Re: [music-dsp] bandsplitting strategies (frequencies) ?

2018-03-27 Thread gm



Am 27.03.2018 um 19:29 schrieb David Reaves:

If what you do involves material with an unusual spectral balance, and/or if 
you use aggressive filter roll offs and/or you use something other than RMS 
detection, then my assumptions may not be useful.



that is understood.
there are not many assumptions I can make so I think pink noise is the 
best match


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Re: [music-dsp] bandsplitting strategies (frequencies) ?

2018-03-27 Thread gm


This actually explains a few misconceptions I had in the past..
Both slopes are filed under "natural spectrum" in my mind.


Am 27.03.2018 um 19:16 schrieb robert bristow-johnson:>


> I believe thats equal energy on a -6dB/octave spectrum and gives figures
> very close

no, that's -3 dB/oct.

pink noise is equal energy per octave and is -3 dB drop every octave.




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Re: [music-dsp] bandsplitting strategies (frequencies) ?

2018-03-27 Thread David Reaves
What I meant when I explained how I derived my crossover frequencies, was that 
I used actual, typical program audio and **its own inherent spectral energy 
density distribution** to determine empirically (over many months work) 
generally where to set the frequencies.

Much typical full-frequency-range music tends to have equal amounts of RMS 
energy above and below a dividing point in the range of roughly 500-600Hz. 
Further splitting those two bands into four equal-program-energy bands resulted 
experientially in the 150 and 1800 splits.

This determination is approximate; these frequencies are not hard and fast, 
never mind “magic,” and there will be exceptions, but the product I designed 
was known for its natural-ness on all music types: classical, pop, jazz, etc., 
and also worked well on voice. The fact that single-pole subtractive filters 
are extremely broad AND sum back to the original with extremely low transient 
distortion, was also helpful.

If what you do involves material with an unusual spectral balance, and/or if 
you use aggressive filter roll offs and/or you use something other than RMS 
detection, then my assumptions may not be useful.

David Reaves


Sent from my iPad

On Tue, 27 Mar 2018 15:10:12 +0200, gm  wrote:
> 
> 
> i keep dividing into equal bands on a log2 scale,
> 
> I believe thats equal energy on a -6dB/octave spectrum and gives figures 
> very close
> 
> to what David Reaves suggested the other day for 4 bands when you set 
> 6300 Hz as the upper limit
> 
> and 150 Hz corner frequency for the bass band (or 45 Hz for the lower limit)
> 

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Re: [music-dsp] bandsplitting strategies (frequencies) ?

2018-03-27 Thread robert bristow-johnson







 Original Message 

Subject: Re: [music-dsp] bandsplitting strategies (frequencies) ?

From: "gm" <g...@voxangelica.net>

Date: Tue, March 27, 2018 6:10 am

To: music-dsp@music.columbia.edu

--



>

> i keep dividing into equal bands on a log2 scale,

>

> I believe thats equal energy on a -6dB/octave spectrum and gives figures

> very close

�
no, that's -3 dB/oct.
pink noise is equal energy per octave and is -3 dB drop every octave.
�
--



r b-j� � � � � � � � � � � � �r...@audioimagination.com



"Imagination is more important than knowledge."

�
�
�
�
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Re: [music-dsp] bandsplitting strategies (frequencies) ?

2018-03-27 Thread gm


i keep dividing into equal bands on a log2 scale,

I believe thats equal energy on a -6dB/octave spectrum and gives figures 
very close


to what David Reaves suggested the other day for 4 bands when you set 
6300 Hz as the upper limit


and 150 Hz corner frequency for the bass band (or 45 Hz for the lower limit)



Am 27.03.2018 um 11:36 schrieb Theo Verelst:

gm wrote:

What are good frequencies for band splits? (2-5 bands)


For standard mastering applications there are norms for binoral and 
Equal Loudness Curve related reasons. The well known PC software 
probably doesn't get there but it may be you want to tune those 
frequencies based on the following criteria:


  - type of filter (FIR/IIR/FFT, resonant or not, congruent with 
standard linear
    (analogue) filter constructions or not) and the associated impulse 
response length

  - the properties of the filter impulse and combinations during standard
    signal reconstruction (at the DAC) or up/down sampling
  - energy distribution for white/pink noise or standard signals for your
    specific application
  - the function of the application in terms of being somewhere on the 
line of
    a High Fidelity slight clipping prevention, over a radio mastering 
with significant
    compression, or a wild tool where the use is as a very significant 
signal alteration

    tool


Theo V.


