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Where do we go from here? How can headphone audio really improve?

Discussion in 'Sound Science' started by sine_wave, Mar 3, 2018.
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  1. sine_wave
    From what I can understand, there is nothing we can do to design a better DAC than we have available now. Any improvement will not be audible, although we may be able to get them to consume less power. The same goes for Amps, we know what there is to know about them and there is nothing we can do to increase their fidelity.

    The 16 bit 44.1 kHz format is able to record and reproduce sound waves perfectly, and no increase in sampling or bit depth is going to improve the listening experience.

    So have we achieved audio perfection? Is there anything we can do to improve the experience of the listener outside of improved design of headphones? Even headphones are old technology, I'm not sure why some headphones command such high prices when we know how to make a transducer with flat frequency responses.
     
  2. ProtegeManiac Contributor
    What flat response? The flattest we have aren't fully flat from 20hz to 20,000hz, like how the HE400i is flat from 10hz to 1000hz then dips above that, rises up at 3500hz, dips again then rises up again in the treble before 10,000hz and then stays somewhat jagged beyond that. We still have a long way to go to get there.

    Another area that can still be improved on is sensitivity. Just because there are headphones with 97dB/1mW++ sensitivity doesn't mean we can stop there since any improvements in sensitivity tends to sacrifice linearity due to driver distortion when making the drivers too light. We haven't seen graphene diaphragms that can deliver both 99dB/1mW++ sensitivity at less than 100ohms impedance let alone completely flat 20hz to 20,000hz response at the same time.
     
  3. amirm
    You don't play formats. You play implementations. :) I have measured DACs that can't reproduce above 10 to 11 bits accurately even though they cost over $2,000!
     
    MrPanda likes this.
  4. amirm
    The other thing we need to improve is instrumentation for headphones. The frequency response measurements are no better than wet thumb in the air as no two measurements can agree.
     
  5. sine_wave
    Can you expand on this? Why is sensitivity so important? For energy savings? Or for being able to drive headphones with weaker amps?

    And based on your statement about frequency response, would you agree that the only area for improvement lies in headphones, and not dacs and amps?
     
    Last edited: Mar 4, 2018
  6. sine_wave

    So you are suggesting that we don't really have the tools necessary to judge how a headphone performs? I see a lot of graphs and computer-like things about headphones that go way over my head, is this stuff not enough?
     
  7. ProtegeManiac Contributor
    You'll barely notice energy savings since you'd have more variances in fluctuation from other ways you use electricity. And it's not even just for being able to use "weaker" amps. You can still use older amps that were designed to deliver more power even at Class A mode.

    Ultimately the goal is to keep distortion low by using a lot less of the amp's output capability (not that you always need a monster amp even now). Basically, to always have a cleaner signal with noise and distortion as far below audibility as technology allows. Absolute power is just to stay farther from clipping, but a powerful Class A/B amp could have a comparatively low THD as a Class A amp but it has crossover distortion. If higher sensitivity headphones can hit 120dB wiht just 64mW then we can have much smaller full Class A drive headphone amps that wouldn't draw as much power as a Class A amp designed to deliver 1500mW at 32ohms, with amp design being focused less on making more power but on keeping distortion and noise even lower, or rather, just managing them to not be higher than they are now, but in a much smaller package.

    So while an amp designed to deliver 250mW at 32ohms (you won't even need a heck ton of voltage at some point since Sennheiser is going down to 150ohms while putting on incremental increases to sensitivity) will not make a noticeable difference in your electricity bill, if its THD+N % is lower even at that output level is even lower than a current 1,500mW amp at the same output level, then we'd get technically better performance, provided that at some point headphoones will not even come close to needing anywhere near 250mW. Now that isn't necessarily an audible difference (and again not with your electricity bill), but amps with simpler circuits will not need to be that much larger than how much space the circuit board needs since 1) it won't need as large a power supply nor 2) a large dissipation area.

    Class D amps can be come more significant with headphones. They've had problems with high THD and noise, which is why they started out as subwoofer amps since you won't hear that, and initially the first fullrange designs had only around 15mW max output per channel but still had THD higher than Class A/B. With impedance and power requirements coming down as Class D circuits improve they'll basically meet in the middle at some point. Heck, it's only Sennheiser reducing the impedance (without any penalty to the response and sensitivity) - a lot of other manufacturers already have high sensitivity, low impedance, decent response headphones like the HE400S. In 10 years you could have an HE400S with response nearly as smooth as the HE400i's response curve but with even higher sensitivity than the HE400S.


    In absolute performance, yes. But again if you don't need a lot of power then later amp designs can be focused more for even lower distortion and noise than output power, plus they'll likely get smaller.

    Some audiophiles will still want more unnecessary power so such amps will still have a market, but smaller Class A amps that can push practically anything in the market to 120dB since those "anythings" don't require a lot will be even more common, instead of just lower power, relatively higher THD products. Not to mention you wouldn't actually listen at a sustained 90dB, even if recordings start being done properly.

