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Testing audiophile claims and myths

Discussion in 'Sound Science' started by prog rock man, May 3, 2010.
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  1. Steve999
    I can imagine that—if the music has more extended frequency response than the dialogue, as it inevitably will, then full range speakers will play the music at a relatively louder volume as compared to the voice—speakers that would be more centered on the vocal range with less extended frequency response would have relatively louder voice playback as it would attenuate the lower and higher frequency parts of the music. Makes sense to me.

    I think a center channel speaker with a surround sound receiver could possibly help—some of the available surround modes are meant to emphasize dialogue during TV watching, e.g., “TV-Logic” on my receiver (though as I look at the manual online that requires a 5.1 configuration on my receiver). Also there are settings to reduce or broaden stereo width that you can play around with with a center channel speaker and stereo speakers. I can also turn up the relative volume of the center channel speaker or separately tweak the EQ on it.

    Although as I just sit here and flip through the modes I have the best luck with just plain Dolby 5.1 surround.

    The headphone situation seems like a puzzler. I don’t know how you’d work around that.
     
    Last edited: Jun 18, 2019
    old tech likes this.
  2. dprimary
    That is the problem with analog recording there never has been an analog recording system that does not change the sound, you are always losing something. The signal from the microphones has never played back on an analog recording sounding anything like what went in. With experience you learn how to get it to kind of sound like the original sound, but it is never really close. 2" tape for multitrack cost over $300 a reel now and gives you 30 minutes, 1/2" to mix the stereo master is $100 reel now. That doesn't mean it can't be pleasing with a great amount of effort.
     
    old tech likes this.
  3. gregorio
    @dprimary response was accurate. Dolby SR was the method most widely adopted for pro reel-reel tape recording and that's presumably what analogsurvivor is talking about because the dynamic range of the best reel-reel tape is around 75dB, plus Dolby's advertised 25dB tape noise reduction would give the figure he quoted of 100dB. However, the 25dB NR is a best case scenario, laboratory conditions, test signals, etc. In the real world, in a studio with musical material, around 90dB is the max. Analogsurvivor seems to read all the marketing of analogue tape/vinyl, take all the positives, ignore or never learn all the negatives OR the practicalities/realities. However, he does the exact opposite with CD, he takes only the negatives, obviously never bothers to actually measure/reliably test to determine the audibility of those negatives and has probably never even seen most the analogue equipment he worships and posts about, let alone actually used it extensively! For example, Dolby NR used compansion (compression/expansion) to reduce noise in one or several bands, Dolby SR was one of the most sophisticated as it used several bands (within the audible spectrum) which change dynamically according to the input signal. Question; How do we divide the spectrum into one or more bands? Answer: We use a series of filters! So with NR we have a series on filters, none of which are linear phase because they're analogue and they're all in the audible band, while with CD we have just one filter which is linear phase and is outside the audible band. He's living in a complete analogue marketing fantasy land which bares no relation to the real physical world!

    There's no single, simple answer to this question, it's a combination of factors. Modern documentaries are mixed in 5.1, when you playback in stereo you're hearing a downmix automatically generated by a Dolby chip, which is also applying some compression scheme. The source (library) music and SFX arrives for mixing already compressed and is then upmixed stereo or processed to be surround (and some of this has to be routed to the LFE channel) but the dialogue which arrives for mixing is uncompressed, is mono and remains mono (which is routed to the centre channel). The combination of all these factors can, with some material and stereo playback systems, end-up with the dialogue sounding quieter than intended relative to the music (and SFX). The only solution to this would be to create a separate dedicated stereo mix but this would cost an unacceptable amount of extra time/money and require separate broadcast/distribution channels and inventory. There is the additional variable of where in the world the documentary was created and where it is being broadcast/distributed, which can affect the mix. Compared to the music world, docos in particular typically have a very convoluted chain between the mix stage and consumer.

    G
     
    PhonoPhi, sonitus mirus and old tech like this.
  4. bigshot
    It's probably a frequency balance issue. Your tablet probably is lopping off a lot of low end in the music. Lowering the bass when you listen with headphones might help. Out of phase material can get very loud with those 3D sound buttons on TV sets, but I don't think you're using that.
     
    Last edited: Jun 19, 2019
  5. KeithEmo
    I can think of a few other things....

    For one, some tables have built-in "sound enhancer modes" that are supposed to make music sound better.
    These may include DSP processing options that are intended to make music sound "more spacious" from those little speakers...
    Many devices with small speakers also use DSP processing to deliberately add harmonic distortion to low bass.
    (By substituting harmonics of the original low bass, which the tiny speaker can reproduce, they mask the fact that it cannot reproduce the original frequency.)
    I would check the sound settings - and look for "extra features" you can turn off.

