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Audio Myths and Human Perception - Explored


mikebse2a3
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44 minutes ago, mikebse2a3 said:

Envelopment from 2 channel reproduction always requires room involvement in my experience. The sound field from 2-channel reproduction is always (with exceptions to some processing manipulation of some recordings) from the plane formed between the 2 loudspeakers with depth perception behind that plane. (ie: a window on the performance). 

There is still room involvement, even in Chris' LEDE treated room.  Later reflections, those from sound that has to traverse the room, are preserved, which helps create the illusion of space.  Those later reflections are also a perfect tonal match to the on-axis response, simply because they mainly ARE the on-axis response, and thus don't call attention to themselves as would the early reflections from the often irregular off-axis response of a wide dispersion speaker.  Also, without the early reflections, all the depth and ambiance encoded in the recording is more fully revealed, giving quite a bit of perceived depth behind the plane of the speakers.  

 

While I think that's about as good as it gets with two channel, it can be a rather "enveloping" experience.

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2 hours ago, Khornukopia said:

But you do recommend measuring the speaker(s) at one meter with REW and adjusting digital PEQs, to get a smooth response from the loudspeakers, correct?

Understand that I'm not saying that automatic room correction software doesn't work.  I'm only saying that it hasn't worked for me in my environment.

 

What has worked is manually EQing using REW, a calibrated microphone, and listening to the results.  The version of Audyssey that I have allows no latitude - it's a "take it or leave it--pig in a poke" proposition.  That doesn't work in my case--at all.

 

Having the ability to see what it is doing and having control over how it makes decisions or what it's making decisions on--other than how many microphone positions to use and their locations--was a necessary capability for my needs.  I've found that EQ, time alignment, and crossover filter optimization is something that has latitude, and that "optimal" filters don't result in optimal listening performance--or anywhere close to it. 

 

Chris

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On ‎8‎/‎13‎/‎2017 at 5:45 AM, Chris A said:

Envelopment is easy to get from the recordings themselves if using loudspeakers with good directivity control--instead of trying to produce envelopment artificially using loudspeakers that splash acoustic energy around the room.  If the recording doesn't have good envelopment, then it will sound thin and piercing.  If the recording engineer took pains to capture envelopment, then when reproduced inside rooms with good directivity control, envelopment will be there. 

 

 

On ‎8‎/‎13‎/‎2017 at 3:56 PM, Chris A said:
On ‎8‎/‎13‎/‎2017 at 3:45 PM, mikebse2a3 said:

Hmmm... Envelopment from 2 channel reproduction always requires room involvement in my experience.

If you talked with Ellery (etc6849) and looked at his (prior) room, I bet you would be surprised to find that he has basically taken the room out of the running...in other words, his experience is the opposite of what you are reporting.

 

I have personally experienced positive effects of farther-field reflections from the back of the room (40 feet away), but I attribute some of that to sitting in the near field at those frequencies (i.e., low frequencies).

 

On ‎8‎/‎13‎/‎2017 at 3:56 PM, Chris A said:
On ‎8‎/‎13‎/‎2017 at 3:45 PM, mikebse2a3 said:

I will also say that the perception of envelopment and clarity are not exclusive of each other when done properly in my experience.

I've found that near-field reflections and clarity are inverses of each other, as described in Griesinger's presentation.  "Properly" seems to be a bit mushy.  Please explain further what you mean.

 

I'm not sure if we are using "envelopment" (in relation to 2ch reproduction) to describe the same thing Chris after reading your comments. To be clear my goal is to always allow the recording's imaging to develop fully and clarity is an intimate part of that and we cannot completely have one without the other. If a recording has really good sound imaging I expect to be able to hear the space that the recording was made in which often consist of reflections/echoes off of the boundaries of the recorded space. The instruments and vocalists will have specific lateral and depth locations and to some degree a sense of vertical height. Vocalist and instruments can appear life size with a sense of body like hearing the vocalist project from their mouth and perceive the chest area as they inhale air and to sense the body of the instruments like piano, drums and guitar for example. If a recording is done with a live audience and this aspect was captured well then when they clap for example there is a sense of spaciousness to some degree but it is limited to in front of me. In a really well acoustically treated room the energy/vibrations from instruments for instance will be perceived as traveling through the air to your body.

