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An Enticing Marketing Story, Theory Without Measurement?

Thomas_A

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I've been reading the whole thread today, and while it is not possible to adress all topics raised, I think one important aspect is: which acoustic space do I want to be in when listening to music ? I think this is a preference and nothing you can argue about. I prefer most of the times to have the event in front of me, but to keep my own room around me. Since sound becomes gradually directional above 80-100 Hz or so, I think this needs to be taken into consideration. Precedence tells us which direction the sound comes in an otherwise reflective environment, but reflections also gives loudness and timbral effects of the direct sound. Reflections from the same direction as the direct sound has no real meaning in precedence (directionality) other than colouring the direct sound. Ideally I should get rid of the front wall and fuse my room it with the room where the musicians are playing. Naturally, I can't do that, but I can treat the wall in front down to 100 Hz (i.e. down to the limit where direction can be sensed). This does not imply that you need very thick panels - you can get very far by having 10 cm rock wool covered by perforated masonite and a further layer of 60 mm foam, i.e. 16 cm. These damping panels should ideally run from floor to roof and behind the speakers (not so between the speakers, they can be reflective). I've experimented with this in the past and it gives tremendous impact on illusion and clarity of the event in front of me. For the rest of the room, I never liked treating it more than normal furniture. (There are other issues with side wall reflections, and I am not sure that the rather large reference room that was used in the research by Toole and Olive can be translated to smaller living rooms in that aspect. This since both delay time and levels are important.)

Last points about stereo reproduction, which has flaws as mentioned a couple of times. It could be significantly improved by using three front speakers, still having the "lounge model" in mind. Replacing the lounge model with the hall model to mimic a "transfer to the event" would require many speakers around you and ideally a recording that is made that way. But those are rather few today.
 

Spocko

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This seems to be a common internet phenomenon.....people going full EQ overkill even above 500Hz to hammer everything super flat, then sharing the graph online, getting praised for it, others copying it, etc.
Wait, how does one "copy" another's EQ curve, with 2 completely different rooms, speakers, etc.??
 

Absolute

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Wait, how does one "copy" another's EQ curve, with 2 completely different rooms, speakers, etc.??
You simply copy the target curve. The end result won't be exactly the same if the room correction system is any good, but it will optimize what it can to get a similar tonality within your constraints.
Does it work? It depends on what you expect. It will not sound the same, at least not using Audiolense or Dirac in my experience. It will however sound somewhat alike.
 

Floyd Toole

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Wait, how does one "copy" another's EQ curve, with 2 completely different rooms, speakers, etc.??
It cannot work as advertised, but that doesn't stop people from doing it. It has its origin in the decades old notion that steady-state room curves are definitive of sound quality. We now know that it is simply not true above a few hundred Hz, but it has validity at low frequencies, which account for about 30% of the factor weighting in subjective evaluations of sound quality. So, because of that "room EQ" might be beneficial. The unfortunate part is that in going full bandwidth it is possible to degrade the performance of well designed loudspeakers.
Toole, F. E. (2015). “The Measurement and Calibration of Sound Reproducing Systems”, J. Audio Eng. Soc., vol. 63, pp.512-541. This is an open-access paper available to non-members at www.aes.org http://www.aes.org/e-lib/browse.cfm?elib=17839

Seemingly endless promotion of "room EQ" algorithms - a for-profit exercise - is partially responsible, aided by human nature which is inclined to believe a good story. It is an ingredient in "faith based" audio - if you believe it, you just might hear it. Even though some EQ exercises "sound similar" does not mean that any are as good as they could be - perhaps the important similarity is at low frequencies.
 

Absolute

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It cannot work as advertised, but that doesn't stop people from doing it. It has its origin in the decades old notion that steady-state room curves are definitive of sound quality. We now know that it is simply not true above a few hundred Hz, but it has validity at low frequencies, which account for about 30% of the factor weighting in subjective evaluations of sound quality. So, because of that "room EQ" might be beneficial. The unfortunate part is that in going full bandwidth it is possible to degrade the performance of well designed loudspeakers.
Toole, F. E. (2015). “The Measurement and Calibration of Sound Reproducing Systems”, J. Audio Eng. Soc., vol. 63, pp.512-541. This is an open-access paper available to non-members at www.aes.org http://www.aes.org/e-lib/browse.cfm?elib=17839

