Parametric FIR audio equalizer

"Andrew Reilly" <andrew-newspost@areilly.bpc-users.org> wrote in message
news:pan.2004.10.20.04.48.13.320576@areilly.bpc-users.org...
> On Tue, 19 Oct 2004 20:54:00 -0700, Bob Cain wrote:
>
> >> I'm wondering whether it would be useful to have a phase controller in
> >> addition to the standard parametric eq controls. The phase controller
> >> would go from minimum over linear to maximum phase response.
> >
> > I think that is a _very_ good idea.  The problem I see is
> > that while those three points are well defined, what you
> > might do between them is enormously flexible.  Any ideas
> > that you would be comfortable discussing publicly?
>
> Many years ago ('95-ish, from memory) David McGrath and I presented a
> paper at an AES conference on "optimal phase" FIR EQ synthesis.  I think.
> It's certainly been a feature of the EQ software for Huron systems for
> about that long.  The user can choose minimum or linear phase, or dial-in
> a desired group delay.  I don't think that we ever bothered to allow
> dialing-in group delays that would result in maximum-phase filters though.
> I'll see if I can dig up a paper reference for you.  The papers used to
> be on-line on the web site, but I think that they've fallen of in one
> of the re-designs.  The implementation is a simple generalization of the
> Hilbert transform process that one usually uses to get a minimum-phase
> impulse response.
> http://www.lake.com.au/driver.asp?page=main/products/huron/modular+software
>
> You might also be interested in Lake's "Contour" product line, which
> includes some fairly fancy arbitrary-curve FIR EQ features, and a neat GUI
> to drive it.  http://www.proaudio.lake.com/ [I do work for Lake, but was
> not invloved directly with these particular products, so I'm afraid that I
> can't tell much more about them.]

What I am curious about is how they do the so-called "Mesa" filters, which have
"the ability to separate the sides of a parametric section, change center
frequencies and adjust slopes independently".  That has to be more than a simple
biquad per band.  Or maybe it is FIR?
http://www.lake.com.au/proaudio/Lake_Mesa.htm

Stephan M. Bernsee <spam@dspdimension.com> wrote in message news:<2tmhj5F216dceU1@uni-berlin.de>...
> On 2004-10-16 06:51:05 +0200, PaavoJumppanen@iname.com (Paavo Jumppanen) said:
> 
> > 
> > Thanks Rick,
> > 
> > We had a bit of an infamous start about a year ago being branded snake
> > oil merchants.
> 
> I must admit I too was about to dig out my popular Furutech CD 
> Demagnetizer link again when I first saw the web site... but not! 
> Apparently this is an EQ of some sort. Even though the MP3s don't 
> really help much (for some tracks, the "before" version sounded better 
> than the processed version to me [too much midrange], but I guess 
> that's just the normal exaggeration on the demo files to demonstrate 
> the effect) I bet it can be used to help correcting problems.
> 
> There's a lot more to a good mix than just the proper overall spectral 
> balance (stereo placement of instruments/stereo width, proper 
> application of reverb, good adjustment of the dynamics etc.) so I 
> wouldn't quite agree with all of the claims made on your web site, but 
> it's a start and probably a nice tool for people who just want to make 
> some quick and easy to set up adjustments.

Marketing is marketing. How often do you read a brochure that doesn't
add some spin.

I'd agree that there is a lot more to a good mix than just spectral
balance but the area that is most commonly stuffed up in music
recordings is the spectral balance, and if you think about it there
are very good reasons for this. Apart from the usual limitations of
human hearing (TTS, masking, loudness effects, fatigue etc) every
recording studio control room will have unique acoustic
characteristics and somewhat unique loudspeaker responses which can
end up colouring the mix for one reason or another leading to a
recording that isn't very transportable. Really good studios will have
well defined acoustics (and perhaps applied EQ) that avoid this issue
but how many really good studios are there in the overall picture.
It's probably only a small fraction and that is certainly reflected in
the quality of my CD collection. In any case, we're not proposing
anything radical hear. EQ in mastering is standard practice and most
commercial CD's these days go through mastering houses. Our software
just makes the process of mastering EQ more objective, more efficient
(time spent wise) and less error prone.

Another issue is the prevalence of multiband compression in popular
recordings these days. I've got so many that simply sound bad because
of compression artifacts. It would appear that much of the problem
comes from a particular portion of the spectrum dominating and hence
preferentially being compressed more by multiband compressors,
resulting in strong changes in instrument colour with time. If the
balance is more uniform to start off with these side effects don't
seem to be as pronounced. That being as it may, I wouldn't be
dissappointed if multiband compression vanished tommorrow but it seems
to be entrenched in the industry today.

Regards,


Paavo.

On 2004-10-20 23:52:57 +0200, PaavoJumppanen@iname.com (Paavo Jumppanen) said:

> I'd agree that there is a lot more to a good mix than just spectral
> balance but the area that is most commonly stuffed up in music
> recordings is the spectral balance, and if you think about it there
> are very good reasons for this.

