Audibility of "typical" Digital Filters in a Hi-Fi Playback

Topic: Audibility of "typical" Digital Filters in a Hi-Fi Playback (Read 328622 times) previous topic - next topic

0 Members and 1 Guest are viewing this topic.

Audibility of "typical" Digital Filters in a Hi-Fi Playback

Reply #300 – 2014-11-18 14:38:24

Quote from: amirm on 2014-11-17 23:25:10

Quote from: Arnold B. Krueger on 2014-11-17 21:29:00
Quote from: amirm on 2014-11-17 21:15:47
For months on AVS Forum we have been discussing the audibility of high resolution audio. After passing ABX DBT after ABX DBT, the claim always went back, "well, Meyer and Moran didn't find this difference and it was peer reviewed so this data must be wrong."

I guess you didn't get the memo Amir (silliy I should expect you to comprehend it, given that it is in a recent post to this thread), but the ABX tests I posted on AVS had a built in flaw that I only very recently became aware of which is that the transition band of my downsampling filter was way too narrow per this certain peer reviewed paper from Meridian.

It was covered in the second part of this post: http://www.hydrogenaud.io/forums/index.php...st&p=881145

We know that the other set of files had other serious flaws of their own.

It thus becomes improper for anybody to say: "After passing ABX DBT after ABX DBT" because there were no proper tests.

Arny's files never had sync problems. But yes, I did resample them using latest version of Audition CC and I could still tell them apart.

The claim above is false - there were never any audible synch problems.

The problem in question had nothing to do with synch.

It had to do with transition bands Were the alleged proper 4416 file available for download I would review them and grant an opinion.

Audibility of "typical" Digital Filters in a Hi-Fi Playback

Reply #301 – 2014-11-18 15:11:57

Good morning there. I must say, that was the shortest goodbye I have seen .

Quote from: greynol on 2014-11-18 03:14:52

FFS, we each don't communicate in a vacuum. You've already been schooled by others on the matter.

You say that as if it is supposed to be something negative. It better not be. I live for days I learn something from these forum interactions as opposed to dealing with male insecurities to get personal.

You have some very knowledgeable members here who for sure could school me. Alas, as it happens, they are the ones without a copy of the paper so can’t speak properly to what the test is all about. As it turns out the people with a copy of the paper don't have expertise in this field so we are honestly reading gibberish from them.

Not saying the above to put folks down. It is the reality of the work in front of us. It is not a school project like Meyer and Moran. Even though the paper describes a listening test, it is extremely dense with jargon of audio signal processing, statistics, and analysis. It is way beyond the knowledge level of a typical forum member who doesn't do this work professionally. I hope to remedy this situation below.

Quote

Any test scores showing rectangular dither didn't affect the results?

If you are asking this question, it means that there is still no understanding of what the paper was about some 12 pages and 300 posts later. So please allow me to give you the summary as to facilitate proper schooling, whichever direction it will go.

Let's start at the top. This is the title of the paper:The audibility of typical digital audio filters in a high-fidelity playback system

No, I am not being pedantic . Please pay attention to what I have highlighted: digital audio filters. That is the mission of the paper. They start with 192 Khz music samples, then apply two filters to it. One is to represent CD sampling rate of 44.1 Khz and the other, 48 Khz. Here is the paper itself in technicolor to make sure these key points are not lost:

2.3. Signal processing and test conditions

Two kinds of linear-phase FIR (fnite impulse re-
sponse) filter were used, both of which operated at
192 kHz and both of which were implemented us-
ing TPDF (triangular probability density function)
dither at the 24th bit. For both FIR filters, the
ripple depth over the passband was a maximum of
0.025 dB, and the stopband attenuation was 90 dB.

The frequencies of the transition bands were 23500-
24000 Hz and 21591-22050 Hz, corresponding to the
standard sample rates of 48 kHz and 44.1 kHz re-
spectively. Fig. 2 shows the amplitude and energy
of the impulse response for the 48-kHz filter.

I have highlighted two key things:

1. The "ideal" TPDF filtering was used contrary to the impression left so far in this thread but I will get to where it is not used and source of confusion in a bit.
2. The filtering is the kind of textbook response that we always say is as good as “perfect” and hence inaudible: a fraction of irregularity over the audio band and strong rejection of out of band spectra.

