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Mastering Captured Vinyl For CD
Arnold B. Kruege...
post Dec 5 2008, 20:39
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QUOTE (Slipstreem @ Dec 5 2008, 07:19) *
QUOTE (Arnold B. Krueger @ Dec 5 2008, 11:55) *
The two samples still don't have the same frequency response +/- 0.1 dB. Therefore, of course they are going to sound different.

Are you seriously saying that the human ear can detect amplitude errors within the passband as small as 0.2dB, or am I misinterpreting this? I thought it was closer to 2dB. Feel free to poke me in the eye with a


In this particular case there were differences of as much as 5 dB in the upper part of the pass band, between the brickwall and so-called gentle filter. I don't know if they are audible or not, but they are big enough so that their presence creates an unanswered question.

In general, we set a +/- 0. 1 dB tolerance, because some variations as small as 0.5 dB are actually pretty easy to hear under some conditions. It's a overkill number, but not very far into overkill.

2 dB is perceptually *huge* compared to the type of differences that are routinely audible in ABX tests.

There are a lot of conditions on what predicts the potential audibility of a FR differnce. They were presented in detail by means of a chart in the 1978 JAES article by Clark that introduced ABX. For example, narrow dips may be hearder to hear than narrow peaks, and narrow variations may be harder to hear than varaitions over wide ranges. Variations near 4 KHz may be easier to hear than variations near 20 Hz or 20 KHz.
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Dynamic
post Dec 7 2008, 00:07
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When I listen to the three files successively in fb2k I hear:

ti ti ti ti ti ti (ringing_original.wav) - sharp transient with generally high pitch

pp pp pp pp pp pp (ringing_4kHz_LPF_gentle.wav) - a series of duller transients with slightly lower perceived pitch.

then the same duller sound,
pp pp pp pp pp pp (ringing_4kHz_LPF_brickwall.wav)
superimposed with similtaneous bright metallic ringing, similar to a teaspoon hitting a mug or more like a metal cold-chisel being hit by a hammer, the resonance damped quickly by a gloved hand.

The difference is night and day - no need for ABX.
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2Bdecided
post Dec 9 2008, 00:02
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I'm glad that some HA regulars were around to answer the points raised by Arny's posts. I was away for the weekend, so couldn't respond.

This worried me...
QUOTE (Arnold B. Krueger @ Dec 4 2008, 23:51) *
I'm very surprised to hear people on Hydorgen Audio dismissing the idea of introducing scientific controls into their listening tests.

I guess this is just a game, and without any serious intent?
... in fact this is quite sad for me. For various reasons, I'd come to regard you Arny as a world authority on blind testing (despite never having corresponded with you). However, your every contribution to this thread is so wide of the mark, and so correctly rebutted by HA regulars, that I guess HA (or its members) just became the de facto world authority.

If you feel any of the points you made haven't been adequately answered, please say which ones you feel have been overlooked, and I shall attempt to address them.

(Anyone else is free to jump in - you're all doing a great job! wink.gif )

Cheers,
David.

P.S. If you're near London, you might be interested to hear tomorrow's AES lecture / interview (it's a "Christmas special"!), which I believe may include discussion of the choice of minimum phase filters instead of linear phase filters for anti-image filtering. I assume this is to reduce pre-ringing, though do not understand how this could be audible at 22kHz!

http://www.aes.org/sections/uk/meetings/index.html#1208

I'll probably be there. This does not mean I'm turning into a subjectivist wink.gif

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Kees de Visser
post Dec 9 2008, 07:59
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QUOTE (2Bdecided @ Dec 9 2008, 00:02) *
...which I believe may include discussion of the choice of minimum phase filters instead of linear phase filters for anti-image filtering. I assume this is to reduce pre-ringing, though do not understand how this could be audible at 22kHz!
That could be an interesting evening. In the ongoing discussions about hi-res (and vinyl?) audio benefits the filters remain an important element. If you do go, could you ask some suggestions for killer samples that can demonstrate filter effects (even in a DBT smile.gif)? I've been thinking about setting up a test but it's a tricky one. If the effect can't be demonstrated in a sighted test, like you did with your 4kHz samples, it's probably a waste of time. Could you please ask as well about speakers vs headphone listening ? Thanks and enjoy the evening.
ps: it would be nice if the "supporting material" (hopefully audio samples) is freely available.
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Arnold B. Kruege...
post Dec 9 2008, 13:33
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QUOTE (Dynamic @ Dec 6 2008, 18:07) *
The difference is night and day - no need for ABX.


