Sweet Spot and Not

[RayDunzl]

I have a microphone set midpoint between the stereo speakers, at a position that would be midpoint between my two ears.

The test signal is pink noise, and the EQ attempts flat at the initial microphone position. It gets pretty close.

I delay the right hand speaker by increments of 0.04 ms, up to 0.5 ms to show the combing that occurs as the microphone goes off the centerline.

I used delay just to illustrate and to be repeatable, rather than move the microphone or the speakers.

This represents the change in the frequency response corresponding to moving the microphone to the left about 3 inches.

I'm not insinuating this is what we hear, but this is what happens in the air at the microphone position when it is slowly moved off the centerline of a stereo pair of speakers.

Here's a little movie: http://screencast.com/t/U15VRbJu3wxg

Start - microphone centered

End - as if the mic had moved left 3 inches

 

[Thomas savage]

You need to chat with Frank, you must be suffering from ' artefacts' as his sweet spot is consistant in any position...

 

[Cosmik]

But this is where the frequency-centric view of audio breaks down. Real music is not usually steady tones, and our hearing almost completely ignores the comb effect when it also hears the changes in timing to each ear of the 'transients' that music comprises. The brain seems able to work backwards from frequency and timing to the original event almost perfectly and effortlessly. You simply don't hear the comb effect. This is why I (probably alone in this forum) am doubtful about electronic 'room correction' - I simply live with the acoustics as they are. Room treatments are fine IMO, however.

 

[Fitzcaraldo215]

But this is where the frequency-centric view of audio breaks down. Real music is not usually steady tones, and our hearing almost completely ignores the comb effect when it also hears the changes in timing to each ear of the 'transients' that music comprises. The brain seems able to work backwards from frequency and timing to the original event almost perfectly and effortlessly. You simply don't hear the comb effect. This is why I (probably alone in this forum) am doubtful about electronic 'room correction' - I simply live with the acoustics as they are. Room treatments are fine IMO, however.

You are entitled to you view, of course. But, it is more complicated than your rationale. I think the following makes that clear:

http://audiosciencereview.com/forum/index.php?threads/perceptual-effects-of-room-reflections.13/

Yes, reflective comb filtering is an issue. But, the ear's insensitivity, "perfectly and effortlessly", to it decreases at lower frequencies. I think that the better EQ tools recognize this and employ response smoothing with increasing frequency in their calculated filters so as not to overreact to all the tiny squiggles caused by comb filtering, similar to the way the ear "integrates" the up/down response of nearby high frequencies.

Also, though the response may be jagged as a result of comb filtering, there is still an overall response envelope, a moving average trend line response that determines whether a speaker/room sounds brighter or softer in the highs. We all sense this with different speakers in the same room in spite of the fact that there is comb filtering affecting each one. I find EQ via its target curve to be an effective means of controlling this smoothed, high frequency envelope to one's liking, though the unsmoothed response still contains the inevitable comb filtering.

Then, of course, there are the room modal issues in the bass below the transition frequency. Especially in the deep bass below 100Hz, these are extremely difficult to deal with via passive treatments because the passive structures required to tame them need to be huge. So, EQ and/or other active means - multiple subs, active traps, etc. - have been found to be effective alternatives that are more feasible in most rooms.

Whatever, I am forever sold on active room EQ for use in my own system. It may not be perfect, not yet at least. And, perhaps the optimum solution for a given room is a combination of both active and passive solutions. But, I find Room EQ to be one of the rare and true great breakthroughs of the past few decades in audio, even used alone without additional treatments.

 

[dallasjustice]

But this is where the frequency-centric view of audio breaks down. Real music is not usually steady tones, and our hearing almost completely ignores the comb effect when it also hears the changes in timing to each ear of the 'transients' that music comprises. The brain seems able to work backwards from frequency and timing to the original event almost perfectly and effortlessly. You simply don't hear the comb effect. This is why I (probably alone in this forum) am doubtful about electronic 'room correction' - I simply live with the acoustics as they are. Room treatments are fine IMO, however.

If your system works great without DSP, then that's awesome. Nobody needs to use DSP. And your objection to it is also very commonly asserted.

The common assumption made with this objection is:

1. DSP correction software can only apply EQ filters generated from a logsweep measurement; and
2. frequency domain and time domain are totally unrelated.

Neither one of the above is true.

 

[dallasjustice]

I love the REW RTA function. I think its often under-utilized.

But I think your assumption about how this is an accurate demo of off-axis frequency response is incorrect.

 

[Cosmik]

You are entitled to you view, of course. But, it is more complicated than your rationale. ...

Well I first got into DSP with the intention of correcting the room - I assumed my passive speakers were fine because they were designed by experts.

