No disputing that. I believe we were discussing why, at the lower frequencies, there is no reflection.
http://www.falstad.com/ripple/
I hit on this config kinda by accident. At the lowest frequency, you can see the inverted phase reflection back from the mouth. After it stabilizes for a few cycles, the reflections are canceling the direct sound and very little sound is getting out of the mouth. Take the frequency a click higher and lots of sound starts coming out of the mouth. Click the import/export button and paste in these numbers.
$ 0 110 1 0 false false 8 1 563 1
s 75 21
c 72 0
w 1 0
c 5 0
w 1 0
c 143 0
l 4511
w 1 0
l 1644
c 5 0
l 440
w 11 0
l 138
c 7650 0
w 1 0
l 149
c 7728 0
I hit on this config kinda by accident. At the lowest frequency, you can see the inverted phase reflection back from the mouth. After it stabilizes for a few cycles, the reflections are canceling the direct sound and very little sound is getting out of the mouth. Take the frequency a click higher and lots of sound starts coming out of the mouth. Click the import/export button and paste in these numbers.
$ 0 110 1 0 false false 8 1 563 1
s 75 21
c 72 0
w 1 0
c 5 0
w 1 0
c 143 0
l 4511
w 1 0
l 1644
c 5 0
l 440
w 11 0
l 138
c 7650 0
w 1 0
l 149
c 7728 0
Attachments
Pipe diameter tough question:
You haven't provided enough information to answer the question.
As the pipe diameter gets larger, the source location becomes more of a factor.
Ask better questions. 😀
You haven't provided enough information to answer the question.
Where is the source located?
As the pipe diameter gets larger, the source location becomes more of a factor.
Ask better questions. 😀
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TL for entertainment?
As far as these "emotionally charged" discussion go-------"People only want to feel good about what they believe and do not care about facts." I believe there is a lot of that emotionally charged stuff in some of these writings. This is shown by emotionally charged statements with lack of useful final measured results.
I have measured hundreds of would be sub systems and found most were not nearly so good as the person with the emotional investment in the sub had believed. High distortion and lack of real bass (less than 3%THD at 100dB) is the common result. I measured a 15 inch JBl pro ported speaker one time at 100dB output and 40Hz sine wave the distortion products had more energy than the fundamental. Most of the speakers I have measured have at least 20% distortion at 100dB out and 40Hz no matter what the enclosure type.
For TL speakers there is probably no other design concept with more variations the the TL. In the end for me it was lots of fun exploring but functionally the worst of the subs. Yes in specific cases in specific rooms it could be okay but for my 2¢ worth the woofer that measured flattest in the room has always been the low Q, less than 0.5, sealed box design in a really solid box.
So if the goal is to have fun the TL is the clear winner. If the goal is to make low distortion bass then the low Q sealed box is the winner.
As far as these "emotionally charged" discussion go-------"People only want to feel good about what they believe and do not care about facts." I believe there is a lot of that emotionally charged stuff in some of these writings. This is shown by emotionally charged statements with lack of useful final measured results.
I have measured hundreds of would be sub systems and found most were not nearly so good as the person with the emotional investment in the sub had believed. High distortion and lack of real bass (less than 3%THD at 100dB) is the common result. I measured a 15 inch JBl pro ported speaker one time at 100dB output and 40Hz sine wave the distortion products had more energy than the fundamental. Most of the speakers I have measured have at least 20% distortion at 100dB out and 40Hz no matter what the enclosure type.
For TL speakers there is probably no other design concept with more variations the the TL. In the end for me it was lots of fun exploring but functionally the worst of the subs. Yes in specific cases in specific rooms it could be okay but for my 2¢ worth the woofer that measured flattest in the room has always been the low Q, less than 0.5, sealed box design in a really solid box.
So if the goal is to have fun the TL is the clear winner. If the goal is to make low distortion bass then the low Q sealed box is the winner.
It doesn't matter where the source is located, I asked about their resonant frequency. At this point I could say:"re-read my questions with some understanding" but I won't.
😀
I'm not seeing anything special.