This is what the test sets out to find out. Remember the title again: it is all about digital audio *filtering*. Key thing to note is that the above transformations are in 24 bit as is the source. Further, the sampling rate in all cases remains at 192 Khz. We are simply looking at what would happen if the bits were filtered down to lower bandwidth that 44.1 and 48 Khz would entail while keeping everything else the same.

Our camp’s position is that no double blind test would ever demonstrate anything an audible difference to statistical confidence. As otherwise it would say the mere conversion of higher bandwidth to CD’s (and that of 48 Khz) is a lossy audible conversion. Let’s see how it turned out.

The paper explains six (6) ways this filtering was tested:

Translating into English, listing tests 1 and 4 (“none”) examine exactly what I described above. Filtering of a 192 Khz/24-bit file down to what it would have been at 44.1 Khz and 48 Khz sampling while remaining in 24-bit mode. Again please allow me to remind you that in both cases TPDF dither is used, not rectangular. So the answer you ask in this regard is “no.” RPDF was not used so it did not interfere with this part of the test.

The other test conditions deal with what would happen if we converted the filtered 24 bit output to 16 bit samples using two different methods. One by simply truncating it or the so called “self-dither.” The extra resolution bits are simply discarded. This is tests #2 and #5.

The other method and what folks have been fixated on, namely conversion of 24 bit to 16 rectangular PDF dither. The theory says this is superior to doing nothing. Results here are surprising as with the filtering.

I hope everyone is with me so far. That we have six (6) independent tests, not just one like Meyer and Moran performed. This allows us to investigate the effect of each processing separately and together.

The Results
Here they are:

Remember, we had three tests for each filtering: no dither (24 bit), truncation to 16 bits, and dithered to 16 bits. And that is what is represented in the above graph.

The horizontal line at 56% shows the 95% level high confidence bar. Please don’t be swayed by the small numerical value of “56%.” The statistics are not for lay people. Just remember that this is the same standard we require of all such tests. If we achieve better than 95% results, we trust the outcome.

We see that five (5) out of six (6) listening tests comfortably cleared the 95% interval both in their mean and standard deviation. Oddly, the 24-bit, 48 Khz sampling did not do so fully when you account for the error range. A further look at the results focusing on critical/more revealing music segments dealt with that by bringing that score above 95%.

So what do we learn? All processing was distinguished from the original to statistics confidence! Filtering with or without conversion to 16 was audibly different to listeners (to statistical confidence). None of this was expected by our camp’s vocal members. And certainly counter to Meyer and Moran’s test indicating these are all transparent conversions.

The rest of the paper theorizes as to why these differences were heard. I won’t get into that now. But I hope it is clear that this test easily schools all of us. That our knowledge of psychoacoustics with respect to digital audio filters/quantization is not complete. All of these tests should have failed to invalidate the null hypothesis but they did not. I am confident this is one of the reasons that peer reviewers were impressed with this work. It is groundbreaking in documenting audible differences this way.

Circling back to your question, if you like to throw out the results of 16 bit conversion with or without dither, do. But then explain why simple filtering of spectrum to 22.05 and 24 Khz resulted in audible differences despite near perfect frequency domain response of this type of anti-aliasing filter.

Audibility of "typical" Digital Filters in a Hi-Fi Playback

Reply #302 – 2014-11-18 18:03:35

Great, and we had the conditions already posted before a few pages back. The focus on the dither was indeed derailing a bit.

What we really need are the original algorithms and software used to do the processing and switching. And someone into statistics really needs to explain what is going on.

Audibility of "typical" Digital Filters in a Hi-Fi Playback

Reply #303 – 2014-11-18 18:16:46

I have a question about the test methodology. The "same or different" choice is subject to statistical bias unless care is taken since human guessing is biased. (Humans tend to pick "c" on multiple choice questions and "different" on "same or different" questions.) Were the number of "same" cases equal to the number "different" cases in each test case? If not, the results might be biased. Can you tell from the paper itself?