Seemingly endless promotion of "room EQ" algorithms - a for-profit exercise - is partially responsible, aided by human nature which is inclined to believe a good story. It is an ingredient in "faith based" audio - if you believe it, you just might hear it. Even though some EQ exercises "sound similar" does not mean that any are as good as they could be - perhaps the important similarity is at low frequencies.
First of all I just want to express my greatest gratitude for your contribution to our hobby, my understanding of audio related stuff and for simplifying this whole road trip for thousands and thousands of former lost audiophiles out there. Your work can't be praised enough! Massive thanks to you, sir.
Over to correction software;

The interesting part here is the similarity in sound quality using both Audiolense and Dirac full range vs limited to bass (below 300 hz). Right now I'm listening through Audiolense and switching back and forth between full range correction and below 300 hz only. My speakers are Kii Three, a speaker designed with your research in mind; https://www.audioxpress.com/files/attachment/2609

Audible differences;

- Full correction sound warmer, fuller and a little more relaxed. A tad less perceived dynamic in the midrange, likely due to the level reduction in that area where I have 5-8 dB higher average due to boundary reflections.

- Partial correction with broad-band shelf-filters to get a downward slope sounds a little "hollow" in the midrange, especially on voices. Some instruments sounds more impressive than full correction.

- No EQ sounds a little voice-focused where everything else is more recessed and "gray" sounding.

Here's frequency responses of no EQ vs bass EQ + broad-band shelf filters vs Audiolense;
Audiolense vs mindsp vs no eq.jpg


There's bigger differences switching between different target curves than switching between full correction and bass only, which points to very conservative algorithms that doesn't kill the sound completely with a heavy hammer.
My question when reading these bombastic statements is; how much testing have you done with these newer kinds of correction software?
I would completely disregard the likes of ARC, RoomPerfect, YPAO and the like, those make a mess out of things.

I do agree wholeheartedly that it's very possible to make the sound worse with any form of EQ, but I don't agree that it's necessarily the case.
 

TimVG

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In the research it's always been the speakers with the most neutral direct sound, and smooth/ consistent dispersion characteristics that win the blind tests. By altering the steady-state response to conform to a set standard curve, you alter the (neutral) direct sound. It doesn't matter through which means.
 

TimVG

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You may want to try the following target (red) for a likely more neutral result

 

JoachimStrobel

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I read the complete thread and am impressed. I have two questions, one for now:

Is the room curve already baked into the recording during the mastering process?

Let me picture a Jazz quartet being recorded in a Studio with mikes on the instruments. During mastering, will a dip at high frequency be build in or would the mastering engineer leave it as is? He could, as my home system will add that room curve through the loudspeaker dispersion and all is fine.
Or will he add a room curve and I will do the same, having a double dip in the end? Sorry for possibly not understanding that correctly, but I find that issue highly confusing. I have heard the opinion, that some engineers will, why others will not, and this is why one needs an old fashioned treble control in the amplifier..
 

j_j

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The reason an omnidirectional mic does not measure loudness is because no mic can measure loudness. Loudness is a subjective parameter in two senses.

The microphone is not the problem. It is possible to measure the term defined specifically as loudness (i.e. subjective intensity) with quite reasonable accuracy, but one must do quite a bit of processing and analysis, not just look at an amplitude or power level out of the microphone, assuming that one knows the entire system gain.

This is an entire subject in itself. If you want to talk about loudness we could start a thread on it.
 

PaulD

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I read the complete thread and am impressed. I have two questions, one for now:

Is the room curve already baked into the recording during the mastering process?
No

Let me picture a Jazz quartet being recorded in a Studio with mikes on the instruments. During mastering, will a dip at high frequency be build in or would the mastering engineer leave it as is? He could, as my home system will add that room curve through the loudspeaker dispersion and all is fine.
Or will he add a room curve and I will do the same, having a double dip in the end? Sorry for possibly not understanding that correctly, but I find that issue highly confusing. I have heard the opinion, that some engineers will, why others will not, and this is why one needs an old fashioned treble control in the amplifier..
Ideal situation:
- Recording take place and is balanced in a studio with, for example, Harman room curve in there monitoring system. (there is no curve baked into the recording)
- Mastering is done in a properly treated room with, for example, Harman room curve. (there is no curve baked in with the mastering)
- Consumer playback takes place in their room, ideally that would match the mastering room (with Harman room curve), but it is in fact highly variable. (there is no curve baked into the source)

Any room curve is used in the monitoring chain, not the recording chain.
 