    Speaking of which...I'm actually more concerned about the Loudness War bullcrap than gear developments. You can invest in any gear you want but if the material you're listening to has crap dynamic range then all you're doing is making sure that downstream in the chainyou don't make it any worse. And yet you're starting off with crap. You're not listening to the best playback, you're just making sure not to make it any worse than the recording company did.
     
  8. castleofargh Contributor
    so you made it ^_^. welcome to the posting side of Headfi.

    you have to be clear about keeping audibility and objective fidelity separated. because of course we can always make better everything that will measure better than the last one. but indeed we may come to a point where we humans fail to notice the difference. in that respect, DACs are now at a level that allow manufacturers to make something really good that will sound very much like another good DAC.
    for amplifiers it depends a little on what we plug into them and how much power they have to deliver. but all in all we also have reached pretty satisfying levels of fidelity.

    what makes us focus more on other part of the audio chain is not so much how good DACs and amps are and how they're all the same. what makes us focus on the rest is how bad the rest is in comparison to DACs and amps. it's just rational thinking and being aware of the magnitudes of differences. like how bad a headphone is compared to a DAC. we consider a headphone with 0.1%THD over the most of the audio range to be great. 0.1% that's 60dB below signal. if my DAC measured like that I'd throw it away.
    a headphone has a messed up frequency response, even if we were to consider that the target response they pick is perfect flat for humans(which is impossible because different humans have different flat), the manufacturing variations from pairs to pairs or even often from left driver to right driver result in more deviations that most DACs would show. and I insist I'm starting with a false axiom in favor of the headphone. in practice we all require a lot of EQ before a headphone is flat to our own ear.
    so it is a fact that transducers in microphones, headphones, speakers, are the weak link in a modern audio chain. and by so much that in comparison being obsessed about improving DACs can seem a little irrational.
    for amplifiers we can still improve on many relevant things, like make one that can handle a wider range of headphones, or one with such a low level of noise that even with a very sensitive IEM, you won't notice any background hiss. or make sure that from one amp to the next we'll get about the same sound thanks to making sure to keep the amplifier output at a very low impedance. when does all that stop being audible is another matter, but there is nothing wrong with trying to make gears more consistent, more reliable, more compatible.

    now there are many things we can improve for headphones, some are just in small increment, some would/will really change the quality of headphones. the incremental improvements are all the design work put into making lighter, stronger diaphragms, ear pads that won't drastically change the sound after we have used them for 200hours, and in general just little improvements here and there, making the headphone light yet heavy enough so that it doesn't shake itself with the music, work on making closed headphones better, so that you can improve your overall sound fidelity by lowering the ambient noise level. in the last decade I'm of the opinion that headphones have come a long way in many areas related to improving the signal we get into our ears.


    other changes are more fundamental. like getting a better understanding of what flat means for a headphone. I believe that Harman research on this in the last years has been copied a lot and served to make many new headphones with a more appreciated signature for the average listener.
    it's only a small step and the real good neutral sound will only come when we get customized signatures. it's a clear necessity but it clashes obviously with industrial manufacturing. also many are still working on trying to define a proper method to find out the ideal neutral for a given user. so this is something that is much more likely to come out as a digital processing than as custom headphones with the acoustic made for my very own head. but it will come, it must come if we care about good audio.
    another aspect of that customization will most likely involve full HRTF compensation and solve how headphones do full left and full right stereo, instead of mixing both the way speakers do in a room. there is also many people working on such things and while they don't necessarily need to be in the headphone, they will ultimately improve the headphone.

    so IMO, there is a lot to be done before we can even dare to call what we do high fidelity, and some obstacles might require to simply get rid of transducers entirely, and just send the signal straight into our brain someday. but we're not quite there yet ^_^.
    same for recording, there is no limit to what we could do, the question is: will it bring any sort of benefit given the fidelity of the playback gears? like we could imagine replacing microphones in a studio with some fancy stuff like Schlieren imaging and crazy fast cameras. that would hopefully remove the influence of the microphone itself(which is limited in fidelity like any other transducers). then again maybe it's a stupid idea with massive flaws, this just came on the top of my head right now so I wouldn't bet too much money on it being the ultimate answer for recordings ^_^. but there is no limit to the amount of dudes with some ideas like I just had. sure enough one of those will be real good at some point.
    and once everything else is so amazing and high fidelity that a DAC is now the weak link, then for sure we'll again be very concerned by DACs. doesn't really matter that it won't be audible, we're are who we are and we will wish to improve what can be. it just won't be important to every audiophiles.
    to conclude, the way things are right now, I personally feel like all the frenzy around DACs is a little silly. because the efforts and concerns are just too disproportionate to the issues, and are far from being a priority in our modern audio chain.
     
