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Strictly audio Saturday

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    Reffub

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    Pollensa1946 - 1 hour ago  » 
    Graham's position appears to be based on an assumption that this seasons recordings were recorded live in 2.0, rather than 5.1 and then down-mixed to 2.0 for (say) broadcast bandwidth reasons. If it was in fact the latter then the degree of compression they may, or may not, have introduced is an unknown. They could for example have compressed the LFE channel. Correct?
    For example, If I rip a cd I can choose FLAC or MP3. I know what sounds better. No argument.

    The current live shows are and were only ever 2.0, I gather that the new studio doesn't have the necessary 5.1 audio mixing equipment. In all the other series I've watched the live show is always 5.1 and the recorded results always in 2.0 as that's by far the easiest option.
    Graham has over simplified a sound engineers job, it's an art they will be creative with sound, especially if they have a LFE channel to play with. I doubt they get overly excited about mixing stereo.

    2.6. of Graham's link lots on automated down mixing for surround to stereo and non HD channels etc nice find but not really any help as the current series wasn't ever 5.1.

    It doesn't matter what the lowest frequency is on a track if it's too compressed it will be next to useless, more bitrate is always better and obviously lossless is better still. I can really feel the difference between AAC and a 1509kbps DTS track when it comes to LFE.

    Drops the mic.......

    | Mon 23 Oct 2017 15:47:22 #21 |
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    Pollensa1946

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    grahamlthompson - 19 hours ago  » ...Seeing as how FLAC is lossless and MP3 very lossy, of course it sounds better, doesn't mean the lowest frequency in one is any different to the other.

    Here we are in the realm of semantics. I would argue that of course they are different. OK, the frequency might be the same but the actual content presented to the speaker is self-evidently different. In the same way that I have some DVD's which carry a 5.1 soundtrack and also a 2.0 version of the same. They sound different in the LFE content.

    | Tue 24 Oct 2017 10:04:00 #22 |
  3. grahamlthompson

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    Pollensa1946 - 2 hours ago  » 

    grahamlthompson - 19 hours ago  » ...Seeing as how FLAC is lossless and MP3 very lossy, of course it sounds better, doesn't mean the lowest frequency in one is any different to the other.

    Here we are in the realm of semantics. I would argue that of course they are different. OK, the frequency might be the same but the actual content presented to the speaker is self-evidently different. In the same way that I have some DVD's which carry a 5.1 soundtrack and also a 2.0 version of the same. They sound different in the LFE content.

    If you check the 2.0 version will not be ac3 compressed. It would be pointless, it's likely to be lpcm to cater for stereo audiophiles or those with older AV kit without ac3 decoding.

    | Tue 24 Oct 2017 12:28:35 #23 |
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    Reffub

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    grahamlthompson - 9 hours ago  » 

    Pollensa1946 - 2 hours ago  » 

    grahamlthompson - 19 hours ago  » ...Seeing as how FLAC is lossless and MP3 very lossy, of course it sounds better, doesn't mean the lowest frequency in one is any different to the other.

    Here we are in the realm of semantics. I would argue that of course they are different. OK, the frequency might be the same but the actual content presented to the speaker is self-evidently different. In the same way that I have some DVD's which carry a 5.1 soundtrack and also a 2.0 version of the same. They sound different in the LFE content.

    If you check the 2.0 version will not be ac3 compressed. It would be pointless, it's likely to be lpcm to cater for stereo audiophiles or those with older AV kit without ac3 decoding.

    That kind of implies that these audiophiles don't want or like low Hz content. You must know some peculiar audiophiles or maybe just ones that can't afford large expensive floor standing speakers ? Personally if I was a stereo audiophile I'd want to hear the full dynamic range of the movie and then some.

    I would of thought a better reason for there being less bass in a 2.0 mix (whether that's AC3 or PCM or whatever) is that stereo is the better option for those using TV's, laptops and headphones etc. Small speakers don't appreciate low Hz signals, they can't reproduce them and any unnecessarily low content will only screw up the sound quality so why bother to add it.

    | Tue 24 Oct 2017 22:10:51 #24 |
  5. grahamlthompson

    grahamlthompson

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    Reffub - 10 hours ago  » 

    grahamlthompson - 9 hours ago  » 

    Pollensa1946 - 2 hours ago  » 

    grahamlthompson - 19 hours ago  » ...Seeing as how FLAC is lossless and MP3 very lossy, of course it sounds better, doesn't mean the lowest frequency in one is any different to the other.

    Here we are in the realm of semantics. I would argue that of course they are different. OK, the frequency might be the same but the actual content presented to the speaker is self-evidently different. In the same way that I have some DVD's which carry a 5.1 soundtrack and also a 2.0 version of the same. They sound different in the LFE content.

    If you check the 2.0 version will not be ac3 compressed. It would be pointless, it's likely to be lpcm to cater for stereo audiophiles or those with older AV kit without ac3 decoding.

