Audio Science Review Review

Discussion in 'Audio Science' started by purr1n, Aug 30, 2020.

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  1. Raimei Templar

    Raimei Templar Friend

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    It can certainly be useful for someone to have the same measurement device if your goal is convince laymen that Amir is doing something incorrectly. Its very easy to handwave away different results (incorrectly) as being the fault of different measurement rigs, and a layman can easily be conceived the cheaper measurements rigs are totally inferior to the big boi expensive AP555 analyzer. That is a misconception I had for a long time as well, I had thought that Schiit for instance was missing some of the measured issues because they had a inferior measurement device (before they also got a AP555). This was incorrect as I was shown in some of my very first posts on SBAF.

    This being said I would also say the cost of the AP555 is very likely not worth that benefit as people will still poo poo your measurements even if they are off the AP555 if they disagree with a person they are convinced is the most objective. I think those who are not religiously loyal can have it explained to them that the measurement devices are comparable as was explained to me.

    As a interesting addition and a real world example of this, Geshelli Labs mentioned that the results they get for their Archel 2.5 amp are far better than the ones Amir presented in his review of the Archel. They have the same calibrated AP555 analyzer as Amir (pretty sure they actually bought it in response to their ENOG 2 measuring "poorly" on ASR). They actually complained of some of the issues shown in this thread, mainly that Amir seems to just randomly and arbitrarily pick voltages inputs and outputs rather than using a consistent method which dramatically skews the results.

    Apparently they were getting lots of angry emails from people accusing them of misleading specs and the like which lead them to post the following on their website "These measurements are taken on a fully calibrated Audio Precision APX555 machine. There is NO volume knob manipulation to try to match certain voltage levels. We simply plug in the device, put the volume knob to FULL (all the way to the right) and take the measurement. We feel this is the best way to show the actual performance of the amplifier circuitry."

    The measurements were already posted before the ASR review in question. Maybe they would have gotten more angry emails if they had a device other than a AP555 but it certainly didn't stop them completely.
     
  2. Vtory

    Vtory Audiophile™

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    You made exact points I thought. Buy a ap555 and hire competent folk to do right research, and disclose everything for free. Please note that opportunity costs could be super, super high (time and resource is limited for everyone). Expected return? Not so high imho -- Socially? questionable (I mean # of benefited people and the amount of benefit) Personally? heck no mostly (no financial return, no career benefit, etc).

    As a person in academia, your assertion sounds too ideal (no consideration for real motivation) for real life I've seen day to day.

    Of course, if you purchase ap555 yourself, send it to proper people, and fund them enough labor costs (think hourly rates of lawyer at the very least). That will be hyper great.. or god-like awesome. Are you really angel enough to do so?
     
  3. gepardcv

    gepardcv Almost "Made"

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    I’ll start saving for this project right away. :)
     
  4. Vtory

    Vtory Audiophile™

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    Just another thought. Let's suppose hypothetical Amir in one of the parallel universes like the following
    • No weird commentaries
    • No weird forum name
    • No weird closing statement ("I can/cannot recommend blahblah")
    • No begging toward AP
    • But post pretty much same measurement (i.e., lots of things done wrong) as he does in this universe with some notes like "Hey this is what I found interesting blahblah"
    Then I am 99% sure I won't rant at all. Maybe I can even subscribe his blog. Noobs always exist as I see myself a peer noob. It's always attitudes that create problems.
     
  5. Mont789

    Mont789 Acquaintance

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    Noticed that there, They cry when a headphone reaches 4% at 20Hz & <1% above 1KHz. But when a $1000 Speaker nothing but a noise generator when pushed hard, suddenly it inaudible and just room artifacts?.

    Linsoul IEM's are just as bad. Either the whole unit dies within a month or they can't even get the tuning stable, It a joke when you can get the ER2SE for under $99.
     
    Last edited: Feb 13, 2021
  6. purr1n

    purr1n Desire for betterer is endless.

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    You mean what @atomicbob does (well, without the weird forum name)?

    The measurements, AP555, spinorama, GRAS - those things are merely vehicles, devices for his narrative:

    I am your audio savior to save you from the lies.
     
  7. LetMeBeFrank

    LetMeBeFrank Won't tell anyone my name is actually Francis

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    What you guys don't know is that Amir's APx555 doesn't output measurements, it outputs golden plates that he must put inside his giant white hat to read. Only he can read them correctly and tell you what they say. Other people might read the plates and see what they believe to be measurements, but only Amir can tell you if it is recommended or not.
     
  8. atomicbob

    atomicbob dScope Yoda

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    Updated comparison for those who would like to play but don't have $11K to $30K for analyzer investment.

    Schiit Modi MB distortion spectrum 1 KHz sine
    -1.1 dBFS for ULmk4+REW
    0 dBFS for dScope and APx555

    MOTU Ultralite mk4 + REW
    20210213 Modi MB THD THD+N  spdif SE Vrms REW+ULmk4.png
    Look familiar?
    Please note the y axis is dBFS for this measurement whereas the dScope and APx555 are dBV. Observe the harmonics maintain the same difference with respect to the fundamental for all measurements. The 2nd harmonic is approximately 82 to 84 dB below fundamental.