Audibility of "typical" Digital Filters in a Hi-Fi Playback

Reply #304 – 2014-11-18 18:57:49

Quote from: amirm on 2014-11-18 15:11:57

Good morning there. I must say, that was the shortest goodbye I have seen .
Quote from: greynol on 2014-11-18 03:14:52
FFS, we each don't communicate in a vacuum. You've already been schooled by others on the matter.

You say that as if it is supposed to be something negative. It better not be. I live for days I learn something from these forum interactions as opposed to dealing with male insecurities to get personal.

You have some very knowledgeable members here who for sure could school me. Alas, as it happens, they are the ones without a copy of the paper so can’t speak properly to what the test is all about. As it turns out the people with a copy of the paper don't have expertise in this field so we are honestly reading gibberish from them.

Not saying the above to put folks down. It is the reality of the work in front of us. It is not a school project like Meyer and Moran. Even though the paper describes a listening test, it is extremely dense with jargon of audio signal processing, statistics, and analysis. It is way beyond the knowledge level of a typical forum member who doesn't do this work professionally. I hope to remedy this situation below.
Quote
Any test scores showing rectangular dither didn't affect the results?

If you are asking this question, it means that there is still no understanding of what the paper was about some 12 pages and 300 posts later. So please allow me to give you the summary as to facilitate proper schooling, whichever direction it will go.

Let's start at the top. This is the title of the paper:The audibility of typical digital audio filters in a high-fidelity playback system

No, I am not being pedantic . Please pay attention to what I have highlighted: digital audio filters. That is the mission of the paper. They start with 192 Khz music samples, then apply two filters to it. One is to represent CD sampling rate of 44.1 Khz and the other, 48 Khz. Here is the paper itself in technicolor to make sure these key points are not lost:

2.3. Signal processing and test conditions

Two kinds of linear-phase FIR (fnite impulse re-
sponse) filter were used, both of which operated at
192 kHz and both of which were implemented us-
ing TPDF (triangular probability density function)
dither at the 24th bit. For both FIR filters, the
ripple depth over the passband was a maximum of
0.025 dB, and the stopband attenuation was 90 dB.

The frequencies of the transition bands were 23500-
24000 Hz and 21591-22050 Hz, corresponding to the
standard sample rates of 48 kHz and 44.1 kHz re-
spectively. Fig. 2 shows the amplitude and energy
of the impulse response for the 48-kHz filter.

I have highlighted two key things:

1. The "ideal" TPDF filtering was used contrary to the impression left so far in this thread but I will get to where it is not used and source of confusion in a bit.
2. The filtering is the kind of textbook response that we always say is as good as “perfect” and hence inaudible: a fraction of irregularity over the audio band and strong rejection of out of band spectra.

The paper goes on to say:

"After filtering with either FIR lter, the signals
were either unchanged or were quantized to 16-
bit. The quantization either included RPDF (rect-
angular probability density function) dither or did
not.

So while the low pass filtering used TPDF dither applied to the 24th bit which due its tiny size is far less important, the requantization to 16 bits which was highly important and in fact one of the two main points that this test was all about used RPDF dither.

So, what we have in the comments above that I am responding to, is yet another failure of reading comprehension.

Audibility of "typical" Digital Filters in a Hi-Fi Playback

Reply #305 – 2014-11-18 19:37:28

Quote from: amirm on 2014-11-18 15:11:57

But I hope it is clear that this test easily schools all of us.

Yes, it teaches how far those with pecuniary interest will spin rigged tests that appear to show some desired results, but with no verification of system transparency/artifacts (that BS and JJ warn about).
But then it creates this dilemma for your side Amir:

cheers,

AJ

Audibility of "typical" Digital Filters in a Hi-Fi Playback

Reply #306 – 2014-11-18 19:47:09

You missed the target a little bit, Arny. You too, AJ.

Taken at face-value, the data clearly shows that 16-bit dither did not matter for the 22 kHz-treated version. It doesn't prove the choice of dither couldn't have affected the results for the 24kHz-treated version, however.

It also doesn't address the other issues raised about the hardware and unknown(?) filter algorithms.

...and now we have at least one sample that appears suspect, as well as statistical chop suey to wade through.