    That kind of implies that these audiophiles don't want or like low Hz content. You must know some peculiar audiophiles or maybe just ones that can't afford large expensive floor standing speakers ? Personally if I was a stereo audiophile I'd want to hear the full dynamic range of the movie and then some.
    I would of thought a better reason for there being less bass in a 2.0 mix (whether that's AC3 or PCM or whatever) is that stereo is the better option for those using TV's, laptops and headphones etc. Small speakers don't appreciate low Hz signals, they can't reproduce them and any unnecessarily low content will only screw up the sound quality so why bother to add it.

    PCM has the same frequency reproduction range as Dolby Digital starting at 20Hz, it's less compressed. Basically the same as CD audio.

    Are you really saying HiFi enthusisasts don't use Subwoofers when required ?

    Many use SACD a lossless audio codec way superior to Dolby Digital as is DTS Master-HD as available on Blu-ray.

    You should check out channel 5-HD on Freesat. The audio is flagged as 5.1, in fact there is only audio data on the front left and front right channels. As the prescence of a lfe channel disables the crossover set in a AV amplifier you actually get less bass unless you happen to have full range front speakers. It would be down to the TV makers to ensure that low frequency content doesn't cause an issue. Postulating that the BBC reduces the quality of DD2.0 to cater for poor equipment is frankly derisory. Look at the quality document which in fact requires the lfe channel in a Dolby Digital 5.1 mix to have a -3dB rolloff. If you think that the bbc boosts 20-150Hz content when on a lfe channel compared to when in 2.0, why don't you just compensate by increasing the gain of your subwoofer ?

    | Wed 25 Oct 2017 8:33:11 #25 |
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    "PCM has the same frequency reproduction range as Dolby Digital starting at 20Hz, it's less compressed. Basically the same as CD audio."

    Okay so you were implying that the unspecified 5.1 track on Pollensa's DVD is DTS and goes lower than 20Hz.
    My old DVD's seem to be mostly Dolby Digital 5.1 & 2.0 but a few have both DD & DTS.

    "Are you really saying HiFi enthusisasts don't use Subwoofers when required ?"

    No I thought you were implying that, BTW you said "stereo audiophiles" NOT HiFi enthusiasts ! I'd expect stereo audiophiles to have two built in subwoofers

    "Many use SACD a lossless audio codec way superior to Dolby Digital as is DTS Master-HD as available on Blu-ray."

    Yes obviously I use DTS-HD MA when available.

    "You should check out channel 5-HD on Freesat."

    I have it's shit, films always seem to be cropped or upscaled too.

    "The audio is flagged as 5.1, in fact there is only audio data on the front left and front right channels. As the prescence of a lfe channel disables the crossover set in a AV amplifier you actually get less bass unless you happen to have full range front speakers. It would be down to the TV makers to ensure that low frequency content doesn't cause an issue. Postulating that the BBC reduces the quality of DD2.0 to cater for poor equipment is frankly derisory."

    I never mentioned BBC it was speculation about Pollensa's 2.0 track on DVD.

    "Look at the quality document which in fact requires the lfe channel in a Dolby Digital 5.1 mix to have a -3dB rolloff. If you think that the bbc boosts 20-150Hz content when on a lfe channel compared to when in 2.0, why don't you just compensate by increasing the gain of your subwoofer ?"

    You are constantly forgetting that the current series was never mixed live in 5.1. You can't compare it to the (edit) old series that was mixed in 5.1 It all depends on how and who mixed it maybe if 5.1 returns to SCD live I won't find it as good as before who knows.

    | Wed 25 Oct 2017 11:12:52 #26 |
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    Okay I did a simple TEST, but I'm not sure how valid it is, as it depends on the down mixing. I played an episode of an old series which was live mixed in 5.1. (I still have a few old programs as my girlfriend likes Lewis Smith among others.) So a series final with the band playing the Final Countdown had good bass at the start and throughout, so I thought I'd use that.
    As I said I'm not 100% certain about the technical side of this test as my AV receiver is down mixing 5.1 to the front channels, I gather from the web that the LFE channel should be just dropped when auto down mixing so any bass comes solely from the fronts.

    First I removed the rear surrounds and centre (not physically of course) and played it with the normal standard Dolby Digital (5.1) setting with fronts and LFE (sub) only
    It sounded fine still had nice bass.

    Next I switched the amp to 2 channel only, plus sub of course (which presumably then got its bass signal from the front channels) and played it again.

    It sounded almost exactly the same still had lots of bass.

    As I'm not 100% sure what the 5.1 downmix is I also turn Dolby off on the Foxsat and listened to it again in 2 channel and it still had good bass.

    So my conclusion is.........

    My av setup is fine.
    I get the same amount of bass from the front channels as I do from the .1 channel.

    So the bass mix for the old live shows IS different to the current show mixed live in 2.0 and the recorded results also in 2.0.