Try this:
$ 0 395 1 3 true false 6 1 655 1
s 182 154
c 21348 0
w 1 0
l 1102
w 1 0
l 339
c 1 0
w 1 0
l 6391
w 2 0
l 480
c 341 0
l 4328
w 2 0
l 480
c 139 0
l 1923
w 1 0
c 341 0
l 3024
w 2 0
l 480
c 342 0
l 3023
w 1 0
c 342 0
w 2 0
l 480
c 137 0
l 4671
w 1 0
c 138 0
l 1442
w 1 0
c 342 0
l 3023
w 2 0
l 480
c 343 0
l 6389
w 2 0
l 480
c 344 0
l 3983
w 2 0
l 480
c 345 0
l 3501
w 2 0
l 480
c 346 0
l 480
w 1 0
c 134 0
l 8176
w 1 0
c 346 0
l 2885
w 1 0
c 134 0
l 961
w 1 0
c 346 0
l 5290
w 1 0
c 134 0
l 2020
w 2 0
l 479
c 250 0
l 615
w 1 0
c 346 0
l 3981
w 1 0
c 347 0
l 3980
w 1 0
c 347 0
w 1 0
c 132 0
l 6119
w 1 0
c 133 0
l 2404
w 1 0
c 347 0
l 3980
w 2 0
l 480
c 348 0
l 3979
w 1 0
c 349 0
l 480
w 1 0
c 131 0
l 6120
w 2 0
l 480
c 132 0
l 1442
w 1 0
c 348 0
l 3847
w 2 0
l 130
w 2 0
l 348
c 131 0
l 1
c 348 0
l 8308
w 1 0
c 349 0
l 3366
w 1 0
c 131 0
l 961
w 1 0
c 349 0
l 3978
w 1 0
c 350 0
l 8787
w 1 0
c 351 0
l 3976
w 1 0
c 352 0
l 39443
w 1 0
l 479
c 128 0
l 1444
w 1 0
l 479
c 1 0
l 481
c 22305 0
Maybe an analogy to a bending bar clamped on one end helps:
A piece of mass attached to the free end of a bending bar will lower its first
resonance at lambda/4. Similar effects occur with masses attached to the
end of strings (which are labda/2 resonators).
A tapered pipe (or a pipe with attached port of smaller cross section at its open end)
will exhibit a lower resonance than a pipe of constant cross section and same length.
The reason for this is in both cases the added mass reactance which changes the
boundary conditions at the end of the resonating structure.
Both structures (bending bar and tapered pipe) can be made "acoustically longer" by
attaching mass at the end while keeping the same length geometrically.
The mass reactance in the tapered pipe comes from particles forced to accelerate, when
volume velocity is kept constant due to cross section getting smaller.
In so far the side walls of the pipe play their role in narrowing the cross section
in direction of travel towards the end of the pipe, where there is maximum verlocity at
lambda/4 .
For diameter of pipe small compared to wavelength, a bend in the pipe would not cause
acceleration, thus a bend would keep the resonant frequency nearly unchanged.
This holds especially for bends which are far away from the velocity maximum (end of the pipe).
For the effect of lowering quarterwave resonance in a tapered pipe, there is no
"reflection at side walls" needed to explain. The reflection at the open end is the
reflection that matters.
For low frequency there is IMO just fluid mechanics. But the side walls play a role
as borders changing the cross section and enforcing particle acceleration.
This is how i explain things to myself in a descriptive manner.
But i did not want to disturb this enjoyful thread ...
Kind Regards
John,
Earlier in this thread Martin said the solutions were for 1-D waves. Your example of a 10' diameter pipe moves the solution into 2-D. His worksheets do take this into account. The results from them depict higher frequency resonances resulting from the wall-wall dimensions of the enclosure.
I'm assuming a point source. You didn't say. Is it a point source? Is the source located in the center of the end of the pipe, or adjacent to the edge? 5' will make a difference.
The solution does depend upon the location of the source.
The question didn't provide enough info.
Just because you can pose a question doesn't guaranty you will like the answer. 😉
Earlier in this thread Martin said the solutions were for 1-D waves. Your example of a 10' diameter pipe moves the solution into 2-D. His worksheets do take this into account. The results from them depict higher frequency resonances resulting from the wall-wall dimensions of the enclosure.
I'm assuming a point source. You didn't say. Is it a point source? Is the source located in the center of the end of the pipe, or adjacent to the edge? 5' will make a difference.
The solution does depend upon the location of the source.
The question didn't provide enough info.
Just because you can pose a question doesn't guaranty you will like the answer. 😉
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Hello,
This may explain why I'm so luke warm when it comes to commercial subs or special loading schemes to extend bass. Something is amiss. The focus in speakers seems to be >60Hz. I understand that this is where most of the music occurs, so it makes economic sense to focus resources there. And then the port or transmission line is used or "sub" is added as an afterthought.
In practical terms >60Hz at a 100db undistorted probably requires an array of bass drivers.
Have you measured any bass towers or bass line arrays? What were your findings? Adding cubic inches may be the ticket. Thanks.
No Ed, the source does not matter - the resonant frequency of a fixed space is the same regardless of where the energy comes from to excite it.
Here's a good question: how do our ears hear bass?
