Locating bass <80Hz?

[Sokel]

Because Griesinger was mentioned: the Lexicon algorithms were not developed because of a stupid theory from people with no ears and no hearing experience, but the contrary: by ear and experiments.

This outrageously dumb theoretical discussions from people not even knowing, how the sound out of a subwoofer changes by distance and orientation, probably is the reason why, after reading forums, so many ppl stupidly seem to be placing their subs somewhere in the room and then they even feel enlightened, if they choose the position because of the frequency response, while having not the slightest idea, how relatively unimportant frequency response is - compared to other factors - that determine sound quality.

Both are important.
My main point is the simplest one, just Hi-fi, staying true to the source.

If there's uncorrelated bass at the recording and that's the way they sold it at the control room, it makes sense to reproduce it the same way.

 

[OHtaru]

Because Griesinger was mentioned: the Lexicon algorithms were not developed because of a stupid theory from people with no ears and no hearing experience, but the contrary: by ear and experiments.

This outrageously dumb theoretical discussions from people not even knowing, how the sound out of a subwoofer changes by distance and orientation, probably is the reason why, after reading forums, so many ppl stupidly seem to be placing their subs somewhere in the room and then they even feel enlightened, if they choose the position because of the frequency response, while having not the slightest idea, how relatively unimportant frequency response is - compared to other factors - that determine sound quality.

This is exactly my experience. I placed my subwoofer in the corner of the room according to monitor placement guides, and they all told me that you can't hear where the bass is coming from. After that, every time I listened to music, I felt that the bass was not centered. Until I moved the subwoofer under the table in the center of the room, I realized I had been fooled.

 

[Snickers-is]

@Snickers-is has been making "earless" conjectures, as are you.

If the sound you are listening to contains frequencies that should not be there, that won't change when you introduce the ears, unless you are deaf above 80Hz.

 

[Suono]

It's simple, the RF measurements tell you that you have 79hz and 158hz perfectly linear but the brain receives them from different positions

 

[TheZebraKilledDarwin]

This is exactly my experience. I placed my subwoofer in the corner of the room according to monitor placement guides, and they all told me that you can't hear where the bass is coming from. After that, every time I listened to music, I felt that the bass was not centered. Until I moved the subwoofer under the table in the center of the room, I realized I had been fooled.

I congratulate you, that you insist on making your own experience and come to your OWN judgement.

The problem with theories being spread among consumers is, that most people do not have the experience and knowledge to understand the constraints and limits of the theories. Especially if the phenomena are so manifold and complex.
Real life in general is not binary, and not in audio, but pros and cons of many factors are contributing to the result. And all these simple acoustic theories give ppl just that binary correct/false paradigm to have a good feeling of doing it "right". Therefore breaking the rules of the theory can result in a much better overall result.
Using the ears means having doubts and weighting pros and cons which is necessary to be able to decide what delivers the best result.

 

[TheZebraKilledDarwin]

Both are important.
My main point is the simplest one, just Hi-fi, staying true to the source.

If there's uncorrelated bass at the recording and that's the way they sold it at the control room, it makes sense to reproduce it the same way.

I think I understand what you mean, but think about the production process.
What could true to the source mean?
How the vocal sounded in the booth?
Or how it sounded after choosing a certain mic and preamp (which are always chosen for the kind of COLORATION they offer)?
Or how it sounded in the mixing room?
Or in the mastering room?

Everything on media was the result of INTENTIONAL decisions.

And just like the journalist writing an article with the intention to create a certain emotion, it is done on film and audio.
There is NO AUTHENTICITY in any kind of media.

If there is no authenticity, it means YOU need to decide for yourself, too, what gives you the best sound in your room.
And that means that you subjectively have to weight all the pros and cons. A theory or a measurement can help to show problems, but it can not decide that for your room and your preference.

How many people believe that a flat frequency response was synonymous with a good sound?
Until they would hear a good system and see the "horrible" frequency response in that room...

 

[Sokel]

I think I understand what you mean, but think about the production process.
What could true to the source mean?
How the vocal sounded in the booth?
Or how it sounded after choosing a certain mic and preamp (which are always chosen for the kind of COLORATION they offer)?
Or how it sounded in the mixing room?
Or in the mastering room?

Everything on media was the result of INTENTIONAL decisions.

And just like the journalist writing an article with the intention to create a certain emotion, it is done on film and audio.
There is NO AUTHENTICITY in any kind of media.

If there is no authenticity, it means YOU need to decide for yourself, too, what gives you the best sound in your room.
And that means that you subjectively have to weight all the pros and cons. A theory or a measurement can help to show problems, but it can not decide that for your room and your preference.

