just looked at your images once more. I think I see 2 issues in your routing.
> 
> All of you AUX channels have same i/p BUSS 3/4. Thus by applying all the levels at the same time as well as thinking about the width of your Mid-Band it's quite a lot of frequencies over there man. So these volumes all together pushes the AUX i/p to the max. I think you should break your BUSSes into more, say LwCm with i/p on BUSS 3/4, MdCm respectively 5/6 and HighCm at 7/8.
> Af course that will only work if you PT have more then say 16 BUSSes. This way you'll separate all you gains and strong levels into parts. Well at least that's what I think about it. Without trying. I'll though. So expect at the least one more post regarding your issue.
> ...


Yes, my test session consisted of a melody track and a percussion track... and I totally realized why the mid-range band was clipping... bahhh.

The two tracks I had bussed to the "multi-band compressor" were pretty full/hot tracks (they were music stems for a tv show). By combining the two it is obvious that the mid-range would clip given that the majority of frequencies will reside in the mid-range plus the fact that, yes, the mid-range band is quite large. So, yes, having maybe 4 bands would be ideal and may be my test environment wasnt so ideal:dontknow:

But, this does prove that it works as long as you're not routing several layered/hot tracks to it.


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## Kirill (Apr 14, 2010)

Hi Joe.

Yes I totally see your point. That was in behind of my mind as well. Cause by looking at the stems they looked pretty thick :whistling: Thus by combining them via BUSSes you'd clip the @$#* out of them. With such a levels. For sure. But seems like problem is solved and you are good to go. But still you should try 4 bands. I think it's a better idea.

Kirill


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