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Re: [music-dsp] bandsplitting strategies (frequencies) ?

2018-03-27 Thread Theo Verelst

gm wrote:

What are good frequencies for band splits? (2-5 bands)


For standard mastering applications there are norms for binoral and Equal Loudness Curve 
related reasons. The well known PC software probably doesn't get there but it may be you 
want to tune those frequencies based on the following criteria:


  - type of filter (FIR/IIR/FFT, resonant or not, congruent with standard linear
(analogue) filter constructions or not) and the associated impulse response 
length
  - the properties of the filter impulse and combinations during standard
signal reconstruction (at the DAC) or up/down sampling
  - energy distribution for white/pink noise or standard signals for your
specific application
  - the function of the application in terms of being somewhere on the line of
a High Fidelity slight clipping prevention, over a radio mastering with 
significant
compression, or a wild tool where the use is as a very significant signal 
alteration
tool


Theo V.


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Re: [music-dsp] bandsplitting strategies (frequencies) ?

2018-03-23 Thread Matt Jackson
Or as I said before, even for N bands, one parameter, “Preset” works wonders to 
describe the purpose and accommodate different use cases.

> On 23. Mar 2018, at 17:44, gm  wrote:
> 
> For equally spaced bands you could do it with 2 parameters, one to shift the 
> middle or base frequency
> and one spread or fan parameter that spreads or narrows the bands.
> 
> The reason I don't want this, is that I don't want too many parameters
> and the user doesn't know how to set the bands either, especially since
> the difference is probably not obvious, sonically.
> 
> But it's an option I am considering.
> 
> 
> 
> Am 23.03.2018 um 16:50 schrieb Matt Jackson:
>> If it’s a distortion or compression and only 2-4 bands, a user set 
>> crossover(s) would usually be desirable.
>> The Ableton Multi-band Dynamics, Waves C4, Ohm Force Ohmacide, Izotope 
>> plugins, Surreal Machines Transient Machines all come to mind.
>> It probably depends on the complexity you are looking for but some presets 
>> for “voice”, "full mix”, “drums” etc. usually go a long way.
>> 
>>> On 23. Mar 2018, at 15:05, gm  wrote:
>>> 
>>> 
>>> The purpose is multiband compression and distortion.
>>> 
>>> So I only have a few bands, 2 to 5.
>>> 
>>> I use ERB scale in my vocoder, which worked slightly better than Bark scale 
>>> for me (it seems better defined at the low range)
>>> 
>>> I was wondering if I should use it here too or if it's better on a log2 
>>> scale.
>>> 
>>> Also I cant decide what upper and lower frequency I should use when I 
>>> divide evenly on a log scale.
>>> 
>>> I chose 100 Hz cause thats the lowest Bark band I think.
>>> 
>>> 
>>> Am 23.03.2018 um 14:39 schrieb Matt Jackson:
 Gabriel,
 
 I think it depends on what you are trying to do. What’s your context?
 
 For example a Vocoder (for voice) might have a different distribution of 
 bands (bark scale) than a multipurpose graphic EQ (even octaves).
 One strange example I know of is the Serge resonant EQ (not crossovers but 
 fixed frequency resonant peaks) has deliberately picked frequencies that, 
 “except for the top and bottom frequency bands, the bands are spaced at an 
 interval of a major seventh. The Resonant Equalizer is designed to produce 
 formant peaks and valleys similar to those in acoustic instruments.”
 
