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A different approach

Paul's Posts — 25 July 2012

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A different approach

Yesterday I promised you an interesting thought challenge that has to do with getting music to sound live in your room – something we mostly all agree our industry and our equipment falls quite short of being able to do.

First, imagine yourself sitting in the center row of an auditorium.  There on the stage is a small combo playing live.  The music’s good, the sound is great, you’re into it.  You close your eyes and you can feel the room around you, the space you’re in, the music that plays to you.  With your eyes still closed, in our imaginary scenario, the combo stops playing and before you can even open your eyes a pair of good loudspeakers replaces the combo and continues their music at the same volume level – only this time from a recording of them.

Chances are pretty good you’d still think they were playing live if you didn’t know any better.  The room is still there, you can still sense the space you’re in, the size of the hall, etc.  The recording of the combo was made with relatively closely placed microphones that don’t capture much of the space the musicians are in – but that’s ok because it’s being played back in the exact same space.

With me so far?

Now, take that same recording and loudspeaker pair, place them in your living room, close your eyes and listen and you find that which once sounded live now sounds recorded and canned.  What happened?  The room changed, of course.

You know – even sitting quietly in the room with nothing playing – the approximate size of the room and the space you’re in.  The group that sounded natural and live in the auditorium now sounds wrong and out of place.  Why?  Well, for one thing if that combo was really in your living room everything would be different for you from an acoustic standpoint.  There would be that number of actual people in your living room as well as their instruments and the reflections and ambient noise levels would all be different.

Bottom line: we can sense, especially in a small confined space, if something is real or not real because of that space and our ability to sense that space.

So how do we fix this?  I’ll tell you tomorrow.

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About Author

Paul McGowan

Paul McGowan is the CEO and co-founder of PS Audio Inc. a Boulder Colorado design and manufacturing company of high-end audio products and services. McGowan has been designing and building high-end products for nearly 40 years. Hobbies include skiing, music, hiking, artisan bread baking, kick boxing and cooking. He lives in Boulder Colorado with his wife Terri and his 4 sons.

(8) Readers Comments

  1. paulsquirrel

    July 25, 2012 at 5:14 am

    Hi Paul.
    That is a great example for highlighting the complexity of our perception.
    However there is one point where I cannot follow your argumentation.
    If you have closely arranged microphones and a small combo or maybe a soloist then the reproduction of the recording via a pair of speakers will inevitably cause crosstalk resulting in combfilter effects. Our brain has to solve the problem of getting at both pinnae a twofold information now from two speakers instead of one single soloist. The brain might be able – having heard the live seession before – to recalculate the remembered impression when listening to the recording: an acoustical illusion comparable to optical illusions.
    I doubt that the same kind of illusion will be possible if I listen to the same recording in a perfectly arranged listening room.

    The solution can only be to record the sound field at my ears (in the concert hall) and recreate this sound field at my ears when sitting in my listening room. The minimum requirements must be: crosstalk elimination from the speakers and minimizing of acoustically relevent room reflections.
    Would you agree.

    I am keen learning more from your next post.

    PS

    That is not a recommendation for headphones lacking the filtering function of pinnae, head and shoulders.

    • July 25, 2012 at 5:59 am

      Good point and in this example – especially if you were far enough away from the stage – mono might even be better. I think you’ll find tomorrow’s solution interesting – at least thought provoking.

  2. Soundminded

    July 25, 2012 at 6:39 am

    I attended two such live versus recorded (LvR) demonstrations in the mid 1960s. One was with an acoustic guitar, the other with a 1905 Nickelodeon. These were conducted by Roy Allison then of Acoustic Research. The speaker was AR3, a model that usually impressed me as not being a particuarly accurate reproducer. What struck me wasn’t that the sounds from the speakers were identical to live but that they were remarkably similar on both occasions. It came as quite a surprise. I knew that the recordings had been made out of doors to avoid the double echo effect but I only learned recently that the Dynaco PAS3X preamplifier treble control had been boosted to compensate for the speakers high frequency rolloff.

    Floyd Toole dismisses the value of LvR demos and even cites Edgar Villchur’s (founder and President of Acoustic Research) papers on the subject.

    Here’s an interview with someone well known who tried an LvR and failed. That part of the clip starts at around 29:00. What’s interesting to me is not only didn’t he understand why he failed but that he had to be told by the audience that he’d failed at all. He evidently didn’t hear it for himself. (Would you trust the pronouncements of such an individual about audio equipment?) BTW, although he’s not a degreed engineer he claims his formal education focused on physics and chemistry.

    http://www.youtube.com/watch?v=_mEsuKqj5wA&feature=relmfu

    So the first question is can the sound of musical instruments as they would be heard in the same room you’re in be duplicated by a recording? What is required of that recording and the playback equipment if this is possible.

    The next question is the biggie. Can you make a recording played in a small room of a few thousand cubic feet which is what you have in your home sound like you’re in a much larger room, say a few hundred thousand cubic feet to over a million cubic feet? If it could be done, how could it be done? If it can’t be done why not? Toole says in another interview it can’t be done. I’m reminded of the fact that recently, within the last few years a mathematician solved a problem that took about 100 years of failed efforts first. I hope we don’t have to wait that long. I’ll be on Social Security by then.

    Since most of what we hear at a live performance at a large public venue is due to the reflections of sound from the large room, this question is of no small importance. I’d say the first order of business if you really want to work on this problem is to figure out exactly how the large room really works, what it’s doing because one way or another you are going to have to do the same thing. The last thing you’d want to do is go shopping for woofers, tweeters, amplifiers, cd players, phonograph cartridges, and speaker cables. You won’t find the answer there.

