[WhatToChoose]

Cool, send him this way. In fact I encourage him to write a paper about this amazing finding cause it's truly groundbreaking stuff. 4 dB increase in low frequencies by simply changing to a brass tube? That's the most significant flinging in headphone Acoustics in years! Quick, stop the press!

I would be interested in an in-depth and professional analysis on this topic, done by both manufacturers and real engineers. It would be quite interesting, since materials are a large marketing push for many IEMs (among other things), especially if it involves a respected manufacturer's input on the subject. Such a discussion would benefit greatly from analysis on empirical data (perhaps scientific studies from other applications). This discussion would have to be kept between real engineers and manufacturers though simply due to the technical nature, not non-technical people, or self-proclaimed and ignorant acoustic engineers who mock others who disagree with them....just as a few examples. I look forward to a fruitful discussion.

 

[WhatToChoose]

Interesting read on details of sound absorption here:
https://www.diva-portal.org/smash/get/diva2:910860/FULLTEXT01.pdf

The article goes through an analysis of material absorption properties based on material and geometry at a microscopic level, as well as absorption vs. frequency. This specific article didn't analyze metals unfortunately, but it does provide some insightful information.

 

[ThomasHK]

Interesting read on details of sound absorption here:
https://www.diva-portal.org/smash/get/diva2:910860/FULLTEXT01.pdf

The article goes through an analysis of material absorption properties based on material and geometry at a microscopic level, as well as absorption vs. frequency. This specific article didn't analyze metals unfortunately, but it does provide some insightful information.

That actually helps my case, thanks. The important info is in the graph on page 13, absorption coefficient as a function of frequency. Absorption is intrinsically linked to wavelength, you'll find that's true in any form or Acoustics. It's why for example bass traps in a room have to be very large to have any impact on low frequencies as the wavelength is inversely proportional to frequency.

Now look up the wavelength of sub 100Hz frequencies and compare that number to the size of an IEM... But that's not even that relevant For IEMs. At low frequencies, sound waves generated by a headphone driver doesn't propagate in the same way as a loudspeaker in a room. The whole system behaves like a pressure chamber.

Any way, I don't want to discuss this here anymore, it's pointless, it's just going to fall on deaf man's ears. I'll summarise my thoughts on this whole material thing in a few bullet points.

• If the internals (i.e. transducers) are the same in those models, the change in low frequency response is created through resistor changes and/or other electrical circuit changes.
• Mid/high frequency differences can also be impacted by changing the acoustic damping in the path way (those dampers you always see in IEMs - NOT the tube material)
• It seems pretty clear to me this is simply a marketing ploy to sell 2 variants of the same earphone model with different tunings and character.

 

[491326]

• If the internals (i.e. transducers) are the same in those models, the change in low frequency response is created through resistor changes and/or other electrical circuit changes.
• Mid/high frequency differences can also be impacted by changing the acoustic damping in the path way (those dampers you always see in IEMs - NOT the tube material)
• It seems pretty clear to me this is simply a marketing ploy to sell 2 variants of the same earphone model with different tunings and character.

I honestly started this discussion doubting Jomo's claims as well.

I have a few questions about the tubing.

From my vague understanding (with no mathematical backing), sound is primarily affected by the length and diameter of tubes. What's a good resource to learn more about this?
Also, if the plastic tubing in iems were changed entirely to metal, would there be any effect on the sound?

 

[jeffreyw311]

I honestly started this discussion doubting Jomo's claims as well.

I have a few questions about the tubing.

From my vague understanding (with no mathematical backing), sound is primarily affected by the length and diameter of tubes. What's a good resource to learn more about this?
Also, if the plastic tubing in iems were changed entirely to metal, would there be any effect on the sound?

Doubtful if everything except for the material is kept the same.

The material doing absolutely nothing has been proven by the JVC FD01. JVC provides three different material tips with the exact same dimensions and claims each different material produces a different result (one is warm, one is detailed, etc). But objectively there’s no difference in the different tips and I sure damn can’t hear an audiable difference between them.

Now, you do see significant differences if you change the bore diameter of the tips by adding material inside them. Which, as you note, is changing the diameter of the tube.

 

[ThomasHK]

From my vague understanding (with no mathematical backing), sound is primarily affected by the length and diameter of tubes.

Correct.

What's a good resource to learn more about this?

I've attached a screenshot from Poldy's work. Note zero reference to materials in these calculations of impedances (resistance/inductance/capacitance) of acoustic volumes/tubes/slits etc...

Also, if the plastic tubing in iems were changed entirely to metal, would there be any effect on the sound?

Nope. The only way I could see this having any effect is if there is some structural resonances being introduced, but that would be through poor design.

Now, you do see significant differences if you change the bore diameter of the tips by adding material inside them. Which, as you note, is changing the diameter of the tube.

Correct.

 

[Mimouille]

Not saying people are not taking advantage of it, of course they are because we live in a consumer-oriented world. I think you have to be beyond naive not to see that there is a good deal of profit to be made. But let's be honest, you too have a $3k DAP and used to have $3k sterling silver IEMs and some expensive cables too, so it is not like you are not seeing any reason to buy the stuff either. And that is not meant as a criticism, just that we spend our money how we see fit and if something happens to appeal to us we spend grossly beyond the sensible. I recently bought a $5k carbon fibre aerodynamic road bike that I ride around on while wearing a backpack that catches wind like a kite. Still love the bike to bits and it is still bloody fast. No excuses, just fun. That is how I see this sort of gear too.

Once again you seem to be mixing it all up in a bag of everything is good we are happy, let us all be fools. Anyone can buy what they want and doesn't have to justify anything. That is one thing.