How many people believe that a flat frequency response was synonymous with a good sound?
Until they would hear a good system and see the "horrible" frequency response in that room...

True to source means true to recording (Deltawave it and get as close as possible) to me or the listen they had at the control room with the artists right before the sell (ok, later needs a good room but lets say we have that).

 

[Suono]

How many people believe that a flat frequency response was synonymous with a good sound?
Until they would hear a good system and see the "horrible" frequency response in that room...

That's not the case, you risk throwing everything away. RF is important, decay is important, diffusion is important, but it depends on how you get it. It's the room that needs to be "phased" with the sound, not the other way around. Let's say a less straight, slightly tormented RF is better than a completely and forcefully straight one. But it takes a lot of work. I've never heard great sounds with terrible RF!

 

[Heinrich]

It causes the volume heard by the two ears to be inconsistent, which is similar to the situation where you are wearing headphones and playing a bass sound, but one side is louder than the other. A very important factor in human ear sound localization is ILD. It is effective at all audible frequencies. We often say that bass can not be localized because in a free field, low-frequency diffraction eliminates ILD, and the long wavelength of low frequencies eliminates phase differences. However, as long as ILD exists, it is still effective even at very low frequencies. Near the notch of a standing wave in a room, the SPL gradient is large enough to cause inconsistent volume between the two ears.

That‘s not the mechanism by which the direction of the energy source would be determined.
On the other hand Griesinger asks for a Max of standing waves. The very same leads to the most linear frequency response.

 

[OHtaru]

That‘s not the mechanism by which the direction of the energy source would be determined.
On the other hand Griesinger asks for a Max of standing waves. The very same leads to the most linear frequency response.

The perceived direction of ILD caused by such standing wave notches is not necessarily consistent with the position of the subwoofer; it can also be the opposite.
I'm saying all this just to solve my problem (off-centered bass image). I read that article by Griesinger and find maybe this kind of off-center is exactly the effect Griesinger wants. But I find it is ILD dominant from my experience. This conflicts with Griesinger's research.
Placing the listening position and the subwoofer on the central axis of the room can produce a centered bass image that I prefer. When working together with satellite speakers, I completely forget where the subwoofer is. The human ear's ability to perceive left and right is stronger than that for front/back or up/down. Whether the subwoofer is in front or behind is not that important, at least for me. Of course, when solo subwoofer with low-passed pink noise, I can still tell where the subwoofer is.

 

[TheZebraKilledDarwin]

True to source means true to recording (Deltawave it and get as close as possible) to me or the listen they had at the control room with the artists right before the sell (ok, later needs a good room but lets say we have that).

I've never heard great sounds with terrible RF!

You can lead a horse to water, but you can’t make it drink.

 

[ChrisG]

Those of you discussing standing waves:
I would estimate that a standing wave might take a couple of cycles to fully stabilise, but it does depend on a load of factors. At 50Hz, that might be 40ms.
I suspect that the human auditory system can detect direction of incidence faster than that.

And besides, when pure/continuous tones are played, what I hear is the room's standing waves. I can tell this because if I move around, the level rises and falls, but the angle of incidence is much more difficult to determine.
It's the time-varying signals which make the subwoofer's location obvious.

I think, then, we can discount the room. I haven't yet tested this effect properly in the free-field, but the weather in the UK is getting worse - that experiment might have to wait until Summer, if anyone is still interested by then.

 

[NTK]

Since Dr Griesinger's statement in his asa05 paper regarding "standing waves preserve the original sound direction information" was brought up in this discussion, I'd think an explanation of the "physics" of standing waves would be in order.

A standing wave is the result when two (or more) sound waves of the same frequency, traveling from different directions, meet each other. One common scenario would be a reflection from a surface perpendicular to the sound source, and is illustrated below. We have a left traveling and right traveling waves (10 cycle tone bursts) of the same amplitude and frequency. This can be thought of as a sound wave reflected by a perfectly reflective wall at x = 0. In this model, the "room" is where x > 0. The right traveling wave starting from x < 0 is the "reflection image" of the left traveling wave in the room traveling towards the wall at x = 0.

As the incident and reflected waves meet each other, they sum to a standing wave. A standing wave looks like a stationary oscillating wave, with the profile of its peaks and troughs stays stationary in space. But it is in fact the sum of a right and a left traveling waves. The two red dots, located at two different null locations (in the "room") are indicators of the sound pressures at those two locations at the given moment. They are to help showing the characteristics of a standing wave.