    Second, most tablets have really tiny speakers, many of which are simply unable to deliver intelligible voices very well.
    And, of course, they may be doing odd things with the downmix.
    (Again, intended to make music sound better, but not necessarily voice.)

     
  6. Steve999
    I am guessing @old tech has two very nice stereo speakers that he would prefer to listen through. A lot of A/V receivers will have a mode that tries to make a downmix to two channels to sound similar to how 5.1 surround sound would, which apparently is what the new documentaries are often mixed in. On my receiver it’s called “Theater-Dimensional.” I’m listening to it now and it sounds pretty good. It’s not true 5.1 Dolby surround sound but it sounds quite good. I’ve read it can have trouble with reverb-heavy original mixes but I haven’t experienced that. I’m pretty sure other manufacturers have variants on the same concept. Something like that might help to maintain the intended balance between voice and music for a 5.1 surround sound program but with only two speakers. Just a thought.
     
  7. old tech
    Yes, that is correct - I listen to the TV through my stereo's (active) speakers. Most of the time it is great.

    It is more some of the later documentaries that seem to have overly intrusive background music. Switching the stereo speakers off and listening through the TV fixes that problem but the trade off then is lousy sound generally.

    I know that for TV/video, the better path is 5.1 than using my stereo's speakers, but I don't use the TV much and the current set up is good enough most of the time. So I've never had the inclination to look into this.
     
  8. bigshot
    You could get a good sound bar for the TV. It might handle it better.
     
  9. gregorio
    Yes, it is ultimately a freq balance issue but the question is why? The doco would have been mixed on a system with a wide freq response, so why did the re-recording mixer not notice that the music/effects were too loud relative to the dialogue? The answer is that in the mix stage the dialogue did balance well with the music and effects, the problem is downstream.
    If anything, the opposite is typically true. Considering the tiny speakers, tablets and mobiles typically deliver intelligible voices very well. We have a great deal of experience over many decades of delivering intelligible voices over tiny speakers, from the telecommunications industry.

    The downmix is typically made by Dolby itself. The format in most countries for the audio on HDTV is Dolby Digital 5.1 and as this is proprietary, any device certified as HDTV compliant (even HDTV "ready") must licence the technology/chip to decode the audio datastream from Dolby. The output is either 6 channels of audio or a 2 channel (stereo) downmix depending on the instructions given by the device in which it's fitted. In the case of a TV for example, that will always be a 2 channel downmix, so if you want 5.1 output you effectively bypass the Dolby chip in the TV, stream the Dolby Digital to say an AVR and then the Dolby chip in the AVR decodes the datastream to 5.1. Of course, once the datastream has been decoded (either to 5.1 or down-mixed stereo) by the Dolby chip, then the AVR is free to do whatever it wants to it, EQ or some other DSP for example. Furthermore, within the Dolby datastream is metadata which instructs the dolby chip to apply one of 6 different dynamic range control (compression) profiles during decoding ("Film light", "Film Heavy", "Music", "Off", etc.). However, this metadata is designed to be overriden by the device settings and most AVRs allow you to do this, although it's often difficult to find/hidden away in the menu structure somewhere. Lastly, in the case of most TV, this metadata is set by the Video Editor, not the re-recording mixer and let's just say that many Video Editors are not particularly knowledgeable when it comes to the audio side of things. Most of the time though, this system works pretty well but the compression profile sometimes has problems with docos, due to the previously mentioned fact that docos use library music which is already compressed, then there's typically other compression applied during mixing and then the decode process is probably adding more again and in this case the result can be somewhat unpredictable and cause the music to sound louder than the dialogue.

    Additionally, "two very nice stereo speakers" is a relative term. Stereo speakers are typically designed for music reproduction and that means they typically enhance the bass somewhat, as commercial music studios typically have a "house curve" that includes a raised bass and therefore high fidelity reproduction likewise requires a raised bass. However, this is not the case in the TV/Film world, we do not have a "house curve" per se, the speaker/room response is standardised and mandated to be more flat.

    Since around 2012, a new loudness paradigm in TV production has gradually been adopted by most of the developed world. There are many advantages with this new loudness paradigm over how it was done previously but as with almost everything "audio" there exists the potential for "better" to actually end-up "worse" under certain unusual circumstances and docos (and even the occasional TV drama) are the most likely to present those circumstances. The combination of your TV speakers having a weak bass response, plus a Dolby DRC profile and dialnorm setting (set by the TV) to optimise dialogue would account for more intelligible dialogue but overall worse sound quality.

    I've obviously tried to keep this relatively simple but when we get into the guts of it, it's actually quite complex and there are some major differences between music production and TV sound production, not least because TV sound is highly specified/regulated while there are pretty much no specifications or regulations for music production.