So I started fiddling with REW and other free bits of software. I thought it maybe helped a bit - aided by the expectation bias of seeing flattened lines and all that - but I was never blown away by it. It was only when I started playing with active speakers and DSP that I realised that what I had thought to be problems with the room were, in fact, problems with the speakers themselves. So now I correct the speaker (I measure the individual drivers), and add only the slightest tweaks to account for the positioning of the speaker in the room. I have never looked back.

I simply don't hear the terrible problems that rooms are supposed to create. There may be reasons for this: I have been running my system in squarish rooms with higher-than-average ceilings, and generally wall-to-wall carpeting. I suppose that the bass must measure terribly in conventional terms, but it sounds terrific to me - I position the speakers away from the walls if possible, and EQ by calculation for a corner frequency and roll-off that I set through an educated guess. Active speakers without ports have a grip on the bass that means they just 'work' - but I may do a little experimentation of shuffling the speakers by a few inches. Three way active speakers are so clean that the top end just 'works' too - assuming some calculated correction for the baffle width.

I think this is the philosophy behind the Kii Three - plug and play without all the faff of measurements, and without breaking the relationship between the time and frequency domains. As I say, my theory is that the brain reconstructs the original sound from the delayed reflections, and that the frequency-centric "comb filtering" view is only a fraction of the information the brain is working on. If the original sound is mutilated by attempting to correct the frequency-centric view but not the timing, it will sound wrong.

I just put it forward as a point of view that is, I think, at least plausible and consistent. If it didn't sound fabulous I would no doubt come up with another "consistent" viewpoint, but as it is, it works for me!

 

[FrantzM]

It is dawning slowly on me that in room smooth low frequency response throughout a large area in the room is a requisite for good sound. I haven't seen any studies or articles to support this opinion however. Call it a hunch... Higher in frequency there is such a thing a sweet spot, it does get larger when response in the bass is smooth within a large area all that IME, YMMV and all the qualifiers, caveats implied by an opinion

 

[fas42]

You need to chat with Frank, you must be suffering from ' artefacts' as his sweet spot is consistant in any position...

Ahhh, but the key here is the subjective experience. To belabour a point, ASA explains what's going on: our minds know how to deal with all the combing effects, and automatically, unconsciously, adjust the subjective, end result in our heads so that what we hear is consistent. But, only if the data coming in matches the expected patterns!! To repeat, this is why we can hear a live piano in a room, and move around everywhere, and the sound picture we experience from the instrument remains consistent - and, the same behaviour can occur from audio playback, when the incoming acoustic data to our ears also matches expected patterns. If one has a system that's on the edge of this quality then it's easy to modulate the behaviour: slightly degrade the quality, and the sound reverts back to conventional hifi - sweet spot behaviour, sound coming from the drivers, all the usual stuff; or, up the ante on quality, and then the speakers disappear, everywhere, and the sound space envelopes the room. One can bounce back and forth between these two modes at will, simply by altering the level of quality of the sound emerging from the drivers.

 

[FrantzM]

Ahhh, but the key here is the subjective experience. To belabour a point, ASA explains what's going on: our minds know how to deal with all the combing effects, and automatically, unconsciously, adjust the subjective, end result in our heads so that what we hear is consistent. But, only if the data coming in matches the expected patterns!! To repeat, this is why we can hear a live piano in a room, and move around everywhere, and the sound picture we experience from the instrument remains consistent - and, the same behaviour can occur from audio playback, when the incoming acoustic data to our ears also matches expected patterns. If one has a system that's on the edge of this quality then it's easy to modulate the behaviour: slightly degrade the quality, and the sound reverts back to conventional hifi - sweet spot behaviour, sound coming from the drivers, all the usual stuff; or, up the ante on quality, and then the speakers disappear, everywhere, and the sound space envelopes the room. One can bounce back and forth between these two modes at will, simply by altering the level of quality of the sound emerging from the drivers.

oooooooooooooook.

Having lived with a piano for most of my life I can tell you the sounds does change with room position. As for what you call the sound "picture" ....

ASA hasn't gained much traction anywhere ... perhaps repeating enough may help.

 

[fas42]

oooooooooooooook.

Having lived with a piano for most of my life I can tell you the sounds does change with room position. As for what you call the sound "picture" ....

ASA hasn't gained much traction anywhere ... perhaps repeating enough may help.

I said, "sound picture we experience from the instrument remains consistent" - not, " sounds don't change with room position". An audio system that is not producing convincing sound will dramatically alter in the presentation as one moves, say, from the side of a particular speaker to the position which people call the "sweet spot" - while a solo piano recording is playing, say. This doesn't occur, subjectively, when a system is working at a high enough quality level.

Yes, the conventional audio world is completely ignoring ASA so far - but it has had major impact in other areas where understanding human auditory sensing is more important, - try something called Google ...

An interesting area that's doing the ASA thing, is using the "tricks" of this behaviour to manipulate the perceived auditory "world" experienced when multiple speakers output sound that's been "massaged" in ASA relevant ways - the concept is to be artistically creative; ASA has become a tool of the music maker, rather than just an explanation of how we hear.