 

On ‎8‎/‎13‎/‎2017 at 3:45 PM, mikebse2a3 said:

Developing Envelopment in 2 channel reproduction means to me that I've been able to remove the effects from interfering reflections causing (despite the actual small physical space of the room I'm listening in) the perception/deception of being in a much larger space than I'm physically in and this is perceived as more relaxing/natural experience with the width and depth of the original sound field recorded preserved within this space.

 

So we all know that the listening room's reflections of sound are what we use aurally to perceive the boundaries and thus size of our listening space and it is easy for us to sense the enveloping difference between a small room such as our listening rooms versus large venues or outdoors spaces even. It is possible to control and use these room reflections to aurally create a perception of envelopment different from the untreated space and in the case of 2ch reproduction in small rooms if we have acoustically treated the room properly we will have excellent imaging, clarity and spaciousness from the loudspeakers while being enveloped with the perception of a larger space that feels relaxing and natural.

 

Anechoic chambers do not feel natural and to spend much time in one would not be pleasant...at least for me and to play our typical 2ch music recordings in one would not be like anything you would experience in a home listening room. You might experience excellent imaging but I doubt anyone would consider it a pleasant place to listen in and when the music goes silent you would immediately sense the unnatural space.

 

Rooms for 2ch reproduction when heavily treated with absorption (and often with little or no acoustically diffusive attention given) can increase the perception of imaging and clarity but will also start to take on an "Anechoic Effect" especially in the higher parts of the audible frequency spectrum and this again in my experience can often lead to perception of beaming at some frequencies and increased listener fatigue. You can tell if your acoustically treated room falls into this category because while these rooms can impress with the increase in imaging and clarity for awhile but over time the negative issues I noted will start to be perceived leading to early listener fatigue and dissatisfaction in the long run.

 

So what do I consider a properly treated room for 2ch reproduction based on my experiences..? and of course YMMV..!!!

 

(1) Attention to and treatments effective for modal issues of the room.

This can be bass absorbers/traps and EQ compensation in certain instances.

 

(2) Attention to First Order Reflections with absorption or diffusion adequate enough to eliminate the perception of image smearing and tonal colorations.

I will often use absorption at the first reflection points on the front and side wall immediately next to the loudspeakers due to the time and energy level of these reflections.

 

I will often experiment with absorption or diffusion on the ceiling at the first reflection point from the loudspeakers and other areas close to the loudspeakers on the ceiling. 

 

I prefer to use 2D diffusors (that suppress the specular reflections) at the first reflection points on the side walls opposite each loudspeaker. The benefits here are decreasing the energy level of the specular reflection while increasing the density and number of directions of the useful reflections after the Initial Time Delay Gap of about 15ms to 20ms.

 

My experience indicates by using diffusers to increase the density and number of direction of reflections after the Initial Time Delay Gap of 15ms to 20ms the room envelopes me with a since of a much larger space while allowing the recording's imaging and clarity to fully develop. The room will be a pleasant, relaxing and natural feeling space with very low listener fatigue.

 

PWK advised us of the importance of and advantage of diffusion in our listening rooms and cautioned the over use of absorption and I believe it is still valid advise.

 

miketn

 

 

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7 hours ago, mikebse2a3 said:

My experience indicates by using diffusers to increase the density and number of direction of reflections after the Initial Time Delay Gap of 15ms to 20ms the room envelopes me with a since of a much larger space while allowing the recording's imaging and clarity to fully develop. The room will be a pleasant, relaxing and natural feeling space with very low listener fatigue.

 

Generally, these reflections wind up their journey to the listening position from behind it.  If your room is much wider than average (and that average is apparently 18 feet from the survey), then the 15-20 ms "ASW" (Apparent Source Width) reflections of less than 80 ms delay can do their final approach to the listening position from the front or sides.

 

The "LEV" (Listener Envelopment) reflections of greater than 80 ms are basically non-existent in standard-sized listening rooms, unless surround loudspeakers are used.  This is why surround sound systems came into being and why I personally have set up my listening room to support these recorded late reflections (5.1), which are the most effective at enhancing envelopment.