 Matt
 
> On 23. Mar 2018, at 13:05, robert bristow-johnson 
>  wrote:
> 
> On 3/23/18 12:01 AM, gm wrote:
>> What are good frequencies for band splits? (2-5 bands)
>> 
>> What I am doing is divide the range between 100 Hz 5-10 kHz
>> into equal bands on a log scale (log2 or pitch).
>> 
>> Are there better strategies?
>> Or better min/max frequencies?
>> How is it usually done?
> conventionally, a graphic EQ might be split into bands with log center 
> frequencies every octave, for a 10 band, or every 1/3 octave for a 31 
> band EQ.
> 
> i think the 10-octave frequencies might be at
> 
> 25, 50, 100, 200, 400, 800, 1600, 3200, 6400, 12800 Hz
> 
> with the bandedges at the geometric mean of adjacent pair of frequencies
> 
> but they might put them conventionally at
> 
> 20, 50, 100, 200, 500, 1000, 2000, 5000, 1, 2 Hz
> 
> you can see there's a bigger-than-octave gap between 200 and 500.
> 
> maybe the 31-band 1/3 octave frequencies might conventionally be at
> 
> 20, 25, 32, 40, 50, 63, 80, 100, 125, 160, 200, 250, 320, 400, 500, 630, 
> 800, 1000, 1250, 1600, 2000, 2500, 3200, 4000, 5000, 6300, 8000, 1, 
> 12500, 16000, 2 Hz
> 
> those are conventional frequencies. not all spacing are exactly 1/3 
> octave.  you can see that 630 is a compromise between twice 320 and half 
> of 1250.  you might want your bands split precisely in 1/3 octaves spaced 
> apart by a frequency ratio of 2^(1/3) which is about 1.26.  that might 
> have bands labeled:
> 
> 20, 25, 32, 40, 50, 63, 80, 100, 126, 159, 200, 252, 318, 400, 504, 635, 
> 800, 1007, 1271, 1600, 2014, 2542, 3200, 4028, 5084, 6400, 8056, 10168, 
> 12800, 16112, 20336 Hz
> 
> 
> -- 
> 
> r b-j  r...@audioimagination.com
> 
> "Imagination is more important than knowledge."
> 
> 
> 
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 ___
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>> 

Re: [music-dsp] bandsplitting strategies (frequencies) ?

2018-03-23 Thread gm
For equally spaced bands you could do it with 2 parameters, one to shift 
the middle or base frequency

and one spread or fan parameter that spreads or narrows the bands.

The reason I don't want this, is that I don't want too many parameters
and the user doesn't know how to set the bands either, especially since
the difference is probably not obvious, sonically.

But it's an option I am considering.



Am 23.03.2018 um 16:50 schrieb Matt Jackson:

If it’s a distortion or compression and only 2-4 bands, a user set crossover(s) 
would usually be desirable.
The Ableton Multi-band Dynamics, Waves C4, Ohm Force Ohmacide, Izotope plugins, 
Surreal Machines Transient Machines all come to mind.
It probably depends on the complexity you are looking for but some presets for 
“voice”, "full mix”, “drums” etc. usually go a long way.


On 23. Mar 2018, at 15:05, gm  wrote:


The purpose is multiband compression and distortion.

So I only have a few bands, 2 to 5.

I use ERB scale in my vocoder, which worked slightly better than Bark scale for 
me (it seems better defined at the low range)

I was wondering if I should use it here too or if it's better on a log2 scale.

Also I cant decide what upper and lower frequency I should use when I divide 
evenly on a log scale.

I chose 100 Hz cause thats the lowest Bark band I think.


Am 23.03.2018 um 14:39 schrieb Matt Jackson:

Gabriel,

I think it depends on what you are trying to do. What’s your context?