Very very many of the golden ears say the exact same thing about their listening tests relating to green pens, magic cables, etc.

So, I guess we're supposed to tell the difference between what the golden ears say, and what you say because... ????

People who "get it" just do the listening test with the relevant controls and report statisitically significant results.

It's pretty obvious who around here gets it, and who doesn't. And, going to AES lectures doesn't seem to help. It's this way in most technologies. Lip service versus actual change in behavior.
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2Bdecided
post Dec 9 2008, 14:07
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I see a line-by-line critique is needed. I'll work on it.

btw, I didn't report "going to AES lectures" to impress, or to imply I had some credentials. For one thing, I've been to a couple in the last decade, and for another, anyone who has ever attended one would not claim that attendance is anything to boast about!

Cheers,
David.
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2Bdecided
post Dec 9 2008, 16:18
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Firstly, I believe in double blind testing. Any genuinely audible difference should be able to be proven as such in a statistically verifiable double blind test.

There may be practical issues (e.g. DBT of speakers is a challenge), but most issues can be overcome with sufficient effort.


Now, let's talk about the current test.

Firstly, should we ABX when "the difference is obvious"? Well, on HA we generally let people off from ABXing "obvious" things, but where there's doubt, people should be happy to ABX for the avoidance of doubt. TOS 8! krabapple has already ABXed, so that's that issue answered.

Secondly, is it appropriate to ABX this? I would say no - most people are claiming an audible difference, and you yourself are not doubting an audible difference. It's the nature of the audible difference that's in doubt, and ABX cannot help here. Blind A/B testing may be useful.

Thirdly, should we level match? Yes, for a fair comparison, we should. However, your methods of doing so are misguided. Where the audible differences may be subtle, and/or where the mathematical change to the signal may be significant, blind application of peak or RMS normalisation may increase the perceived level difference between signals, rather than remove it. ReplayGain would be an answer if it was perfect, but it is not. It might be the "least bad" solution in some circumstances, but not here.

The best solution available is to manage all processes that introduce a level difference, and mitigate them - or to design the experiment to avoid introducing level differences entirely. In the current example, the energy within the flat part of the passband is identical in all three examples. For this type of signal, that's about as good as it gets. There are corrections you could apply for the non-flat part of the pass band, but that would break this experiment by introducing an audible difference into the flat part of the pass band.

Fourthly(!), you demand the frequency response be matched to +/-0.2dB. If we were ABXing two things that should sound the same and/or be the same, this would be relevant - but in this case we are comparing a brick wall filter (which you say does not ring, and I say does) with a non-brick wall filter (which I say rings far less). These have different time and frequency domain responses. This is the nature of the experiment.

If I were to take a brick wall filter, and try to conduct this test whilst staying with +/-0.2dB of the brick will filter, then the other filter would also be a brick wall filter - I would be comparing two brick wall filters! Not very useful, I'm sure you'll agree.

Fifthly, you said...
QUOTE
Very very many of the golden ears say the exact same thing about their listening tests relating to green pens, magic cables, etc.

So, I guess we're supposed to tell the difference between what the golden ears say, and what you say because... ????
Let's get one thing very clear: green pens, magic cables etc create no measurable, objective difference. Whereas the difference we're examining here is visible in the waveform plot, and in a spectrogram. Also, if you look at, and measure, the audio signal, and compare it to the nearest relevant psychoacoustic data, you'll see that the ringing is predicted as being audible.*


Maybe you can't hear it. It's well known that absolute thresholds vary between individuals, and that masked thresholds vary even between individuals with identical absolute thresholds. I would speculate that sensitivity to temporal masking varies even more widely between individuals than sensitivity to spectral masking.

However, it's been ABXed, and multiple posters have now reported hearing the same thing. Added to the fact that it's visible on a spectrogram, this demolishes the idea that it's imagined.


