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Skeptico Saloon: An Objectivist Joint

Discussion in 'Sound Science' started by gnarlsagan, Jun 27, 2013.
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  1. imackler
    This is super helpful! But where does the .707 number come from? Is that the damping ratio?
  2. StanD
    It's the Square Root of 2 divided by 2. Which is 0.70710678118654752440084436210485 if you want to be more precise.
  3. StanD
  4. castleofargh Contributor

    you're right about nwavguy recommendations, but if you read it right, you see that 115db is his worst case scenario, not something he would do in real life. to get to 115 you need to listen about as loud as you can muster, while using to the most dynamic track you can find. even if the amp and headphone end up ok with that, your ears might not enjoy it for long. ^_^
    if you know you're not like analogsurviver trying to get your canon explosion from a headphone to actually sound as loud as in real life because that's how it was played, then it is safe to go with less than 115db as your needs and stick with 110 or even 105 instead. it's really all about you and how loud you listen to music.
  5. StanD
    Don't you just love the guys that think you can never have enough wattage. They want 4 or more Watts for headphones that'll hit 119 dBSPL at 1 W. What would happen if they listened to typical pop music that is heavily volume compressed and cranked the amp up all the way?  smiley-whacky078.gif
  6. earthpeople
  7. bigshot
    Nigel Tuftnell's amp goes to 11
  8. StanD
    Death by SPL.  smiley-violent041.gif
  9. cel4145


    For movies, Dolby and THX reference levels for movies is 105db peaks from the speakers, with 115db from the subwoofer (because of the LFE channel). And that's extremely loud, and louder than many home theater systems are going to get.

    But I'd probably shoot for 110db based on amp calculations from manufacturer specs since I don't trust manufacturers not to be a bit overly optimistic when it comes to audio equipment (and that's saying it nicely).
  10. bigshot
    The problem with movies is that 5.1 spec for movies is 10 dB lower in the LFE channel than the sub channel in music SACDs in 5.1. I ended up just splitting the difference and music is a little too high in sub bass and movies are a little too low.
  11. dprimary
    I have to wonder how loud people listen to headphones. Even with a first generation iPod I could drive 600 ohm AKG K240 DF to levels high enough to cause hearing damage. 
  12. imackler
    Have you skeptical headfiers ever heard a dac or amp that measured well and was appropriately powered for your headphone but didn't sound good? Can an amp sound bad that measures good? Is there ever a reason besides power requirements to get an external amp?

    And do you think that everything that measures well sounds the same? Does the magni 1 and 2; e12diy w/ diff opamp/buffer combos; cirrus and wolfson dacs, all as examples sound the same, when compared to each other? Is there such a thing as a warm-sounding dac or amp if there is the only measurement differences are beyond the threshold of human hearing?

    I've been appreciating all the feedback/interaction. I'm far more skeptical of the advertising machine than I am of you all :) I'm in no way confrontational... Just hear to learn.
  13. uchihaitachi
  14. StanD
    Unless the electronic device is designed poorly, built badly or used improperly most/all gear sounds the same. If one uses an amp with a load it is not designed for, or requires more power than it can deliver, one cannot expect proper results. Keep in mind, "An audiophile and his/her money is easily separated."
  15. maverickronin
    Pretty much no.  I've never reliably heard this myself and I've never seen any evidence of anyone demonstrating this under appropriately controlled listening conditions.
    Kind of.  There's a little bit more than strictly power requirements.
    Balanced Armature IEMs are a good example.  Most will go ear-splittingly loud from just about about anything but there are reasons besides power they can benefit from a proper amp.  One is noise floor.  Since many are super sensitive you may need an amp with a lower noise floor to get rid of background hiss.  Then there's output impedance.  Small amounts of output impedance can affect the FR of BA IEMs much more noticeably than other kinds of headphones.  Also some amplifiers may have capacitor coupled outputs which can cause the bass to roll off early with lower impedance headphones but work just fine with higher impedance models.
    All of these things are relatively basic electrical theory and easily measured though.  Nothing magical or unknown
    Pretty much yeah.  The only times that I've reliably heard differences between amps/DACs/etc also corresponded to measurable differences that were within known thresholds of audibility.  As I mentioned above, no one has properly demonstrated those kinds of differences either.
    OTOH, it switching certain opamps into certain circuits may make measurable differences.  Usually this will be for the worse (unless the original was particularly poor quality or unsuited for the job) but it could me measurable and/or audible under some circumstances.  I would think the most common case of an actual audible difference would be someone switching an expensive high bandwidth opamp into a circuit designed for a lower bandwidth opamp, resulting in oscillation and high frequency distortion.
    Assuming all measurable differences are beyond the limits of human hearing then no, it's not really possible.
    OTOH, it's just barely possible that something with a few incomplete measurements might measure extremely well in one published specification but abysmally in another metric that the manufacturer leaves out and such a difference might account for such a phenomena.
    I think it's not just the advertising machine.  I think that a lot of people/companies selling the more obvious snake oil know that it's BS but plenty of others really do believe it.  Especially with thing like amps and DACs which are far more plausible than for example, $150 power cables.  It's not hard to see why they'd believe it either.  It's very easy for humans to fool themselves into believing things which aren't true.  Exception bias, conformation bias, and a host of other cognitive errors are the default mode of human thought.  Everyone falls prey to them to some degree and the scientific method along with a skeptical mindset are the only tools which can mitigate such errors.
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