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iPhone AAC vs. Aptx and Aptx-hd real world

Discussion in 'Sound Science' started by neil74, Oct 4, 2017.
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  1. shortwavelistener
    What i really meant about the post that you quoted earlier is that i was referring to the differences in transparency between AAC and another lossy codec, which in this case is aptX, HD or not. I didn't even mentioned anything about lossless codecs.
    Last edited: Jul 21, 2018
  2. Brooko Contributor
    My apologies - I had read your reply incorrectly. I had taken it that you were suggesting that aac 256 was not audibly transparent. Clearly you are saying the opposite to be true?
  3. shortwavelistener
    Yes. AAC 256 may be transparent to the average ear, but comparing them to other lossy BT codecs (e.g. aptX, LDAC) using high-end equipment is like day and night.


    Last edited: Jul 21, 2018
  4. Brooko Contributor
    Sorry can you clarify this further. Because you are not being very clear at this point.

    1. Are you saying that aptX and LDAC are audibly different, and you do realise that night and day means that in a volume matched test - everyone should be able to tell them apart. Its one of the terms a lot of people use but they have very little idea of the meaning.
    2. Are you also saying that as far as transparency goes - aptX / LDAC are better or worse? I'm assuming worse because aac is already audibly transparent, and you did say there was a night and day difference.
    I saw the quote from Dan - unless he's performed a double-blind volume matched ABX with subject files all transcoded from the same master recording, then his observations are as anecdotal as anyone else's.
  5. shortwavelistener
    So far i never did any comparison between LDAC and aptX HD on real equipment (because i don't have any LDAC compatible devices - except for my Sony car stereo of course), so no, i don't even know the differences between LDAC and aptX IRL.

    However AAC is transparent enough to average ears on average entry level audio equipment. However if someone claims to have "golden ears", knows what artifacts to listen, and has very high end audio equipment, then it's not impossible for them to diiferentiate AAC's transparency with aptX/LDAC. But the results are likely to be 50/50, depending on which song that they will listen to. The flaws are more likely to be discovered in classical music.
    Last edited: Jul 21, 2018
  6. Brooko Contributor
    So again (and I realise I am perhaps sounding pedantic) - what was the reference to night and day about?

    Do you have any peer reviewed testing data showing differences between the codecs?
  7. shortwavelistener
    I referred the night and day as how easily you can perceive the differences in soundstage between AAC and aptX. In terms of SQ i know it's audibly transparent.

    And no, i don't have any "authentic" peer data showing differences between aptX and AAC, but this is the closest that I can get to:



    (Note that i'm not an expert, hence don't bash me)
    Last edited: Jul 21, 2018
  8. Brooko Contributor
    Would never bash anyone - just interested in increasing my own learning :)

    Have you done this in a double blind abx with volume matching (same tracks)? I guess it would be pretty difficult to set-up. I've never personally noticed a difference between the two (in relation to Bluetooth transmission), and definitely not in terms of sound stage (which in my experience relates more to the transducer and the recording than codecs). Obvious exception would be if there is DSP involved.

    How did you set up your tests?
  9. shortwavelistener
    Well i literally used my Dell Optiplex 760 (running Win Vista) in which i installed an ASUS Xonar Essence STX soundcard which is connected to my Trond USB BT transmitter dongle via headphone out. And for listening i just used my Sony MDR-XB650BT cans.
    Last edited: Jul 21, 2018
  10. Brooko Contributor
    Thanks - how did you switch between aac and aptx? How did you check volume matching? Time lapse between switching?
  11. shortwavelistener
    I can't switch between AAC and aptX using my PC. However for AAC i used my iPhone 5S connected wirelessly to my headphones, while for aptX it's PC > bluetooth dongle > headphones.

    For ease i connected my cousin's Macbook Pro
    (At times i also hooked up the BT dongle to my Mac so that i could have aptX-HD)

    And also my MBP allows the switching between AAC and aptX. But my PC has a better sounding soundcard / DAC.
    Last edited: Jul 21, 2018
  12. Brooko Contributor
    OK - so different sources. What about volume matching and time delay? Its normal to hear slightly louder volume as clearer, more detailed, with wider stage etc. When volume matched - the previous "day and night" differences disappear.
  13. shortwavelistener
    For PC i used Foobar2000 with the ABX Comparator plugin. The plugin

    For Mac i just run Foobar2000 using Wine along with the ABX plugin.

    I just use the options to get the plug in to level match for me automatically.
  14. Brooko Contributor
    But how did you ABX when you are using two different Bluetooth sources - as far as I know that is impossible. With ABX plugin you can compare 2 different containers (FLAC vs aac for example) very easily. How did you manage aptX?
  15. shortwavelistener
    For the last ABX test i used my Macbook Pro. And of course i use lossless files for ABXing, either on my PC or Mac. MBP natively supports the aptX codec for BT devices. And i compared two files, one AAC and ALAC/FLAC in the ABX plugin. I'm just comparing how well those lossy BT codecs encode those lossless/lossy files.
    Last edited: Jul 21, 2018
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