For example a Vocoder (for voice) might have a different distribution of bands 
(bark scale) than a multipurpose graphic EQ (even octaves).
One strange example I know of is the Serge resonant EQ (not crossovers but 
fixed frequency resonant peaks) has deliberately picked frequencies that, 
“except for the top and bottom frequency bands, the bands are spaced at an 
interval of a major seventh. The Resonant Equalizer is designed to produce 
formant peaks and valleys similar to those in acoustic instruments.”

Matt


On 23. Mar 2018, at 13:05, robert bristow-johnson  
wrote:

On 3/23/18 12:01 AM, gm wrote:

What are good frequencies for band splits? (2-5 bands)

What I am doing is divide the range between 100 Hz 5-10 kHz
into equal bands on a log scale (log2 or pitch).

Are there better strategies?
Or better min/max frequencies?
How is it usually done?

conventionally, a graphic EQ might be split into bands with log center 
frequencies every octave, for a 10 band, or every 1/3 octave for a 31 band EQ.

i think the 10-octave frequencies might be at

25, 50, 100, 200, 400, 800, 1600, 3200, 6400, 12800 Hz

with the bandedges at the geometric mean of adjacent pair of frequencies

but they might put them conventionally at

20, 50, 100, 200, 500, 1000, 2000, 5000, 1, 2 Hz

you can see there's a bigger-than-octave gap between 200 and 500.

maybe the 31-band 1/3 octave frequencies might conventionally be at

20, 25, 32, 40, 50, 63, 80, 100, 125, 160, 200, 250, 320, 400, 500, 630, 800, 
1000, 1250, 1600, 2000, 2500, 3200, 4000, 5000, 6300, 8000, 1, 12500, 
16000, 2 Hz

those are conventional frequencies. not all spacing are exactly 1/3 octave.  
you can see that 630 is a compromise between twice 320 and half of 1250.  you 
might want your bands split precisely in 1/3 octaves spaced apart by a 
frequency ratio of 2^(1/3) which is about 1.26.  that might have bands labeled:

20, 25, 32, 40, 50, 63, 80, 100, 126, 159, 200, 252, 318, 400, 504, 635, 800, 
1007, 1271, 1600, 2014, 2542, 3200, 4028, 5084, 6400, 8056, 10168, 12800, 
16112, 20336 Hz


--

r b-j  r...@audioimagination.com

"Imagination is more important than knowledge."



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Re: [music-dsp] bandsplitting strategies (frequencies) ?

2018-03-23 Thread David Reaves
I designed a four-band AGC for broadcast about 20 years ago, using single-pole 
subtractive band split filters. I used RMS detection, and wanting each band’s 
processing to be doing roughly equal ‘work,’  determined the crossover 
frequencies on the basis of typical energy distribution. This worked out to 
around 150 Hz, 500 Hz and 1800 Hz, and the processor sounded extremely natural 
on pretty much all sources.

Kind Regards,

David Reaves
Recklinghausen, German


> On Mar 23, 2018, at 5:01 PM, music-dsp-requ...@music.columbia.edu 
>  wrote:
> 
> Date: Fri, 23 Mar 2018 15:05:47 +0100
> From: gm >
> To: music-dsp@music.columbia.edu 
> Subject:
> Message-ID:  >
> Content-Type: text/plain; charset=utf-8; format=flowed
> 
> 
> The purpose is multiband compression and distortion.
> 
> So I only have a few bands, 2 to 5.
> 
> I use ERB scale in my vocoder, which worked slightly better than Bark 
> scale for me (it seems better defined at the low range)
> 
> I was wondering if I should use it here too or if it's better on a log2 
> scale.
> 
> Also I cant decide what upper and lower frequency I should use when I 
> divide evenly on a log scale.
> 
> I chose 100 Hz cause thats the lowest Bark band I think.

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Re: [music-dsp] bandsplitting strategies (frequencies) ?

2018-03-23 Thread Matt Jackson
If it’s a distortion or compression and only 2-4 bands, a user set crossover(s) 
would usually be desirable. 
The Ableton Multi-band Dynamics, Waves C4, Ohm Force Ohmacide, Izotope plugins, 
Surreal Machines Transient Machines all come to mind.
It probably depends on the complexity you are looking for but some presets for 
“voice”, "full mix”, “drums” etc. usually go a long way.

