Please HelpMe Understand Something About dBs

Discussion in 'Sound Science' started by jthew, Dec 4, 2017.
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  1. jthew
    Will any of this be as much of an issue with single driver, tweeter-less, over er headphones?
     
  2. 71 dB
    So you don't burn your tweeter with 200 Hz sine waves, but people usually listen to music. Somehow people have managed to burn their tweeters with weak amps.
     
  3. pinnahertz
    You could burn out a tweeter with a 200Hz sine wave, it's just very unlikely, and usually impossible. Yes people listen to music and burn out tweeters, but not because of weak amps. I used a sine wave so the difference in clipped vs un-clipped spectrum would be easy to see, but the difference in power spectrum between unclipped music and music 10dB above clipping is almost indistinguishable. Which also proves that clipped audio does not produce additional damaging spectrum.

    As you drive an amp into clipping with any signal, the output RMS level goes up, but not as fast as it does if you don't clip.

    In the past some amps would become unstable when forced into clipping. If the instability took the form of high level ultrasonic oscillation, that might cook a tweet, but fortunately those days are pretty much gone.
     
  4. 71 dB
    Okay, I believe you. I haven't burnt my tweeters so I am not an expert of this issue. I read about it in the past, apparently it was more or less nonsense. Perhaps the more relevant thing with underpowered amps is that clipping sounds bad?
     
  5. pinnahertz
    The audibility of clipping is a function of the degree of clipping (dB over threshold), the duration of clipping (short clips are not audible), the ability of the content to mask clipping, and the characteristic of clipping "hardness", how quickly does clipping happen as voltages exceed the threshold. Some amp designs, most in fact, clip hard above a maximum output voltage, others (some valve amp designs) sort of "mush" into clipping gradually, which still results in pretty severe distortion, but it's not as audible.

    Just like THD audibility, clipping audibility is never accurately expressed by a single figure of merit, it's a multi-dimensional problem. But if you stay out of clipping, you never have that issue, so yeah, better not to clip.

    A slight tangent...deliberate clipping is a valid means of loudness processing, and when done correctly and under control, it's surprisingly inaudible. Broadcast audio processors use deliberate clipping extensively.
     
    71 dB likes this.
  6. jthew
    Thread's been hijacked! That's ok.

    I'm trying to digest the entire post. But, yes, I was aware of the equal-loudness contours. (I'll go off-topic now....those contours are one of the arguments I use against audiophiles who refuse to do any eq. They would have to listen to music at the same volume as those who created it, in order to hear it as it was intended.) I had understood that hearing tests at the audiologists compensate for this. I'm working off of my results from hearing tests only. My goal is to hear all of the inadequacies of a headphone system like I could when I was younger. The exception is that I only want to do ⅔ of the recovery of my deficient areas, and do a total cut above 10k. Thanks for pointing this out.

    I'd really like to continue with what I'm testing. If anyone has a suggestion on Amp/DAC and eq that I can use with my HiFiman HE-400i headphones to continue with my tests, please respond to my other thread I mentioned earlier in this thread. Cost limit is $500, new or used.
     
  7. pinnahertz
    Why the total cut above 10k?

    The best little EQ I've found to date is the miniDSP 2x4. $100, and tons of flexibility. You'll still need an amp. They make an amp/headphone EQ too, but it's expensive.
     
  8. jthew
    I've been in touch with them. They were nice enough to tell me that their amp/DAC/EQ combo probably didn't have enough juice for the HE-400i and what I was trying to do. I wouldn't even have started this thread if that thing would work. At $325, well within budget. Their specs are only 100mW @ 32ohms.

    Does the miniDSP 2x4 have any advantages over software eq? I don't need to make any measurements with a mic or anything like that.

    The total cut is a guess I'm making from my hearing tests. The rate at which my hearing drops off with frequency is very fast. The highest frequency measurement from the docs is at 8kHz. The amount of compensation I would have to do above 10k would have to be really, really huge. So, I figured I would just cut to 0 to make it easier on the amp and headphones. But, I'll check it once I get the gear.

    I should also mention that I am not looking for anything above redbook resolution.
     
  9. pinnahertz
    Only that it doesn't have to be tied to a computer to work.
    I wouldn't cut it, just don't boost it either.
    If you're going to do any DSP (like EQ), you may want something a little over rebook. Hardware EQ all is anyway. Software depends on the environment it's plugged into. Nothing worth worrying about though.
     
  10. pinnahertz
    Oh yeah...standard audiologist hearing tests are notoriously poor at measuring high frequency response. That's why they stop at 8kHz. But that doesn't mean your hearing actually does. It might, it might not. You may need to find a university hearing lab or teaching hospital to get a better test.
     
  11. jthew
    Still digesting....