Just bassiness-
You see my "avatar" is a little array 😀 but have not measured any others recently other than hear. You have pro stuff nailed and ports are so small that no thought is usually it- they go into power compression. 60Hz is the bottom end low bass in most pro stuff. Earlier in this thread I posted the pic of the double 10 box that will do 103dB 40Hz 3% distortion. I use DSP tuning of course. (Media Matrix) Did use 5 of these double 10 in one live studio...lots of DSP and ended up +3dB at 20Hz ±2 from 25-100Hz. Started at ±11, yuk! Of course every room must be tuned individually. Actually I do not even measure speakers except in the room used even for my little home system and then DSP a fix.
I have made 6 people sick with the bass at home playing Madonna Erotica... even me once.
And it was not out of balance or anything- just gut crushing.
I love to measure though- am around the KC area if there are any volunteers I would really consider coming by with a small raft of test gear and making a graph.🙂
You see my "avatar" is a little array 😀 but have not measured any others recently other than hear. You have pro stuff nailed and ports are so small that no thought is usually it- they go into power compression. 60Hz is the bottom end low bass in most pro stuff. Earlier in this thread I posted the pic of the double 10 box that will do 103dB 40Hz 3% distortion. I use DSP tuning of course. (Media Matrix) Did use 5 of these double 10 in one live studio...lots of DSP and ended up +3dB at 20Hz ±2 from 25-100Hz. Started at ±11, yuk! Of course every room must be tuned individually. Actually I do not even measure speakers except in the room used even for my little home system and then DSP a fix.
I have made 6 people sick with the bass at home playing Madonna Erotica... even me once.
And it was not out of balance or anything- just gut crushing.I love to measure though- am around the KC area if there are any volunteers I would really consider coming by with a small raft of test gear and making a graph.🙂
Using Martin's software I can model a TL for a specific driver, optimizing the line's resonant frequency for that driver, and end up with, let's say, an F3 of 30 Hz from the line whose 1/4-wavelength resonant frequency happened to be 25 Hz. Now if I increase the line's volume by increasing its CSA uniformly along its length, the line's 1/4-wave resonant frequency will not change, but the system F3 will now be lower simply because the enclosed line volume is larger. Now I'm not comparing two hugely different line areas or volumes, but isn't this the same as in your example? I modeled, I'd guess, hundreds of TLs, and built quite a few, and anytime the line area/volume is changed, without any changes to the line length (or taper, if tapered), there is no change to the system's resonant frequency but there sure is a change in F3. So, are the two pipes with 10:1 diameter ratios actually resonating at different frequencies, or is the larger pipe simply able to "support", for lack of a better word, lower frequencies?
Paul
Paul
He has no idea what he's talking about. Ignore him or tell him to go **** up a rope.
No, that's absolutely incorrect. Black body divergence, the nature of spectra, why EM transformed via Lorentz, the failure of aether models, the actual nature of gravity (as opposed to "it's 1/r just because")... that was a period of HUGE ferment. This is something that keeps coming up again and again in audio discussions, and it makes me despair of our educational system.
John, it doesn't matter if your source is 1/3 of the way down a line or 1/4 or 1/1.6143579, long wavelengths can't and don't "reflect" from the side walls. There is no "wave" in that sense, since the frequencies are so low. The transverse dimension is only a small fraction of a wavelength. That's also why polar patterns get circular at low frequencies, right?
The whip cream analogy is not a good one- whipped cream or any other foam like that is thixotropic and air isn't.
http://www.diyaudio.com/forums/multi-way/161961-real-expert-just-self-proclaimed-35.html#post2108903
It depends on how low we consider as no reflection. Not measureable by one means does not necessarily mean it does not exist. But as long as it's low enough that we don't have to worry about it, we normally "consider" it non-existant.
When we hear low frequency sound do we need to stand still to catch all of the wave? Do we need to be a certain distance away from the source to hear it? Is our perception of the tone in some way compromised by the fact that we are only receiving a very small portion of the wave? How does the ear drum work? By vibration from sound waves bouncing off of the membrane, that's how. How can a low frequency sound wave bounce off an eardrum if it is unable to reflect from a solid object?
Sy you lament the education system, so do I but I really have a problem with people who absolutely refuse to look at the logical evidence presented and hold fast to ideas that they can't explain themselves.
I'm waiting for someone to prove me wrong here. You can repeat that same chant over and over again - I'm not buying it.
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Yes I completely agree. People have this perverse sense of what modern physics did. It's like everything before was wrong!! That's simply not the case. In Quantum Mechanics there is a fundamental principle that states that any correct QM system MUST be consistant with Newtonian mechanics in the non quantum domain. Nothing about Newtonian physics was ever wrong, its just not applicable at the atomic level or the universe level.
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