Well first foremost, it is a bigger challenge to keep a source away from the walls if the source gets big enough, that is common sense. 76" wide source in a 86" wide room for exampleNow we only need to simulate a big driver vs a small driver in the same room that has the right size, you choose the distance we need.
Let's see if there's a difference in room interaction between those two scenarios. You know, based on this theory:
If it really works like camplo indicates, wouldn't the bigger driver have a bigger problem to stay away from room boundaries, purely based on size alone
Just because you want something to be true doesn't make it true... Now if you take more sources/drivers, that would change things up a bit...
Increasing Radiation area increases the volume (3d proportions) of pressurized air the driver creates...unlike increasing excursion, increasing Radiation area, increases the volume (not level) of Direct Sound emitted from the Radiator. Think volume (3d proportions) not velocity. Velocity does not create more direct energy persay but it probably can extend the radiation mass forward, I dont know for sure
If we can simulate the radiation mass/impedance of a small and larger driver, volume matched, they will not be identical. It will tell the same story I describe, or maybe different.
@fluid would you be bothered to sim a 4" and 18" to demonstrate the volume matched impedance/radiation mass? At I dunno...50hz?
Or any others fluent in Akabak.
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You are welcome, there is plenty to study and some of it seems contradictory. I found it interesting that I could hear the clicks turn into tones more quickly when the frequency went down, it probably makes sense but it wasn't what I initially thought would happen.Thank you fluid, very generous reading list
Plenty to study...
I've noticed how a click-turns-into-tone, like in the last link you posted, when wavelet burst tests on drivers .
Only digging into the first paper so far, ...it sure does seem like the ear is going to resolve low frequencies faster than taking several periods...but yikes, so much to learn here....
I imagine that Earl @gedlee might be able to condense it into some more practical information from his experience and research into this area. I know I would appreciate it if he was inclined to do so.
Here is another one that presents a different piece of the puzzle too
https://assets.ctfassets.net/4zjnzn...04_karjalainen_antsalo_makivirta_valimaki.pdf
Time is too precious to waste. I find it hard to let bad information go unanswered so the best way I can help myself is by ignoring your posts. The forum ignore function is engaged now because I know I would otherwise get sucked back into it.
As I continue to try and prove my point. Here's another way to look at it;
volume (2: the amount of space occupied by a three-dimensional object as measured in cubic units (such as quarts or liters) : cubic capacity)
The volume of indirect sound in a room is sort of static.....theres only so many walls to give you reflections. The amount of reflections you get from the room only change if directivity from the speaker changes. So in the omnidirectional spectrum, Direct Sounds volume increases by increasing radiation area
The room will provide a fixed amount of indirect reflected signals.
The direct signals are limited to the amount of radiation area.
Its simple math.
volume (2: the amount of space occupied by a three-dimensional object as measured in cubic units (such as quarts or liters) : cubic capacity)
The volume of indirect sound in a room is sort of static.....theres only so many walls to give you reflections. The amount of reflections you get from the room only change if directivity from the speaker changes. So in the omnidirectional spectrum, Direct Sounds volume increases by increasing radiation area
The room will provide a fixed amount of indirect reflected signals.
The direct signals are limited to the amount of radiation area.
Its simple math.
Volume Velocity seems to fit.
The Radiation source, has a VV.
The Reflected energy from the Boundaries has a VV.
In the omnidirectional spectrum of a Driver, As you increase the Radiation area, Volume goes up for Direct Sound. Volume is fixed for a set room and speaker position. Velocity of the room is contingent on velocity from the source. Less velocity from the Source, Less velocity from the Room. Since Volume is fixed for the rooms input, Increasing Volume of the Source (aka increasing radiation area) will move you to a more Diffuse response.
Whats there to disagree with here?
@GM @gedlee
The Radiation source, has a VV.
The Reflected energy from the Boundaries has a VV.
In the omnidirectional spectrum of a Driver, As you increase the Radiation area, Volume goes up for Direct Sound. Volume is fixed for a set room and speaker position. Velocity of the room is contingent on velocity from the source. Less velocity from the Source, Less velocity from the Room. Since Volume is fixed for the rooms input, Increasing Volume of the Source (aka increasing radiation area) will move you to a more Diffuse response.
Whats there to disagree with here?
@GM @gedlee
Before GM or Geddes replies I'm after more info
what you mean by diffuse response? What is more diffuse response and what is less diffuse response? What you are after thinking this low level stuff like volume velocity, to learn?To my knowledge these concepts, volume velocity, particle velocity and radiator size, acoustic energy, what have you, all come back to just to SPL at given point, frequency response and directivity, which are more practical measures thinking loudspeaker systems in room.