I think you've spent too long around subjectivist audiophiles. Your knee jerk "magic cable" response is incorrect and unjustified.


Your original assertion - that brick wall filters do not ring - belies such a fundamental misunderstanding of filtering and hearing that I expect this thread to run for a while yet. But let's see if we can't resolve our differences over the ABXing of these files first.

Cheers,
David.

* That's despite the fact that the nearest data uses a burst of white noise, while the current test uses a tiny click! Even the white noise can't drag the masking thresholds sufficiently high in a pre-masking experiment in order to mask the ringing measurably present in a brick wall filtered signal.
Pre masking data, white noise masking tone, here:
Gehr, S. E.; and Sommers, M. S. (1999).
Age difference in backward masking.
Journal of the Acoustical Society of America, vol. 106, no. 5, Nov., pp. 2793-2799.

This post has been edited by 2Bdecided: Dec 9 2008, 16:21
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2Bdecided
post Dec 10 2008, 16:49
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I went to the lecture last night, and am happy to post a report, but I'd rather get the above issues resolved first.

Cheers,
David.
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Arnold B. Kruege...
post Dec 10 2008, 20:11
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QUOTE (2Bdecided) *
Fifthly, you said...
QUOTE
Very very many of the golden ears say the exact same thing about their listening tests relating to green pens, magic cables, etc.


Let's get one thing very clear: green pens, magic cables etc create no measurable, objective difference.


Actually, magic cables generally do have measurable differences. Speaker cables of any signficiant length are even a little like amplifiers, in that they all measure differently, but most if not all of the measurable differences are too small or of the wrong kind to matter.

Many interconnects are just a little microphonic. The stuff we can reliably measure today can be just crazy!

Green pens have a number of measurable effects on CDs, but they rarely if ever show up in the audio domain.

The point is that trying to defend not doing an ABX test on the grounds that there was a measurable effect just doesn't work out in real life.

The goal is to reduce subjectivity and judgement calls as much as possible. Of course, we still end up making judgement calls.
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Arnold B. Kruege...
post Dec 10 2008, 20:31
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QUOTE (2Bdecided @ Dec 9 2008, 10:18) *
Your original assertion - that brick wall filters do not ring - belies such a fundamental misunderstanding of filtering and hearing that I expect this thread to run for a while yet. But let's see if we can't resolve our differences over the ABXing of these files first.


One of your real serious problems is that you make a lot of presumptions, and you personalize way too much.

You presume that my assertion is an indication of defficiencies in my basic education. In fact my education ain't all that bad. I've probably known about, worked with, and had some fairly useful understanding of the Gibbs phenominon for maybe 45 years.

Nahh, what happened is that I've been thinking about this for several weeks just lately, taking a sort of a blank paper approach.

I've been told for decades that the brick wall filters in 44 Khz ADCs and DACs clearly and audibly corrupted sound quality, but I know for a fact that a well-done pair of 44 KHz ADCs and DACs are sonically transparent in demanding real-world tests.

Of course they all appear to ring to some degree. What's your explanation for all the apprarent ringing and yet all the ABX tests with null results?

Last time I challenged established thinking about digital like this, I came up with the concept of self-dither, which is now rather widely recognized. My main opponent in that debate was very, very abusive. He got to be wrong. ;-)
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Woodinville
post Dec 10 2008, 21:33
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QUOTE (Arnold B. Krueger @ Dec 10 2008, 11:31) *
I've been told for decades that the brick wall filters in 44 Khz ADCs and DACs clearly and audibly corrupted sound quality, but I know for a fact that a well-done pair of 44 KHz ADCs and DACs are sonically transparent in demanding real-world tests.

Just for kicks, you ought to look at some of the half-band filters used in some of the common sigma-delta convertors out there. I wouldn't use the term "brick wall", though. This may be a separate discussion, though, of actual implimentation compared to how it should be done.
QUOTE
Of course they all appear to ring to some degree. What's your explanation for all the apprarent ringing and yet all the ABX tests with null results?


Ringing is nothing more than the impulse response of any sharp filter. FIR, IIR, whatever, if it's a sharp (in terms of small transition band) filter, it's going to "ring".

Is it audible?