    G
     
  10. TheSonicTruth
    Perhaps I'm naive, or grossly misinformed, but I've always thought, for nearly as long as I've been a live, that hi-fidelity reproduction - of music, movies, toilets flushing, anything - requires a flat response.

    As for TV sound, in general, I find it to be theee most dynamically compressed, not necessarily loudness-processed, but more compressed than even the most recent pop or rock CD release. If anyone here is a racing fan, and specifically of NASCAR, they have a 30-40sec. segment called 'Crank It Up!' during broadcast of the race.

    During such segment, all network and driver-related graphics exit the screen, and viewrs are encouraged to turn up the sound on their TV sets or home theater systems. Now I have attended the races, and what i'm 'cranking up ' sounds NOTHING like it does at the actual track! Even through my big speakers, it sounds.

    like.

    mush.

    PBS(U.S.) is about as dynamic as it gets on broadcast television. I can crank up things like 'This Old House', and from the kitchen it sounds like an actual renovation is taking place in the living room! Same for their Saturday nigh feature classic movie. For the most part, the original screen aspect ratio and sonic impact of those films is passed along to viewers. I wish the major networks could do the same, especially with sports.
     
    Last edited: Jun 20, 2019
  11. dprimary
     
  12. dprimary
    Are they adding distortion to "create bass" of is the distortion a side effect of using the rumble motors to extend the bass making the whole tablet a LF driver. Much like the old servo drive subwoofers, except without a direct connection to the driver surface and a whole lot of real time math.
     
  13. bigshot
    Recently, I've seen small sound services mixing on small speakers for TV. I've never worked that way myself. I always mix to full range first, and then check on small speakers to see if anything causes problems. It may be that the documentaries he's talking about are just handing the mix to a DIY guy who isn't working to professional standards. It pays to do things right. I had a project once where the budget had been blown through and they tried to cheap out on post. It bit them in the ass.
     
  14. KeithEmo
    I've never heard of someone effectively "making an entire tablet into a low frequency driver".... although I have heard of putting vibration drivers in headphones to "simulate low bass".
    The catch is that, compared to a speaker cone, and entire tablet is quite heavy, and so would take a lot of power to actually move enough to make bass.

    What I have frequently seen, with small powered speakers and Bluetooth speakers, is specific and carefully controlled harmonic generation.

    The principle is simple.....

    Let's assume you have a small desktop speaker that is unable to make significant output below 100 Hz.
    You do NOT want any frequencies below 100 Hz being sent to the amplifier that powers that speaker.
    They won't be reproduced properly, they'll probably cause distortion, they'll waste amplifier power, and they'll reduce dynamic range by bringing the speaker closer to its power limit.
    Therefore, you'll apply a high-pass filter to block frequencies below 100 Hz.
    Unfortunately, by doing so, you will significantly alter the overall tonal balance.
    And, beyond even that, some instruments that produce mostly low fundamental notes will simply disappear from the mix.

    The simplest solution is to boost frequencies right above that cutoff point to produce an illusion of more bass.
    This is often done with bass reflex speakers.... they are sometimes deliberately tuned with a bump in response above their cutoff point to compensate for the lack of bass below that point.
    The result is a speaker that plays drums with a lot of "punch" - even though the actual lowest notes are weak.
    This works well with some content... but only some.

    However, modern DSP technology offers more advanced options.
    First of all, a high-pass filter, and a slight boost in frequencies right above the cutoff point, are both set.
    Then the DSP is programmed to artificially create harmonics to go with the lowest fundamentals which are being filtered out.
    These harmonics aren't just noise - because they are harmonically related to the original content.
    So, for example, instead of simply being removed, the lowest noted from that big drum are filtered out, and replaced with a little burst of harmonics of their frequency.
    The end result is that the bass drum has a lot less boom, but has some extra punch to make up for it, and ends up not sounding all that bad.

    The concept is quite elegant...
    Instead of simply blocking the frequencies the little speaker can't play...
    They are instead replaced with newly generated content that is "perceptually similar" - but which the speaker can play...
    The end result, if you do it correctly, is something that sounds very much like the original - at least superficially.
    (Of course, this sort of processing is all proprietary, and is quite complex, which is why it sometimes seems to work very well, and sometimes not so well.)

     
    sonitus mirus likes this.
  15. gregorio
    1. Yes, that is somewhat naive. Each have somewhat different requirements for hifi reproduction. For example, movies have what's called the "x-curve" which is applied to the monitoring (B-chain) during mixing and reproduction (although this isn't applicable to home reproduction), TV is essentially flat and the common/usual trend for several decades with music is for a house curve with a raised bass but as there are no mandated specifications/requirements (unlike TV and film) this house curve can essentially be whatever the individual studio wants. In general, a slightly raised bass in the consumer reproduction chain would therefore give a more hi-fidelity reproduction and many/most consumer transducers have this built-in (for example, it's one of the typical differences between a "speaker" and a "monitor"). A flat response will certainly give a more hi-fi reproduction than whatever is the natural response of speakers+room acoustics in a consumer listening environment but ideally, most of the time, for the highest-fidelity music reproduction, you should achieve a flat response and then raise the bass a little. A flat response is therefore somewhat of an audiophile myth.

