I have been reading the archives about people using various types of sound dampening sheets on the inside of their disc players.
Dynamat makes a sheet that is also layered with aluminum. Besides dampening the case from vibration, would this aluminum layer offer any additional shielding?
What can anyone else add about this tweak?
I asked about Dynamat Extreme and the benefits of the aluminum layer. Not rollers and points!
The original Dynamat, and similar products, are simply gooey, heavy sheets that stick to the car metal and offer limited damping while adding a lot of mass. Added mass is bad, because it reduces the combined structure's resonant frequency. This increases the excursion of the vibrations and makes it harder to tame them with other means.
Constrained-layer damping forces the damping gooey material to be placed into what is called "shear" in order for the structure to vibrate. This dissipates a lot more energy per unit weight of the damping material, so you get a lot more damping action without adding a lot more weight.
The aluminum layer on Dynamat X-treme is designed to give good damping with typical car body sheet metal. That it also works on most audio component box and chassis metal is good for us, because it is sold into the car market rather than the high-end. There are plenty of extremely expensive high-end alternatives that are probably more effective under the right circumstances, but much more costly than what this experimenter is willing to pay.
To finally answer your question, now that you know why it is there, no it is not likely to give good shielding. For one thing, it is not grounded by installation, and grounding it securely would be a major PITA. It is not designed to have thickness or resistivity appropriate for electrical shielding. Since it is usually attached to metal, having it there is not necessarily bad. However, there may be cases where the fact that it is electrically floating would cause problems.
If you need to have additional shielding, you can attach an appropriate copper sheet with polyurethane construction adhesive to the aluminum side. This would increase the constrained-layer damping effectiveness, as the polyurethane rubber is also a dissipative material.
Be careful with Dynamat X-treme on thick metal objects, like the typical upmarket component front panel. It is not effective on such objects, and makes their ringing worse by lowering their resonant frequency.
for effective shielding to occur, you would need to completely surround the object you're trying to shield, and also connect the shield to ground. I'm definitely not an expert on shielding, though. If you don't soon get some good answers, you may want to try re-posting with a more specific subject line (something like 'Foil Shielding - advice wanted)- lots of people with good information only have time to scan the subjects and will only read the ones which look interesting to them.
Anything you can do to reduce vibration inside AND outside of the enclosure will operate to improve the sonics of the player i.e. it should resolve more detail that is now being smeared by the vibration. In most CD players the transport mechanism, especially the disc hold down, is atrociously inadequate. Try filling the cavities of the somewhat triangular hold down with lead tape (available at golf supply shops). Suspension systems (i.e. sorbothane feet, etc) for the chassis/enclosure are actually spring systems and must be precisely loaded to function optimally : like putting VW shocks on a Cadillac or vice-versa. The best way to isolate the enclosure from vibration fed into it from the shelf is to suspend the enclosure using 3 archery arrow points resting on metal discs. This reduces the enclosure's contact with the shelf to the combined area of the arrow points so that virtually no vibration can be fed into the enclosure from its' shelf, which is usually the major source. To block most airborne vibration put an oversize 4-sided wooden enclosure over the CD enclosure (open only at the bottom (already isolated) & front. Maple is a very efficient vibration absorber.
are you sure you can make that statement?
I'm sure there are a lot of other schools of thought here. Given I have done what you are doing among many other "best ways to isolate" the player, and have arrived at a very different solution, I may not be going out on a limb to say that your statement is "debatable"
It's better than slapping the player on the shelf directly, but I highly doubt that a few archery points are the best vibration isolation out there.
try some DIY roller bearings and compare.
Points and cones do not prevent vibrations from the shelf- they couple the component to the shelf. They are desighned to drain vibrations from the component to the shelf. Suggest you search the archives to find the best solution to your conditions.
"Points and cones do not prevent vibrations from the shelf- they couple the component to the shelf. They are desighned to drain vibrations from the component to the shelf."
The "drain" argument neglects the fact that coupling results in a two way path (i.e. what allows vibrations to leave also allows them to enter). In my view, it was created by marketing folk.
Oddmanout's statement is true, and I would have to disagree with the overall message in your reply in the given context. I think for some reason you've filed Oddmanout's comments in the same category in which people believe the cones/points are isolators (or mechanical diodes) and not couplers.
Oddmanout correctly and explicitly states that cones/points do not prevent vibrations from entering the component from the shelf. He is also correct in stating that one of the main benefits of such a coupler is they will allow vibrations present in the component (such as self-generated and airborne-induced vibration) to travel to the shelf where those vibrations can potentially be converted to another energy form. If a component were to be thoroughly isolated from everything, the energy from these two types of vibration must be dissipated in the component itself, which is not an ideal situation. This is the reason I am favorable to the term vibration management .
Vibration management is a combination of isolation, coupling, and damping techniques, and recognizes the fact that there are types of vibration that pure isolation actually exacerbates, rather than reduces.
Much as some marketing campaigns have misused the word, I think the word 'drain' was used appropriately here.
If you examine the thread, you'll notice the points/cones in question are archery points, which can be purchased quite cheaply.