It is POSSIBLE (but unproven as far as I know, barring some results being established here, perhaps) that exactly the wrong kind of ringing, perhaps from a not-well-designed FIR filter could lead to perceptable pre-echo under some very, very special conditions...

Please notice all of the qualifications in that statement.


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2Bdecided
post Dec 11 2008, 11:11
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Arny,

Let's get back on the same page. I've made no claim that anti-alias filters are audible.

I challenged your statement that brick wall filters do not ring.

I said...
QUOTE (2Bdecided @ Dec 3 2008, 17:32) *
the sharper you make the cut off of a linear phase filter, the longer it will ring for. If the transition band is in the audible range, and there is original content in the vicinity of the transition band, you will hear the ringing.

To back this up, I provided some samples with a brick wall filter at 4kHz.

http://www.hydrogenaudio.org/forums/index....st&p=602827

I think the ringing (or whatever you want to call it) is clearly audible. "Dynamic" seems to hear the same. You seem to hear something different. What do other people think/hear?


QUOTE (Arnold B. Krueger @ Dec 10 2008, 20:31) *
I've been told for decades that the brick wall filters in 44 Khz ADCs and DACs clearly and audibly corrupted sound quality, but I know for a fact that a well-done pair of 44 KHz ADCs and DACs are sonically transparent in demanding real-world tests.

Of course they all appear to ring to some degree. What's your explanation for all the apparent ringing and yet all the ABX tests with null results?
The ringing is at 22kHz. I can't hear 22kHz.

That's why I provided samples with a cut-off frequency of 4kHz.


We're confusing two completely different issues in this thread - audibility of ultrasonic ringing, and audibility of ringing within the audible band. I initially thought you were only talking about the former, but then you provided an example to prove that ringing at 6kHz was inaudible - I don't accept this at all.

No more personal comments. I don't have any "problem" with you - I was just holding you to a far higher standard than anyone else due to your background, so made far harsher criticisms of things I didn't agree with. I apologise.

Cheers,
David.
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bandpass
post Dec 11 2008, 13:47
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QUOTE (2Bdecided @ Dec 11 2008, 10:11) *
I think the ringing (or whatever you want to call it) is clearly audible. "Dynamic" seems to hear the same. You seem to hear something different. What do other people think/hear?

I agree the ringing at 4k is clearly audible. I tried increasing the filter frequency and it becomes less audible---ABXing would be needed at higher frequencies.

Back at 4k, I also tried sliding the phase response around, and using an intermediate phase response, managed to achieve a reduction, but not elimination, of the audible ringing. Minimum phase still sounds pretty bad (when the source signal is clicks).

-bandpass

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Kees de Visser
post Dec 11 2008, 15:42
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QUOTE (2Bdecided @ Dec 11 2008, 11:11) *
I think the ringing (or whatever you want to call it) is clearly audible. "Dynamic" seems to hear the same. You seem to hear something different. What do other people think/hear?
I also hear a pitched noise around 4kHz in the brickwall version, which is hardly audible in the gentle version.
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krabapple
post Dec 11 2008, 19:31
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QUOTE (Arnold B. Krueger @ Dec 9 2008, 07:33) *
QUOTE (Dynamic @ Dec 6 2008, 18:07) *

The difference is night and day - no need for ABX.


Very very many of the golden ears say the exact same thing about their listening tests relating to green pens, magic cables, etc.

So, I guess we're supposed to tell the difference between what the golden ears say, and what you say because... ????

People who "get it" just do the listening test with the relevant controls and report statisitically significant results.

It's pretty obvious who around here gets it, and who doesn't. And, going to AES lectures doesn't seem to help. It's this way in most technologies. Lip service versus actual change in behavior.



2bdecided "gets it". He's most definitely a 'white hat' on audio matters, as are most of the regular posters here.

And HA is most definitely not Usenet -- suspicions and accusations appropriate for, say, the rec.audio groups, aren't applicable here.

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krabapple
post Dec 11 2008, 19:47
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QUOTE (bandpass @ Dec 11 2008, 07:47) *
QUOTE (2Bdecided @ Dec 11 2008, 10:11) *

I think the ringing (or whatever you want to call it) is clearly audible. "Dynamic" seems to hear the same. You seem to hear something different. What do other people think/hear?