 

[Phelonious Ponk]

I said, "sound picture we experience from the instrument remains consistent" - not, " sounds don't change with room position". An audio system that is not producing convincing sound will dramatically alter in the presentation as one moves, say, from the side of a particular speaker to the position which people call the "sweet spot" - while a solo piano recording is playing, say. This doesn't occur, subjectively, when a system is working at a high enough quality level.

Yes, the conventional audio world is completely ignoring ASA so far - but it has had major impact in other areas where understanding human auditory sensing is more important, - try something called Google ...

An interesting area that's doing the ASA thing, is using the "tricks" of this behaviour to manipulate the perceived auditory "world" experienced when multiple speakers output sound that's been "massaged" in ASA relevant ways - the concept is to be artistically creative; ASA has become a tool of the music maker, rather than just an explanation of how we hear.

You've implied here that ASA has discovered techniques utilizing multiple speakers that allow the artists to alter the listeners' perceptions. I'd love to hear more about this.

Tim

 

[Speedskater]

There seems to be much more enthusiasm for room equalization in the audiophile community than in the expert community.

That would be:
j.j. Johnston
Siegfried Linkwitz
Floyd E. Toole
David Griesinger

 

[fas42]

You've implied here that ASA has discovered techniques utilizing multiple speakers that allow the artists to alter the listeners' perceptions. I'd love to hear more about this.

Tim

Sorry Tim, I hadn't picked up your comment here until now - I mentioned the link here, http://audiosciencereview.com/forum/index.php?threads/auditory-scene-analysis.236/page-8#post-10311, the concept is Spatio-Operational Spectral Synthesis. And a link to another viewpoint on Bregman, the man, can be found here, http://audiosciencereview.com/forum/index.php?threads/auditory-scene-analysis.236/page-8#post-10237

 

[ceedee]

this is why we can hear a live piano in a room, and move around everywhere, and the sound picture we experience from the instrument remains consistent

I definitely disagree; we can still tell that it's a piano, sure, but the perceived sound will change drastically as we move around.

As far as listening to your hifi at home: what about imaging? Doesn't the stereo image change as you move around?

One can bounce back and forth between these two modes at will, simply by altering the level of quality of the sound emerging from the drivers.

How do you do this?

 

[Phelonious Ponk]

Sorry Tim, I hadn't picked up your comment here until now - I mentioned the link here, http://audiosciencereview.com/forum/index.php?threads/auditory-scene-analysis.236/page-8#post-10311, the concept is Spatio-Operational Spectral Synthesis. And a link to another viewpoint on Bregman, the man, can be found here, http://audiosciencereview.com/forum/index.php?threads/auditory-scene-analysis.236/page-8#post-10237

I was hoping to get the Cliff Notes, Frank, for a couple of reasons; 1) to get your understanding of it. 2) to not wade through papers that ultimately are irrelevant to the existing body of recordings. I understand you may not have time to explain in detail, but on the latter, is anyone currently using these techniques in the studio?

Tim

 

[RayDunzl]

is anyone currently using these techniques in the studio?

I don't know. Other than talks and toot-toot examples, there is this:

Here's a longer version if still interested: https://soundcloud.com/eric-wubbels/auditory-scene-analysis-part-i

"The music I’m writing recently draws on ideas from acoustics, cognitive science, and Buddhist philosophy to explore the transcendence of the boundaries of individual consciousness and personality that group musical performance offers as one of its most powerful experiences.

Bringing this off usually demands an extreme degree of concentration and/or physical exertion from the performers (one of whom I often am) in order to create for the listener a sense of perceptual confusion, sensory overload or the sustained illusion of a ‘compound instrument’ made of multiple players.

In the end, the musical form this takes can be “simple” or “complex,” but my goal is that it be simultaneously rich and confusing, visceral and opaque. Something is experienced, nothing is understood."

- Eric Wubbels - http://music.columbia.edu/columbiacomposers/?page_id=307

 

[Phelonious Ponk]

I don't know. Other than talks and toot-toot examples, there is this:

Here's a longer version if still interested: https://soundcloud.com/eric-wubbels/auditory-scene-analysis-part-i

Lord help me. They couldn't have demonstrated with something listenable? Oh and they had the ungodly noise of that nonsense playing over the narrator. Couldn't understand a word she was saying. Oh well, thanks for the link, but I know no more than I did before.

Tim

 

[Fitzcaraldo215]

Hey, don't dismiss it. It uses Buddhist philosophy in achieving its transcendence, so it must be "closer" to God himself and to ultimate "truth".

And, there is nothing better than music where "something is experienced, nothing is understood". Gotta love that as an aesthetic principle.

 

[RayDunzl]

It uses Buddhist philosophy in achieving its transcendence, so it must be "closer" to God himself and to ultimate "truth".

Huh?

http://www.buddhanet.net/e-learning/qanda03.htm