Thank you, Amir, for finally presenting something based on the actual test data.

Audibility of "typical" Digital Filters in a Hi-Fi Playback

Reply #307 – 2014-11-18 20:08:14

I wonder about one simple thing. Please don't shoot me because i am just one of these hobby noobs around here.
If that tweeter for playback really has such a strong resonance shouldn't music with content at that resonance frequency trigger some unwanted behaviour that even sounds different as with music without content there?
As a sidenote, i really love magnetostats.

Audibility of "typical" Digital Filters in a Hi-Fi Playback

Reply #308 – 2014-11-18 20:17:29

Quote from: greynol on 2014-11-18 19:47:09

Thank you, Amir, for finally presenting something based on the actual test data.

I could post more graphics from the paper if there was some easy cheap way to host them. Some forums host uploaded graphics. Does this one?

Audibility of "typical" Digital Filters in a Hi-Fi Playback

Reply #309 – 2014-11-18 20:26:10

Yes. Just dump them in the thread you created in the uploads forum and link to them here.

Audibility of "typical" Digital Filters in a Hi-Fi Playback

Reply #310 – 2014-11-18 20:40:46

Quote from: Wombat on 2014-11-18 20:08:14

I wonder about one simple thing. Please don't shoot me because i am just one of these hobby noobs around here.

Modesty speaks . You are more than qualified to discuss this topic.

Quote

If that tweeter for playback really has such a strong resonance shouldn't music with content at that resonance frequency trigger some unwanted behaviour that even sounds different as with music without content there?
As a sidenote, i really love magnetostats.

The system measurement in the paper does not show that resonance from stereophile review. It has rather smooth response extending to 50 Khz (vertical scale is too squished to read accurately but this is more or less the picture). There is certainly no 12 db peak at 26 Khz.

Audibility of "typical" Digital Filters in a Hi-Fi Playback

Reply #311 – 2014-11-18 20:45:33

Quote from: greynol on 2014-11-18 19:47:09

It also doesn't address the other issues raised about the hardware and unknown(?) filter algorithms.

There is good bit of discussion of the filters in use including both frequency and impulse responses. They can definitely be duplicated although the person has to be considerably less lazy than me to do so .

Quote

Thank you, Amir, for finally presenting something based on the actual test data.

My pleasure.

Audibility of "typical" Digital Filters in a Hi-Fi Playback

Reply #312 – 2014-11-18 20:54:52

Quote from: Arnold B. Krueger on 2014-11-18 18:57:49

The paper goes on to say:

"After filtering with either FIR lter, the signals
were either unchanged or were quantized to 16-
bit. The quantization either included RPDF (rect-
angular probability density function) dither or did
not.

So while the low pass filtering used TPDF dither applied to the 24th bit which due its tiny size is far less important, the requantization to 16 bits which was highly important and in fact one of the two main points that this test was all about used RPDF dither.

So, what we have in the comments above that I am responding to, is yet another failure of reading comprehension.

I will take another shot at summarizing the paper but if that doesn't work, someone else has to explain it to you Arny.

Almost every bit of recording done today is in 24 bit and at sampling rates > CD. In conversion to CD, two steps need to be performed.

1) Reducing the bandwidth down to 22.05 Khz (44.1 Khz sampling). This is a low pass filter and what is tested in the report.
2) Convert the bits from 24 to 16.

The report shows with high confidence that the transformation in #1 is audible. If so, it doesn't matter what #2 is. The sum of #1 and #2 by definition would be audible since the first step is audible. To make a case that CD is transparent, you need to demonstrate why #1 is wrong. Since that filtering used TPDF, then you have no argument with respect to dither.

On #2, they found audible differences between all three methods they tested: no dither, truncation and rectangular dither. And paradoxically using rectangular dither that on paper does much better than truncation, did the opposite, scoring lower. So based on this report, there is little reason to think that using TPDF dither would have improved the situation.

Edit: fixed typos.

Again, feel free to discard #2 and answer how #1 is consistent with your views and that of prior tests such as Meyer and Moran.

