[LAU] [Sort of OT] Ringing in filters

[Joel Roth]

On Thu, May 13, 2010 at 12:58:15AM -0700, Ken Restivo wrote:
> On Wed, May 12, 2010 at 10:14:41AM -1000, Joel Roth wrote:
> > Some time ago, Julien Claassen forwarded to me the
> > results of his exchange with Fons regarding reasonable defaults for
> > a three-band mastering network for Nama.
> > 
> > As Fons writes here, the sum of the bandsplitting filters
> > is unlikely to add up to the original signal, however
> > we did adopt what we believe to be a reasonable compromise,
> > with just a couple dB error.
> > 
> > I'm appending the default settings for the LADSPA effects
> > we are using. Each of the low/mid/high branches gets a compressor
> > and a spatialiser.
> > 
> >                 +-- low --+
> > mix ----> eq ---+-- mid --+-- boost ---> output
> >                 +-- high -+
> > 
> > You could create a similar network in Ardour or any other
> > sufficiently flexible software.
> > 
> > 	eq: Parametric1 1 0 0 40 0.125 0 0 200 0.125 0 0 600 0.125 0 0 3300 0.125 0
> > 
> > 	low_pass: lowpass_iir 106 2
> > 
> > 	mid_pass: bandpass_iir 520 800 2
> > 
> > 	high_pass: highpass_iir 1030 2
> > 
> > 	compressor: sc4 0 3 16 0 1 3.25 0
> > 
> > 	spatialiser: matrixSpatialiser 0
> > 
> > 	limiter: tap_limiter 0 0      
> > 
 
> This is interesting. Never thought of building a DIY
> mastering system out of LADSPA plugins, but I guess it
> couldn't hurt.
 
Hi Ken,

The network here is based on the one used in Jamin.

> I'm not sure how to match up the settings you have here
> with the ASCII diagram above. i.e. where does the
> spatializer and limiter fit in? 

                +-- low --+
mix ----> eq ---+-- mid --+-- boost ---> output
                +-- high -+

The low/mid/high branches each get a spatializer
and compressor. 

The limiter goes on the boost track. Could be a
brick-wall limiter, however the scaling limiter
is OOTB defaut.

> And why is the parametric
> in front of the three high/mid/low pass filters, and what
> purpose does it serve? 

Same as any equalizer: for boosting/cutting various
frequency ranges, which may not correspond to the
low/mid/high bands.

> Also, I'm assuming that the SC4 has
> the same settings for each band, at least for starters.

Yes, zero compression is the default (see Julien's notes
below).
 
> Also, I'm not sure how to route this in stereo. I thought
> SC4 was mono anyway. I'd guess that the compressors for
> each band should be stereo compressors, ganged togehter in
> some way (RMS?), like perhaps the Calf Compressor is.

In this case, Ecasound is hosting the LADSPA effects.
I believe Ecasound gangs the effect if necessary
to obtain the correct number of channels.
 
> I feel limited here by ASCII art, and also by how to do
> the routing in for example Ardour, which might be really
> complex, or maybe in something like Ingen.

Well, you could try installing Nama. Then you get
your mastering network by issuing 'master_on' at
the prompt.
 
> The GLAME settings make sense to me: all 2-pole filters,
> with the lowpass rolling off at 106, the bandpass at 520
> and 800, and the highpass at 1030.

Under Nama, if you want to use GLAME plugins instead of the
default filters, you can just substitute the plugin name or
LADSPA Unique ID into the appropriate configuration file
lines quoted above.

(Incidentally, I'm just getting ready to release a 1.0x
version. I've just today uploaded version 1.056 to CPAN,
but it has yet to show up. 1.055 is broken.)

> How would these LADSPA filters compare to, for example,
> postfish? 

In my untutored opinion, all conventional mastering tools
will use a somewhat similar network and similar effects.

If you understand how to use the individual effects, I think
there will not be any unfathomable mystery in the aggregate.
The mystery and artistry will be in your own creative
choices.

What I think Jamin does better than the others is that
it allows you to use different mastering parameters (scenes)
for different parts of the song.

Ron Parker is a respected engineer who not only approves of
Jamin but also wrote the mastering with Jamin tutorial.

http://jamin.sourceforge.net/en/tutorial.html

You say you hear some artifacts. Did you ever approach
the author?

> I'm really starting to wish I'd used postfish
> instead of JAMIN now.

Is Postfish current? It's not on the Linux Sound and MIDI
Applications page, and the last journal entry for postfish 
I see is 2004:

http://xiphmont.livejournal.com/595.html


# Julien Claassen's Notes on Mastering effect defaults
# 
# Eq: All sections are initially off. You can turn them 
# on as needed, one at a time. 
# 
# Bandpass: Default settings are courtesy of Fons
# Adriaensen, who says they will be within 1.5dB of
# flat settings. 
# 
# Compressor is turned off, with reasonable default values 
# set. 
# 
# Spatialiser and limiter: both initially off so you can start out
# clean and slowly work your way from there.

best,

Joel 

> -ken

-- 
Joel Roth