If you are after how to make sound better I think you should look at psychoacoustics. Then, when you have psychoacoustics sorted, and know your room, you can design loudspeakers system that best fits your plans without ever calculating volume velocity, or acoustic energy. It doesn't hurt to know them though, to get more understanding whats going on.
edit.
From https://www.acoustic-glossary.co.uk/sound-fields.htm
"Diffuse Sound Field is the region in a room where the sound pressure level is uniform i.e. the reflected sound dominates, as opposed to the region close to a noise source where the direct sound dominates.
In a diffuse sound field, the sound pressure and the particle velocity are not in phase so the net sound intensity is zero and the sound doesn't appear to have a single source.
Diffuse Sound Field Definition (IEC 801-23-31) sound field which in a given region has statistically uniform energy density, for which the directions of propagation at any point are randomly distributed."
What I Googled few minutes ago volume velocity reflected of a wall is proportional to reflection coefficient and what the input volume velocity was coming to the wall. So, reasoning from this you can get less diffuse sound if you reduce the reflected volume velocity in relation to direct sound volume velocity. In other words manipulate the reflection coefficient of wall(s) adding absorber or assuming omni directional radiation manipulating relative distances of source, wall and listener? Isn't it easier to think with directivity, room size and psychoacoustics what is required to change perception, no?
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It was said that the experience I described from the theater was strongly influenced by the diffuse response of the room at LF
It was said that the experience I described from the theater was strongly influenced by the diffuse response of the room at Lf
A diffuse signal, to me, simply means that it spreads out into space, lacking reflections.
"Diffuse Field Distance is where the sound pressure of the direct sound is equal to the sound pressure of the reverberant sound in the room containing the source. Also known as the criticaldistance."
So after reading that, I understand better what Dr. Geddes was saying. As seen in the above definition, direct sound and indirect sound (reverb) are the major components.
What I've been going on about is the idea that increasing the radiation area, increases the direct sound portion of spl, in a room. For example, I believe that for a set room and speaker/listener position... increasing driver size, will increase Direct Sound contribution, in the omnidirectional spectrum vs a smaller woofer... 15" vs 4" at 50hz.... the 15" will deliver more direct sound. That is what I propose and it seems the math/science agree but I am not 100%
To create a more diffuse sounding response in the room, increase radiation area. Its more diffuse simply because direct sound portions have increased in a LF mode dominated room (indirect energy is dominate as opposed to balanced with Direct Sound)....
With that, I think I've stayed within the bounds of technically correct. I went on to propose that we can sense the proximity of pressure in a tactile way and that the less the room responds, the more we can sense pressure in a tactile way, from the radiation source, instead of the room.
It was said that the experience I described from the theater was strongly influenced by the diffuse response of the room at Lf
I like to look at it as direct and indirect sound. It is likely my experience in sound design that causes this preference. The wet/dry adjustment of reverb is very much like an indirect/direct adjustment if not identical.
A diffuse signal, to me, simply means that it spreads out into space, lacking reflections.
"Diffuse Field Distance is where the sound pressure of the direct sound is equal to the sound pressure of the reverberant sound in the room containing the source. Also known as the criticaldistance."
So after reading that, I understand better what Dr. Geddes was saying. As seen in the above definition, direct sound and indirect sound (reverb) are the major components.
What I've been going on about is the idea that increasing the radiation area, increases the direct sound portion of spl, in a room. For example, I believe that for a set room and speaker/listener position... increasing driver size, will increase Direct Sound contribution, in the omnidirectional spectrum vs a smaller woofer... 15" vs 4" at 50hz.... the 15" will deliver more direct sound. That is what I propose and it seems the math/science agree but I am not 100%
To create a more diffuse sounding response in the room, increase radiation area. Its more diffuse simply because direct sound portions have increased in a LF mode dominated room (indirect energy is dominate as opposed to balanced with Direct Sound)....
With that, I think I've stayed within the bounds of technically correct. I went on to propose that we can sense the proximity of pressure in a tactile way and that the less the room responds, the more we can sense pressure in a tactile way, from the radiation source, instead of the room.
Such long wavelengths require big room. Geddes says it very clearly in the quote, difference in sound is in the room size.
I'm by means no expert on this, just googling around, but thinking the definition of diffuse sound field as simple terms it understand it so that in diffuse sound field sound is smooth accross an area, you can move freely in diffuse sound field and the sound is the same. However, when wavelength is long, like size of the room, the diffuse sound just does not happen as there are modes, standing waves, peaks and dips in response. Sound changes as you move in the room, its not diffuse. I think this is the difference.