> On 23. Mar 2018, at 15:05, gm  wrote:
> 
> 
> The purpose is multiband compression and distortion.
> 
> So I only have a few bands, 2 to 5.
> 
> I use ERB scale in my vocoder, which worked slightly better than Bark scale 
> for me (it seems better defined at the low range)
> 
> I was wondering if I should use it here too or if it's better on a log2 scale.
> 
> Also I cant decide what upper and lower frequency I should use when I divide 
> evenly on a log scale.
> 
> I chose 100 Hz cause thats the lowest Bark band I think.
> 
> 
> Am 23.03.2018 um 14:39 schrieb Matt Jackson:
>> Gabriel,
>> 
>> I think it depends on what you are trying to do. What’s your context?
>> 
>> For example a Vocoder (for voice) might have a different distribution of 
>> bands (bark scale) than a multipurpose graphic EQ (even octaves).
>> One strange example I know of is the Serge resonant EQ (not crossovers but 
>> fixed frequency resonant peaks) has deliberately picked frequencies that, 
>> “except for the top and bottom frequency bands, the bands are spaced at an 
>> interval of a major seventh. The Resonant Equalizer is designed to produce 
>> formant peaks and valleys similar to those in acoustic instruments.”
>> 
>> Matt
>> 
>>> On 23. Mar 2018, at 13:05, robert bristow-johnson 
>>>  wrote:
>>> 
>>> On 3/23/18 12:01 AM, gm wrote:
 What are good frequencies for band splits? (2-5 bands)
 
 What I am doing is divide the range between 100 Hz 5-10 kHz
 into equal bands on a log scale (log2 or pitch).
 
 Are there better strategies?
 Or better min/max frequencies?
 How is it usually done?
>>> conventionally, a graphic EQ might be split into bands with log center 
>>> frequencies every octave, for a 10 band, or every 1/3 octave for a 31 band 
>>> EQ.
>>> 
>>> i think the 10-octave frequencies might be at
>>> 
>>> 25, 50, 100, 200, 400, 800, 1600, 3200, 6400, 12800 Hz
>>> 
>>> with the bandedges at the geometric mean of adjacent pair of frequencies
>>> 
>>> but they might put them conventionally at
>>> 
>>> 20, 50, 100, 200, 500, 1000, 2000, 5000, 1, 2 Hz
>>> 
>>> you can see there's a bigger-than-octave gap between 200 and 500.
>>> 
>>> maybe the 31-band 1/3 octave frequencies might conventionally be at
>>> 
>>> 20, 25, 32, 40, 50, 63, 80, 100, 125, 160, 200, 250, 320, 400, 500, 630, 
>>> 800, 1000, 1250, 1600, 2000, 2500, 3200, 4000, 5000, 6300, 8000, 1, 
>>> 12500, 16000, 2 Hz
>>> 
>>> those are conventional frequencies. not all spacing are exactly 1/3 octave. 
>>>  you can see that 630 is a compromise between twice 320 and half of 1250.  
>>> you might want your bands split precisely in 1/3 octaves spaced apart by a 
>>> frequency ratio of 2^(1/3) which is about 1.26.  that might have bands 
>>> labeled:
>>> 
>>> 20, 25, 32, 40, 50, 63, 80, 100, 126, 159, 200, 252, 318, 400, 504, 635, 
>>> 800, 1007, 1271, 1600, 2014, 2542, 3200, 4028, 5084, 6400, 8056, 10168, 
>>> 12800, 16112, 20336 Hz
>>> 
>>> 
>>> -- 
>>> 
>>> r b-j  r...@audioimagination.com
>>> 
>>> "Imagination is more important than knowledge."
>>> 
>>> 
>>> 
>>> ___
>>> dupswapdrop: music-dsp mailing list
>>> music-dsp@music.columbia.edu
>>> https://lists.columbia.edu/mailman/listinfo/music-dsp
>>> 
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Re: [music-dsp] bandsplitting strategies (frequencies) ?