    Compare to previously posted graphs:

    dScope
    20210212 Modi MB THD THD+N  spdif SE Vrms t6 graph only.png

    APx555
    20210212 Modi MB THD THD+N  spdif SE Vrms APx555.png
     
    Last edited: Feb 13, 2021
  9. wadec22

    wadec22 Almost "Made"

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    any guides or recommended how-to reading to measure headphone amps? I tried the super search but didn't find anything here. I have a couple cool units here now that I would like to test and share some noob measurements with you guys.
     
  10. atomicbob

    atomicbob dScope Yoda

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    All of my technical measurement posts includes this in the prologue:

    Standard Prologue
    If you are unfamiliar with audio measurements please use a search engine with the query:
    "audio measurements" or "audio measurement handbook"
    Look for publications by Richard C. Cabot and also by Bob Metzler, both from Audio Precision. There are other useful publications as well. These will provide basic knowledge.

    Here is an example from the search described above
    http://www.audiomeasurements.com/?page_id=2349
     
  11. wadec22

    wadec22 Almost "Made"

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    yes, I had seen the prologue. I guess I am looking for something other than a traditional text. more your run of the mill online tutorial or guide. no worries.
     
  12. atomicbob

    atomicbob dScope Yoda

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    Ok, try this:

    https://enjon.uk/2019/09/01/a-diy-approach-to-distortion-measurements-for-audio-amplifiers/

    substitute the 8 ohm resistor for 30 to 300 ohms depending on which type of load you want for measurements. A safe way to begin is with headphone amplifier running at 0 dB gain and use 0.775 Vrms (0 dBu) source stimulus to the amplifier. This will keep power down to safe levels.of 20 to 2 mW.

    *edit*
    The better results may be obtained with better audio interfaces. RME ADI-2 Pro will have much greater potential than the interface shown in that link.
     
  13. Psalmanazar

    Psalmanazar Most improved member; A+

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    What about recordings? Commercially released recordings are all heavily distorted.

    1. No commonly used recording mic is flat or totally clean. They were voiced to sound good.
    2. Those signals from the mics have to hit mic pre amps to reach line level. Well you want a wire with gain? That doesn't exist. Those meme super clean pres? Well those are mostly clean but not clear but don't sound as good as the older, more euphonic pre amps. You can make a lower gain tube pre that sounds fine. Higher gain? Well you need something that sounds good when you push the gain structure and since if you're recording something, you're in a never ending way with noise and distortion, you go with what sounds good. Those modern opamp pres might be super clean at 50 db of gain (they're not cheap), but you want 70 db of gain? They get dirtier than old school iron, glass, and silicon. They were again all voice to sound good.
    3. None of what you're recording sounds as you hear it in the room due to mics and your brain not filtering it when you see it or imagine it. So you need to process that audio. You better hope your EQ can smear it a bit after you mangle it so it doesn't sound artificial. Old analog eqs used parts that were voiced to do this. After about 1980, this stopped. And they wouldn't let you totally mangle anything with sharp cuts until the mid 70s. They were voiced to sound good.
    4. Dynamics. All non-linear processes produce distortion. Compression is used to raise the volume. Unfortunately the compression inherently makes things smaller and shittier if you go beyond shaping the transient envelope of something. So you had better hope your compressor is converting all of that sound pressure energy into distortion that sounds good. More distorted compressors sound better. All of your old stereo LPs hit a Fairchild 670 or TAB U73b. The old school 1176, LA2A lightbulb compressors, and SSL bus are distortion machines. The analog parts and modulation in the control systems used provide distortion. The gear was all voiced to sound good when compressing.
    5. Digital? Did not lead to cleaner recordings. They're using the same shit minus tape. It mostly led to recordings that were distorted in a much less pleasant way. That modern sheen and nasty high end is all distortion. You want a clean digital mix down? Well that's been possible since the late 90s without adding a ton of IMD and harmonic distortion. It will just be boring, small, and dull.

    Well what about money? Even with money, hardly any of the common recording consoles used the cleanest gear of the time. Once you get past the TAB stuff funded by the West German government, they're mostly heavily compomised until you get the to the late 90s SSLs that cost half a million dollars... and still didn't use the cleanest opamps. They were still voiced to sound good.

    Amir core cheap pro gear? TOTAL CRAP. Pretty much anything under the price of the project box, made in Texas, FMR gear, is dog shit. Chinese clones? Dog shit. Behringer? Kill yourself. Modern Focusrite? It will just break.
     
    Last edited: Feb 13, 2021
  14. wadec22

    wadec22 Almost "Made"

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    I have a MOTU Ultralite mk4 I've been using for about a year that I was going to start with.
     
  15. Pancakes

    Pancakes Friend

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    Oh god. I pray there aren’t any recording engineers bowing down to Amir...
     
  16. Tekker

    Tekker Facebook Friend

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  18. Mont789

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    Are they really dissing Stax for it FR, while at the same touting the HD800S at handling EQ?. Never had Stax but I'd pick the L300ltd(used) + EQ over the HD800 anyway. I hate when Head fi does that where I can be 2 pages of a headphone being muddy, But then implode when told to cut the 150Hz area by few db?.
     
  19. bboris77

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    Another classic line from Amir:
    “The A30Pro is the heftiest and most serious looking enclosure from Topping with its manly venting holes on top.”

    I never knew that a hole can be referred to as “manly”. Perhaps he meant “many”. The review and accompanying video are riddled with spelling and technical errors that people are pointing out to him. Very entertaining.
     
  20. Thad E Ginathom

    Thad E Ginathom Friend

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    Maybe the thing ejaculates to the music. Could make a mess of the room.
     
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