Oddmanout also ended his post with advice with which I believe you would agree: study the Asylum Tweak Archives and decide for yourself on a vibration management scheme.
"I think for some reason you've filed Oddmanout's comments in the same category in which people believe the cones/points are isolators (or mechanical diodes) and not couplers."
In my post, I responded to the statement saying "They are desighned to drain vibrations from the component to the shelf." and didn't "file" the statement with those made by anyone else. Your disagreement suggests that coupling the component via such means will allow vibrations "to travel to the shelf where those vibrations can potentially be converted to another energy form." This presupposes a systematic approach utilizing some kind of absorptive material below the cones. I agree, especially with your use of the word "potentially". Whether converting the vibrations emanating from a component to another energy form after providing a means for said vibes to travel to another object leaves the original component with fewer vibrations is something I would tend to doubt (since it will continue to generate them), though I can easily see how the sound would *change* by coupling the resonant characteristics of two objects.
Where I do not agree (and please notice I used the words "in my view") is with the concept of "draining" which is not the same thing as providing a conductive path. I can put a pipe between two tubs of water and that pipe will provide an effective means for the water to travel from one tub to the other (in either direction). This however, isn't the same thing as saying that pipe will necessarily "drain" water from one tub to the other, regardless of the shape of the pipe.
Further, to my mind, the concept of draining implies something will be removed, leaving behind a smaller quantity of that something than before the draining was applied. So, again from my perspective, what we've created is a conduit and nothing more.
"...Vibration management is a combination of isolation, coupling, and damping techniques..."
Though I frequently enthuse about isolation, I don't believe I've ever said anything that would suggest I don't agree with that statement.
I don't know if you've ever seen it but the link below will take you to one of the better articles I've read regarding cones (or spikes, arrowheads, nails, etc.). I've found much to agree with in this article and hope you find it interesting.
We're mostly in agreement, as usual. A good part of what we don't agree upon could be considered semantics, since we do seem to agree upon the fundamental concepts. I have read the article you linked a few times and it's got a lot of good stuff in it - I don't think there's anything I disagree with in it (with perhaps the exception of the claimed magnitude of sonic changes attained by putting footers atop a component versus underneath - I do agree there will be a change in sound, however).
The use of the word drain is the only thing we really disagree upon. I thought of using a bathtub anaolgy when I wrote my post, but decided against it because I don't feel it's entirely analogous, particularly the two bathtub scenario. Waves and particles do not behave alike.
The biggest problem I have with the two bathtub example is that there is nothing to represent the forces involved with a typical stereo rack. You have two connected bodies of water and nothing acting on them except gravity.
The only way to have a drain for vibration is to couple two or more things together. Since we're talking about a component being coupled to a shelf, which is eventually coupled to the floor, the component has quite a large vibration sink available to it - I don't see why couplers placed between a component and the floor can't be considered a drain, or at least part of a drainage system. Certainly less than 100% of the vibrational energy that travels thru those couplers returns to the component (yes, some amount will be reflected back, but always less than 100%). The only way to prevent some drainage from occuring is to achieve perfect isolation between an object and everthing else.
I can see how this issue can get very cloudy, since all couplers will transmit vibrations both ways between the coupled objects (which is technically a simplification, since vibration can travel in any of the six directions). I would agree that more floorborne vibration is typically entering the comoponent versus component generated vibration leaving, but that has more to do with the natural magnitude of these vibrations than anything else. If you were to do an analysis of what happens as an upward floorborne-generated wave meets a downward component-generated wave, it would be much the same as analyzing what happens when two waves meet in a pool - two frequencies, two magnitudes, two phases, one resultant wave.
Even in the presence of floorborne-generated vibration, less than 100% of component generated vibration returns to the component so long as it is effectively coupled to something.
I think the tub analogy does work because nothing is "driving" the contents of one tub (let's assume a horizontal pipe between tubs) to the other.
With a component coupled to a shelf, nothing is "driving" the vibrations one way or the other. Perhaps there is an exception to this when the shelf is a highly damped surface but still the concept of "draining" remains.
According to Webster, the definition of "drain" is:
"to draw off (liquid) gradually or completely
b : to cause the gradual disappearance of c : to exhaust physically or emotionally". "Deplete" is given as a synomym.
Since nothing is being "gradually or completely" drawn off and nothing is gradually disappearing or being exhausted or depleted, I personally deem "drain" to be a euphemistic definition of this case at best.
I can see calling it providing a conduit for vibrations to go into some absorbent support but still it appears to me the sum quantity of vibrations in the component remains the same since more internal vibrations are being constantly generated.
So we appear to agree in general but disagree on a definition and perhaps exactly what is occurring. But you know, I think this is great. I like challenges to ideas. How else can one be confident unless they've examined a given idea from all perpectives all the way to 180 degree opposite? This is how ideas evolve. Posts from others who've given a concept a lot of thought and spent the time to listen are one of the great values of this forum. I'm grateful and very happy to have met folks like yourself and David A, as well as many others.
