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Bass and subwoofers

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youngho

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tested, and of those, only 5-6 turned out to be any good. David told me the problem was the microphone technique they used. If I were to provide a subjective impression of the sound of those recordings, the ones that turned out to be "good" were the ones that had the lowest direct to reflected sound and captured the revberberant sound of the space the most. One of those recordings I had heard when it was recorded, it was a saxaphone and Organ in a Church. What I heard in real life and what I heard in the final recording never jived. I would guess that our brains ability to ignore these reflections (the precedence effect) made it sound more "direct" in real life than in the recording, where such cues are obfuscated in the recording.
Interesting notes on the types of recordings--I wonder if certain techniques like Blumlein or the typical approach of certain labels like Yarlung might be more conducive to this effect.

Yes, there's certainly the visual aspect in directing attention, but also the problem of presenting diffuse field reverberation from the frontal direction...
 

anotherhobby

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We found that virtually no current music had stereo bass of any kind meaning there is no phase variation in low frequencies. You can point to classical or live natural music, but that isn't what most people listen to and it is not the majority of music right now. So ultimately I found it not even useful for new music. With older music, it was a mixed bag. Sometimes it was there and sometimes it wasn't. With the music halls (which again, is a very small portion of the music people listen to now), it was only ever audible with music supplied to me by David and it was extremly subtle, easily disturbed, and not obviously better.
I run a 2.4 setup with stereo subwoofer pairs in my office (one front and rear sub per side). I also run a display with 2 spectrum analyzers on it. The top is L/R split full range, and the bottom is L/R split in the subwoofer range specifically. It makes it immediately visible if the music is stereo bass or mono bass (clearly stereo bass in the pic below).

I listen to mostly Jazz, Jazz fusion stuff, downtempo electronica, and smattering of Americana/folk. Most of the music that goes thru my system is clearly visibly stereo bass. I admittingly do not listen to pop music, but when people say almost nothing has stereo bass I am flabbergasted because I can see it in almost everything I listen to.

Note: the red outline and descriptive text is not part of the display and was just added to help explain the display layout/use

cava_display.jpeg
 
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Chromatischism

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It is an older article so of course it references older material. It was inspired by a years worth of experimentation with David specifically to hear this effect, as I had been unfamiliar with the concept before talking with him. However, I walked away more unimpressed than anything.
Thanks for chiming in and adding context. Makes me glad I posted your article, which I did because I wanted to help weave together this story as it's unfolded in various places on the internet.
 

j_j

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1) Welti's approach requires sending a mono signal to all subwoofers. Yes a mid wall placement is consistent with one of his setups, but it must recieve a mono signal to work. Soundfield management is contingent on the input to the DSP being mono. Same for MSO. Same for Geddes approach. So they all take this stereo bass signal and sum it to mono.
2) My comment is specific to current as in pop music, not classical or audiophile music.

Good for you. Now, since you have claimed that I do not understand either of the two approaches that I've rejected, perhaps you can actually tell me what my position is?

Can you do that?
 

j_j

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Yes, there's certainly the visual aspect in directing attention, but also the problem of presenting diffuse field reverberation from the frontal direction...

*ding* give that man a cigar! :) People confuse phase shift with diffusion all the time, it seems.
 

Thomas Lund

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AE is undoubtedly a fundamental human percept, recognisable even by very young and very old naive listeners, discussed e.g. at the Tonmeistertagung conference last November.

Expectations about reproduction of potential envelopment appears to be a topic where monitoring and recreational listening differs markedly. Recreational sound seems to generally take the pragmatic approach, that AE is difficult, if not impossible, to control under a domestic setting. Maybe therefore, most effort is directed at an even LF frequency response across the listening space, thereby at least ensuring other elation.

Many studies on LF reproduction, and on the use of subwoofers, were based on old “stereo” content where LF collapse was more prevalent, especially in pop music. New pop collapsers may still be found, despite there no longer being technical reason for doing so. It is sad, however, if such practice is continued merely to increase the loudness a bit more, or because of fora like this where old dogma are uncritically repeated.

Do yourself a favour and listen under controlled conditions, see earlier posts about requirements, including test tracks and E/L magnitude vs freq graphs. Chances are, it will be an auditory revelation following you literally to the end.
 

