There seems to be a lot of handwaving in your post, contradictory things. I can see at least four examples, I almost don't know where to start.
Well start with the most obvious, like how I'm right...or wrong... make sure to be descriptive
Ps- Handwaving is something one does to impress, I'm trying to communicate a technical idea effectively, with my limited knowledge on the subject in order to get the best answer in the shortest amount of time... not the same thing 😊
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Fair enough. Handwaving is a new term for me 😉
In any case, let's start here...
In any case, let's start here...
As my diagram was intending to suggest, these are both point source wavefronts. They have the same source size. They will do the same thing.
Ok perfect! Allen you always given me the benefit of the doubt lol...
So, once again I missed details, leading to confusion... I took your images and rearranged it to express my idea.... I turned A and B into radiators...
The listener receives a larger portion of direct sound with the larger radiator... a larger volume if direct energy has a direct path the listener. Also a larger initial wave size, leading to a larger wave front reaching the listeners body.
They could be wavefronts or they could be an array of small drivers arranged along line B, the result for our purposes is the same.
That result is that the sound will continue to spread evenly.
You seem to suggest it is going to change and focus down toward the listening position? (I'm not meaning to quote you too dramatically here, but try to see it as continuously expanding instead. Such is the nature of this wavefront shape.)
That result is that the sound will continue to spread evenly.
You seem to suggest it is going to change and focus down toward the listening position? (I'm not meaning to quote you too dramatically here, but try to see it as continuously expanding instead. Such is the nature of this wavefront shape.)
I mistakenly left out details.
In my diagram, I am displaying 2 different sized radiation sources. The red and blue line being the radiators surface
The blue area represents straight signal paths from the source to the listening point.
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Wavefronts don't move in the way the diagram depicts them. If the wavelength is high enough to be constrained by the sides, the radiation will follow that pattern. When the wavelengths get long enough it is as if those sides don't exist.
Are you still talking about 50Hz because if so you need to draw two circles, one a small one and one a big one.
As Earl said above the idea of direct sound and reflected sound ceases to apply in the same way when the frequency gets low enough.
The point is, once again......straight paths....to the listening point from radiation source.
This isn't exactly a matter of directivity. So lets focus on the omnidirectional spectrum.
In this diagram below I've added straight paths to the boundaries of the room.
The chartreus line separating the direct sound paths to the listening point
The magenta lines separating the direct sound paths headed to the boundaries of the room
I am highlighting, straight paths. In the omnidirectional spectrum, there will be more, Straight paths, of direct sound, to the listening point.
Omnidirectional sound, moves omnidirectionally from every point of the radiator, thus there is at least 1 straight path from every surface of the radiator, in the omnidirectional spectrum, to the listener.
Ps. There is a front baffle in white....free space in checker unless I painted over it.. The small radiator is in a waveguide, unintentionally... Still as long as we focus on straight paths, it should work out.
This isn't exactly a matter of directivity. So lets focus on the omnidirectional spectrum.
In this diagram below I've added straight paths to the boundaries of the room.
The chartreus line separating the direct sound paths to the listening point
The magenta lines separating the direct sound paths headed to the boundaries of the room
I am highlighting, straight paths. In the omnidirectional spectrum, there will be more, Straight paths, of direct sound, to the listening point.
Omnidirectional sound, moves omnidirectionally from every point of the radiator, thus there is at least 1 straight path from every surface of the radiator, in the omnidirectional spectrum, to the listener.
Ps. There is a front baffle in white....free space in checker unless I painted over it.. The small radiator is in a waveguide, unintentionally... Still as long as we focus on straight paths, it should work out.
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What you have drawn doesn't help to understand how LF is perceived, I have quoted Earl directly below and bolded his point.
Have a look at this spectrogram, in it you can see holes in the frequency response at certain times and sometimes the peak energy is delayed, what you hear is some combination of all of it.
OK so this is true to the auditorial senses but what about the sense of touch??? This matters because bass is also a tactile experience
No, I got that.. Let me try explaining it in a different way...
Say you're in an imaginary space, completely free of all reflective surfaces. Somewhere nearby you there is an ideal point source.
Now, an ideal point source has the same directivity regardless of frequency. Just a sphere of radiation, and there's nowhere else for sound to go because it already goes everywhere, and it does this evenly as it traverses every spherical wavefront size on it's way to being large enough to reach your listening position.
The only thing about it which is able to be changed, while still being a point source, is the level at the source.. and surely that's not what you're talking about.
At typical room sizes the room becomes (somewhat) pressurized at LFs, so this is all you feel, i.e. no distinct frequencies, we only hear, perceive its higher harmonics.
Camplo, think wavelength. For example the mentioned 50Hz is almost 7 meters long, or 22 feet, much bigger than you, perhaps bigger than your room and you could take Geddes words how it is perceived.
If you think some shorter wavelength, wavelength size of the transducer or array of transducers, then you could start drawing stuff like you've drawn except I think you are missing some points about sound. Perceived sound is pressure variation in air and at listening position it is just that, variation of pressure. Meaning that you can just make more excursion with what ever transducer you have and get more pressure, "energy", at listening position to the limits of the transducer capabilities. What you can do is enlarge the surface area to get more pressure for the same excursion, volume displacement.