I don't agree. I think the use of too may effects like reverb, cheap 
equipment (or using too many of the free effects plug ins on the 
software side) and poor placement of instruments in a mix is about as 
popular as spectral imbalance (to borrow the subject line of another 
topic). To quote a former employee of a German audio software company 
recently sold to a video company "the fact that you can purchase a 
hammer in a store doesn't mean that you can successfully build your own 
house". IOW: even if you have access to the same tools as the "pros" it 
doesn't mean your mix will sound that way. That's the primary reason 
why bad mixes exist in the first place, and it accounts for 90% of the 
income of mastering facilities (I know because I used to work for one).

> Another issue is the prevalence of multiband compression in popular
> recordings these days. I've got so many that simply sound bad because
> of compression artifacts. It would appear that much of the problem
> comes from a particular portion of the spectrum dominating and hence
> preferentially being compressed more by multiband compressors,
> resulting in strong changes in instrument colour with time. If the
> balance is more uniform to start off with these side effects don't
> seem to be as pronounced. That being as it may, I wouldn't be
> dissappointed if multiband compression vanished tommorrow but it seems
> to be entrenched in the industry today.

Yes, that's indeed the case. Since the appearance of a very popular MBC 
device made by a danish company and its success in the 1990s things 
have become a lot worse than before, when only a few engineers had such 
a device at their disposal. But we've seen this type of misuse before: 
in the 1980s, people came to the mastering facility with tapes or DATs 
that were almost unusable due to excessive use of exciters and stereo 
width enhancers. In the 1990s the multiband compression era began, and 
now it appears we're still right in the middle of the pitch 
quantization decade. Of course you could point your finger at me saying 
that because I'm working at a company involved in developing these 
devices I am partly responsible for this, too (and I wouldn't 
disagree), but it's always a problem with people using and mis-using 
things. But if it's any comfort, I can hardly turn on the radio these 
days without hurting my ears from all the artifacts and effects - if 
you're into developing this stuff you tend to develop a 
hypersensitivity to them. :-)

MBC, if used correctly, does balance the overall spectral shape of a 
recording and makes it sound more pleasant. However, it can easily 
squeeze the life out of a recording, too. If I understand correctly, 
your device balances the overall spectrum without that disadvantage 
because it's an EQ and not a dynamics compressor. The snake oil smell 
probably comes from people who fell for the marketing of matched 
filtering devices and software that claims to accurately model 
microphones, or to transfer the sound of one mix to another. This is a 
dangerous claim because in most cases the trick won't work right and 
people are disappointed.

For you, that's just tough luck I think...
-- 
Stephan M. Bernsee
http://www.dspdimension.com

Stephan M. Bernsee <spam@dspdimension.com> wrote in message news:<2tp1o6F238b6qU1@uni-berlin.de>...
> On 2004-10-20 23:52:57 +0200, PaavoJumppanen@iname.com (Paavo Jumppanen) said:
> 
> > I'd agree that there is a lot more to a good mix than just spectral
> > balance but the area that is most commonly stuffed up in music
> > recordings is the spectral balance, and if you think about it there
> > are very good reasons for this.
> 
> I don't agree. I think the use of too may effects like reverb, cheap 
> equipment (or using too many of the free effects plug ins on the 
> software side) and poor placement of instruments in a mix is about as 
> popular as spectral imbalance (to borrow the subject line of another 
> topic). To quote a former employee of a German audio software company 
> recently sold to a video company "the fact that you can purchase a 
> hammer in a store doesn't mean that you can successfully build your own 
> house". IOW: even if you have access to the same tools as the "pros" it 
> doesn't mean your mix will sound that way. That's the primary reason 
> why bad mixes exist in the first place, and it accounts for 90% of the 
> income of mastering facilities (I know because I used to work for one).

Yes, and a large reason for that is cos there are many people doing
recording who haven't got a good understanding of what they are doing
and why. A big reason for that is not being able to correlate the wat
things sound and what you need to do to improve it. Our customers tell
us that our product helps them in this regard by better training there
ears, since they learn to correlate certain overall tonalities with
the spectral shapes they see in the analysis.

...snip...

> 
> MBC, if used correctly, does balance the overall spectral shape of a 
> recording and makes it sound more pleasant. However, it can easily 
> squeeze the life out of a recording, too. If I understand correctly, 
> your device balances the overall spectrum without that disadvantage 
> because it's an EQ and not a dynamics compressor. The snake oil smell 
> probably comes from people who fell for the marketing of matched 
> filtering devices and software that claims to accurately model 
> microphones, or to transfer the sound of one mix to another. This is a 
> dangerous claim because in most cases the trick won't work right and 
> people are disappointed.
> 
> For you, that's just tough luck I think...

You make it sound much worse than it is (ie. the snake oil tag). That
tag has long gone along with any carping that we had, and we have
never taken the line that you should use this software to try and copy
a mix from another track since it is the wrong thing to do. It ignores
the intentions of the producer in coming up with a particular mix in
the first place. That is why our software is "manual  adjustment
only". There are no magic one button fixes or presets to go with (much
to the dissappointed insistense of a couple of users). I think a some
of our supposed claims come from reading between the lines things that
were never said in the first place, though, like I made out earlier,
it isn't an issue anymore. It only was for the first few months until
we had a host of positive magazine reviews. Contrary to normal
practice we openly offer a 30 day money back guarantee on our software
and we have a refund rate of 2% or less so I guess most people who buy
it are more than satisfied with how it can help them.

Cheers,


Paavo.