Yes, we are bcoming a lost generation.
Over the bandwidth you are talking about, the vertical / elevation thresholds will be pretty much unmeasurable.
As far as localization in the horizontal, then thresholds will be a few to several degrees at the the upper range (300 Hz) and fall rapidly as you go down frequency (at least 10-20 degrees, if not more, at 200 Hz or so). At 50 Hz they would be unmeasurable, although there may be some artfacts due to measurement problems (listener actively moving around for instance).
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Well, I seem to remember one... I'm 55 though, and I remember it being in the 50's and I believe it was RCA who did it. Back when I found out, if you didn't have a library card you didn't know anything! Where are we now?
Results were that below 250Hz, humans loose that ability. Based on that, the woofer could be center channel and mono in a theater and no one would notice or care!
No links, no copy, just my old 2Cents???
Results were that below 250Hz, humans loose that ability. Based on that, the woofer could be center channel and mono in a theater and no one would notice or care!
No links, no copy, just my old 2Cents???
Thanks, guys. Though, as Wikipedia would say: [citation needed]!
However, since most of your unsubstantiated opinions seem to match my own baseless biases, I am willing to accept them into evidence.
If my memory is not a substitute for the gospel truth, then the references would start with Mills "On the minimum audible angle" (JASA, 1958) and continue from there. That was a classic paper and a "must read" for new grad students back many years ago.
Bill
I have always agreed with your hypothesis and often stated so around here. There are a lot of people who just don't want to believe that it is true no matter what kind of logic and data one presents. I see you also get the classic "Well then prove its not!" line - the classic cop-out.
It is only reasonable that as the frequency falls the differences in level and timing at the two ears must vanish. This is simple physics. As such the spatial resolving power of our two ear system must also vanish. What is not so clear is the speed that this happens. I think that WithTarragon has it correct in that the resolution is pretty well gone at 50 Hz and pretty well apparent at 300 Hz. My question would be "is this in a free field?" where I would certainly assume that it has to be (otherwise what are the conditions?) That means that adding in the effect a small room has - the fact that the sound is now arriving at all kinds of different angles within even a ms. - and the resolution cannot possibly go up - it has to go down. Hence for me, I would find that LF localization in a small room would be pretty poor up to about 100 Hz. It will improve up until the spatial resolution is dominated by the rooms early reflections (which limit the spatial resolution at higher frequencies, aka imaging.)
Now the LF resolution I have stated above assumes a reverberant field. If one is close to the source then there are near-field and direct-field effects that could be more audible than the reverberant field effects. For example, there could be differences in level at the two ears from the 6 dB falloff with distance, or near-field phase effects that differ at the two ears.
I have always agreed with your hypothesis and often stated so around here. There are a lot of people who just don't want to believe that it is true no matter what kind of logic and data one presents. I see you also get the classic "Well then prove its not!" line - the classic cop-out.
It is only reasonable that as the frequency falls the differences in level and timing at the two ears must vanish. This is simple physics. As such the spatial resolving power of our two ear system must also vanish. What is not so clear is the speed that this happens. I think that WithTarragon has it correct in that the resolution is pretty well gone at 50 Hz and pretty well apparent at 300 Hz. My question would be "is this in a free field?" where I would certainly assume that it has to be (otherwise what are the conditions?) That means that adding in the effect a small room has - the fact that the sound is now arriving at all kinds of different angles within even a ms. - and the resolution cannot possibly go up - it has to go down. Hence for me, I would find that LF localization in a small room would be pretty poor up to about 100 Hz. It will improve up until the spatial resolution is dominated by the rooms early reflections (which limit the spatial resolution at higher frequencies, aka imaging.)
Now the LF resolution I have stated above assumes a reverberant field. If one is close to the source then there are near-field and direct-field effects that could be more audible than the reverberant field effects. For example, there could be differences in level at the two ears from the 6 dB falloff with distance, or near-field phase effects that differ at the two ears.
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A tiny note on this often discussed subject. As far as I know there is solid evidence to the effect that it is not possible to locate sound sources that play pure sine waves below a certain frequency - say 60-80Hz or thereabouts. But the ear is extremely sensitive to any impulse (we needed to be when we ran about in the woods as hunters and gatherers!) - i.e. a sound stopping or starting. And music rarely consists of pure sine wave sound. First off: Most musical notes (bar perhaps pedal notes from organs) have a distinct "attack" (i.e. impulse) when the tone is initiated. Secondly: There are always harmonics. What this might amount to is 1) we'll locate where a low note stops or starts - and 2) we can easily locate the source of the third harmonic of the c. 40 Hz low string of a double bas - thus with a single subwoofer placed somewhere between the two side systems the ear-brain combination will notice the stopping/starting of a note somewhere between the speakers and the location of the harmonics somewhere else. If all this is true it spells a confused ear-brain-combination.