 

Toole's book somewhat interesting.  He gives you the impression that he's got all the bases covered, but when you dig a little into things like clarity--there's no discussion at all. His discussion of very nearfield reflections (less than 8 ms) that give us the most issues issues with soundstage imaging is neither clear nor concise, in my assessment.  Perception of modulation distortion is also AWOL--but the acknowledgement that partially horn-loaded speakers [like the JBL Everest, which has DR woofers] sound clear at even very loud SPL is a dead giveaway that he's heard low modulation distortion reproduction, but has chosen not to write on the subject.  Other topics of interest to the home hi-fi enthusiast seem to be missing.  For the volume of material that he presents, he seems to have some pretty big holes leftover.

 

By way of contrast, if you look at David Griesinger's web site, I get very clear answers to the subjects that he covers, with clear rationale and even listening examples to illustrate.  His papers are generally much more recent.  Griesinger is a distinguished acoustician and has written on subjects of interest to hi-fi enthusiasts. 

 

Chris

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39 minutes ago, mikebse2a3 said:

Interesting room design...

MyRoom_Design-white_paper.pdf

 

Screenshot_2017-08-16-11-27-59.thumb.png.c3053d473dd3dd3e1339e5a58198b619.png

 

Screenshot_2017-08-16-11-28-51.thumb.png.36ec2cf0f2a36dd982319c5504bd0052.png

 

I hate to point this out, but that room looks like it's barely 8 feet wide, and they're doing mastering in there(?).  Additionally, what do you think the directivity of those monitors are versus frequency?  And that huge desk at the rear looks like it is significantly interfering with the surround loudspeakers via nearfield reflections.  The front loudspeakers appear to be way too close to the listening position.

 

If I were to make recommendations, I'd mention finding a room that's at least double that width, lose the table at the back, and find some controlled directivity loudspeakers that significantly decrease the need for all that "diffusion". 

 

JMTC.

 

Chris

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6 minutes ago, Chris A said:

 

I hate to point this out, but that room looks like it's barely 8 feet wide, and they're doing mastering in there(?).  Additionally, what do you think the directivity of those monitors are versus frequency?  And that huge desk at the rear looks like it is significantly interfering with the surround loudspeakers via nearfield reflections.  The front loudspeakers appear to be way too close to the listening position.

 

If I were to make recommendations, I'd mention finding a room that's at least double that width, lose the table at the back, and find some controlled directivity loudspeakers that significantly decrease the need for all that "diffusion". 

 

JMTC.

 

Chris

 

The information and reasons/goals and perception results are in the paper.

 

miketn

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That's pretty expensive lipstick on the pig...;)  i think headphones would have been a bit cheaper.

 

So if you look at the RT60 measure in Griesinger's papers, I think that you'll see that it's not really the measure of merit that's the most important.  Additionally, using thick wall coverings--like those diffusion panels, only makes the problems worse from the standpoint of room modes.  I bet that they're having trouble controlling room modes at 250 Hz or perhaps higher frequencies.  For a studio, I'd think that they would want to push the room mode problems down at least an octave lower, or perhaps more.

 

Chris

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On 8/13/2017 at 11:18 AM, Ski Bum said:

Chris, that "envelopment broadening" you mentioned a couple posts up is exactly what Toole has extensively covered in his books and articles on reflected sound, perception, and preferences.  Seems that those of us who prefer 'less room' and to let the recordings paint the picture are in the minority.  Toole acknowledges our existence, but doesn't shine the light on the approach as much as he does on the direct radiator types the masses prefer.  And it's kind of ironic, since you're absolutely correct that "envelopment is easy" with the right method.  

 

I still have tons of respect for Toole and his willingness to aggregate all the research.  For the Toole fans, or just those who want to learn more about acoustics, there is a new edition of his book coming out, if it's not out already.  (Seems relevant given the thread title.  Great reference, full of myth-skewering and pragmatic info, even if those of us who use horns and controlled dispersion speakers have to kind of determine what best applies to us.) 

SB,

Thanks for the heads up.  The new edition of Toole's book (called the 3rd edition, but it's really the 2nd edition) has apparently been released but Amazon hasn't received paperback versions. The 3rd ed. electronic version apparently hasn't been released on Amazon (I've really taken advantage of the pdf first edition version that someone put online, for extracting snippets of information).  I've put my name in the queue for a third edition paperback version.  No date on when it will appear.

