Why We Measure Audio Equipment Performance

Discussion in 'GENERAL AV Discussions' started by admin, Jan 31, 2012.

  1. admin Audioholics Robot Staff Member

    admin
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    This article explores the question why we measure audio component performance. We take you on a tour of the various A/V components we review, and how our measurements can and cannot be correlated audibly. After Audioholics covers a product and its readers weigh in with their opinions in our forums, you can rest assured the product performance is pretty well covered. You'll know what to expect should you plan on buying it for your own usage. Nobody has all of the answers but collectively we can at least approach an educated assessment to help other Audioholics reach their goal of sonic nirvana while weeding out the average from exceptional performing audio equipment.
    [​IMG]

    Discuss "Why We Measure Audio Equipment Performance" here. Read the article.
    Last edited by a moderator: Jan 31, 2012
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  2. 3db Audioholic Overlord

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    Very well written. :)
    3db,
  3. kevon27 Annoying Poster

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    You measure because it gives Audioholics street cred. with the hardcore AV people. If it ain't got charts, graphs, numbers they ain't gonna read.

    You measure because if all Audioholics did was to gave glowing reviews and a few stars then you'll be equal to about 90% of the other AV "review" site out there.

    Lastly: You measure because what's the point of having an electrical engineering degree and you can't show off your skills..
    Last edited: Feb 1, 2012
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  4. MinusTheBear Audioholic Ninja

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    Good read! For product reviews having this linked somehow preceding the technical measurements section might help out the casual reader of Audioholics make greater understanding of the review as a whole.
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  5. rjplummer Audiophyte

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    Questions

    I was an avid audiophile until I had kids, in the early digital age. Sine then, I've bought audio components largely by comparing reviews rather than paying attention to specs. This article sparked my interest almost as much by what wasn't said:

    Preamps:
    Since you didn't mention it, I assume you rarely find preamps rarely introduce audible noise or distortion. Is this true? What about volume controls? It seems like it would be desirable to integrate volume control directly into the DAC chip since reducing the volume digitally removes information from the signal and reducing the volume after the DAC introduces some non-linearity. Is this how it works today?

    DACs/Decoding:
    I'm surprised you say so little about DACs. Is that because, "Bandwidth, SNR, drive level vs. distortion, etc. can call be easily quantified"? Do these specs identify most audible differences among DACs? What about downmixing, e.g., Is the DTS-HD downmixing algorithm part of the spec and if not, are the differences measurable/quantifiable?

    Source Devices:
    Again, since you didn't mention it, I again assume retrieving data from an optical-disc is essentially error-free. Is this true?
  6. GranteedEV Audioholic Ninja

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    AH needs to review Onkyo gear :eek:
  7. gene Audioholics Master Chief Administrator

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    Preamps and Dacs are generalized in the preamp section of the article. We measure drive level, distortion, SNR, crosstalk, etc.

    As for source devices, if the disc is read it usually transfers digital correctly or we would see a BER issue. Some devices do negatively affect sound quality when down converting a high res bitstream to PCM. As long as the player can pass a bitstream then the bulk of the sound quality depends on the AV receiver or processor.
    gene,
  8. rjplummer Audiophyte

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    Re: Questions

    Thanks for the quick response. I realized upon reading your response that what would be nice would be a description of each segment of the signal path, what types of degradation can occur in that segment, how you measure that degradation and what you can't measure.

    You did this well with in the cable, subwoofer and loudspeaker sections. The separate poweramp measurement article fills in the details for amps.

    Further up the signal chain there's less explanation. For instance, in your response, you say, "Some devices do negatively affect sound quality when down converting a high res bitstream to PCM." I immediately want to know: Can you/Do you measure this? What does the reduction sound like? But it sounds like your experience is that there's rarely significant degradation until the sound gets converted to analog.

    It appears Audioholics doesn't review standalone DACs. But I think most of the audible differences among digital source components are due to differences in the DACs. Aren't there measurements that reflect these differences?

    A good article, since it made me think about what I didn't know.
  9. gene Audioholics Master Chief Administrator

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    I honestly don't focus that much effort into stand alone dac's. I test the DAC section of receivers and Blu-ray players to make sure they are operating correctly. By correctly, meaning they are outputting HD bitstreams error free. I rarely test how they decode these signals since most people have newer AVR's that do the decoding.

    The bitstream to PCM conversion I don't see too often on recent products.

    You can see how we measure Blu-ray player digital and analog audio quality here:

    Oppo BDP-83SE / BDP-83 Blu-ray Analog Audio Measurement Supplemental — Reviews and News from Audioholics

    and here:

    Oppo BDP-93 & BDP-95 Universal Blu-ray Player Measurements Report — Reviews and News from Audioholics
    gene,
  10. MinusTheBear Audioholic Ninja

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    This blog below focuses a lot on objective parameters on DAC's and such.

    NwAvGuy
  11. agarwalro Audioholic Ninja

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    "Because we can" - I'm badassss and I know it ;):D. Lol!

    The editorial got me wondering about the dearth of articles on room treatments. If there were objective measurements of their benefits, it would be easier to convince people to invest in them.
  12. Irvrobinson Audioholic Ninja

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    I think measurements give you important information about a product that complements use and listening experiences. For loudspeakers, especially, knowing the actual performance parameters can tell you a lot about how you might react to the product over time. For example, a big mid-bass bump, or being a little too hot in the upper frequencies, might produce an exciting demo, but then later on you're finding the technicolor presentation a little tiring, and it might be difficult to correct the perceived problems with conventional means (like room treatment, placement, or equalization).

    Even for electronics I appreciate measurements. I like to see really low SNRs, pristine distortion plots, and, for amplifiers, some evidence of what their power output characteristics are into varying loads. All of this stuff tells you so much more than a singular THD number or a simple watts per channel rating.

    Personally, I think the Audioholics reviews are shaping up very nicely. And you still need trained interpretation of the results, because as anyone that produces measurements and metrics for almost any field knows, you've got to know something about how the measurements were generated, what was really measured in context, and how they describe (or really don't describe) the big picture. The poster child for this need for interpretation was the recent Velodyne DD18+ review. The measurements were revealing, but it was clear you needed to know what you were looking at.
    Last edited: Feb 2, 2012
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  13. agarwalro Audioholic Ninja

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    There is a limit to how detailed these articles can be before they start alienating all but the most hardcore. IMHO, the subwoofer reviews are already dangerously close to that fine line. The SVS PB-13 Ultra by Josh Ricci was a technical tour de force and even with my technical background left me a little lost and searching for understanding at times.
  14. gene Audioholics Master Chief Administrator

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    Agreed, I'm learning to tone things down a bit to appeal to a wider readership. I wish I had someone to simply dumb down my long tech articles for those that want a short concise report. Perhaps down the road we will rank articles based on their tech level for understanding. The same applies to reviews.
    gene,
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