I agree the ringing at 4k is clearly audible. I tried increasing the filter frequency and it becomes less audible---ABXing would be needed at higher frequencies.



I too heard a 'brighter' or slightly metallic presentation in the gentler filter, compared to the steeper one, in my ABX comparisons. There was also a sensation that the gently filtered sample was pitched slightly higher than the steeply-filtered one; these perceptions were how I was able to ABX them, without level-matching.
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Arnold B. Kruege...
post Dec 12 2008, 12:18
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QUOTE (krabapple @ Dec 11 2008, 13:31) *
QUOTE (Arnold B. Krueger @ Dec 9 2008, 07:33) *

QUOTE (Dynamic @ Dec 6 2008, 18:07) *

The difference is night and day - no need for ABX.


Very very many of the golden ears say the exact same thing about their listening tests relating to green pens, magic cables, etc.

So, I guess we're supposed to tell the difference between what the golden ears say, and what you say because... ????

People who "get it" just do the listening test with the relevant controls and report statisitically significant results.

It's pretty obvious who around here gets it, and who doesn't. And, going to AES lectures doesn't seem to help. It's this way in most technologies. Lip service versus actual change in behavior.


2bdecided "gets it".


I'm sticking to what I said. People who "get it" just do the listening test with the relevant controls and report statisitically significant results.

I reported the first ABX test results from this particularly comparison, showing that I practice what I preach.

QUOTE
He's most definitely a 'white hat' on audio matters, as are most of the regular posters here.


To some degree. He seems to be naive about measurable differences in audio cables, for example.

QUOTE
And HA is most definitely not Usenet -- suspicions and accusations appropriate for, say, the rec.audio groups, aren't applicable here.


I dunno, I've had more than enough suspicions and false accusations thrown at me so far. :-(

Not nearly as bad as RAO (little is!), but probably worse than RAP.
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Kees de Visser
post Dec 12 2008, 13:38
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QUOTE (Arnold B. Krueger @ Dec 12 2008, 12:18) *
I'm sticking to what I said. People who "get it" just do the listening test with the relevant controls and report statisitically significant results.
Fair enough, but we might need your help.
Two stimuli are presented that are known to be different. Their frequency spectra differ by more than 0.1 dB in the audible range. IIRC you stated earlier in this thread that an ABX test is not valid when the spectra are not within a 0.1 dB margin. How can this test be made valid in your opinion ?
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Axon
post Dec 12 2008, 16:57
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For that matter, I'm still not convinced that Arny's normalization process (and therefore his ABX test) was ever valid to begin with. It's my understanding that the passband spectrum was exactly the same between all the samples, so the normalization process actually denormalized them.
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Arnold B. Kruege...
post Dec 12 2008, 20:30
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QUOTE (Kees de Visser @ Dec 12 2008, 07:38) *
QUOTE (Arnold B. Krueger @ Dec 12 2008, 12:18) *
I'm sticking to what I said. People who "get it" just do the listening test with the relevant controls and report statisitically significant results.
Fair enough, but we might need your help.
Two stimuli are presented that are known to be different. Their frequency spectra differ by more than 0.1 dB in the audible range. IIRC you stated earlier in this thread that an ABX test is not valid when the spectra are not within a 0.1 dB margin. How can this test be made valid in your opinion ?


ABC/hr ?
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Arnold B. Kruege...
post Dec 12 2008, 20:42
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QUOTE (Axon @ Dec 12 2008, 10:57) *
For that matter, I'm still not convinced that Arny's normalization process (and therefore his ABX test) was ever valid to begin with. It's my understanding that the passband spectrum was exactly the same between all the samples, so the normalization process actually denormalized them.


Seems like a moot point since it is a matter of fact that the two signals vary by several dB in the passband.

So far nobody has matched the levels of these signals in such a way that they were indistingushable in an ABX test. Closer analysis suggests that could well be mission impossible. Perhaps this is not the test that will resolve the question at hand?

The experiment that would resolve this question would process the input signal twice, each time producing a signal whose spectral energy content, etc. matched the other processed signal very closely.