I remember vaguely having read a paper outlining these thoughts, but I am sorry to say that I don't have the slightest recollection of any bibliographical details. Yet, it may all be wrong - the fact remains, though, that I have never ever experienced a system with a single subwoofer that performed convincingly.
I remember vaguely having read a paper outlining these thoughts, but I am sorry to say that I don't have the slightest recollection of any bibliographical details. Yet, it may all be wrong - the fact remains, though, that I have never ever experienced a system with a single subwoofer that performed convincingly.
The "rumble" of thunder is more likely higher frequencies with some lows and you detect the highs. Still, the resolution can be pretty bad when the thunder is far off - at least that's my experience.
Consider an earthquake - can you tell where it is coming from? That's all LFs. But perhaps there is more to it for an earthquake.
Consider an earthquake - can you tell where it is coming from? That's all LFs. But perhaps there is more to it for an earthquake.
While this is not a cited source, my meanderings are very highly regarded in my own mind. It's entirely possible that the resolution of LF directionality is enhanced by the presence of the HF directional cues. While that sounds like "You're just determining the location with the HF", what I mean is that the LF could potentially be easier for our ear to resolve when given a "starting point". A synergistic relationship. Not sure how one would test this, but I find that we're very sensitive to inconsistency in any audio app, and thus LF directional cues that are consistent with HF directional cues may be easier for us to pick up on.
In a small room, as mentioned, getting meaningful bass directionality is less than simple.
In a small room, as mentioned, getting meaningful bass directionality is less than simple.
Hmmmm. I have stereo bass in my living room ( 55Hz crossover) not because I think I hear stereo bass, just because that is the way the crossover and amps worked out. Multiple subs in close proximity to the mains is a plus for response, but localization? I am under the impression that the vast majority of music is mixed with mono bass anyway. I am not in the recording business, so this is only hearsay.
I use a steep crossover, so if my mains are turned off, it is very hard to even tell where my subs are. Now, in many a showroom of HT stuff, I can point to which sub along the wall is playing. Poor crossovers and too high of course. In my other rooms where I have one sub, I still use at least 4th order crosssovers at 60 Hz and I don't hear the position of the sub at all. This limited non-scientific experience would suggest below 60 is not localizable.
Is this really an issue of how deep? 100Hz, yea, I can localize that. 80? Not sure. 60? Don't think so. Even at 100, could I hear a difference in music if the 100 and below was shifted? Or is the reduced distortion of using both speakers a bigger advantage?
Simple question. Lots of issues. I will continue to believe mono is fine below 60 as the localization clues are come from higher frequencies.
I use a steep crossover, so if my mains are turned off, it is very hard to even tell where my subs are. Now, in many a showroom of HT stuff, I can point to which sub along the wall is playing. Poor crossovers and too high of course. In my other rooms where I have one sub, I still use at least 4th order crosssovers at 60 Hz and I don't hear the position of the sub at all. This limited non-scientific experience would suggest below 60 is not localizable.
Is this really an issue of how deep? 100Hz, yea, I can localize that. 80? Not sure. 60? Don't think so. Even at 100, could I hear a difference in music if the 100 and below was shifted? Or is the reduced distortion of using both speakers a bigger advantage?
Simple question. Lots of issues. I will continue to believe mono is fine below 60 as the localization clues are come from higher frequencies.
Most of the papers I have read have good data showing that woofer localization occurs at 60Hz - 80Hz in small listening rooms. Tests where bass transient signals were used have good data for 60Hz. Tests where 2nd order slope crossovers are used have good data for 60Hz. Tests where 4th-8th order slope crossovers are used have good data for 80Hz. There is a large difference in the type of speaker construction required for a 60Hz satellite vs. a 80Hz satellite, so the THX HT standard is 80hz LR4.
The early research on woofer localization used bass transients, bass sine waves, and music for blind testing as well as for measurement. Conclusion: bass transients over 60Hz can be localized.
F. Toole, “Loudspeakers and Rooms for Stereophonic Sound Reproduction"
F. Toole, "Loudspeakers and Rooms - Working Together"
Current research on woofer localization is heavily influenced by home theaters where many companies are invested in marketing/selling multiple small speakers with one shared subwoofer. Conclusion: in small rooms, bass transients under 80Hz cannot be localized when steep crossovers are used..
AES COUNCIL Multichannel surround sound systems and operations Document AESTD1001.1.01-10
Current research on high quality bass in small rooms includes the reduction of room modes from multiple subwoofers.
