Back thataway several posts I opined that the most important component in your audio system is the recording engineer responsible for capturing the original musical performance. It’s a fact, kids. So now what’s next? Surely it’s time to think about D to A converters, or low distortion speaker cables made only with organic oxygen free copper, or yada yada yada. Nope. The second most important audio component in your system is your listening room.
Since the goal is (repeat again after me) to produce the most believable sonic image of the original, we need to be able to transmit this sound to your ears from your speakers in the most accurate and uncolored way possible. This means we need to keep from adding or subtracting any sound levels that were not part of the original. The truth is, our ears are not too smart. But our brains will instantly call fowl if the spectral balance is messed up.
So how do we go about dealing with this? There are several things to consider about the room (and the space within it) which will have a huge effect upon how convincing the sonic image is to our brains. Let’s take them one at a time.
First, we need to understand a bit about room acoustics. Walls are required in most rooms. Sonically they can do good things or bad things. Which they do depends upon their construction, dimensions, and placement relative to one another. I will spare you the math associated with how to answer this question in favor of some general do’s and don’ts:
- Parallel walls are bad;
- Curved or non parallel walls are good;
- Sloping ceilings are good;
- Sloping floors are good for sound but can be dangerous;
- Avoid a room where walls (including the floor and ceiling) are equal or multiples Eg: 10x10x10 is the worst possible; 10x20x10 is nearly as bad;
- Having large heavy objects in the room is good (unless they are the listener);
- Walls should be rigid. 16″ on center studs and drywall is not a wall at 40 Hz;
- Room size is also dependant upon your speakers and available amplifier power. More on this later too;
OK Second, we need to determine the optimal location for your speakers. The distance between your speakers and a rigid surface (such as a wall or floor) will have a big effect upon bass response. Um, no. The speakers will respond almost the same no matter where you put them. What I should say is, it will have a big effect on how loud and the how smooth the bass sounds to you depending upon where your ears are in the room. Again there is a ton of math you can use to determine this but for most folks there are practical considerations about where your speakers end up in your home environment (such as marital bliss). So more do’s and don’ts:
- Putting speakers deep in corners of the room is very bad. It’s scary in there for them;
- Sitting on the floor is bad (if you are a speaker);
- Speakers need some distance between them. For now let’s just consider a classic 2 channel stereo system. A good starting point is the distance between them should be roughly the same as the distance to your ears;
- Let your speakers away from the wall. They like to join the party;
- Try to maintain an equal distance between each speaker and an adjacent wall. Symmetry is good;
Remember: All this is primarily about the bass reaching your ears. For a simple classic two speaker system, it matters not how much you spend on “technology”. No amount of equalization will cure a bad listening room acoustic problem. The uniformity of amplitude across the low end of the spectrum as well as the absolute low frequency limit will both be highly influenced by the room shape, construction, contents, where you are, and where your speakers are in it. This is laws of physics folks. Get used to it.
Middle and high frequencies are a different problem for room design. They react to their surroundings in quite a different way from the low end. Bass energy tends to go through surfaces easily. Middle and especially high frequencies are easily reflected by hard surfaces and much more readily absorbed especially by soft materials such as rugs or drapes. In general, at least some broad surfaces should have damping (rugs, drapes, wall hangings). The exact amount of these soft acoustically absorbent materials will depend upon your speakers and the size of the room. Too much softness and the sound will lack openness and sparkle. Too little softness will mean unpleasantly bright and hollow audio. Given the right balance, the sound from the loudspeakers will reach your biotransducers (ears) in tact and with the least amount of coloration from your listening room. Listening trial and error will carry the day on this one.
Next time: Speakers 101
Sooo we are stuck with having to be sonically transported to the place where the recording was made / “You Are There”. This presents a whole different list of psychoacoustic problems. First off there is a vast difference between recording a symphony in a concert hall, and, say, a jazz trio in a club. The concert hall is huge compare to the club. Reflections from the concert hall will be slow compared to the jazz club because of the time it takes for the sound to reflect (we call this “Ambience”) from the large hall. We have to rely on the skill of the recording engineer to select the best microphones and place them in such a way that they will pick up a convincing balance of direct sound and ambience. He really is the most important component!
