Wednesday, 6 July 2016

“Tell Them We’ve Already Got One!”

Let me describe something I was very fortunate to be able to try one time, but which very few of us will get the opportunity to experience.  I am talking of entering an anechoic chamber.

An anechoic chamber is a room specially designed for the purpose of conducting carefully calibrated acoustic measurements.  In normal rooms, any sound generated anywhere within the room will travel rapidly to all other parts of the room by bouncing off the walls (including the ceilings and floors).  Therefore, if we attempt to measure the sound in a room we very quickly find that it is impossible to distinguish between sounds which originate directly from the source and those which have travelled via multiple bounces off the room boundaries.  This is important, because these multiple signal paths cause the signal to be reinforced, cancelled out, or anything in between, thereby rendering many forms of measurement entirely useless.

The solution is to create a room in which sound waves, when they hit one of the walls (or floors, or ceilings), is instantly and totally absorbed and none of it is reflected back into the room.  Such a room generates no echoes, and is therefore termed ‘anechoic’.  These are particularly useful for designing things like microphones and loudspeakers, and enable detailed and accurate measurements to be performed in a way that would be virtually impossible otherwise.  You’d think that every loudspeaker manufacturer would have one, but they don’t.  They all wish they did, but most of them can’t afford such a preposterously expensive luxury.  The best they can hope to do is rent time in somebody else’s (most likely in a university research centre, or some other such institution).

What is particularly instructive is to get somebody to step into an anechoic chamber for the first time, and ask them to sing a song or play an acoustic instrument.  You can bet your mortgage that they will stop singing or playing within less than a second.  What they hear are sounds so alien to them that they can’t help but stop abruptly.  It only works first time, because once you know what is going to happen you aren’t so taken aback.

The sound of a voice or an instrument in an anechoic chamber is so utterly unlike anything you have ever heard before that it just stops you dead in your tracks.  Same goes for a loudspeaker playing in an anechoic chamber.  It is a totally dry sound, devoid of all character, expression, depth, or life.  After stopping abruptly, the second thing you will do is lick your lips, because the sound is so dry, so arid, so utterly parched, that it seems to draw the moisture from every pore in your body.  It is a profoundly unnatural environment.

And yet, the sound of a voice or an instrument in an anechoic chamber is the most accurate representation of that sound.  That is precisely what that voice or instrument actually sounds like.  Only the sounds travelling directly from the source to the listener will reach the listener.  All other sounds will be totally absorbed as soon as they hit any of the walls.  This is as accurate as it gets.

Outside of the anechoic chamber, the sound you hear is the sound of that instrument playing in a given room.  The difference between what you heard inside the chamber and outside is the contribution of the room to the sound.  That contribution is colossal.  Indeed it is fundamental to how we perceive the sound.  The magnitude of the difference serves to ram home the point that everything we hear every day is the product of the various sound sources modified by the environments in which we both exist.  The same orchestra, for example, playing in two different concert halls often sounds like two different orchestras.

This is important to grasp, because it serves to illustrate the futility of one of the holy grails of the audio industry - or more precisely of many of the critics who presume to influence the industry as to what it should be doing.  This particular sacrament requires that the goal of a high-end audio system is to recreate the sound of the original instrument.  But the sound of the original instrument is the desiccated sound from the anechoic chamber, and that is not what people want to hear.  What they want to hear is the sound of the original instrument played in the original location, but they want to replay it in a different location.

That presents us with two separate philosophical problems.  First, how are we to know what the original performance actually did sound like in the original location?  Unless we were there at the time, we can’t.  Second, our loudspeakers are located in their own separate and different acoustic environment.  If ‘simply’ reproducing the musical instruments themselves in our own listening environment is challenging enough, it is a different challenge entirely to reproduce the audio environment of one room inside an entirely different room.  Just consider recording a violin in an anechoic chamber, and then trying to reproduce the sound of that anechoic chamber in your own listening room.  Take it from me, it is not possible to come even close.

So what is it we actually want from our systems?  I believe we just want to be convinced.  We listen to something and ask ourselves how convinced we are by the illusion that our system has created.  The best sound systems do recreate a good illusion of a complete acoustic space.  However, for most - if not all - of our recordings, we have no idea whether that space is the same as the one in which the recording was made.  But if we can be convinced by what we hear - transported into a listening experience - surely that is all we can realistically ask.  I have long ago stopped asking myself if the sound I was getting was ‘correct’.  There is no ‘correct’.  Nowadays I ask only whether - and to what degree - I am convinced.

I think this goes some way to explaining the pangs that most of us face as we periodically upgrade our sound systems.  Critics charge that we are never satisfied, so why bother in the first place.  And there is a lot of truth to that.  We buy a system, express our happiness with it, listen to it for a few years, and then upgrade it.  Rinse and repeat.  With each new system, not only are we satisfied that it is better than the old system, but suddenly the old system - to which we were formerly devoted - is now somehow inadequate and no longer lovable (other than through the distorted lens of nostalgia).  We cannot go backwards down the audio path and still retain the same sense of joy that powered us on the way up.  All this, of course, assumes that the upgrade path was always followed wisely and judiciously.

What is happening, I suggest, is that on each path up the upgrade chain we are re-setting the bar against which our system’s ability to ‘convince’ us is measured.  The whole point of a significant upgrade is to significantly enhance your system’s ability to convince you that it is better recreating the original soundscape.  If it can pull that off, it will permanently re-set your bar.  It now takes an even greater level of fidelity to improve upon the trick of convincing us.  Once you’ve heard something, you can’t ‘unhear’ it.

When I was a young man just setting out with this hobby, most critical evaluation of audio systems - particularly loudspeakers - was focussed on the degree to which the sound took on identifiable tonal colourations.  And indeed, back in those days colourations were indeed a dominant factor.  One product which I recall having a particular impact in the marketplace was the Kef R104aB loudspeaker, which was noted for having particularly low levels of colouration.  I used a pair once for a few weeks and confirmed that yes, indeed, they did have a particularly uncoloured sound.  But at the end of my time with them I realized that while they were undeniably uncoloured, they didn’t seem to float my boat any more as a consequence.

I wasn’t smart enough yet for the penny to drop, but yes, shortly thereafter it did so.  I have long since realized that for my own particular musical enjoyment, tonal colourations are not a major limiting factor.  I am more than willing to put up with them if they are the price I have to pay to realize the type of performance which does float my boat, which are imaging stability and soundstaging, dynamic range (both micro and macro), and what is dismissively called PRAT (Pace, Rhythm And Timing).  With all those requirements satisfied, I am willing to put up with tonal colourations that other people might find to be cause for criticism.  Having said that, though, major advances have been made in the elimination of tonal colourations since the good old ’70’s.

So that’s where I put my stick in the ground.  As far as tonality is concerned there are no absolutes.  Tonal colour is only partially provided by the instrument itself, and is dominated by the acoustics of the room.  So when it comes to judging sound reproduction there can be no such thing as Harry Pearson’s much vaunted “Absolute Sound”.  There are no absolute points of reference other than an anechoic chamber, and nobody would want to listen to anything that sounded like that.  The most important milestone of any audiophile journey is when you finally understand what it is that YOU want out of your system - whatever that is - and achieve comfort in the knowledge that that is way more important than what some other audiophile wants out of his.

BTW, have any of you figured out the reference in this post’s title? :)