Why not? The matter arose as an audio example of dispersion (frequency dependant wave propagation velocity), because the wave behaviour in this case is naturally dispersive. Whether it happens in practice depends on specific driver and frequencies.
I'm seeing something on my scope that looks like it could be popcorn noise through a LP filter, like a random sawtooth wave with a period of rarely less than 1mS. It's about 800uV p-p at the output of an I-V converter someone sent me. I'm thinking it could be from parasitic oscillation of a MOSFET, or just the VMOSFET's inherent noise (what does that look like on a scope?).
Any suggestions?
Any suggestions?
Yes I would think that the bending modes would be frequency dependent. Originally this conversation came out of the question about the speed through a composite material and if the different materials would have different propagation speeds. That question was answered in the fact that the absolute speeds between the different solid materials would be so close as to not matter but the elastic resin holding all of that together would be a separate issue perhaps. That is where the transverse waves came in and the conversation changed to this about whether a cone bends or not. If the cone is in a box, we also have to consider the air pressure on each side of the diaphragm as being unequal, this is also going to induce bending I would think?
ES,
So the chain on the bottom of my bike isn't pushing the back chain wheel around while the top of the chain is pulling!
I would think that in your instance of a hanging array that the important factors would be the total column weight and the load on the top enclosure as it would see the maximum load, the bottom enclosure only its own weight. So you would have to look at the shear loading of those 1/4" bolts and as long as there are no threads through the loaded section that would be a fairly high shear force to shear a 1/4 steel rod purely by shear force and no bending forces. I would think your PE would find that problem fairly simple and start forward.
ES,
So the chain on the bottom of my bike isn't pushing the back chain wheel around while the top of the chain is pulling!
I would think that in your instance of a hanging array that the important factors would be the total column weight and the load on the top enclosure as it would see the maximum load, the bottom enclosure only its own weight. So you would have to look at the shear loading of those 1/4" bolts and as long as there are no threads through the loaded section that would be a fairly high shear force to shear a 1/4 steel rod purely by shear force and no bending forces. I would think your PE would find that problem fairly simple and start forward.
I am sorry to inform you that the opposite is true.
Your link shows cones operating in their break up modes. You will recall that early on in our discussion I already mentioned that your bending wave thing is what you see after cone break up. It is called break up for a reason. The cone geometry literally breaks down and waves and all other sorts of resonant modes become apparent.
The reason Kevlar and pvc cones were used is that they transition smoothly so that you can operate them well into their break up regions. This is also the reason you don't see them in quality gear any more. It just ain't good enough, you want pistonic behavior.
Edit: in post #69529 SY writes on group delay. If I missed a contribution from Scott on this matter, please let me know the correct post no.
Well thanks guys for trying to give me the answer as to what 'real' delay is. Unfortunately, I am still in the dark, because (I think) that Richard Heyser never really answered his own question. I found a reference, #26 in his Jan'69 article (part 1) on time delay that I am not sure that he ever published.
It is:"Group Delay, Excess Delay, and Overall Time Delay" that was to be published. Anybody ever see a copy?
In his AES article he constantly references this paper I have never seen. No wonder there is so much confusion.
It is:"Group Delay, Excess Delay, and Overall Time Delay" that was to be published. Anybody ever see a copy?
In his AES article he constantly references this paper I have never seen. No wonder there is so much confusion.
Precisely it depends on driver design and frequency. So if you are designing a driver you already know from frame size where the pattern narrows and that sets a reasonable upper frequency limit. The cone linear movement sets the reasonable low frequency response. This is well covered in the books that the transducer designers are familiar with.
Now there certainly are and have been drivers that did not have pistonic motion in the range of interest. As one of my friends used to say the only advantage he had over the off-shore manufacturers was his Klippel system. These days Klippel markets even there.
One of my favorite ceiling loudspeakers was an Altec 803 8" coaxial model. Often copied but few sounded the same. Now when you analyzed it and fixed it with equalization it sounded not very good! It was designed with very basic equipment and "voiced" by ear to sound good. Take out the frequency aberrations and you unmasked all of the distortions and other problems. Yes it had what is by today's standards a floppy cone and lousy coaxial tweeter.
Yes I would think that the bending modes would be frequency dependent. Originally this conversation came out of the question about the speed through a composite material and if the different materials would have different propagation speeds. That question was answered in the fact that the absolute speeds between the different solid materials would be so close as to not matter but the elastic resin holding all of that together would be a separate issue perhaps. That is where the transverse waves came in and the conversation changed to this about whether a cone bends or not. If the cone is in a box, we also have to consider the air pressure on each side of the diaphragm as being unequal, this is also going to induce bending I would think?