Audibility of "typical" Digital Filters in a Hi-Fi Playback

Reply #313 – 2014-11-18 21:07:47

I should have read more carefully. ajinfla already noticed the resonance in the dome may influence its sound.
Since the dome itself because of its hard material still has this resonance but a linear frequency response there is very likely some notch filter working inside the active speaker.
I still can imagine there is interaction of music signals coming in at the notch filters frequency or not.

Audibility of "typical" Digital Filters in a Hi-Fi Playback

Reply #314 – 2014-11-18 21:08:24

Quote from: mzil on 2014-11-18 20:40:05

Here's the spectral plot of the constant subsonic rumble in the third excerpt Arny has posted from the last second where the main music has faded away. it shows here as being 50 dB down, or so, but compared to the actual music content of this short sample it is only 30 dB down from the average peak levels, by my eye, hence rather loud.

[Let's see if this uploading of attachments from that sub forum section works for me. Here goes.]

Arny, whatever mic made these recordings has an impressive range from subsonic to ultrasonic! I'm not as experienced as you, so tell me, is this fairly loud LF rumble which seems to peak at a frequency even lower than 16 Hz (the lowest our spectrum analyzer shows) just an artifact or rather a real, I believe you call it "room tone"?

Note, although it is present in the entire passage of your third posted segment, I show it here in isolation where the music has faded away at the very last second or so. It's actually only 30 dB down from the musical peaks of the passage itself, or unusually loud IMHO.

Haydn_string_quartet_in_D__Op76_No5_finale_presto_Arny_segment_final_second.jpg

I'm no mic expert but does the <16hz to >33kHz capability narrow it down to only a handful? [I see Arny has answered that he suspects HVAC in the attachment thread before I could even figure out how to post this!]

Audibility of "typical" Digital Filters in a Hi-Fi Playback

Reply #315 – 2014-11-18 22:06:53

Quote from: mzil on 2014-11-18 21:08:24

I'm no mic expert but does the <16hz to >33kHz capability narrow it down to only a handful?

The company 2L uses various models of DPA microphones. Freq.response of small diaphragm condenser (sdc) microphones is in general from <20Hz to >30 kHz. Other brands have similar specs. DPA is quite popular amongst classical engineers though. (I've been using them for over 30 years)

Audibility of "typical" Digital Filters in a Hi-Fi Playback

Reply #316 – 2014-11-18 22:12:08

Quote from: Arnold B. Krueger on 2014-11-18 14:38:24

Quote from: amirm on 2014-11-17 23:25:10

Arny's files never had sync problems. But yes, I did resample them using latest version of Audition CC and I could still tell them apart.

The claim above is false - there were never any audible synch problems.

Hi Arny. I say your files never had sync problems and you repeat the same but add that my claim is false? How is that possible?

Quote

It had to do with transition bands Were the alleged proper 4416 file available for download I would review them and grant an opinion.

And I post results from my version of Audition CC which is a few generations more recent than yours and representative of what is in Stuart's paper, with the filter at 50% setting. I still managed to tell the files apart with the same ease as your version. So your theory that you created the files wrong is well, wrong itself .

But I can live with you saying that moving a slider in resampler is enough to create reliable audible differences. So don't stop on my account .

Audibility of "typical" Digital Filters in a Hi-Fi Playback

Reply #317 – 2014-11-18 22:22:13

Quote from: ajinfla on 2014-11-18 19:37:28

Quote from: amirm on 2014-11-18 15:11:57
But I hope it is clear that this test easily schools all of us.

Yes, it teaches how far those with pecuniary interest will spin rigged tests that appear to show some desired results, but with no verification of system

AJ, once more the paper has won peer-review award. It would have to be rigged pretty good to fool the minimum of two people who reviewed the work, yes?

And what do mean by verification? The system frequency and impulse response is documented in the paper. Have you read the paper or keep posting these things devoid of said knowledge?

Quote

But then it creates this dilemma for your side Amir:

Your question has been answered. See the summary of the test I post. Every step of conversion to 16/44.1 was found to be audible to high confidence. Yes, they didn't try TPDF in the quantization step. You can try to prove how adding that to filtering that had audible effect would keep things transparent. You can do that AJ?

