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 Forum index » Clavia Nord Modular » G2 FAQ
Low, mid and High bandsplit.
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BobTheDog



Joined: Feb 28, 2005
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PostPosted: Sun Dec 18, 2005 1:42 am    Post subject: Low, mid and High bandsplit.
Subject description: This is not right, any advise would be much apreciated.		 Reply with quote  Mark this post and the followings unread
Hi Everyone,

I am trying to do something that I thought would be easy but my ignorance has proved me wrong again.

What I would like to do is split a signal into High, Mid and low bands so I can process each band.

In the enclosed patch I am trying to get 0-250hz for low, mid as 250Hz to 2.5Khz and high above 2.5Khz.

Now I don't know if the patch is the correct way of going about this, it works in a basic way but if I add the Low, Mid and high bands I find I have lost alot of the original sound.

I'm pretty sure this is to do with the fact I am loosing stuff at the edges of each band, should the frequencys on the "Low Band" filter and "Mid & high band" (and "mid" and "high" filters) overlap for some amount to compensate the rolloff of the filter, if so by how much? Is there a formula to use?

Also as a side issue if I just wanted to have two knobs, one setting the low split requence and one setting the high split frequency how would I go about this?

Any help or direction would be really apreciated.

Cheers

Andy

BandSplitPleaseHelpMe.pch2
 Description:
Example of how not to split bandwidth into Low, Mid and high sections!

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 Filename:  BandSplitPleaseHelpMe.pch2
 Filesize:  1.59 KB
 Downloaded:  1886 Time(s)
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ian-s



Joined: Apr 01, 2004
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PostPosted: Sun Dec 18, 2005 2:23 am    Post subject: Reply with quote  Mark this post and the followings unread
Here is a slightly different way of doing it. The Mix2-1 module combined with a lowpass filter creates a highpass output by subtracting the input from the LP output. Two of these gives you your 3 band split with a single control for each split point.

I noticed that at 6dB, the output is a close match for the input but higher orders seem to emphasize the split point frequencies.

BandSplit.pch2
 Description:
3 band sig splitter

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 Filename:  BandSplit.pch2
 Filesize:  1.26 KB
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BobTheDog



Joined: Feb 28, 2005
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PostPosted: Sun Dec 18, 2005 2:50 am    Post subject: Reply with quote  Mark this post and the followings unread
Hi Ian,

Thanks for this, I like your solution, less modules, less load, two knobs for the frequencies and no loss of sound, excellent.

I had been wondering how to do a subtract for a while so you have helped me with that as well!

Once again thanks for the help.

Cheers

Andy
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elektro80
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PostPosted: Sun Dec 18, 2005 4:57 am    Post subject: Reply with quote  Mark this post and the followings unread
You guys are trying to make a Drawmer 3-sum?
http://www.drawmer.com/new/three_sum.pdf

Smile


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Rob



Joined: Mar 29, 2004
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PostPosted: Sun Dec 18, 2005 5:45 pm    Post subject: Reply with quote  Mark this post and the followings unread
g2ian wrote:
Here is a slightly different way of doing it. The Mix2-1 module combined with a lowpass filter creates a highpass output by subtracting the input from the LP output. Two of these gives you your 3 band split with a single control for each split point.

I noticed that at 6dB, the output is a close match for the input but higher orders seem to emphasize the split point frequencies.


Using the LP filters in parallel instead of in series works even better. If all bands are mixed together again serial filters will still have an audible phase shift when changing the cutoffs (due to the accumulative phase shifts in the filter cascade that later interfere while mixing together). In 'parallel mode' this is not an issue and makes the thing 'phase linear', though the bands tend to sound less sharp (which actually isn't that bad when processing audio while e.g. making a master mix).

The 'mixing math' for parallel filters is:
Low band = lowest filter
Middle band = highest filter minus lowest filter
High band = original input minus highest filter

It is also more easy to create more bands without even more accumulative phase shifts. It would be like:

    LP1
    LP2 minus LP1
    LP3 minus LP2
    LP4 minus LP3
    Input minus LP4

for a five band filter.

The only 'weird' behaviour is in e.g. a threeband filter that when the middle band is muted and the highest filter is tuned lower as the lowest filter the middle band reappears and is even boosted by some dB. But there is logic to this when looking at all the adding and subtracting.

CrossoverFilters.pch2
 Description:
'Phase linear' multi-band crossover filters

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 Filename:  CrossoverFilters.pch2
 Filesize:  1.85 KB
 Downloaded:  1746 Time(s)
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BobTheDog



Joined: Feb 28, 2005
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PostPosted: Mon Dec 19, 2005 11:52 pm    Post subject: Reply with quote  Mark this post and the followings unread
elektro80 wrote:
You guys are trying to make a Drawmer 3-sum?
http://www.drawmer.com/new/three_sum.pdf

Smile


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Yep your correct.

Have a look at http://electro-music.com/forum/topic-9142.html for an example of this idea with seperate compressors and saturation.

Cheers

Andy
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BobTheDog



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PostPosted: Mon Dec 19, 2005 11:53 pm    Post subject: Reply with quote  Mark this post and the followings unread
Hi Rob,

Thanks for the info, I am trying to digest it now.

Cheers

Andy
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monobass



Joined: Nov 30, 2004
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PostPosted: Sun Jun 04, 2006 12:52 pm    Post subject: Reply with quote  Mark this post and the followings unread
aha.. it looks like I duplicated this thread Smile

http://www.electro-music.com/forum/post-79042.html#79042

I can't download Rob's patch above though.. it just hangs for ages and fails.. anyone else have this problem?
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blue hell
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PostPosted: Mon Jun 05, 2006 1:58 pm    Post subject: Reply with quote  Mark this post and the followings unread
Steve, are you still having trouble with the patch ?

It loads fibe here.
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Jan
also .. could someone please turn down the thermostat a bit.
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monobass



Joined: Nov 30, 2004
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PostPosted: Mon Jun 05, 2006 2:03 pm    Post subject: Reply with quote  Mark this post and the followings unread
Yeah it's fine now Jan, sorry I forgot to mention in this thread.
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