Now, this isn't a room mode yet (it is more akin to SBIR). This illustration only shows the sum of the incident and reflected waves for a single reflection, and thus the resultant peak pressure cannot exceed twice that of the incident wave (6 dB increase). A room mode happens when there is another reflecting surface (e.g. for an axial mode, the wall at then other end of the room, at a distance that conforms to what is required at that particular room mode frequency) reflecting the wave back. And when duration of the excitation is sufficiently long that the wave can bounce back and forth in the room more than once or twice before the excitation terminates, we build up a room mode and the built up pressure peaks can be many times that of the original excitation, depending on the Q (how much damping) of the mode.

We can also see that, for the room mode to build up, the repeated wave reflections will have to come and go in the same direction. Therefore, the directions of travel of the opposing waves in a standing wave stay constant, and this gives our binaural hearing the opportunity to sense its directional nature. (Note that for spatial bass Dr Griesinger is talking about the sensations of spaciousness, envelopment, and externalization, not source location.)

Below show the direction of wave propagation for the 3 types of room modes for a rectangular cuboid room.

Picture source:

Understanding acoustic treatment & room modes within your studio

Acoustic treatment certainly isn’t going to alleviate any disgruntled neighbours complaining about the thumping low end emanating from ...

mixdownmag.com.au

 

[Heinrich]

Dr Griesinger is talking about the sensations of spaciousness, envelopment, and externalization, not source location.)

But the original question is about source localization, namely of a single subwoofer placed somewhere. I can't care less about Dr. Grieseinger's musings, when considering the question in consideration. Btw, that happens all too often, pulling random things in, only because "one knows". That has nothing, really nil or less to do with the topic, but sounds "scientific"--as they think.

Dr Griesinger's ideas, useful or not are NOT at all related to the origininal question.

You explain the uprising of a standing wave correctly, but then depart from serious argumentation in order to rescue Dr Grieseinger's.

In that context you say: "... this gives our binaural hearing the opportunity to sense its directional nature. " No, it does not. No way--if I ask you by what, in physical reality, there will be nothing. Please explain otherwise, and please describe the physical electrical signal generated in the cochlea transfered to the neural network post-processing it to eventually make it a message to a human mind.

And sure, you're correct, it is the same as with "quantum" in cable discussions, only misusing audio-psycho-acoustics instead.

And only to round-up the impression: someone else with a higher acedemic degree, and, alas, "authority", once commented on Griesinger's experimentation at Harman's exceptionally "reserved", if you will.

 

[Snickers-is]

Standing waves are really not of any interest for this topic. What is interesting is room modes appearing like standing waves, making very localized cancellations in the room. This is one of the large sources of error tied to this topic.

The other one can be split into several sub categories, but they are all about high frequency content.

In order to determine if we can locate bass at <80Hz, we need anechoic conditions, and we need to make sure there are no timing information left above 80Hz. A test that violates these conditions does not give us information about our ability to locate bass at <80Hz.

As an extension to this, locating bass and hearing a phase issue is not the same. If we can locate bass, then we can tell with certainty where the bass comes from, based on only hearing. Hearing some kind of phase distortion usually leads to the bass source being determined as not being in the center.

To elaborate on why there are no timing information left in bass signals, we need to define what timing information is to begin with, and what it is not. When dealing with sine waves, timing information is not a thing. It is replaced by phase. Timing information is what we get when more frequencies coincide to build a leading edge of some kind. When filtering out the higher frequencies, we take out all the frequencies that coincide with the start of the bass tone. When we trigger an 80Hz burst, we can look at the frequency content as a function of time. In the beginning, very little 80Hz energy is present. The curve is built from a set of higher frequencies. The 80Hz content kind of slowly fades in as the higher frequencies slowly fades out.

So when we try to filter out the <80Hz, we are left with a sine wave that slowly climbs out from the noise floor.

The interesting thing is that when we put back these >80Hz frequencies, we can very easily locate the sound. However, if we add a significant delay to the subwoofer, invert the phase, move it, distort the frequency etc, we will still locate it just as easily based on the higher frequencies.

We can not say with certainty that we are unable to locate a <80Hz sound source. But we do not have any evidence that we can. Until someone performs a serious experiment, we do not have such evidence. If someone wants to do it, I will offer to hold their beer.

 

[olieb]

We can also see that, for the room mode to build up, the repeated wave reflections will have to come and go in the same direction. Therefore, the directions of travel of the opposing waves in a standing wave stay constant, and this gives our binaural hearing the opportunity to sense its directional nature. (Note that for spatial bass Dr Griesinger is talking about the sensations of spaciousness, envelopment, and externalization, not source location.)