Speaking of challenges to ideas, I recently had to revise an idea I've had for years. When setting up stereo mics to make a recording, I've had the mics spaced about 6 feet apart for the past several years (preferring the sound of small diaphragm omnis to all other mics I've ever heard). I figured the time it takes a signal to travel from left mic to right mic should (closely) match the time it takes from left speaker to right speaker. While I've been very pleased with the results in general, there were certain aspects I wanted to improve upon, specifically, how slightly off center images were positioned on playback.
About a month ago, I started some experiments where I'd walk across the soundstage, knocking on a piece of wood, all the while announcing just where I was on the stage (e.g. "left mic", "half way to center", "three feet to left of left mic", etc.). I recording this several times, each time changing the arrangement of the microphones. I used the old 6 foot spacing and several others, all the way to ~7" "ear spacing" and even XY (coincident). On some occasions I added a baffle in between mics.
After listening back and comparing all the recordings, I was quite surprised as to which gave me the closest approximation of my announced postions on the soundstage. It wasn't my trusted 6 foot spacing, in spite of what I had deemed the "soundness" of the theory behind it. When theory and direct experience don't jive, in my view, it's time for a new theory. Now I need a new theory to explain why the new spacing works better.
You didn't mention what you found to be the best mic arrangement! I would guess that it was the 7" (human head) spacing/arrangement, but that's a pure guess. I would also guess that you'd find a different optimum arrangement if you were recording for headphone playback rather than loudspeaker playback. While I have a strong interest in recording, I have little experience.
We may have to agree to disagree on the bathtub analogy, and that would be OK. I will continue the debate in the meantime, however, since I'm still convinced the bathtub analogy doesn't work (and I like debating).
I think it's important to note that I'm not discerning between an effective drain and any drain at all. The question here is drain or no drain, not the quality of any drain that exists.
If you want to convice me the bathtub analogy is valid, you'd need to start by explaining how fluid (particle) movement relates to wave propogation. I don't feel that it relates well at all in this context.
"I think the tub analogy does work because nothing is "driving" the contents of one tub (let's assume a horizontal pipe between tubs) to the other.
Right reasoning, wrong conclusion. It is because there is no horizontal force (energy) acting on the water that your horizontal pipe is not a drain of any type. I don't see at all how this would relate to a stereo rack, where there is energy input in the form of vibration. There is nothing analagous in the specified tub system to the vibrational energy input of a typical stereo system.
"Since nothing is being "gradually or completely" drawn off and nothing is gradually disappearing or being exhausted or depleted...."
I would have to say that this statement is false, and you've not supplied any information supporting the statement. I refer back to my claim that if any coupling at all exists between two objects, and vibration is generated within one of those objects, some of that generated vibration will enter the second object, and of the portion of vibration that enters the second object, less than 100% of it will return to the first object. This is distinctly different than what happens if the first object were to be coupled to nothing, and happens to fit your stated definition of the word drain (draw off gradually). If no coupling were present between the two objects, 100% of the vibrational energy would need to be dissipated within the first object itself, whereas with coupling, *some portion* of the first object's vibrational energy travels elsewhere never to return again.
From my post:
"Since nothing is being 'gradually or completely' drawn off and nothing is gradually disappearing or being exhausted or depleted..."
From your post:
"I would have to say that this statement is false, and you've not supplied any information supporting the statement. I refer back to my claim that if any coupling at all exists between two objects, and vibration is generated within one of those objects, some of that generated vibration will enter the second object, and of the portion of vibration that enters the second object, less than 100% of it will return to the first object. This is distinctly different than what happens if the first object were to be coupled to nothing, and happens to fit your stated definition of the word drain (draw off gradually). If no coupling were present between the two objects, 100% of the vibrational energy would need to be dissipated within the first object itself, whereas with coupling, *some portion* of the first object's vibrational energy travels elsewhere never to return again."
My tub analogy was to show two "containers" coupled by a conduit. There's no intention of likening fluid to audio; only containers and a conduit.
Maybe its the sematics. I understand the point you're making about coupling providing the path. But to my mind, the word "drain" implies we'll end up with less of whatever it is being drained. Since the vibrations in this case are internally generated, the concept of a drain doesn't work for me. But that's just me.
As to supplying "information supporting that statement", I thought I did. If there are still vibrations being constantly generated within the component, from my perspective, the component is still vibrating and I don't see why it would be vibrating any less than if the conduit wasn't there. After all, we're not talking about a finite quantity of vibes but a never ending supply. (This assumes of course, we're leaving the component powered. If we suddenly shut it off, tnen for a short amount of time, a very short amount, I'll buy the drain idea.)
For stereo microphone arrangements, once I found I could beat the localization from a pair with a 6 foot spacing, head spacing is what I too would have suspected as best. I tried it. Another surprise. While it was very good (and is perhaps optimal for headphone listening), I'm seeking to optimize localization over loudspeakers and found something on the order of 15-16" worked better. The addition of a small baffle (to add intensity and frequency cues to the temporal ones supplied by the spaced omnis) proved to be a great benefit, acting almost like a lens, adding significant solidity (I won't use the word palpability; just don't like that it has been used to death) to the image, particularly the center.
The experiments continue but right now I've been making recordings with omnis spaced about 15" with a ~12" baffle (a la Jecklin) between them.
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