    Obviously what Graham was saying is correct regarding bass in the front channels. So I technically I don't miss the LFE channel I just miss the overall bass mix from the old 5.1 shows as the current series and results old and knew aren't as good bass wise. The old 2.0 results show always sounded flatter bass wise as does the current live 2.0 and recorded show.

    | Wed 25 Oct 2017 14:37:12 #27 |
  8. grahamlthompson

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    Reffub - 4 minutes ago  » 
    Okay I did a simple TEST, but I'm not sure how valid it is, as it depends on the down mixing. I played an episode of an old series which was live mixed in 5.1. (I still have a few old programs as my girlfriend likes Lewis Smith among others.) So a series final with the band playing the Final Countdown had good bass at the start and throughout, so I thought I'd use that.
    As I said I'm not 100% certain about the technical side of this test as my AV receiver is down mixing 5.1 to the front channels, I gather from the web that the LFE channel should be just dropped when auto down mixing so any bass comes solely from the fronts.
    First I removed the rear surrounds and centre (not physically of course) and played it with the normal standard Dolby Digital (5.1) setting with fronts and LFE (sub) only
    It sounded fine still had nice bass.
    Next I switched the amp to 2 channel only, plus sub of course (which presumably then got its bass signal from the front channels) and played it again.
    It sounded almost exactly the same still had lots of bass.
    As I'm not 100% sure what the 5.1 downmix is I also turn Dolby off on the Foxsat and listened to it again in 2 channel and it still had good bass.
    So my conclusion is.........
    My av setup is fine.
    I get the same amount of bass from the front channels as I do from the .1 channel.
    So the bass mix for the old live shows IS different to the current show mixed live in 2.0 and the recorded results also in 2.0.
    Obviously what Graham was saying is correct regarding bass in the front channels. So I technically I don't miss the LFE channel I just miss the overall bass mix from the old 5.1 shows as the current series and results old and knew aren't as good bass wise. The old 2.0 results show always sounded flatter bass wise as does the current live 2.0 and recorded show.

    If the lfe is present it is used discretely to feed the subwoofer (it ignores the crossover settings set during setup of your AV receiver and your surround speakers). This can be automatic using a small microphone like audyssey as used by Denon kit. Only in the absence of a lfe is the crossover settings used. Any audio below the crossover setting (normally about 100-120Hz but can be lower than 100Hz given larger surround speakers) goes to the subwoofer. Basically each of the 6 discrete channels in DD5.1 is routed to the appropriate speaker. A audio source say halfway between front right and rear right has 50% in each of the two channels.

    With a Video editor with 5.1 mixing like Sony Vegas Pro, it's quite easy to use a single mono sound source and pan it around your room by simply dragging it to where you want the sound to come from. Because low frequency is not directional about the the only thing you can alter on the lfe channel is the gain, which of course like the other channels you can alter over time using a volume envelope.

    If I could find a non encrypted copy of SCD in 5.1 I could show the respective audio waveforms on a editor timeline. I used this technique to track down audio dropouts on BBC 1 HD Father Brown which was also aired in 5.1. There's a thread about this (I think it was on AV Forums) somewhere.

    | Wed 25 Oct 2017 15:00:27 #28 |
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    Reffub

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    Sorry no idea what your point is with that last post but I presume you don't agree with me.
    But you seem to think that all 6 channels will be downmixed with Dolby 5.1 when the Dolby metadata guide which you mentioned says....

    "In all downmixes the LFE channel is not included."

    Other downmixes for Oppo etc don't use the LFE channel either for stereo downmix.

    And I presume I was only getting stereo when I turned off Dolby on the Humax, bass unchanged though, which is good.

    | Wed 25 Oct 2017 15:58:14 #29 |
  10. grahamlthompson

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    Reffub - 16 minutes ago  » 
    Sorry no idea what your point is with that last post but I presume you don't agree with me.
    But you seem to think that all 6 channels will be downmixed with Dolby 5.1 when the Dolby metadata guide which you mentioned says....
    "In all downmixes the LFE channel is not included."
    Other downmixes for Oppo etc don't use the LFE channel either for stereo downmix.
    And I presume I was only getting stereo when I turned off Dolby on the Humax, bass unchanged though, which is good.

    Presumably you meant you changed the digital audio output to stereo from surround. In fact you downmixed Dolby Digital to very lossy mpeg 1 layer 2 (mp2 similar to mp3) as used on SD digital TV. Kind of proof that the bitrate and sampling rate has little effect on bass. It would have reduced the dynamic range of the full frequency audio.

    Vastly inferior to lossless pcm as found on the DVD. Multichannel pcm can be used to deliver the full DTS Master HD audio experience when playing back from blu-ray using older AV kit without Master-HD decoding.

    My older Denon used multichannel pcm when playing back DTS Master HD from blu-ray.

    I think you might be swayed by knowing one is DD2.0 and one DD5.1 bass wise. In a blind test guessing you would find it hard to tell which was which if you muted the surround channels when playing back 5.1.

    | Wed 25 Oct 2017 16:25:48 #30 |

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