Actually, you do. If you make a claim and someone calls you on it, then it is your obligation to back it up or forfeit the argument.
This is the crux of the biscuit that we have been batting back and forth. As an engineer you know the scientific method. If you intend to make a convincing argument you have to prove your point, not make a baseless claim and say, "Prove it isn't true."
"U will be toward the open end for a compression wave, and in the opposite direction if the wave is an expansion wave."
This is an interesting theory. While we're on the subject of conservation of energy, mass, and momentum, what happened to the wave (half wave) "traveling in the opposite direction" that's adjacent to it in time?
No need for much information. Just show us the measured free field impedance/phase of the driver, and the impedance/phase measured using the same driver in the TL enclosure. Very basic DIY level stuff should not be that difficult would it? You don't need to tell us what the driver model is.
I think almost everybody responding is familiar with the acoustics of waves in pipes. You seem to be the odd man out, everybody else seems to be on the same page. Does that trigger any questions or doubts in your own thinking? It should.
It shocks me that somebody who claims to have a significant technical education, a backgroud in the topics, and claimes to read so many technical books/articles can be so far out in left field.
To write software that works well and correlates with tests of applicable speakers you need to have derived all of the math/acoustics involved and have a detailed understanding of what is being programmed. It is not a coincidence that the software works for many diverse users. You can poorly apply software to the wrong problem, that is caused by a lack of understanding of the end user. But if the software functions correctly it is due to the understanding of the originator.
Bottom line is that you make many claims, put down people with a proven understanding of acoustics, write arrogant and insulting responses, try to lead the discussion in any and all tangent directions while avoiding direct questions, and in the end provide nothing to back up your own positions/theories.
I don't think the results of my investigation into Natkaniec's claims are that far out "in left field". The sum of wave peaks under 100hz for a driver with a free air resonance Fs is going to occur at an average distance of 1/6th the Fs wavelength away from the driver when it is placed in a pipe - damped or otherwise. This correlates with Augspurger's data and Shultz' data - but instead of giving a range of values, it gives an exact number. Is this left field? Do we really need to delve into a discussion of the physical implications of standing wave theory? I don't think so. If someone wants to model acoustic properties with electrical circuit analogies - they're free to do so. It doesn't necessarily guarantee a better or worse outcome. And it doesn't mean that anyone who chooses not to use such methods is out to lunch.
Do keep in mind that Shultz's data is all generated from Augspurger's software. What part of Augspurger's work supports your thesis?
Martin has taken care of an earlier argument you had based on Augspurger.
dave
Over at HTG, I posted a Hornresp sim showing the mouth reflections with alternating positive positive and negative phase in the impulse response. This was modeled with a straight pipe in front of the driver and ignores the back wave of the driver. Villastrangiato thought about it for a while and decided he didn't believe it because there couldn't be a reflection at the mouth (the Earth is flat, therefor it can't be round. 🙂 ) I suggested at the time that he try the experiment himself with a speaker, a pipe and a microphone. I make the same suggestion again. A simple measurement would put this thing to bed.
Attachments
IOW, no, you have no experimental data nor detailed modeling. That's not exactly making me believe...
And where have you posted or published these results?
Okay, enough is enough...
It's time for you, as they say, to "step up to the plate", "show us what you got", and "put up or shut up"! You've offered no proof of what you speak in a form that all can critique and I doubt you ever will (because I'm confident you can't). Perform a community service on this forum and either offer valid proof in some form other than words and tangential topics, or stop criticizing and demeaning all those that disagree with you, followed by ending your useless posts on this subject. PLEASE!
Paul
It's time for you, as they say, to "step up to the plate", "show us what you got", and "put up or shut up"! You've offered no proof of what you speak in a form that all can critique and I doubt you ever will (because I'm confident you can't). Perform a community service on this forum and either offer valid proof in some form other than words and tangential topics, or stop criticizing and demeaning all those that disagree with you, followed by ending your useless posts on this subject. PLEASE!
Paul
That's true as far as it goes. However, we usually measure and hear pressure rather than displacement and the situation is reversed there. Pressure reflections keep the same phase at the closed end and invert phase at the open end.