Audibility of "typical" Digital Filters in a Hi-Fi Playback

Reply #318 – 2014-11-19 01:28:16

Quote from: Wombat on 2014-11-18 21:07:47

I should have read more carefully. ajinfla already noticed the resonance in the dome may influence its sound.
Since the dome itself because of its hard material still has this resonance but a linear frequency response there is very likely some notch filter working inside the active speaker.
I still can imagine there is interaction of music signals coming in at the notch filters frequency or not.

Hi Wombat,
As it turns out those peddling the BS paper don't have expertise in this field so we are honestly reading gibberish from them.
The possibility of speaker generated artifacts is way beyond the knowledge level of a typical forum member who doesn't do this work professionally.
You can't look at the terribly scaled on axis FR data to determine this as I will teach to hobbyists in my further response.

cheers,

AJ

Audibility of "typical" Digital Filters in a Hi-Fi Playback

Reply #319 – 2014-11-19 02:11:11

Quote from: amirm on 2014-11-18 22:22:13

AJ, once more the paper has won peer-review award. It would have to be rigged pretty good to fool the minimum of two people who reviewed the work, yes?

The "award" is meaningless to the validity of the paper and no, it simply depends on who reviewed and awarded, which you have no clue.
Having read it and knowing your interests, unsurprisingly, you are greatly spinning the results.

Quote from: amirm on 2014-11-18 22:22:13

And what do mean by verification? The system frequency and impulse response is documented in the paper. Have you read the paper or keep posting these things devoid of said knowledge?

Before you were assuming I hadn't, now you don't seem so sure.
I'm not surprised when hobbyists view things, they are different from those who work professionally. The FR and impulse are the same thing, just a different view and shed zero information regarding the concerns of artifacts at the extreme levels (near max) they drove the system. That "squished" FR is on axis only and practically useless, other than to show the response does indeed extend out to 40KHz. Not shown is the off axis, which may reveal the resonance around 30k:

Actually, I strongly suspect these are the DSP7200 tweeters. What is needed is some distortion data for that tweeter to see if IM products are present downstream in the audible range when it is driven without band limiting, at extreme levels for a DR dome. Absolutely nothing in this regard is presented in the paper. But hobbyists or those in over their heads can't be cognizant of these things.

Quote from: amirm on 2014-11-18 22:22:13

Quote
But then it creates this dilemma for your side Amir:

Is that blatantly false info being perpetrated by BS/Meridian and what recourse do owners have about such false info it the BS Test shows otherwise?

No, it is correct information consistent with Stuart's previous journal paper work. You would do well to read more of that manual as it will teach you a ton about signal processing. It makes your AVR manual look like chicken scratchings on toilet paper: https://www.meridian-audio.com/download/Han...ies/518user.pdf

As expected, complete obfuscation.

Quote from: amirm on 2014-11-18 22:22:13

Yes, they didn't try TPDF in the quantization step. You can try to prove how adding that to filtering that had audible effect would keep things transparent. You can do that AJ?

You still have no clue, I don't have to prove a damn thing.
Now having read the BS paper, I am more convinced it's bollocks. I've seen JJ skewer folks over the "smearing" nonsense they keep referencing and the fact that they "emulated" filtering rather than use an actual converter, have not a single thing showing system transparency, switching, etc.
You're lucky he won't come on here anymore to publicly comment on this paper. Whose conclusions are vastly different from yours.

cheers,

AJ

Audibility of "typical" Digital Filters in a Hi-Fi Playback

Reply #320 – 2014-11-19 02:32:59

Quote from: ajinfla on 2014-11-19 02:11:11

Quote from: amirm on 2014-11-18 22:22:13
AJ, once more the paper has won peer-review award. It would have to be rigged pretty good to fool the minimum of two people who reviewed the work, yes?

The "award" is meaningless to the validity of the paper and no, it simply depends on who reviewed and awarded, which you have no clue.
Having read it and knowing your interests, unsurprisingly, you are greatly spinning the results.

It is the old bear story AJ. How fast do you need to run from the bear? Faster than the guy with you.

