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Damping Mechanical Energy Distortion of STAX and other phones with SORBOTHANE and other materials.

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  1. richard51

    i think that you are right.... sorb. taped on the headband will reduce crosstalk greatly.... But i think that the point of our new creative friend Mogimu is precisely demonstrate the great extent at which crosstalk affect the perception of music... and i think that his experiment is very interesting....
  2. castleofargh Contributor
    thanks for the link, I found the thinking and process even more interesting than the test itself. I started reading this and looking at the measurements thinking the dude was on drug. I've never come remotely close to measure that sort of electrical crosstalk in my headphone even trying some really weird IEM cables on it. but then I turned on my second brain cell for a change and noticed how he went for a series of low impedance headphones(why?). that of course changes everything. the amp used here has a 100% chance of outputting worst crosstalk when plugged into a low impedance load. and same for the cable with relatively significant current flow in the circuit.

    still if there is no big flaw in his testing, the vibrations do seem to be high enough to kind of matter (I tend to disregard crosstalk below -40dB because that's where I start to fail noticing it in an ABX). I expected this to happen but not to reach such magnitudes TBH. so now I admit I'm curious. and as I always end up picking comfy and light over good sound, it should greatly increases my chances of having vibration issues, I will add fooling around on this matter to my to-dio list.
  3. Mogimu
    Hi Ed - I will tke a look at the process involved in posting photos here in the near future. Meanwhile, in answer to your question about the point of my skull experiment : it is just an experiment, not a solution. I wanted to see if any significant vibrational energy is being transferred to the skull via the headband, even though the headband is already completely treated with fo.Q tape. My results suggest that it is, and that the sound is audibly improved by any measures taken to absorb vibrational energy between phones and skull, and even in the skull itself. Headphones are a special category of listening device because they make contact with your head, unlike speakers. They may require a new approach to vibration control.
    I chose to use fo.Q tape rather than foam padding because of its ability to convert vibrational energy into heat. Foam would merely reflect the unwanted vibrations back into the headband, making the smearing and crosstalk worse throughout the entire headphone structure.
    If you send me your mailing address via PM, I will send you the fo.Q tape samples you requested. I notice that you have been generous enough to have done the same for others earlier in this topic.
    Oregonian and richard51 like this.
  4. Mogimu
    It may be very difficult to achieve complete acoustic decoupling of the headphones and headband. For example, Audeze LCD-3 phones appear to be reasonably adequately decoupled, with the use of a single screw to attach each earcup to the headband. However the headband still transfers significant vibrational energy into the skull resulting in audible distorion, which can be controlled to some extent with the use of specialized damping materials.
    It's also important to remember that headphones and head are acoustically and mechanically coupled, and that vibrational energy transfer is a two-way process.
    Last edited: Aug 7, 2017
  5. Hutnicks
    Not the case. I have yet to see any phone that actually takes reasonable care to decouple the cups from the headband. Pet peeve of mine. Single screw or whatever if you take a few SECONDS of your time and a piece of metal tubing to make sorbo grommets for the cup attachments on any phone you will see a vast improvement. It is not much different from motor mounts in an automobile. Yet even the mightiest of manu's with their 5K a pop phones do not condecend to do this for the end user.

    This aint rocket science it is simple vibration decoupling which has been around since the middle ages. We have better materials now and yet we accept less than medieval technology for outrageous prices.

    Putting damping materials on a headband itself is nothing more than putting on a condom after you have had sex.
    Henery, nick n and Mogimu like this.
  6. Mogimu
    That's a great idea and I will try it. As I said in an earlier post, I have only become aware of the importance of the headband issue over the past couple of weeks. I don't see the point of your condom analogy though, since fo.Q tape on the headband actually works.
  7. edstrelow Contributor

    As I recall Mitchell's article ( the link has died) he was responding to a criticism of an earlier report that electrical crosstalk may have contaminated his measurements. I have emailed him a few times and he has been very helpful. Among other things he advised me to try constrained damping, i.e. backing the damping material with something, in my case a two layers of electrical tape. It improves the effectiveness of the damping material.
    Last edited: Aug 10, 2017
  8. edstrelow Contributor
    I would suspect that if you put enough force on a sorbothane gromet to give you effective clamping of the earcups to the ear, the gromet would become compressed enough to act like a solid object and still transmit vibrations. I am not stating this as a fact but it would seem to be one of those things that you try and see how it works.