2018-03-23 Thread gm


The purpose is multiband compression and distortion.

So I only have a few bands, 2 to 5.

I use ERB scale in my vocoder, which worked slightly better than Bark 
scale for me (it seems better defined at the low range)


I was wondering if I should use it here too or if it's better on a log2 
scale.


Also I cant decide what upper and lower frequency I should use when I 
divide evenly on a log scale.


I chose 100 Hz cause thats the lowest Bark band I think.


Am 23.03.2018 um 14:39 schrieb Matt Jackson:

Gabriel,

I think it depends on what you are trying to do. What’s your context?

For example a Vocoder (for voice) might have a different distribution of bands 
(bark scale) than a multipurpose graphic EQ (even octaves).
One strange example I know of is the Serge resonant EQ (not crossovers but 
fixed frequency resonant peaks) has deliberately picked frequencies that, 
“except for the top and bottom frequency bands, the bands are spaced at an 
interval of a major seventh. The Resonant Equalizer is designed to produce 
formant peaks and valleys similar to those in acoustic instruments.”

Matt


On 23. Mar 2018, at 13:05, robert bristow-johnson  
wrote:

On 3/23/18 12:01 AM, gm wrote:

What are good frequencies for band splits? (2-5 bands)

What I am doing is divide the range between 100 Hz 5-10 kHz
into equal bands on a log scale (log2 or pitch).

Are there better strategies?
Or better min/max frequencies?
How is it usually done?

conventionally, a graphic EQ might be split into bands with log center 
frequencies every octave, for a 10 band, or every 1/3 octave for a 31 band EQ.

i think the 10-octave frequencies might be at

25, 50, 100, 200, 400, 800, 1600, 3200, 6400, 12800 Hz

with the bandedges at the geometric mean of adjacent pair of frequencies

but they might put them conventionally at

20, 50, 100, 200, 500, 1000, 2000, 5000, 1, 2 Hz

you can see there's a bigger-than-octave gap between 200 and 500.

maybe the 31-band 1/3 octave frequencies might conventionally be at

20, 25, 32, 40, 50, 63, 80, 100, 125, 160, 200, 250, 320, 400, 500, 630, 800, 
1000, 1250, 1600, 2000, 2500, 3200, 4000, 5000, 6300, 8000, 1, 12500, 
16000, 2 Hz

those are conventional frequencies. not all spacing are exactly 1/3 octave.  
you can see that 630 is a compromise between twice 320 and half of 1250.  you 
might want your bands split precisely in 1/3 octaves spaced apart by a 
frequency ratio of 2^(1/3) which is about 1.26.  that might have bands labeled:

20, 25, 32, 40, 50, 63, 80, 100, 126, 159, 200, 252, 318, 400, 504, 635, 800, 
1007, 1271, 1600, 2014, 2542, 3200, 4028, 5084, 6400, 8056, 10168, 12800, 
16112, 20336 Hz


--

r b-j  r...@audioimagination.com

"Imagination is more important than knowledge."



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Re: [music-dsp] bandsplitting strategies (frequencies) ?

2018-03-23 Thread Matt Jackson
Gabriel,

I think it depends on what you are trying to do. What’s your context?

For example a Vocoder (for voice) might have a different distribution of bands 
(bark scale) than a multipurpose graphic EQ (even octaves).
One strange example I know of is the Serge resonant EQ (not crossovers but 
fixed frequency resonant peaks) has deliberately picked frequencies that, 
“except for the top and bottom frequency bands, the bands are spaced at an 
interval of a major seventh. The Resonant Equalizer is designed to produce 
formant peaks and valleys similar to those in acoustic instruments.”