Resonance Tube
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Spot on. IP's match.
But lets keep talking TL's, gentleman.
After all, there's a lot to learn from the smarter guys here. 🙂
So, did it really come to that? Someone who is determined to stay ignorant, actually goes to Wikipedia and changes it to match his proven wrong ideas?
What's someone like that doing here??
jd
Why can't you fellows just let the guy have his say, agree or disagree with him (or keep silent like some of us) but leave the taunting out of it? It's really not becoming for some of you to stoop to that level.
This thread is filled with this behaviour - earlier there was the question of his credentials, like that matters at all and then for his real name.
This thread is filled with this behaviour - earlier there was the question of his credentials, like that matters at all and then for his real name.
I can't stop laughing. How can you not be entertained by this??
p.s. I'm rather disappointed this was discovered before it could be referenced as supporting evidence
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More than a theory, that's pretty much how wave propagation works at a discontinuity of line impedance. Same as with RF waves in a coax. The wave travelling in the opposite direction isn't adjacent in time, it's going the other way. That one goes back to the cone (except the portion that gets turned to heat by losses like stuffing) and affects the impedance.
The diagrams provided by JohnK from this website show a loudspeaker that is not sealed to a pipe
The Open Door Web Site : IB Physics : Waves : Resonance in Air Columns
Did any of you read this quote at the beginning of the section on open pipes?
"Resonance can also occur in pipes which are open at both ends."
This minor detail you all seem to be overlooking makes all the difference in the world.
I'll repeat my earlier question - what happened to the negative pressure portion of the travelling wave? Clearly, on the end of a sealed cavity - it has nowhere to go - so with Mr. JohnK's assertion of conservation of momentum and energy - what happened to it?
Dear everybody
Enough already with the incoherent chanting of meaningless dogma!
I hereby respectfully request that any further posts on the topic of loudspeakers by members of CAC (Cult of the Acoustically Clueless) be summarily deleted in terms of the forum's "No Religion" policy, with bin time for repeat offenders.
Seriously.
Yours sincerely,
Grumpy old man
😡
Enough already with the incoherent chanting of meaningless dogma!
I hereby respectfully request that any further posts on the topic of loudspeakers by members of CAC (Cult of the Acoustically Clueless) be summarily deleted in terms of the forum's "No Religion" policy, with bin time for repeat offenders.
Seriously.
There are perhaps half a dozen worthwhile posts in this thread, diluted by more than 20 pages of arrant nonsense and the rebuttal thereof.
Yours sincerely,
Grumpy old man
😡
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I'll provide a direct link to the page in question for Resonance in Open pipes:
Resonance in Open Pipes
Resonance can also occur in pipes which are open at both ends.
Consider a source of sound close to one end of a pipe, of length, , as shown below.
The Open Door Web Site : IB Physics : Waves : Resonance in Air Columns continued
Maybe to you this is a minor detail, but my analysis was entirely formed and confirmed by the response sweeps generated by George Augspurger in his tests. It addresses the exact location of peaks and nulls occurring outside the pipe - which are not based on the pipe length but are in fact based on the linear behavior of the driver. And no end correction mathematical fudging is necesarsy. 😉
Resonance in Open Pipes
Resonance can also occur in pipes which are open at both ends.
Consider a source of sound close to one end of a pipe, of length, , as shown below.
The Open Door Web Site : IB Physics : Waves : Resonance in Air Columns continued
Maybe to you this is a minor detail, but my analysis was entirely formed and confirmed by the response sweeps generated by George Augspurger in his tests. It addresses the exact location of peaks and nulls occurring outside the pipe - which are not based on the pipe length but are in fact based on the linear behavior of the driver. And no end correction mathematical fudging is necesarsy. 😉
Sorry to be such a burden Godrey. I may be 45 years old, but I don't think I've stopped learning yet. So if there's anyone on this thread who would still care to enlighten me further about the conservation of mass, momentum, and energy - I'm all ears. Learning for me is fun. I'm not afraid to learn something new - it generally doesn't mean I'm a lesser person. So teach me about the physical laws that govern this aspect of acoustics as you see them.
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