By the same token, yes, peer review does not in at all guarantee correctness of the paper. But it sure as heck blows away your theory of a "rigged test. " You are making a hit and run empty accusation. The peer review easily trumps anonymous hobbyists on a forum saying otherwise.

Audibility of "typical" Digital Filters in a Hi-Fi Playback

Reply #321 – 2014-11-19 02:47:41

If these DSP7200 were used, the tweeter indeed reacts a lot on axis response with its hefty resonance.
page 16:
http://www.meridian-audio.info/public/meri...1%5B3099%5D.pdf

Audibility of "typical" Digital Filters in a Hi-Fi Playback

Reply #322 – 2014-11-19 02:56:46

Wombat that's the DSP7200, non SE (special edition) version, with a different tweeter made of aluminum, among other things, although there may (or may not) be similarities.

Audibility of "typical" Digital Filters in a Hi-Fi Playback

Reply #323 – 2014-11-19 03:03:18

Quote from: ajinfla on 2014-11-19 02:11:11

I'm not surprised when hobbyists view things, they are different from those who work professionally. The FR and impulse are the same thing, just a different view and shed zero information regarding the concerns of artifacts at the extreme levels (near max) they drove the system.

You are wrong in the specific here but let's put that aside. You say that I don't know this fact. Well, read this article I wrote on WBF Forum with respect to relationship of Time vs Frequency in acoustic measurements: http://www.whatsbestforum.com/showthread.p...e-and-Frequency. Do you have a write-up like that so that we can see you know the topic and not just repeating what you have read in Dr. Toole's research?

On page #2 I say this: http://www.whatsbestforum.com/showthread.p...ll=1#post141558

"In layman terms, this means that the amplitude fully describe system behavior and hence, modification of it must by definition also modify its time response since the two define the same signal. They are two sides of the same coin."

So you have shared nothing new despite boasting about professional experience. Since when a hobbyist putting speakers together become a professional anyway?

Quote

That "squished" FR is on axis only and practically useless, other than to show the response does indeed extend out to 40KHz.

Which in this case is something to be verified! Remember we don't have anything remotely like that from Meyer and Moran. No measurements of any sorts were provided.

Quote

Not shown is the off axis, which may reveal the resonance around 30k:

Actually, I strongly suspect these are the DSP7200 tweeters. What is needed is some distortion data for that tweeter to see if IM products are present downstream in the audible range when it is driven without band limiting, at extreme levels for a DR dome. Absolutely nothing in this regard is presented in the paper. But hobbyists or those in over their heads can't be cognizant of these things.

In other words, this is pure speculation. You don't even know if this is the tweeter they used. You don't know if it is that it generates IM distortion in-band.

The paper includes specific references to intermodulation:

An experiment conducted by Ashihara and Kiryu
[27] found that at least some of the work demonstrat-
ing auditory sensitivity to the presence of ultrasonics
could have suered from intermodulation distortion
introduced by the loudspeakers used to present the
signals. Intermodulation distortion caused by the in-
teraction of high-frequency components played from
the same loudspeaker could have provided a cue to
the presence of the ultrasonics.

Your theory is that with full knowledge of issues surround intermodulation, they entered the test blind and fell victim to it anyway?

Audibility of "typical" Digital Filters in a Hi-Fi Playback

Reply #324 – 2014-11-19 03:06:53

Quote from: Wombat on 2014-11-19 02:47:41

If these DSP7200 were used, the tweeter indeed reacts a lot on axis response with its hefty resonance.
page 16:
http://www.meridian-audio.info/public/meri...1%5B3099%5D.pdf

The SE version uses a different tweeter. They say it is their own design: https://www.meridian-audio.com/en/campaigns...sary/upgrades/#

Beryllium-dome Tweeter - for clearer highs

[NEW MERIDIAN-DESIGNED
BERYLLIUM-DOME TWEETER]

The stiffness of the tweeter cone helps determine how pure and uncoloured the sound is at high frequencies. Beryllium is many times stiffer than aluminium, the material usually used in tweeter cones. Being stiffer, the dome acts as a more perfect piston – delivering more accurate transients and lower colouration. In addition, its extended high frequency response is ideal for getting the best out of today’s high-resolution recordings.

Notice