What I think you are chasing at is basically just turning volume knob up to get more pressure for the transducer you have. The other thing you might be talking about, without knowing, is directivity. Directivity, or coverage angle, affects relative sound pressure at listening position to sound pressure somewhere else in the room. Still, no matter what the directivity, or coverage angle, is you can increase pressure by volume displacement, turning amplifier louder.
Except, when pressure peak and dip superimpose at listening position you get cancellation and less pressure variation even if it was set out with great volume displacement. The room makes destructive interference on the long wavelengths and its possible pressure doesn't increase much as two coherent propagating pressure variations cancel each other out at some point in space. On shorter wavelengths its reflections from boundaries that could be opposite polarity and cause destructive interference, and of course when wavelength is similar or shorter than size of the transducer, sound emanating from different spots on the transducer surface interfere each other and we get beaming, constructive interference on center axis, averaged out / destructive interference on other axis.
If you think some shorter wavelength, wavelength size of the transducer or array of transducers, then you could start drawing stuff like you've drawn except I think you are missing some points about sound. Perceived sound is pressure variation in air and at listening position it is just that, variation of pressure. Meaning that you can just make more excursion with what ever transducer you have and get more pressure, "energy", at listening position to the limits of the transducer capabilities. What you can do is enlarge the surface area to get more pressure for the same excursion, volume displacement.
What I think you are chasing at is basically just turning volume knob up to get more pressure for the transducer you have. The other thing you might be talking about, without knowing, is directivity. Directivity, or coverage angle, affects relative sound pressure at listening position to sound pressure somewhere else in the room. Still, no matter what the directivity, or coverage angle, is you can increase pressure by volume displacement, turning amplifier louder.
Except, when pressure peak and dip superimpose at listening position you get cancellation and less pressure variation even if it was set out with great volume displacement. The room makes destructive interference on the long wavelengths and its possible pressure doesn't increase much as two coherent propagating pressure variations cancel each other out at some point in space. On shorter wavelengths its reflections from boundaries that could be opposite polarity and cause destructive interference, and of course when wavelength is similar or shorter than size of the transducer, sound emanating from different spots on the transducer surface interfere each other and we get beaming, constructive interference on center axis, averaged out / destructive interference on other axis.
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On the other hand if you mean some "instantaneous pressure variation" that can be felt in the body? then I don't know what the threshold is, how much pressure difference at which time interval is perceived with bodily sensation. I mean are you thinking stuff like: When snare drum was struck and recorder it has certain impulse on the recording, but when played back on multi-way system into a room, how can we preserve the original recorded impulse to be perceived at listening position? Is this what you think? Btw, also here, to get more energy, to get the bodily feel, its matter of turning up the volume. Or would you want relatively more than what is in the original recording to have more of a sensation?
Its possible to have the impulse spread in time so that "instantaneous pressure variation" is smeared in time and its impact reduced, its not as great as the recorded pressure variation. Or if some frequencies are attenuated for some reason, flip side of the coin. Just make your playback system wide bandwidth and low group delay. Then use volume knob to increase pressure, and implement narrower directivity to reduce interaction with room for short wavelengths and employ other methods for room sized wavelengths, or get rid of the room 😀 Also, use center speaker because two speaker stereo will make you perceive the center panned snare with wrong timbre as there is comb filter happening. Or any other methods, tricks, substances, what ever, as its the brain we need to make happy, provide such stimuli through circumstances we have for it to concentrate on the sound, and perhaps get fooled into the recorded sound environment, right? But, people often have rooms, earbuds have very tiny ones, cars, what have we circumstances. You could optimize for one if you wish, for room, in which case you must have a room to optimize against.
Its possible to have the impulse spread in time so that "instantaneous pressure variation" is smeared in time and its impact reduced, its not as great as the recorded pressure variation. Or if some frequencies are attenuated for some reason, flip side of the coin. Just make your playback system wide bandwidth and low group delay. Then use volume knob to increase pressure, and implement narrower directivity to reduce interaction with room for short wavelengths and employ other methods for room sized wavelengths, or get rid of the room 😀 Also, use center speaker because two speaker stereo will make you perceive the center panned snare with wrong timbre as there is comb filter happening. Or any other methods, tricks, substances, what ever, as its the brain we need to make happy, provide such stimuli through circumstances we have for it to concentrate on the sound, and perhaps get fooled into the recorded sound environment, right? But, people often have rooms, earbuds have very tiny ones, cars, what have we circumstances. You could optimize for one if you wish, for room, in which case you must have a room to optimize against.
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The larger radiation source, the wave generated from it, is less distorted by the time it reaches the listener. There will be less Oscillations
Less oscillations would only mean a lower tone, wouldn't it? 😉 as in 49 Hz vs 50 Hz. One less cycle...
Good paper, thx.
Do you have any links that explain the number of cycles it takes the ear to identify low frequencies ?
A downloadable version can be found here;
https://www.researchgate.net/publication/8436733_Hearing_at_low_and_infrasonic_frequencies
i cant quite then understand the arguments against ported enclosure about group delay.