  9. amirm
    The instruments are faithfully producing what they are told to measure. The problem is we try to measure headphones using dummy heads and ears with the measurement mic inside the latter. Given the tiny air space and distances, even minute changes in how the headphone is put on dummy head, creates different graphs. And forget about comparing two different measurements with two different dummy heads. There are kludges like averaging multiple runs, etc. but even that doesn't do anything to fix the larger problem. It is all busy work making people feel good that there are measurements.

    One of the biggest benefits of measurements is the reliability and repeatability, i.e. they are objective in nature. Take that away and their usefulness shrinks hugely. See this example: https://www.innerfidelity.com/content/how-do-measurements-sound-audeze

    upload_2018-3-4_9-13-55.png

    I can't even remote match the measurements Innerfidelity makes with my dummy head.

    Even blind tests are fraught with problems because listeners can tell which headphone is which from the feel of the headphone on their heads.

    This is the reason for the wild west environment of headphones with each one being so different than another.
     
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  10. bigshot


    That is simple...

    1) Listen to better recordings. (Read this one over and over and do it!)
    2) EQ to balance the response of your cans and correct for any shortcomings.
    3) Use DSPs to sweeten your listening experience. Don't worry about accuracy. Find what sounds best to *you*.

    Both audiophools and armchair scientists love to overcomplicate things. They focus on details you can't hear and exceptions to the rule that you will never run into. I can totally understand how someone with a little bit of OCD would be sent into a feedback loop by reading audio forums. But good sound isn't about inaudible details, and it isn't about protecting yourself from problems that don't exist. It's about practical approaches to problem solving.

    1) Listen to your system carefully and analyze what you hear.
    2) Identify what your problem areas are.
    3) Research what the probable cause of your problem is and see if anyone has any practical solutions to suggest.
    4) Apply the solution.
    5) Listen to your system carefully and determine if you have solved the problem.
    6) Rinse and repeat.

    Too many people get roped into solving problems that don't exist. Jitter is a great example. Lots of companies advertise "OUR JITTER IS LOWER!" But it doesn't matter because jitter in home audio equipment is always inaudible. They want you to spend money on a problem you can't even hear! How stupid is that?! I only address problems that I can hear. I don't pay attention to theoretical problems. It's OK to break rules or live with jitter in your life or not spend a million dollars on equipment as long as you listen carefully and analyze to identify your problems, and work to eliminate the ones you can hear.

    One more suggestion.

    Focusing on the music is the key. There's a lot of great music that isn't well recorded. But to not listen to that would be cheating yourself of some of the greatest creative achievements of modern times. Don't focus on the wrong thing. If you follow none of my other suggestions, follow this one...

    1) Listen to a lot of great music and focus on the music. If you do that, sound quality won't matter.
     
    Last edited: Mar 4, 2018
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  11. amirm
    It is? What if I quote someone from your signature saying otherwise?

    upload_2018-3-4_10-37-11.png

    This is jitter measurement of a very popular DAC over S/PDIF:

    [​IMG]

    I measured the new version of this DAC and it is even worse now. Again, this is a wildly popular DAC.

    This is what I told the OP: that formats are not the same as products. You better get objective data before running off with generalization and assumptions.
     
  12. bigshot
    Near the edge of audibility isn't audible. When it comes to a miss, an inch is as good as a mile! And 7.6 nanoseconds is still well below the threshold of audibility. Double it and it's *still* below the threshold. Measurements aren't what we hear with. We hear with human ears.

    Jitter is designed to appeal to people with OCD. It's the audio equivalent of excessive hand washing.
     
    Last edited: Mar 4, 2018
  13. amirm
    I showed you example of a very popular DAC with levels orders of magnitude worse than HDMI measurements. Best not going around making generalizations without objective data.

    Jitter is an indication of engineering competence. Plenty of products achieve excellent jitter measurements which are not even expensive. To ignore it is like the 19 century people who didn't know the benefits of washing one's hands. They thought what they could not see could not hurt them. Before you buy a DAC, insist on manufacturer showing you proper measurements of the DAC including jitter. Otherwise you would very well be sticking your head in the proverbial sand. Which you could do of course but don't advocate it to others.
     
  14. bigshot
    I can go to Amazon and search for digital audio and throw darts at fifty different random products while blindfolded and not hit a single one with audible jitter. It just isn't an issue that people need to worry about any more than they need to worry about getting struck by lightning.
     
  15. amirm
    If you are in this forum and throw such dart, you have good chance of hitting one with awful jitter.

    But sure, as long as you don't care to know and don't read this forum, you can whistle dixie and be happy.

    As to doing the same on Amazon, you have no data to base that on. Just because you think it, doesn't make it true. It is not like you have done a good sampling of that to arrive at such a conclusion. You have done no analysis, no research and no personal analysis. Just a belief you like to pass on.
     
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