    • Soundminded

      July 26, 2012 at 8:20 am

      So where did Atkinson make his mistake? Where did he go wrong? He seemed to skirt the answer dancing around it without ever actually putting his finger on it. He matched the timbre and loudness of the piano but the sense of “bigness” was missing. Was it the physical size of the speakers being too small as he suggested? That may be part of it but IMO it’s the least of the difference. The real difference is in the way the piano launches sound into the room and the way the speaker launches it. Most of the sound coming from a piano is launched in directions away from the audience. In fact if you sit on the sofa in my music room you will not see or be in direct earshot of the harp, the strings, the sounding board, the elements where the sound comes from. If the lid is closed or in a concert hall removed entirely, ALL of the sound will reach you indirectly. The case is 1″ thick hardwood, not much sound will come through it directly to you. There will be some early reflections reaching you from near the piano helping you locate it but most of the sound will fill its end of the room and the reflections that constitute what you hear will suggest a large powerful source. What’s more the spectrum of the sound propagated in all directions will be about the same. Now what about the loudspeaker (I can perform the same experiment in my room with exactly the same result Atkinson got.) It launches a lot of its sound directly at you. As the frequency gets higher for each driver the angle of propagation gets smaller and smaller. For the tweeter, the energy in the top octave is practically beamed entirely directly at you. The reflections from the room are very different, much more restricted. What arrives at your ears is very different. It’s a small intense and rather feeble sound by comparison.

      Looking at the construction of most musical instruments and how they are played shows they almost all have one thing in common, they direct most or all of their sound away from the audience. For string instruments and percussion instruments this is rather obvious. The shape of the sond waves are approximately cylindrical or spherical. But what about for horns, that is reed and brass instruments, don’t they aim their sound mostly in one direction? Yes but for many that sound is directed away from the audience. For a tuba it’s up, french horn sideways, oboes, clarinets, bassoon’s down at the floor. For trumpets and trombones it’s a little different. they aim their horns diagonally down towards the floor but they are usually seated behind two or more string players in a symphony orchestra. The players in front of them, their music stands, and instruments block most of the direct sounds from reaching the audience. So most sound produced by most instruments arrives at our ears indirectly.

      What if a speaker system did the same? One that actually produces a spectrally accurate representation of the sound of these instruments produce would sound very much like those instruments were they in the same room with you. They’re no longer small sounding appearing to be coming out of a box. But what about instruments that aim much of their sound at you like a human voice or are small sources like a banjo, will they sound big and stretched out? Practical experience with just such speakers shows that the answer is no, they have the same perceived degree of bigness (or smallness) you’d expect them to. Why? Quite frankly I just don’t know.

  3. hahax

    July 25, 2012 at 7:02 am

    So the problem may be treat the room to eliminate it as much as possible and do recordings with all the cues on the recording. But can we do that?

  4. Tom Devey

    July 25, 2012 at 9:14 am

    I find it interesting that this comparison is always done with a small combo and the criteria is can you recreate the ‘feeling’ of that small combo in your listening room.

    What about a recording of a pipe organ playing Widor’s Toccata in a large European cathedral? There are plenty of spatial cues in such recordings. You can usually just get the sense of a large acoustical space simply through the ambient noise of the building which is captured in the silent moments of the recording. And the echos and die-offs associated with musical notes can provide at least a convincing illusion of the the acoustical space.

    Could it be that, like in RF, a recording in a large acoustical space is far away from the source (far field) and is reasonably well behaved, whereas the close miked combo is effectively in the near field and more difficult to capture the sense of space. Perhaps in the recording of the combo the ‘music’ overwhelms the sense of space whereas in the organ recording the space is an integral part of the sound, since you typically record an organ from a location in the building, and not in the organ chambers.

    Perhaps it is that the acoustical space is an integral part of the organ’s sound whereas with almost every other instrument this is not the case. Perhaps this is where ‘surround sound’ recording is of benefit, in providing that sense of space not typically captured in ‘live’ recordings.

    • Soundminded

      July 25, 2012 at 9:39 am

      “What about a recording of a pipe organ”

      In the mid 1950s members of the NY Audio League, predecessor to the Audio Engineering Society brought 4 AR1Ws along with 150 watt Western Electric amplifiers to Riverside Church in NYC for an LvR against an Aolean Skinner pipe organ. The rest as they say is history. Acoustic Research went on to become the most widely sold loudspeaker brand in the USA at one point garnering about 1/3 of the entire component speaker market. AR3 is exhibited at the Smithsonian Institution as an example of excellence in American engineering and manufacturing.

      As for reproducing the acoustics of a gothic cathedral or a concert hall elsewhere, that is at this point in time beyond the current state of the art. All publicized efforts have failed due to flawed technology. However, I give credit to anyone who thinks about it and even more to those who try even if they fail. At least they have the intellectual honesty and courage to not accept the existing technology this industry offers as a failure trying to disguise itself as success by redefining the problem from one it can’t solve to one that it can.

  5. hahax

    July 25, 2012 at 3:10 pm

    This is just me thinking. We’ve been discussing the problem of scale in music reproduction and we’ve been talking about the room and alluding to speakers being small as large factors in the problem. And I agree. But maybe we are forgetting other factors in scale reproduction that are at least significant contributors.

    I just put a new phono stage in my system(Iwas without one for years and I had at least 1000 LPs). And this phono has a reputation for sounding big(not really a precise term I know), bigger than most phonos. And sure enough after some breakin it’s really starting to sound big with good impact, bigger than lots of phonos. And I’ve noticed a similar affect when messing with my CD source and other electronics.

    It seems that we could have a weakest link situation. If any link in the reproduction chain sounds small in scale, the system sense of scale is diminished. This is one of the difficulties of a hobby like audio. With so many factors in the chain it’s a real problem to make a good chain and it can be difficult to find a weak link in such a long chain. And this is furthur complicated by the interaction of the audio links.

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