    Are headphones so much less flat than speakers that most head-phoners do a lot of eq? I was thinking that if I corrected things by applying the inverse of my hearing deficiencies, I would be able to hear any headphone the way a person with normal hearing would hear them. Is this not correct?
     
  12. bigshot
    It's the other way around. It's easier to control the frequency response of two little transducers an inch from your ears than it is to control the response of sound traveling through a room. Most headphones are closer to flat out of the box than speaker systems are.

    Your theory about applying correction for your hearing loss will only work so far as your hearing loss is an attenuation of a specific frequency and boosting the volume of that frequency will bring it back up to a level you can hear it. I would ask an audiologist about that, because boosting the volume in your problem areas might cause further hearing loss, and boosting the level of a frequency range that you are stone deaf to won't help at all. You'd probably do better to focus on only certain bands of frequencies where your imbalance is fairly small. I don't think gross corrections are going to accomplish what you want, and they may be detrimental to your hearing.
     
    Last edited: Dec 10, 2017
  13. castleofargh Contributor
    that's quite the statement. agreed on how it's easier to control the frequency response on a headphone. absolutely disagree that most headphones are closer to flat out of the box. forget neutral, most headphones aren't even close to each other.

    I believe that a lot of people don't EQ their headphones for various reasons. from total misunderstanding of what is going on(that would be most audiophiles at this point). like some with silly ideas that you mustn't touch the signal to get the sound like the artist intended, forgetting all about how the headphone wasn't flat for their ears to begin with. to simply not feeling comfortable enough with EQ and not knowing how to set one by ear. which is indeed not as easy as I wish it was and can have a long learning curve. and some just don't EQ because whatever they use as a source for their headphone doesn't have an EQ or have one that is overly simple and can't help them. so for the most part, the concept of neutral probably remains a concept for a great deal of users.

    about applying the inverse of your hearing test result, as I said, it will depend on the compensation applied by the audiologist and how close it is to what was your original equal loudness contour. I honestly have no idea if or when you would be able to hear a headphone the way some other random youngster is hearing it. our hearing isn't calibrated on any actual neutral, it is calibrated from experience. when we progressively lose our hearing, it doesn't seem like the FR is changing much because the brain has a life long storage of references and it's constantly compensating to make us get what we expect to get(think of wearing colored sunglasses, after half an hour it's like they're not colored anymore, until we take them off). obviously once we really can't perceive signal to relevant to our interpretation, like mid frequencies for speech, then the brain can't just compensate anymore because it doesn't get enough to know what it was supposed to hear. from then I have no idea what happens in the brain.
    so I don't know if or how long it would take for your brain to get back to the idea that the headphone sound is the norm. it's not like a hearing aid that you keep all day long and learn to live with. here we're talking casual use of a headphone so the brain wouldn't get to mistake it for real daily life. I honestly have no idea how it would go.
    just like I have no idea if increasing the loudness for the remaining hair cells at a frequency will feel the same as quieter sound with way more cells to vibrate to it. I understand that an audiologist would try to sell you hearing aids, and the more expensive the better, as a result he might tell you not to do the headphone thing just so that he can try to sell you stuff. but he's also the only guy who might really know enough to help you on your idea and tell you if it's really a bad one. I'd love to help but I am just not qualified to answer your questions. a doctor is.
     
  14. jthew
    Let me make an analogy about how my hearing/brain seems to be working. Let's say you wear glasses, but you haven't been to an eye doctor in 15 years. The doc claims that your eyes have changed quite a bit during that time, and you get new glasses. You'll be hard pressed to find someone who doesn't recognize this change to be an improvement, and realize this new prescription is the way things are supposed to be.

    The testing I have done with the 9 band software equalizer in my AVR indicate that this is the case with my hearing. When I dial in the inverse of my hearing test, it sounds great to me. And when I get it wrong, and boost frequencies at which my hearing is normal, it sounds bad.

    One of my reference songs is "Sailing" by Christopher Cross. If any of you want to hear what music sounds like to me, listen to the song. Notice the 'tinkling bells'. Now, play it again with about a 25dB cut on everything above 2kHz. Listen for those same bells - they're gone. Welcome to my world.
     
  15. Dulalala
    Sure you’ll recognize the change, no one here is saying you won’t. However, your analogy isn’t exactly accurate, unlike wearing a pair of glasses, blasting louder sounds into your ear MAY cause further damage. Another analogy would be, say if you had sensation loss, if you don’t feel the tip of the needle on your skin and you just press harder and harder until you feel it. That’s obviously going to cause damage to your body, especially if you go past a certain amount of pressure applied isn’t it.

    We aren’t audiologist... (well I don’t think anyone here is) and we’ve warned you of the damages you might do to yourself if you did this. You seemed to have figured out a way to make it sound better music sound better for you and props on that. In my opinion, you seem pretty dead set on doing this, and with good reason, I’d be pretty upset if I couldn’t listen to music anymore.
     
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