Curvature

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Thanks. I am using Auditory Envelopment (AE) solely about the sensation elicited by low frequency inter-aural fluctuations, so it is an elementary, perceptual definition narrower than Listener Envelopment (LEV) used in acoustical engineering. Over decades of research into reverb and spatialisation, we found AE to be one of the most important percepts of audio production and reproduction; to an extent listening testers started craving that particular quality.

“Distortion” in this context is therefore any influence during distribution or reproduction that changes potential AE, i.e. prevents it from reaching a listener. Overall frequency response is not so important, if it is reasonably smooth, and it extends to 50 Hz, individually per channel. In a small room, LF stasis between 40 and 700 Hz because of room modes (see earlier comments on movement) is generally the main enemy. A large room, however, may blur or even replace potential AE with a certain time-domain signature of its own.

Considering reproduction, deliberate acoustical treatment can help reduce AE-destructive modes of a (small) room. It can also be effective when the listening room is imposing its own time-domain signature, washing out AE contrasts in the content. Control of loudspeaker directivity below 700 Hz, or moving closer to lhe loudspeakers when monitoring, may also help.
Is there any specific published research on your comments and recommendations?

Why would being closer to the loudspeakers help given the wavelengths at play? What wavelengths are even of interest in AE?

You've also frequently said that humans can localize down DC. Not just perceive (the infrasound research I've seen confirms this), but localize. Can you provide a paper?

Many studies on LF reproduction, and on the use of subwoofers, were based on old “stereo” content where LF collapse was more prevalent, especially in pop music. New pop collapsers may still be found, despite there no longer being technical reason for doing so. It is sad, however, if such practice is continued merely to increase the loudness a bit more, or because of fora like this where old dogma are uncritically repeated.
By "technical reasons" for "LF collapse" do you mean mastering techniques for bass in vinyl?

What kind of production environment are you thinking of in your comments? A control room? If yes then are you comments relevant for 2-channel stereo or do you have immersive or multichannel in mind?

This really is a crucial question for production that I really want to understand.

Thanks.
 

Thomas Lund

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Is there any specific published research on your comments and recommendations?

Why would being closer to the loudspeakers help given the wavelengths at play? What wavelengths are even of interest in AE?

You've also frequently said that humans can localize down DC. Not just perceive (the infrasound research I've seen confirms this), but localize. Can you provide a paper?

By "technical reasons" for "LF collapse" do you mean mastering techniques for bass in vinyl?

What kind of production environment are you thinking of in your comments? A control room? If yes then are you comments relevant for 2-channel stereo or do you have immersive or multichannel in mind?

Good questions. An explosion, thunder or other natural sources can provide outdoor opportunities to notice direction of even infrasound; or a subwoofer in an open field may be used in controlled experiments. Either way, the azimuth of a VLF sound source is easy to tell, also for a child, and that superpower is not lost when we step into a room.

I can't share findings related to reverb research, but a paper covering most of your AE questions is included in a proceedings journal, with publication expected last month. Must be close now.

Wavelengths conducive to the sensation of AE generally range from 0.5 to 8.5 m in air. The reason why nearfield or even ultra-nearfield listening may be relevant when monitoring for potential AE (i.e. AE latent in the content) is to reduce LF interference from the listening room. In a fine room, however, potential AE can be experienced at a distance of 3 m or longer. Stereo is capable of this, but *good* 3D reproduction even more so.

You are right that vinyl is an example of calculated LF collapse, though pick-up rumble itself actually is not in phase. Collapse can also happen in distribution (lossy codec, format conversion etc.) or in reproduction (bass management, listening room LF time-domain distortion etc.)
 

Chromatischism

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An explosion, thunder or other natural sources can provide outdoor opportunities to notice direction of even infrasound; or a subwoofer in an open field may be used in controlled experiments. Either way, the azimuth of a VLF sound source is easy to tell, also for a child, and that superpower is not lost when we step into a room.
It is confounded by the room, but you allude to that later:
Wavelengths conducive to the sensation of AE generally range from 0.5 to 8.5 m in air. The reason why nearfield or even ultra-nearfield listening may be relevant when monitoring for potential AE (i.e. AE latent in the content) is to reduce LF interference from the listening room.
 
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