So, the radiator size just doesn't matter at all when wavelength is very long, closing in size of the room, because its the room that prevents diffuse sound for the long wavelengths. All you can do with small room is to mimic diffuse sound field as well as you can, with multisub setup, reduce peaks and valleys to make sound smoother through out the room.
I'm by means no expert on this, just googling around, but thinking the definition of diffuse sound field as simple terms it understand it so that in diffuse sound field sound is smooth accross an area, you can move freely in diffuse sound field and the sound is the same. However, when wavelength is long, like size of the room, the diffuse sound just does not happen as there are modes, standing waves, peaks and dips in response. Sound changes as you move in the room, its not diffuse. I think this is the difference.
So, the radiator size just doesn't matter at all when wavelength is very long, closing in size of the room, because its the room that prevents diffuse sound for the long wavelengths. All you can do with small room is to mimic diffuse sound field as well as you can, with multisub setup, reduce peaks and valleys to make sound smoother through out the room.
@tmuikku
" After many "paper" studies of the situation (including a PhD thesis) I arrived at the best "approximate" solution and that is multiple subs. This yields much more diffuse LF signal along with a much more uniform response."
He was not talking about large rooms yielding a "much more diffuse" LF signal in this sentence. All I took it as, is that with multi sub it will be more Diffuse like...not actual Diffuse....The only thing more diffuse like is the increase in Direct Sound
One of the easiest ways to express a trend is to exaggerate the cause
Lets say that all the Red space is Radiator area. The green guy is the listener....The system is playing 50hz, omnidirectional to both systems....If you think that the lower room will have the same Direct sound vs Indirect sound compared to the upper...I'd say that you might misunderstand what direct sound is.....A diffuse response is balanced between room (indirect) and source (direct) input.....A small room is normally Dominated by Modes in the LF......Modes of indirect sound. If I increase Direct sound....I am one step closer to evening out Direct vs Indirect sound. SPL is a sum of Direct +Indirect......That is all.
I rather move on to proving right or wrong....How does one measure Direct Sound vs Indirect, So I can prove this to be true and move on
" After many "paper" studies of the situation (including a PhD thesis) I arrived at the best "approximate" solution and that is multiple subs. This yields much more diffuse LF signal along with a much more uniform response."
He was not talking about large rooms yielding a "much more diffuse" LF signal in this sentence. All I took it as, is that with multi sub it will be more Diffuse like...not actual Diffuse....The only thing more diffuse like is the increase in Direct Sound
One of the easiest ways to express a trend is to exaggerate the cause
Lets say that all the Red space is Radiator area. The green guy is the listener....The system is playing 50hz, omnidirectional to both systems....If you think that the lower room will have the same Direct sound vs Indirect sound compared to the upper...I'd say that you might misunderstand what direct sound is.....A diffuse response is balanced between room (indirect) and source (direct) input.....A small room is normally Dominated by Modes in the LF......Modes of indirect sound. If I increase Direct sound....I am one step closer to evening out Direct vs Indirect sound. SPL is a sum of Direct +Indirect......That is all.
I rather move on to proving right or wrong....How does one measure Direct Sound vs Indirect, So I can prove this to be true and move on
Thanks fluid, nice paper for the context!
Although most of it is over my head it concludes "An important conclusion of the paper lies in the fact that
a diffuse field can be established in a room that exhibits
strong modal behavior.". There is also mention that bandwidth where diffuse field can exists has at least 20-30 modes are required, which gives rise to critical frequency which depends on room size. There is also example which calculates critical frequency and it comes close to "Schroeder frequency". If I understood this correctly diffuse field can be established above this critial frequency.
Well, even if I missed the main message on the paper I'm quite certain after reading it that the diffuse and modal stuff is about room acoustics, size, and transducer size doesnt matter
Although most of it is over my head it concludes "An important conclusion of the paper lies in the fact that
a diffuse field can be established in a room that exhibits
strong modal behavior.". There is also mention that bandwidth where diffuse field can exists has at least 20-30 modes are required, which gives rise to critical frequency which depends on room size. There is also example which calculates critical frequency and it comes close to "Schroeder frequency". If I understood this correctly diffuse field can be established above this critial frequency.
Well, even if I missed the main message on the paper I'm quite certain after reading it that the diffuse and modal stuff is about room acoustics, size, and transducer size doesnt matter
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Yeah you are right, its just not possible to increase direct sound in LF without also increasing the indirect sound (reflections) because the sound radiates allover from any transducer that fits inside the room. You'd need to absorb the "indirect sound" in a small room. When wavelength is room size, or bigger, you cannot fit in a structure that would restrict sound to walls, at the long wavelengths.@tmuikku
" After many "paper" studies of the situation (including a PhD thesis) I arrived at the best "approximate" solution and that is multiple subs. This yields much more diffuse LF signal along with a much more uniform response."