Nice animation and explanations.
But I don't think the quoted text describes the mechanism for "localisation" of subs in a (small) room. A room mode has no direction, it is a pattern of nodes and peaks that do not move. (It will be different if several/enough modes are excited in concert and I assume that was, what Griesinger was talking about.)

@OHtaru explained earlier that this pattern might give rise to significant SPL differences at the two ears. This will create a "localisation perception" (there are other effects that can create localisation impressions of course, like distortion, motor or port noises ...).
The direction of this SPL-gradient can show in any direction and in general it will be different for different frequencies but by playing around with REW room sim it seems to me that the statistical dominant gradient is directed towards the sub location.
All this is from steady state results. On top of that there is the transient situation, so all this can depend on the time, too.

I made a small and simple (horizontal only) simulation in Ripple Tank to give an impression. Just watch the amplitudes of the probes (representing the ears) during the propagation of a burst (6 periods, followed by 24 periods of pause) in a rectangular room.
Loudness difference at the ears fluctuates during the process and again will be different for different tones in a sound and somehow the brain will try to make sense of all that.
You might want to speed up the simulation.

https://falstad.com/ripple/Ripple.html?rol=$+3+512+64+4+0+664+0.048828125 s+2+347+75+2+0.06402289117132867+0+588.8380101765896+2355.3520407063584+1+0 b+0+5+12+450+431+0 P+1+220+234 P+1+248+235

 

[levimax]

In order to determine if we can locate bass at <80Hz, we need anechoic conditions, and we need to make sure there are no timing information left above 80Hz. A test that violates these conditions does not give us information about our ability to locate bass at <80Hz.

For purposes of the OP's question, i.e. "Can sound <80Hz be localized in a small room?" does it really matter if we can locate bass at < 80Hz in anechoic conditions or not? Several of the articles sighted point out that the room and the position in the room all play a part in the ability to localize LF sound. To me the most likely answer is that under anechoic conditions, it is much more difficult to locate bass, than in a small room. Then the next question is that for integrating a sub in a small room do we need to take these "small room localization effects" into account?

 

[Snickers-is]

For purposes of the OP's question, i.e. "Can sound <80Hz be localized in a small room?" does it really matter if we can locate bass at < 80Hz in anechoic conditions or not? Several of the articles sighted point out that the room and the position in the room all play a part in the ability to localize LF sound. To me the most likely answer is that under anechoic conditions, it is much more difficult to locate bass, than in a small room. Then the next question is that for integrating a sub in a small room do we need to take these "small room localization effects" into account?

If we can not locate bass in anechoic conditions, it simply means we can not locate bass.

If we feel like we still can locate bass in a small room, it means there has to be some other effect that makes us feel like we are locating the sound source.

So in order to figure out if we can locate bass in a small room, we need to figure out if what feels like we are able to locate the bass is not the source itself, but a mode that plays with our ears. The only way to figure out this is to rule out modes, and that means we need to test this in an anechoic chamber.

 

[TheZebraKilledDarwin]

I don't even understand why is everyone trying to interpret the question as a theoretical one?
All theory is gray.
It’s the actual sound that matters, not the abstract rules, based on waaaay too simple models.

The question understood as a question for practically useful advice to improve the sound:

Are 80 Hz as crossover frequency enough to achieve the best quality in imaging?
Does the sub’s placement affect the resulting overall sound quality?

Answer:
Forget the theory, move the sub closer to you, to the center, and simply listen...
Does the center-image improve? Do male voices become more center-focused? If you play mono pink noise, is it less spread out and more center-focused?
How does an improved center image impact the L/R/depth imaging?
Do you perceive pads and strings to become wider, while vocals become more focused?
Do sounds in the center channel become more "as one"?
Do dry sounds feel more intimate, feel "closer"?
Do bassy sounds, like shut car doors, feel more compact, punchy, direct?

Then reduce the crossover frequency, if your speakers allow it, and listen again. But not necessarily for the amount of bass, but for the sound quality and the effect the lower XO has on imaging.


Get a measurement mic and REW to find additional cues for improvement.
But always let your ears decide.

 

[OHtaru]

You can't discuss transients excluding band-limiting. The gif seems nice, but the corner brings high frequencies. If the wave is band-limited, the transients smears. I still insist that all time-domain information is secondary compared to ILD when it comes to bass localization. Especially when the satellite speakers work simultaneously, the time-domain part will be strongly attracted by the satellite speakers, which is similar to the masking effect. I think it is unlikely to capture the time-domain information of the subwoofer under the strong guidance of the time-domain information from the satellite speakers.