 

A few days ago (perhaps a week...), I started on a little review on the first/second edition which I lost in editing over a day or so.  But basically, the discussion went something like this:

 

Toole's book looks so comprehensive that it seems to have all bases covered.  However I've found some real holes in it, such as:

  • Loudspeaker modulation distortion--almost not discussed--instead referring to Geddes's JAES presentation that says that modulation distortion isn't correlatable to listening perception--except that all of his testing was limited to 80 dBA at the test subject's ear drums,
  • Clarity--which was not discussed at all,
  • Just Detectable Distortion (JDD), was not really discussed at all--which is the most surprising omission of all when talking about loudspeaker design,

...and other fairly glaring holes.  Google books has published several pages of the third edition, which shows that Toole did indeed redesign the front of the book extensively in order to present a more linear narrative than the 1st ed.  It appears, however, that the holes that I identified above are still not addressed.  In my opinion these are gaping holes when talking about loudspeaker and room design. That's why I recommended Griesinger's presentations above.

 

Of all people that should be talking about these issues, it should be Toole, since he headed the largest  loudspeaker engineering organization that existed then.  However, I believe that he didn't accept the findings of John Eargle (who worked for him) on at least the subject of modulation distortion.  The clarity discussions are basically brand new--within the last 4-5 years, and the JDD subjects, which you would think that Toole would have devoted the most resources into defining for his engineering organization that was designing loudspeakers...and perhaps they did but didn't publish the results. 

 

Chris

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  • 3 weeks later...
On 8/19/2017 at 9:26 AM, Chris A said:

Google books has published several pages of [his book's] third edition, which shows that Toole did indeed redesign the front of the book extensively in order to present a more linear narrative than the 1st ed.  It appears, however, that the holes that I identified above are still not addressed.  In my opinion these are gaping holes when talking about loudspeaker and room design. That's why I recommended Griesinger's presentations above.

I've been going through this new edition for a couple of weeks.  Perhaps a discussion of this third edition of his book needs a separate thread for these discussions.  I'll try to collect some of my thoughts and start a new thread.

EDIT: Here is that thread...

 

Chris

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Yes, I saw that.  Thanks for the heads up.  I will likely try to engage him there if there aren't too many others also vying for attention there.

 

I think though that there are points to be made in this forum that relates to PWK's and Roy's ideas that obviously are not shared by Toole (at least at the same level of importance)...and the implications of those differences in terms of which kind of loudspeakers/crossovers and room placement/treatments that you wind up with.  There are some big differences there.

 

In addition, I think that there are points that can be made that Toole stated but that he didn't emphasize strongly enough (IMO)...that really should be brought forward and discussed.  Overall, there is a perspective that Toole presents that is fairly subtle and understated, i.e., a very "Canadian" (laid back) approach.  That is the intended focus of the review/discussion thread that I mentioned, above.

 

Chris

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13 hours ago, Ski Bum said:

Chris, you could probably engage him directly.  He's been pretty active over at avsforums with the book coming out. 

 

 

 

I'm not very familiar with that forum.

 

What does he go by on the forum? 

Any links to active discussions he is in?

 

Thanks, 

miketn 

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1 hour ago, mikebse2a3 said:

 

I'm not very familiar with that forum.   Thanks, miketn 

There are a lot of us here who are members there.  I started there on the DIY forums.

 

They have a Klipsch Owners thread that has been active since 2006 with nearly 3 million views, 53,000 posts.

http://www.avsforum.com/forum/89-speakers/680426-klipsch-owner-thread.html

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I'm surprised that this discussion hasn't included Cardas' work on speaker placement (unless someone posted the following link and I didn't notice it):

 

http://www.cardas.com/room_setup_rectangular_room.php

 

Mike mentioned "envelopment" in some post above.  All I can say is that by using the proposed speaker placement the envelopment, regardless of listening level (I have tried this at listening position levels of around 60 to 85 db in multiple sytems), is totally extraordinary.  And, the best part is that it doesn't require any fussing or bothering with acoustical treatments or equalization.  I invite anyone who is blessed with having a dedicated listening room to try this.  

 

Maynard 

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