    Certainly Stax blew it with their SR007 by creating a headband of two metal strips and screwing them directly to the metal earcups.

    Even if you get rid of mechanical crosstalk, this is only part of the problem as you still have the degrading effect of the vibrations in the same-side earcup. One of my more interesting experiments was damping cheap earbuds which of course have no headband and yet still improved greatly with added sorbothane.
  9. Mogimu
    My initial thoughts exactly. My experiments with a rudimentary grommet for the LCD-3 seem to confirm it. The fo.Q tape on the headband works much, much better, and is still effective with or without the grommet.
  10. edstrelow Contributor
    I picked up a catalog and saw,"constrained layer damping" being advertised in a new Mobile Fidelity. turntable. You may recall that Keith Mitchell advised me to do that with sorbothane. What is it?

    "Constrained-layer damping is a mechanical engineering technique for suppression of vibration. Typically a viscoelastic or other damping material, is sandwiched between two sheets of stiff materials that lack sufficient damping by themselves.
    Constrained-layer damping - Wikipedia

    Recall that sorbothane is a viscoelastic.
    For me constrained layer damping meant backing the sorb with two layers of electrical tape.

    Upon Googling the term further I see two speaker companies adding this to their speakers, ATC and KEF.

    This is big news, speaker manufacturers are adding constrained layer damping materials to their speakers, i.e. sorbothane or similar materials. I have been doing this for a while, I especially like 1/2 inch sorbothane on the front panel. Here is a KEF advert. https://microwire.info/kef-ls50-wireless-complete-fully-active-system-singapore/
    Last edited: Aug 23, 2017
    Henery and richard51 like this.
  11. Henery
    Italian loudspeaker manufacturer Sonus Faber uses viscoelastic driver de-coupling in some of their models. http://www.sonusfaber.com/en-us/products/the-sonus-faber . Some models, such as Lilium, use infra-woofer in separate mechanically de-coupled sub-chamber. Interesting vibration isolation ideas indeed.
    richard51 likes this.
  12. edstrelow Contributor
    Double post.
    Last edited: Aug 28, 2017
  13. edstrelow Contributor
    Re: Sonus Faber: "The suspension system permits inhibiting the mechanical transmission of vibrations to the environment and consequently eliminates the creation of spurious resonance and sound feedback."

    However it also uses vico-elastic (i.e. sorbothane or similar materials) in the cabinet.
    "The double walls in okoume plywood with dual curvature are uncoupled by a “constriction damped” visco-insulating layer. The dual curvature increases rigidity compared to techniques used in the past, while the dampening eliminates the last traces of resonance."

    So they are using a double dose of damping techniques. " Constriction damped" sounds like "constrained layer damping."
    Last edited: Sep 3, 2017
  14. edstrelow Contributor
    I came across another speaker manufacturer using " constrained layer damping." This is Epos and the discussion relates to their ST 15 speaker.


    Like most such reports they don't identify the damping material itself although they state that it is not specifically designed for this use. Probably they want to keep this information as a proprietary secret to give an advantage over competitors. Unlike most such reports they actually give some measurements of the vibrational damping they achieve. Unfortunately I can't open their pictures.

    Quite some pages back I reported that putting backing onto sorbothane gave better results than unbacked sorb and I use backing on all my systems now. However I am simply using a double layer of electrical tape for backing. I compared tape vs metal clips on the headbands of Stax Lambdas and heard no advantage for the metal. However I would not say that is definitive rather it is merely some data points on a complex problem.

    If you google this issue you will come across various mechanical engineering studies. This pdf looked helpful.

    Last edited: Sep 8, 2017
    richard51 likes this.
  15. DangerClose
    ok, I'm tired of searching, and I think the answer is actually in a T50rp thread, and was never asked or answered in this thread.

    For sorbothane that doesn't come with self-adhesive, which side goes down? Shiny side? Or dull side?
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