ES,
So the chain on the bottom of my bike isn't pushing the back chain wheel around while the top of the chain is pulling!
I would think that in your instance of a hanging array that the important factors would be the total column weight and the load on the top enclosure as it would see the maximum load, the bottom enclosure only its own weight. So you would have to look at the shear loading of those 1/4" bolts and as long as there are no threads through the loaded section that would be a fairly high shear force to shear a 1/4 steel rod purely by shear force and no bending forces. I would think your PE would find that problem fairly simple and start forward.
Please stay away from box issues, life is way too short.
You can push the chain back but don't try to transfer energy by pushing on a chain.
My P.E. did the calculations, they matched within reason what we measured. But as you might have picked up some folks would argue with numbers even from an expert.
ES
P.S. Lucky if you just want to argue then "You seem to have a grasp of the basics..."
ED,
I try not to ever build square boxes but that is just me! I won't start up a conversation on cabinet vibration. we will never get back to John's electronics if we go there!
As far as real delay, it seems there is no true meaning to that word, or at least an agreed upon definition. I would think that would be a contextual usage of those words. Someone may talk about using a delay which could be an echo chamber while someone else talks about the actual delay in an electrical circuit, only the conversations seems to determine the usage.
I try not to ever build square boxes but that is just me! I won't start up a conversation on cabinet vibration. we will never get back to John's electronics if we go there!
As far as real delay, it seems there is no true meaning to that word, or at least an agreed upon definition. I would think that would be a contextual usage of those words. Someone may talk about using a delay which could be an echo chamber while someone else talks about the actual delay in an electrical circuit, only the conversations seems to determine the usage.
More information, like a schematic, would be helpful. As to 1/f noise, it is distinct from popcorn noise per se and doesn't look like it in the time domain. The guess of parasitic oscillation may be a good one, with something involving that, and something that detects it, having a threshold that gates the impulsive part of the sawtooth.
I don't know any of the parameters of the I-V but 800uV peak is a lot.
Hypothetical: what if you were able to simulate a point source that had worked equally well acting in "both" directions. I know that the action of a voice coil is not perfectly linear.
If you were able to place this point (or plane source ) so that the sound were directed in the desired direction using the aid of the enclosure, would the resulting response exhibit delay in the nearfield, and what about greater distances other than use as a PA. I've attached a quick sketch.
In many ways, this is what a reed does does in a wind instrument. It's a partial comparison because audible sound is generated by the reed not only vibrating but also attenuating the air column creating air turbulence inside the instrument itself. However, many notes can be played using the same embouchure and air pressure by changing the length of the air column and attenuating the pattern of the exits by which the turbulence leaves the instrument.
So if such a device can be attenuated with minimal delay (unsure if this falls into the "real" delay category), can this be applied using a full range capable configuration?
This is going out very far beyond the edge of the precipice, so I apologize in advance. Then would such a configuration have any application such as a ES(D) mounted mounted sideways like this have any meaningful application.
Ill Conceived? If off topic, not intentional.
If you were able to place this point (or plane source ) so that the sound were directed in the desired direction using the aid of the enclosure, would the resulting response exhibit delay in the nearfield, and what about greater distances other than use as a PA. I've attached a quick sketch.
In many ways, this is what a reed does does in a wind instrument. It's a partial comparison because audible sound is generated by the reed not only vibrating but also attenuating the air column creating air turbulence inside the instrument itself. However, many notes can be played using the same embouchure and air pressure by changing the length of the air column and attenuating the pattern of the exits by which the turbulence leaves the instrument.
So if such a device can be attenuated with minimal delay (unsure if this falls into the "real" delay category), can this be applied using a full range capable configuration?
This is going out very far beyond the edge of the precipice, so I apologize in advance. Then would such a configuration have any application such as a ES(D) mounted mounted sideways like this have any meaningful application.
Ill Conceived? If off topic, not intentional.
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Nope, its a B&W link and it shows plots and animations for, amongst things, impulse response of a 15cm driver, which appears to have a propagation time from inner to outer of about 0.3mS. Not only is there a waterfall plot which clearly shows the impulse radiating from centre to rim in about 300uS, one can see the dispersion as the impulse speads due to different frequencies propagating at different velocities. Nothing to do with cone breakup, everything to do with normal operation as illustrated by the impulse response.
Here's the B&W link again Tools of the trade - laser measurements | Society of Sound
One post above, #69528..........he posted the B&W link there.vacuphile said:
PS: on that B&W page you can also see the echoes and reflections from the impulse, which had just about settled down after 1.4mS in that driver ! The wave propagation velocity for the impulse in that cone seems to be about 200m/S, far slower than the speed of sound in the cone material (c 2600m/S).