Thomas_A

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No


Ideal situation:
- Recording take place and is balanced in a studio with, for example, Harman room curve in there monitoring system. (there is no curve baked into the recording)
- Mastering is done in a properly treated room with, for example, Harman room curve. (there is no curve baked in with the mastering)
- Consumer playback takes place in their room, ideally that would match the mastering room (with Harman room curve), but it is in fact highly variable. (there is no curve baked into the source)

Any room curve is used in the monitoring chain, not the recording chain.

Agreed that there is no room curve applied in the recording room, other than there is a room (with reflections) and adjustments at the mixing console/EQ. Same with the live event. The room with its reflections is played back in the home/mastering room (including the effects of the reflections, i.e. coloration of the recording room, or with "multichannel" to reproduce the reflections of the recording). The overall balance in the home room is added, so you either have two rooms fused (recording room + yours/mastering room), or a complete surround recording (one room ideally). To "hear the live event" the only thing that should "acoustically disappear" is the wall between you and the musicians, i.e. the wall between recording/mastering room aka the front wall in your home.
 

JoachimStrobel

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No


Ideal situation:
- Recording take place and is balanced in a studio with, for example, Harman room curve in there monitoring system. (there is no curve baked into the recording)
- Mastering is done in a properly treated room with, for example, Harman room curve. (there is no curve baked in with the mastering)
- Consumer playback takes place in their room, ideally that would match the mastering room (with Harman room curve), but it is in fact highly variable. (there is no curve baked into the source)

Any room curve is used in the monitoring chain, not the recording chain.

This is the ideal situation, indeed: Mastering is done with loudspeakers that have a room curve included. Either naturally, as they have a great off-axis decay or via a DSP, all optimized for the engineers listening position. Can I count on that as a consumer? I read the chapter about control room sound in Toole’s book - I did not understand all of it, but my impression is, that it could be a non-perfect setup too. Potentially the audio industry could put a remark on the CD booklet about the mastering parameters.
 

PaulD

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I'd like to see standard monitoring levels and standard rooms used in music production, not unlike is done in post audio production. There is probably zero chance of this happening (market forces, home and budget studios, apathy of the pro's etc), but it is a logical way to move the industry and practice forward in a way that would greatly benefit consumers (consistently better product) and also practitioners (less hearing damage etc). There has been a little work done on this, but no where near enough.
 

Thomas_A

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"Circle of confusion" is just a branding term from some researchers of a problem that has always been there. Everybody who thinks about it would just realise the problem, irrespectively what it is called.
 

Floyd Toole

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"Circle of confusion" is just a branding term from some researchers of a problem that has always been there. Everybody who thinks about it would just realise the problem, irrespectively what it is called.

As the researcher who created the "brand" let me simply say that it is demonstrably true that the incompatibility of recording and playback facilities is not universally recognized. As you say it is to easy understand and identify and it has been with us forever. Subjective audiophiles and reviewers routinely assume that recordings are flawless and attribute differences they hear to all manner of causes, many of which defy the laws of physics.

It is encouraging to see discussion sessions on the 'circle of confusion" in the upcoming and a few past AES conferences addressing the issue. The basic problem is a lack of meaningful standards in the pro domain - the existing ones from ISO and EBU simply add to the problem because they are wrong. I discuss this in the 3rd edition of my book, especially in section 13.2.2. Once a practice has existed for decades it is very difficult to change it - see also the Cinema X-curve (Chapter 11). Most pros and consumers simply use what they think they like, not what might have a chance of being timbrally neutral.

If a catch phrase or "brand" generates discussion in the topic, that seems like a good thing.
 

Spocko

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As the researcher who created the "brand" let me simply say that it is demonstrably true that the incompatibility of recording and playback facilities is not universally recognized. As you say it is to easy understand and identify and it has been with us forever. Subjective audiophiles and reviewers routinely assume that recordings are flawless and attribute differences they hear to all manner of causes, many of which defy the laws of physics.

It is encouraging to see discussion sessions on the 'circle of confusion" in the upcoming and a few past AES conferences addressing the issue. The basic problem is a lack of meaningful standards in the pro domain - the existing ones from ISO and EBU simply add to the problem because they are wrong. I discuss this in the 3rd edition of my book, especially in section 13.2.2. Once a practice has existed for decades it is very difficult to change it - see also the Cinema X-curve (Chapter 11). Most pros and consumers simply use what they think they like, not what might have a chance of being timbrally neutral.