The only difference between the two signals would be that one processed signal had the waveform abberations that are typical of the Gibbs Phenominon, and the other did not.

It's been suggested that there may exist some minimum phase filter that is less intrusive than other non-minimum phase filters, but provides the same output spectral energy content. The phase shifting of the two signals can be expected to be different.
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Woodinville
post Dec 12 2008, 22:07
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QUOTE (Arnold B. Krueger @ Dec 12 2008, 11:42) *
It's been suggested that there may exist some minimum phase filter that is less intrusive than other non-minimum phase filters, but provides the same output spectral energy content. The phase shifting of the two signals can be expected to be different.



Are you using a "linear phase" (constant delay) filter as your non-minimum-phase filter? Are these FIR's, if so how long?

Given a set of coefficients, one can create (for any zero pair that is not on the unit circle) another FIR that is more closely minimum-phase than a standard symmetric FIR quite trivially, or in fact create a maximum-phase filter as well.

Still done via FIR, but resulting in non-symmetry.

A short example:

Columns 1 through 9

0.0047 0.0213 0.0045 -0.0388 -0.0581 0.0227 0.1970 0.3467 0.3467

Columns 10 through 16

0.1970 0.0227 -0.0581 -0.0388 0.0045 0.0213 0.0047


versus

cc =

Columns 1 through 10

0.0153 0.1036 0.2420 0.3467 0.3107 0.1353 -0.0528 -0.1211 -0.0607 0.0264

Columns 11 through 16

0.0518 0.0205 -0.0095 -0.0128 0.0033 0.0015



These two filters have identical (magnitude) frequency response to the level of rounding in the printout. I'm not feeling energetic enough to print them to double precision right now.

The only question in this process is "is Matlab's rooting algorithm able to do the filter roots right". If the answer is yes, invert all zeros with magnitude over 1, and you get as close to minimum phase as you can get.

This post has been edited by Woodinville: Dec 12 2008, 22:17


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2Bdecided
post Dec 12 2008, 23:47
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QUOTE (Arnold B. Krueger @ Dec 12 2008, 20:42) *
The experiment that would resolve this question would process the input signal twice, each time producing a signal whose spectral energy content, etc. matched the other processed signal very closely.

The only difference between the two signals would be that one processed signal had the waveform abberations that are typical of the Gibbs Phenominon, and the other did not.
With a linear phase filter, this is impossible. The ringing is proportional to the steepness of the transition band. If the "spectral energy content" matches, then, for linear phase, the amount of ringing will match. It will be two copies of the same filter - there are no other variables.

QUOTE
It's been suggested that there may exist some minimum phase filter that is less intrusive than other non-minimum phase filters, but provides the same output spectral energy content. The phase shifting of the two signals can be expected to be different.
Indeed so, but that would allow you to compare two (or more) brick wall filters with the ringing shifted about due to phase differences. This is all very interesting, and I could guess with some certainty at the audible result, but this isn't the exact point I was making.

It's easy enough to do, but requires MATLAB or similar, not Cool Edit Pro - unless you want to try one of its IIR filters, one of which might be minimum phase, and time reverse the result, which hence might be maximum phase.

Any takers?

Cheers,
David.
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bandpass
post Dec 13 2008, 15:31
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QUOTE (2Bdecided @ Dec 12 2008, 22:47) *
It's easy enough to do, but requires MATLAB or similar, not Cool Edit Pro - unless you want to try one of its IIR filters, one of which might be minimum phase, and time reverse the result, which hence might be maximum phase.

Any takers?

Here you go: phases.zip

000 = minimum phase, ..., 050 = linear phase, ..., 100 = maximum phase

-bandpass

This post has been edited by bandpass: Dec 13 2008, 18:01
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2Bdecided
post Dec 13 2008, 19:17
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Thanks bandpass.

The difference is night and day.

Minimum phase sounds like someone flicking/tapping a slightly damped wine glass, as you'd expect. Sharp start, then decay. The other two have a soft start.

For the doubters, I confirm that the magnitude response is identical, though you need a very long FFT to check it.

How did you generate these? (Not that I doubt - just interested).

Cheers,
David.

This post has been edited by 2Bdecided: Dec 14 2008, 15:26
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