Here's a quote from the B&W page: "The initial impulse applied to the voice coil causes first the central section to move, after which a double circular wave moves to the outer edge of the diaphragm. You can then detect a wave being reflected back to the centre, after which the outer portion continues to flap. This sort of ringing motion obviously results in sound radiation well after the original excitation signal has stopped and causes a reduction in clarity."
Here's a quote from the B&W page: "The initial impulse applied to the voice coil causes first the central section to move, after which a double circular wave moves to the outer edge of the diaphragm. You can then detect a wave being reflected back to the centre, after which the outer portion continues to flap. This sort of ringing motion obviously results in sound radiation well after the original excitation signal has stopped and causes a reduction in clarity."
can you send copy to me or where i can get it? group delay is well understood but how R.Heyser applied it , isnt so well known.
THx-RNMarsh
On the topic of delay, I don’t want to derail or detract from this thread so if anyone knows about my question, please PM me; and at the end I will leave an article possibly interesting from a historical if not technical perspective. I have been reading here learning about delay; I have zero technical knowledge, but am more of a live sound reinforcement historian. I finally pinned down and want to know more about Dennis Fink’s UREI Model 927 four-channel delay unit http://www.jblproservice.com/pdf/Vintage JBL-UREI Electronics/UREI-927.pdf if anyone has ever used it or knows more about what its design morphed into.
I cracked the nut of finding the first useful delay device for this purpose in a PA, by reading, at least to me, a very fascinating article on the beginning use of time alignment in speakers that has a pretty in-depth explanation of its use in the first live PA starting on page 52 of the magazine. http://www.americanradiohistory.com/Archive-Recording-Engineer/80s/Recording-1980-12.pdf [you may have to copy and paste the links]
I cracked the nut of finding the first useful delay device for this purpose in a PA, by reading, at least to me, a very fascinating article on the beginning use of time alignment in speakers that has a pretty in-depth explanation of its use in the first live PA starting on page 52 of the magazine. http://www.americanradiohistory.com/Archive-Recording-Engineer/80s/Recording-1980-12.pdf [you may have to copy and paste the links]
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The cone does not break up at all, rather it exhibits near exactly the behaviour expected of a waveguide.......the impulse remains intact even after a few reflections from the rim and centre.
No, much of that B&W page presents graphs and animations based on single impulse response. Seems sensible to me.
Here's a quote from the B&W page "In this next example, we look again at the whole cone, but now the excitation signal is an impulse. (..) The initial impulse applied to the voice coil causes first the central section to move, after which a double circular wave moves to the outer edge of the diaphragm. You can then detect a wave being reflected back to the centre, after which the outer portion continues to flap. This sort of ringing motion obviously results in sound radiation well after the original excitation signal has stopped and causes a reduction in clarity. Reflection actually occurs wherever there is a boundary between dissimilar materials. So it happens not only at the coil to cone joint and where the surround sticks to the chassis (or basket), but also where the cone and surround meet."
Particularly interesting is the air pressure animation in front of the cone, which you can see is a halo radiating first from the centre and developing outward toward the rim. Maybe this is why most speaker radiators have a conical shape.......to compensate for arrival time differences from the centre and the rim parts of the driver surface ??
Lucky,
I can't say the percentage of cones that are conic vs curvilinear, this does have an effect on the radiation pattern coming off the cone. Many very small speakers have very flat profiles and these would appear to operate more as a plate than as a rigid cone.
I once produced cones for an auto sound amplifier company for a sub-woofer application. The cone was for a 10" driver and had a concave curved shape with a molded ring on the back for the former attachment. I could literally stand on the back of that cone at the former attachment point and it would hold my entire weight without collapsing, I weigh about 180 lb. ( 82 kilos). They were stupidly stiff but the object was a heavy cone for very low resonance frequency, fs.
I can't say the percentage of cones that are conic vs curvilinear, this does have an effect on the radiation pattern coming off the cone. Many very small speakers have very flat profiles and these would appear to operate more as a plate than as a rigid cone.
I once produced cones for an auto sound amplifier company for a sub-woofer application. The cone was for a 10" driver and had a concave curved shape with a molded ring on the back for the former attachment. I could literally stand on the back of that cone at the former attachment point and it would hold my entire weight without collapsing, I weigh about 180 lb. ( 82 kilos). They were stupidly stiff but the object was a heavy cone for very low resonance frequency, fs.
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