I will still explain my reasoning, even though I don't have to. For the cases you mentioned, I bought the WM1Z after careful side by side sessions with AK380 and WM1A. And I still love it. Honestly, in this case, I don't credit the casing much, but there are other internal changes, and I liked the sound. End of story. The Hyla was an impulse buy and a stupid one at that. But in this case, more because it was pretty.

Now as to manufacturers, they do owe us a fairly honest and transparent communication. Plainly inventing stuff is just not ethical business. At least that is my position. I am not saying it is the case with Jomo as I think Joseph is nice and he didn't really have the opportunity to defend his case here. I am just staying, if you make technical decisions on a technical product, you should know what you are doing if you are going to charge luxury prices for it.

 

[Wyville]

Any way, I don't want to discuss this here anymore, it's pointless, it's just going to fall on deaf man's ears. I'll summarise my thoughts on this whole material thing in a few bullet points.

I think you underestimate people's interest. There might be quite a few acting like idiots here (I happily plead guilty on that charge), but when it comes to scrutinising things there is a lot of knowledge and understanding here.

I personally reserve judgement on claims regarding changes caused by materials because I am not an acoustic engineer and I have enough experience in science to know that sometimes things that theoretically should not happen, can still happen. That does not mean that I don't trust your expertise, I certainly do, but I don't want to brush off something that has only been addressed theoretically from a distance. Ideally, I would put examples in your hands and let you dissect.

Once again you seem to be mixing it all up in a bag of everything is good we are happy, let us all be fools. Anyone can buy what they want and doesn't have to justify anything. That is one thing.

I will still explain my reasoning, even though I don't have to. For the cases you mentioned, I bought the WM1Z after careful side by side sessions with AK380 and WM1A. And I still love it. Honestly, in this case, I don't credit the casing much, but there are other internal changes, and I liked the sound. End of story. The Hyla was an impulse buy and a stupid one at that. But in this case, more because it was pretty.

Now as to manufacturers, they do owe us a fairly honest and transparent communication. Plainly inventing stuff is just not ethical business. At least that is my position. I am not saying it is the case with Jomo as I think Joseph is nice and he didn't really have the opportunity to defend his case here. I am just staying, if you make technical decisions on a technical product, you should know what you are doing if you are going to charge luxury prices for it.

I completely understand what you mean and actually agree with you a lot more than you might realise, but that is simply not the world we live in. To give you an example of something I have first-hand experience with. Pharmaceutical companies spend billions on the development of a single drug and I think you can imagine that regulations are very strict when it comes to marketing a drug, yet you would be surprised by how little these companies know of "why" a drug works. Once they know enough to get it to the market, they stop asking questions. So for any basic scientist working with pharmaceutical companies it can be extremely frustrating that you are forced to ignore questions that arise from your research simply because it is no longer deemed a sensible business investment. I see parallels with this as well. We (audiophiles) might like to know how everything works in nauseating detail, but that is not in the interest of a business. So like you did with the 1Z, I just focus on what I hear and make decisions based on that. To show my cynical side, I am not that tempted to spend $2k or $3k anymore, as I think the more interesting developments are happening below that. I can't help but be interested by the really expensive stuff, but I am still considering focusing my reviews differently (in terms of price range).

 

[ThomasHK]

I think you underestimate people's interest. There might be quite a few acting like idiots here (I happily plead guilty on that charge), but when it comes to scrutinising things there is a lot of knowledge and understanding here.

I personally reserve judgement on claims regarding changes caused by materials because I am not an acoustic engineer and I have enough experience in science to know that sometimes things that theoretically should not happen, can still happen. That does not mean that I don't trust your expertise, I certainly do, but I don't want to brush off something that has only been addressed theoretically from a distance. Ideally, I would put examples in your hands and let you dissect.

I give up... this is not just theory. I've simulated and confirmed simulations of IEMs in several projects. Simulations accurate to be within 1-2dB. Material parameters? Zero.

But believe what you want to believe, I won't try to convince you guys anymore. If you think brass earphone nozzle will make it sound warmer, great.

 

[Mimouille]

I give up... this is not just theory. I've simulated and confirmed simulations of IEMs in several projects. Simulations accurate to be within 1-2dB. Material parameters? Zero.

But believe what you want to believe, I won't try to convince you guys anymore. If you think brass earphone nozzle will make it sound warmer, great.

Well if you heat up the nozzle beforehand, maybe it can make your ear warmer...so conductivity of metal plays a part.

 

[ThomasHK]

Well if you heat up the nozzle beforehand, maybe it can make your ear warmer...so conductivity of metal plays a part.

Hahaha troll!

 

[MrLocoLuciano]

I give up... this is not just theory. I've simulated and confirmed simulations of IEMs in several projects. Simulations accurate to be within 1-2dB. Material parameters? Zero

Would love to see / read that. Can you share ?

 

[ThomasHK]

Would love to see / read that. Can you share ?

This is just one example, I can't share actual project work. It's just a little exercise I did as a joke when evaluating this particular simulation package (there are many, they're all based on lumped parameter modelling).

See if you can guess what classic BA based IEM this is.



I didn't even have the real tube dimensions, I just estimated it by eye balling it. Still within just a few dB accurate up to 8kHz. If I new the actual position of the damper and more accurate tube length it would get even closer.

 

[EagleWings]

ER4 obviously

 

[ThomasHK]

ER4 obviously

You win a cookie!
So just so people fully grasp what they're looking at: this simulation shows an ER4, measured in a 711 eleven coupler, including resistor, BA, damper, tube and front volume of 711. Accuracy within +/- 1dB upto 8kHz, not a single material related parameter.