He was not talking about large rooms yielding a "much more diffuse" LF signal in this sentence. All I took it as, is that with multi sub it will be more Diffuse like...not actual Diffuse....The only thing more diffuse like is the increase in Direct Sound
One of the easiest ways to express a trend is to exaggerate the cause
View attachment 1105705
Lets say that all the Red space is Radiator area. The green guy is the listener....The system is playing 50hz, omnidirectional to both systems....If you think that the lower room will have the same Direct sound vs Indirect sound compared to the upper...I'd say that you might misunderstand what direct sound is.....A diffuse response is balanced between room (indirect) and source (direct) input.....A small room is normally Dominated by Modes in the LF......Modes of indirect sound. If I increase Direct sound....I am one step closer to evening out Direct vs Indirect sound. SPL is a sum of Direct +Indirect......That is all.
I rather move on to proving right or wrong....How does one measure Direct Sound vs Indirect, So I can prove this to be true and move on
For short wavelengths this works fine thoigh, because we can increase directivity, we can focus more sound towards the listener direction and reduce towards boundaries. Horns, waveguides, arrays, but only so big fit into a room. Its all about wavelength.
You are just missing the bigger picture. If one were to cause LF to beam it will lower indirect sound portion and raise direct sound portions to the listener standing in the Beam.....A room that is Diffuse at LF has certain characteristics to it.....IF you can bring Some of the characteristics to your small room, your room will sound more Diffuse...that doesn't make it actually Diffuse at LF. A small room+system to listener might be 9parts indirect sound and 1part direct sound.....If directivity were to change that to 5 parts indirect sound and 5 parts Direct sound....it is a more Diffuse like response
You think that at 50hz that the signal will be the same at listening point in these 2 rooms!? how?!?!? Impossible
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This is the devils advocate to my "Big Point", and yet to be proven true..... My first thought was the whole Velocity thing, Remember we have to lower velocity to compensate SPL to that of the smaller radiation room.
Can I measure this With my Umik? Direct vs Indirect sound?
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You were talking about multisub all along? I misunderstood, thats the best you can do I think, biggest and simplest system that fits into a room. You could have wall size transducer if you wanted but you dont have to, because of the long wavelengths.
Have you checked out the "double bass array"? Basically multiple subs on front wall and backwall. Idea is to send plane wave across the room and then output inverted one at the backwall when the sound gets there, to cancel the reflection.
Have you checked out the "double bass array"? Basically multiple subs on front wall and backwall. Idea is to send plane wave across the room and then output inverted one at the backwall when the sound gets there, to cancel the reflection.
Well thats just it....Having, once again, direct sound coming from multi directions, is definitely going to increase Direct sound....There will be more intersects at the listening point that have not Reached a boundary yet. Mulitsub is essentially an increase in Sd ie, Radiation area.
The more paths you can draw to the listener, the more Direct Sound the listener is getting. Directivity allows one to draw less lines to the boundaries and potentially more to the listener....increasing Radiation size, increase the amount of lines you can draw straight to the listener.....
The part you added in is the idea that more lines will be drawn to the walls as well....So it gets complicated. I think what happens is, there is still a larger amount of Straight lines that reach the listener First before the reflections arrive, From the Larger Source, Than with a Small Source,
Do you get what I am trying to say now....So at this point I am reminded that we do not perceive LF until many cycles? So the Ear part is null....
What I am saying now is that the more Lines I can draw from the the Radiation source to the listener....The more I can feel the sound coming from that direction of the lines.
The part you added in is that idea that more lines will be drawn to the walls as well....So it gets complicated. I think that what happens is, there is still a larger amount of Straight lines that reach the listener First, From the Large Source, Than with a Small Source...
The more paths you can draw to the listener, the more Direct Sound the listener is getting. Directivity allows one to draw less lines to the boundaries and potentially more to the listener....increasing Radiation size, increase the amount of lines you can draw straight to the listener.....
The part you added in is the idea that more lines will be drawn to the walls as well....So it gets complicated. I think what happens is, there is still a larger amount of Straight lines that reach the listener First before the reflections arrive, From the Larger Source, Than with a Small Source,
Do you get what I am trying to say now....So at this point I am reminded that we do not perceive LF until many cycles? So the Ear part is null....
What I am saying now is that the more Lines I can draw from the the Radiation source to the listener....The more I can feel the sound coming from that direction of the lines.
The part you added in is that idea that more lines will be drawn to the walls as well....So it gets complicated. I think that what happens is, there is still a larger amount of Straight lines that reach the listener First, From the Large Source, Than with a Small Source...
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