Matt

> On 23. Mar 2018, at 13:05, robert bristow-johnson  
> wrote:
> 
> On 3/23/18 12:01 AM, gm wrote:
>> What are good frequencies for band splits? (2-5 bands)
>> 
>> What I am doing is divide the range between 100 Hz 5-10 kHz
>> into equal bands on a log scale (log2 or pitch).
>> 
>> Are there better strategies?
>> Or better min/max frequencies?
>> How is it usually done?
> 
> conventionally, a graphic EQ might be split into bands with log center 
> frequencies every octave, for a 10 band, or every 1/3 octave for a 31 band EQ.
> 
> i think the 10-octave frequencies might be at
> 
> 25, 50, 100, 200, 400, 800, 1600, 3200, 6400, 12800 Hz
> 
> with the bandedges at the geometric mean of adjacent pair of frequencies
> 
> but they might put them conventionally at
> 
> 20, 50, 100, 200, 500, 1000, 2000, 5000, 1, 2 Hz
> 
> you can see there's a bigger-than-octave gap between 200 and 500.
> 
> maybe the 31-band 1/3 octave frequencies might conventionally be at
> 
> 20, 25, 32, 40, 50, 63, 80, 100, 125, 160, 200, 250, 320, 400, 500, 630, 800, 
> 1000, 1250, 1600, 2000, 2500, 3200, 4000, 5000, 6300, 8000, 1, 12500, 
> 16000, 2 Hz
> 
> those are conventional frequencies. not all spacing are exactly 1/3 octave.  
> you can see that 630 is a compromise between twice 320 and half of 1250.  you 
> might want your bands split precisely in 1/3 octaves spaced apart by a 
> frequency ratio of 2^(1/3) which is about 1.26.  that might have bands 
> labeled:
> 
> 20, 25, 32, 40, 50, 63, 80, 100, 126, 159, 200, 252, 318, 400, 504, 635, 800, 
> 1007, 1271, 1600, 2014, 2542, 3200, 4028, 5084, 6400, 8056, 10168, 12800, 
> 16112, 20336 Hz
> 
> 
> -- 
> 
> r b-j  r...@audioimagination.com
> 
> "Imagination is more important than knowledge."
> 
> 
> 
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Re: [music-dsp] bandsplitting strategies (frequencies) ?

2018-03-23 Thread robert bristow-johnson

On 3/23/18 12:01 AM, gm wrote:

What are good frequencies for band splits? (2-5 bands)

What I am doing is divide the range between 100 Hz 5-10 kHz
into equal bands on a log scale (log2 or pitch).

Are there better strategies?
Or better min/max frequencies?
How is it usually done?


conventionally, a graphic EQ might be split into bands with log center 
frequencies every octave, for a 10 band, or every 1/3 octave for a 31 
band EQ.


i think the 10-octave frequencies might be at

25, 50, 100, 200, 400, 800, 1600, 3200, 6400, 12800 Hz

with the bandedges at the geometric mean of adjacent pair of frequencies

but they might put them conventionally at

20, 50, 100, 200, 500, 1000, 2000, 5000, 1, 2 Hz

you can see there's a bigger-than-octave gap between 200 and 500.

maybe the 31-band 1/3 octave frequencies might conventionally be at

20, 25, 32, 40, 50, 63, 80, 100, 125, 160, 200, 250, 320, 400, 500, 630, 
800, 1000, 1250, 1600, 2000, 2500, 3200, 4000, 5000, 6300, 8000, 1, 
12500, 16000, 2 Hz


those are conventional frequencies. not all spacing are exactly 1/3 
octave.  you can see that 630 is a compromise between twice 320 and half 
of 1250.  you might want your bands split precisely in 1/3 octaves 
spaced apart by a frequency ratio of 2^(1/3) which is about 1.26.  that 
might have bands labeled:


20, 25, 32, 40, 50, 63, 80, 100, 126, 159, 200, 252, 318, 400, 504, 635, 
800, 1007, 1271, 1600, 2014, 2542, 3200, 4028, 5084, 6400, 8056, 10168, 
12800, 16112, 20336 Hz



--

r b-j  r...@audioimagination.com

"Imagination is more important than knowledge."



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