OK. For now let’s pretend we have the amplifier power and speakers to handle the dynamics of both. How do we handle the problem of our reflected sound in our listening room? Won’t this additional “return” confuse our ears and make the sound seem unnatural? Or do we have to haul our system outside where there are no walls or ceilings?
Hold on. There is good news kids. If we listen in a reasonably small area, several things happen. We find ourselves relatively close to the speakers. In this “near field” environment, the ratio between the direct sound from the speakers to the reflected sound from the room is quite low. Your ears will not be aware of the small amounts of “room” acoustics choosing instead to “believe” the much louder near field energy. And with it comes the ambience which has been recorded from the concert hall along with the direct sound from the instruments. “You Are There”. More good news: There are things you can do to your listening room to improve things further.
Next time: “The Second Most Important Component”
Hi kids! I’ve been kinda’ busy with my day job and haven’t had a chance to resume our audio safari. I promise to do better.
But for now please have a look at this article about formats and recording. Sound familiar???
OK just to review: The holy of holies of audiophillia is to create a sound field in the home that is indistinguishable from what you would hear were you listening to the original performance. Sounds simple enough. For now we are going to ignore any of the other possibilities such as creating a sound field that is completely believable but never really existed either in the studio or concert hall.
The guy (or woman) behind the glass in the recording studio has almost all the control over what you hear in your home. True, we can make a lot of changes to the recording in the home, and in fact do whether we want to or not. But once the music is in the can, most of the things that the recording engineer has decided to do, can’t be undone.
The first decision he has to (or should) make is whether to make the artists sound as if they are in the space of a concert hall, or actually in your relatively tiny listening room. Will they be here or will you be there? How in the world is that accomplished?
To answer that question we need to take a trip to Africa about a half million years ago. Your great great great (etc) grandpa is out in the savannah looking for a meal. He is not alone. There is also this big hungry cat with sharp teeth and claws about to make grandpa his lunch. The cat moves through the bushes making a rustling sound. Instantly grandpa freezes in his tracks, turns, and runs for his life for safety. He was able to save himself because he had developed some pretty sophisticated natural listening technology and signal processing. And lucky for us, we are the recipients of this evolutionary prize ability without having to contend with saber tooth tigers.
Our hearing enables us to precisely and almost instantly identify arrival time and volume differences between the sound detected by our two ears. And the processing power of our brains instinctively (remember the big cat) determine location and distance to the origin of the sound.
Now if the man behind the glass is an engineer worth his salt, he knows all this. And he also knows how to place his microphones and select his recording environment to create your (the listener’s) point of view.
If he wanted to bring the performers into your listening space, he would need to go back to Africa and put them outdoors where the their music will arrive at the microphones directly from the performers without them picking up any sound being reflected off of concert hall walls or ceilings. That way, when it is played back, what you here is the performers modified only by the walls and ceiling (and floor) of your listening room. They would be here.
Problem is that it’s hard to record outside with wind and aircraft and wildlife all adding their voices. And it’s impractical to record in an anechoic room (one where all the surfaces absorb sound instead of reflecting it). And unless all the reflected sound is eliminated, your ears and brain know there is something unnatural going on. This is because they would be hearing two different sonic time arrivals, one from the hall acoustics at some distance, and a much closer set of arrivals from the acoustics of your small room. And no matter what kind of fancy processing you choose, the sonic damage has been done.
To be continued…
So what does that mean “Down in the Noise”? Several possibilities. The literal definition is an attribute which is so small that it is masked by background noise. We will talk about background noise and dynamic range later. For now I want to use it in a more figurative sense. Namely some (usually unwanted) attribute or characteristic of our reproduced sound that in practice makes no difference to achieving the goal of completely realistic reproduction. It could be distortion, or lack of smooth frequency response, or even digital artifacts. But none of these are deal breakers. They can easily be down in the noise.
OK. Hold on. I can hear you all now saying” I thought you said achieving perfect accuracy in reproducing the original sound field was required.“ Well it is a nice idea but for all practical purposes it is unfeasible. The guy behind the glass has other priorities. And no matter what you spend on your system (or room acoustics) you will never achieve a perfect copy of the original. It’s a good thing we all have a brain (no comedians please). Because in reality all you need to do is to fool your brain into believing the sound field is authentic. More on this later too. Still with me?