    2. While TV can be quite heavily compressed, it is nowhere near the levels of compression applied to much pop/rock music. Even going back as far as the late 1960's, pop and rock genres often/routinely drove compressors to (and beyond) distortion. In fact with quite a few sub-genres, heavily over-driven compression is a required sonic characteristic of the genre. This is never the case with TV. Also, since 2012, it absolutely IS "necessarily loudness-processed"! This isn't just different, arbitrary loudness specifications/requirements of individual TV channels/networks, in the USA (and some other countries) it's an actual legal requirement. In the case of the USA, it was enshrined in law by the CALM Act (2010).
    2a. The workflow with live events is necessarily entirely different to films and other TV content which is not live, such as docos, dramas, etc. With docos for example, the dialogue of the interviews is recorded at the same time as the filming. Once all the footage has been acquired, it is edited and then passed to the audio post production team, who clean up the production dialogue, source, edit and sync all the sound effects, add the music and narration and then mix all of it together to create a 5.1 mix. This mixing process (called "Re-recording" in the TV/film world) involves balancing all the elements, applying noise reduction, EQ, compression, reverb, etc., writing "automation" to ensure balance not only within each scene but obviously between scenes and finally this mix (along with the other required deliverables) is recorded ("printed"). We do of course entirely control the dynamic range of each of the elements and of the completed mix and constantly tweak all of this during mixing according to taste but obviously within the loudness specifications. While the time, cost, exact details and number of personnel involved in audio post varies greatly, this is broadly the workflow of all TV/Film, with the obvious exception of live events and most ENG (news), where there is no audio post process! However, live events still have to comply with loudness specifications. I have no direct experience of doing the sound for NASCAR or other motor racing events but what effectively seems to happen is that an independent mic and/or set of mics is associated with each camera position (appropriately balanced/processed) and then as the director changes camera/angle, the sound switches to the mics associated with that camera. The exact setup and workflow for such events has evolved over decades, therefore considerable experience is required and particularly at events such as motor racing, where there can be very high SPLs and wide dynamic range, then considerable compression typically has to be applied, in order to play it safe and remain within loudness specifications, baring in mind that you obviously can't go back and tweak it a few weeks later in audio post.
    2b. When you have attended races, are you "at the actual track" or are you in the audience stands? It's obviously going to sound significantly different if your ears are in a significantly different location to the mics and that's in addition to the compression, NR, crossfading and other processing required in order to: Maintain a similar loudness between different cameras/mic setups, allow the commentary to be intelligible and comply with loudness specifications. Considering all the practical difficulties of creating 5.1 mixes with multiple 5.1 mic setups, such high SPLs and dialogue/commentary that has to sit above it and that it's all compliant with loudness specs, I'm amazed at how good the sound usually is.

    3. Your "wish" is significantly different to that of most other consumers. The vast majority of consumers want to watch a sports event live, within a few seconds of it being filmed, they don't want to wait weeks (or in the case of films, many months) until after the event is filmed, to allow for audio post and the creation of high fidelity, wide dynamic range, etc.! Also, rather ironically, you've actually got this completely backwards! Particularly in film, pretty much none of the sound is "real", none of the Sound FX were recorded during filming, they are created and recorded in a completely different environment, with different equipment and different people using it, even much/most of the dialogue was recorded weeks/months after the filming. With a live sports event though, it's the opposite, ALL the sound you hear is the actual sound that's occurring at that event and that instant in time.

    At the end of the day, loudness and other specs have to be met, penalties are severe for not doing so and as you say, bites them in the ass. Docos are generally near the bottom of the genres budget spectrum though, so sound quality is generally nearer the minimum required to pass QC. A lot of docos are mixed on relatively small speakers but with bass management (with a sub), so they still have a somewhat "full-range". This can't really be avoided as 5.1 has been a standard requirement for quite a few years. Most commonly, docos are mixed on good systems by very experienced personnel because although it costs a lot more per hour, the number of hours required is a lot less and the end result more reliable. The issue described by @old tech is known about but isn't easily solvable, it's a fairly uncommon, unpredictable consequence of 5.1, unavoidable professional workflows, loudness specs and consumer playback equipment.

    G
     
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