If a catch phrase or "brand" generates discussion in the topic, that seems like a good thing.
I assume the easiest approach to a "standard" is to automate the assessment into a software system like Dirac or GLM, where the software can identify gaps in the "circle" such that either the shortcomings can be corrected by the recording engineer or at least the metadata can be included in the song so that the end user can upload a correction curve to mitigate the confusion?
 

Thomas_A

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As the researcher who created the "brand" let me simply say that it is demonstrably true that the incompatibility of recording and playback facilities is not universally recognized. As you say it is to easy understand and identify and it has been with us forever. Subjective audiophiles and reviewers routinely assume that recordings are flawless and attribute differences they hear to all manner of causes, many of which defy the laws of physics.

It is encouraging to see discussion sessions on the 'circle of confusion" in the upcoming and a few past AES conferences addressing the issue. The basic problem is a lack of meaningful standards in the pro domain - the existing ones from ISO and EBU simply add to the problem because they are wrong. I discuss this in the 3rd edition of my book, especially in section 13.2.2. Once a practice has existed for decades it is very difficult to change it - see also the Cinema X-curve (Chapter 11). Most pros and consumers simply use what they think they like, not what might have a chance of being timbrally neutral.

If a catch phrase or "brand" generates discussion in the topic, that seems like a good thing.

Sure, all ways that get us better quality for us that care about Q it is good, I am with you there. My point being that the problem will always will be there no matter what we call it, and there is no way we can eliminate it, only reduce it. Active high quality speakers for studio use have been there since before 1980 but never became industry standard. Hopefully there is a fresh restart at least with better Q on speaker side, like "industry standards" of brands similar to JBL, Genelec, Adam, Neumann speakers replacing past NS-10 or similar poor performing "gold standard" studio speakers. We are still left with other problems with standards and education etc, but at least it is a start.
 

Floyd Toole

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Sure, all ways that get us better quality for us that care about Q it is good, I am with you there. My point being that the problem will always will be there no matter what we call it, and there is no way we can eliminate it, only reduce it. Active high quality speakers for studio use have been there since before 1980 but never became industry standard. Hopefully there is a fresh restart at least with better Q on speaker side, like "industry standards" of brands similar to JBL, Genelec, Adam, Neumann speakers replacing past NS-10 or similar poor performing "gold standard" studio speakers. We are still left with other problems with standards and education etc, but at least it is a start.

Interestingly Genelec, up until recently at least - I have not checked lately - followed the guidance of the ISO and EBU standards (they are the same) because of their business with the broadcast industry. In brief, these standards require loudspeakers with anechoic (1/3 octave smoothed) on axis responses that are flat within +/- 2dB. OK. But then they tell users to measure steady-state in-room curves and adjust as necessary to make them flat (with a large tolerance). Unless one is listening in a non-reflective environment, or extremely close to the speaker, one cannot have both. There are more shortcomings of the standards, but this is a very bad start. In normally reflective rooms the steady-state room curve from well designed, neutral, loudspeakers will tilt downwards - they are flat and smooth on axis as measured in an anechoic space.

This emphasis on steady-state room curves above the transition frequency is wrong - it is a poor correlate of sound quality. My JAES paper cited in the first post in this thread explains, as does my book. It is embarrassing to look at the performances of some "reference" pro monitor loudspeakers over the years. Several spinoramas are shown in my book, especially Chapter 18.
 

Thomas_A

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Interestingly Genelec, up until recently at least - I have not checked lately - followed the guidance of the ISO and EBU standards (they are the same) because of their business with the broadcast industry. In brief, these standards require loudspeakers with anechoic (1/3 octave smoothed) on axis responses that are flat within +/- 2dB. OK. But then they tell users to measure steady-state in-room curves and adjust as necessary to make them flat (with a large tolerance). Unless one is listening in a non-reflective environment, or extremely close to the speaker, one cannot have both. There are more shortcomings of the standards, but this is a very bad start. In normally reflective rooms the steady-state room curve from well designed, neutral, loudspeakers will tilt downwards - they are flat and smooth on axis as measured in an anechoic space.

This emphasis on steady-state room curves above the transition frequency is wrong - it is a poor correlate of sound quality. My JAES paper cited in the first post in this thread explains, as does my book. It is embarrassing to look at the performances of some "reference" pro monitor loudspeakers over the years. Several spinoramas are shown in my book, especially Chapter 18.

Thats bad, but I hope it will change if it has not done so already. Proper education of technicians in the studio is needed, now when you more freedom to adjust those active speakers.
 
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