Low-Frequency Optimization Using Multiple Subwoofers* TODD WELTI AND ALLAN DEVANTIER
The early research on woofer localization used bass transients, bass sine waves, and music for blind testing as well as for measurement. Conclusion: bass transients over 60Hz can be localized.
F. Toole, “Loudspeakers and Rooms for Stereophonic Sound Reproduction"
F. Toole, "Loudspeakers and Rooms - Working Together"
Current research on woofer localization is heavily influenced by home theaters where many companies are invested in marketing/selling multiple small speakers with one shared subwoofer. Conclusion: in small rooms, bass transients under 80Hz cannot be localized when steep crossovers are used..
AES COUNCIL Multichannel surround sound systems and operations Document AESTD1001.1.01-10
Current research on high quality bass in small rooms includes the reduction of room modes from multiple subwoofers.
Low-Frequency Optimization Using Multiple Subwoofers* TODD WELTI AND ALLAN DEVANTIER
I had a little 8" ported sub. It had a low order crossover.
I started playing around with tones to hear how it played down low. It dropped off like a rock around 70Hz. Really horrible sub.
When I first started using it, it was so easy to localize. It was louder above 70 hz. I had to turn the crossover down to 60 or lower, and it then got rather quiet. Not much usable sound. Amp was too small and sub was too small and not tuned well.
I unplugged the 8" woofer, and hooked up the amp to a bigger sealed box with a 10" in it.
I also got a different receiver with adjustable crossover with 18db slope.
Set at 80 on both, now it's really hard to localize. I am sitting in my not normal listening position which is next to the sub, and I can feel the vibrations on the couch, but it's hard to even tell it's immediately to my left. I'd say it's tuned just right!
I started playing around with tones to hear how it played down low. It dropped off like a rock around 70Hz. Really horrible sub.
When I first started using it, it was so easy to localize. It was louder above 70 hz. I had to turn the crossover down to 60 or lower, and it then got rather quiet. Not much usable sound. Amp was too small and sub was too small and not tuned well.
I unplugged the 8" woofer, and hooked up the amp to a bigger sealed box with a 10" in it.
I also got a different receiver with adjustable crossover with 18db slope.
Set at 80 on both, now it's really hard to localize. I am sitting in my not normal listening position which is next to the sub, and I can feel the vibrations on the couch, but it's hard to even tell it's immediately to my left. I'd say it's tuned just right!
That's possible (the high frequencies I mean). Fortunately I can't comment on the earthquake example because I've never experienced one directly (at least not at audible levels).
A good paper, as all his papers are, but isn't the topic different than the one being addressed here? David is talking about the "spaciousness" of LFs not its perceived direction or localization. They are entirely different things IMO.
I completely agree with him on all aspects of that paper. That sound in a large room becomes randomized by the reverb and that does not happen in a small room (it does but to such a small extent as to be meaningless.)
Some years back I did a small study of why the bass in a small room is so lacking compared o a large venue. If one compares the modal density and looks at the impulse responses that this difference creates then it is easy to see how the small room is less randomized when compared to a big room. So my idea was to add "artificial modes" to the response. When I did this - in a software model - I found what was called a 'de-correlation filter". In other words, if each LF source where sent through this filter the outputs would be de-correlated from each other. So what did this filter look like? Simple - it was just a random chain of impulses of decreasing amplitude. In other words reverb. It seemed to me at the time that using a reverb unit on each sub (all but one actually) - different taps of course - would create a LF sound that was a kin to that which we hear in a bigger room.
This was tested in a very simple program with just a few taps. It was clear that the effect was to create a more spacious sound, but with just a few taps it was colored. That project was cancelled and I never went any further, but from what I have done it was clear that the idea has merit.
While that's the paper's emphasis, it starts with localization (..format spacing and effects added for emphasis):
Griesinger page 3:
"..However it is widely believed that the direction of sound incidence cannot be perceived in a small room. It is assumed that the presence of room modes makes localization impossible.
The statement that low frequencies cannot be localized is easily shown to be true when a sine tone as used as a signal.
However it is equally easy to show that an broadband – such as low-pass filtered noise or a low-pass filtered click – is easily localized in most rooms.
In free field we detect the azimuth of sounds at low frequencies by detecting the time differences between the zero-crossings of the pressure waveform at the two ears.
Human perception is particularly sensitive to sounds with sharp onsets. We tend to localize the beginnings of sounds. We can localize an impulsive sound at low frequencies in part because it takes time for standing waves to establish themselves.
But there is a second reason.
The second reason is that standing waves preserve the original sound direction information if you average over enough of them. Low frequency noise or a pulse will excite many room modes all at once, and the time differences between the ears will correspond to the source azimuth."
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