The Art and Science of Audio System Tuning: Part Three
|The Art and Science of Audio System Tuning: Part Three|
|Mike Vans Evers|
All Audio Electronics = Superset
Note: Areas 1-6 are subsets of the super set: All Audio Equipment.
A.P.T.: This stands for Asymptotic Pure Tonality and is a goal for both systems and components. (Please note: This is not necessarily THE goal, but it is definitely A goal.) Once a product/system has achieved exceptional levels of measured performance (a high degree of static neutrality) as well as an evenly balanced resonance response (a high degree of dynamic neutrality), its tonality will approach that of real life. However, nothing man-made is perfect, and we will always be approaching, but never reaching, the "Pure Tonality" of real life. (The definition of an "asymptote" is a straight line that continually gets closer and closer to a line with an infinitely extended curvature, but never intersects it.)
High Degree of Static Neutrality: There are numerous tests and measurements based upon sine and square waves: distortion, phase shift, frequency response, slew rate, dispersion, signal-to-noise-ratio, and other measurements such as rise time. These tests are representative of conventional thinking on the possible distortion mechanisms of audio components. For a system/component to occupy this subset of the larger set "Accurate," most conventional tests must be passed at the highest levels possible.
High Degree of Dynamic Neutrality: An even distribution of low-Q resonances, with few irregularities, is required for an audio system or component to reside in this subset of the set "Musical." At the present time, the test methodology relies on the human ear/brain combination.
"Accurate": Systems and components that measure well in at least a few of the many conventional measurements reside in this group.
"Musical": Systems and components that have a pleasant sound, rather than an "analytical" sound, reside here.
Not Musical & Not Accurate: Plastic clock radios, many boom boxes, and some rack systems.
It will not be possible to predict true sonic comparability between components from a manufacturer's "spec sheets," until a component's resonance response is MEASURABLE and is utilized as an everyday design tool by all audio equipment manufacturers. Why? Because this readily audible but as yet unmeasurable quantity is always AS significant as the conventional quantities that are measurable (distortion, frequency response, output impedance, etc.) In fact, a component's resonance response is quite often MORE sonically significant than any conventional quantity. Why? Because, as higher and higher levels of static neutrality are achieved, there will be less and less to cover up the sonic influences due to resonances (and other little understood phenomena). An audio system's resonance response has become much more audibly significant than vanishingly small levels of distortion.
A Tone Balancing Rationale
Products used to change the sound of an audio system, even though they aren't actually IN the accepted audio signal path, are often called "tweaks." When you "tweak" an audio system, you are actually "tone balancing" it. The physical nature of every tone balancing /tuning product (tweak) mandates that the resonance response of any system it is used with must change; if it is to be put on, around, under, or over a piece of audio equipment, IT HAS TO CHANGE the RESONANT SIGNATURE of the SYSTEM. Because the resonances have changed, the tonality and therefore the sound of the system must also change.
Resonance balancing is a skill that you can learn. The first step is to trust your ears. You know what you like. The available arsenal for making your system sound better is really quite formidable. Cones, pucks, dots, oils, bricks, platforms, and a host of other tuning products are readily obtainable. A suitable selection should become a part of your audio toolbox. Care should be exercised, however: just as no one wrench can turn every bolt, no one tuning product can fix all sonic problems. Tone balancing products are tools that are handy when it and the problem match up; otherwise they just take up space. There are no bad tools, just inappropriate ones.
Cones bricks, dots, pucks, jackets, discs, isolation platforms, etc. all change the resonant energy in audio components and accessories. These changes directly influence the harmonic balance and imaging of your audio system, thereby affecting your perspective on the music.
Tone balancing an audio system is like taking a saw, or other tool, to a piece of wood. The basic engineering of the wood is already done for you. All you have to do is to make it fit your own particular situation. The sound of your audio system is like that piece of wood.
Why Would I Want to Tone Balance My System?
While most audio companies have achieved a high degree of Static Neutrality through use of conventional tests like THD and frequency response, other elements that are major contributors to dissonance have been overlooked until now and can cause a lack of synergy between high-tech components.
Non-signal-path products are the main focus of this article because their use will significantly alter the resonance response and thus the harmonic balance of your audio system. While signal-path products also alter the resonance response, they usually cost considerably more than most tone balancing products. This makes learning how to balance your system a cost effective approach for achieving musical satisfaction.
By learning some simple balancing techniques, audiophiles will be able to: 1. Realize high quality sound without wasting thousands of dollars. 2. Eliminate the frustrations caused from buying a "latest and greatest" product that isn't so great after all (at least for you...it may be for someone else). 3. Bridge the gap between now and the time when a product's measurements ARE an accurate guide to its compatibility with the rest of your system.
It is not necessary to completely understand or believe in these techniques in order to begin using them. Don't be afraid to experiment. These changes will be far easier to undo than trying to get back the old amp that your new amp was SUPPOSED to trash.
In addition to these practical considerations, there is also this artistic consideration:
Pictures taken from slightly different angles or offset in small increments of time will sometimes portray vast differences in meaning. In the same way, the sound of most musical artists' material will vary from performance to performance. In part, this results from the artistic interplay between the various musicians (as well as from varying acoustics and sound reinforcement elements). This artistic interplay is the wellspring from which emotion and meaning are communicated to the audience. Because each artist brings a new perspective to each performance (sometimes the change is subtle, sometimes not), his ability to communicate with the other band members and with the audience also changes on a day-to-day basis...sometimes for the better, sometimes for the worse.
Occasionally, it is refreshing to be able to achieve a new perspective on a piece of music that is very well known. With the balancing methods outlined in this article, changes can readily be made to an audio system's sonic perspective that will enable the listener to derive new enjoyment from an "old friend." This is also an instance of artistic interplay and, as such, is as valid as any other aspect in the production and reproduction of recorded music. After all, this manipulation of perspective is the stock-in-trade of recording, mixing, and mastering engineers the world over.
What Is Tone Balancing?
Tone Balancing is tweaking with a twist; it is an approach that focuses on the audio system rather than the component or the tweak; it is the antithesis of the standard operating procedure. The hot-new-whatever will sonically help some systems a little, and help some systems quite a bit. However, the hot-new-whatever will sonically HURT some systems a little, and significantly hurt other systems.
Tone Balancing is the author's term for a system of techniques and a rationale that came about because audio components and systems were seldom, if ever, sonically neutral. When balancing a system, i.e. adding and subtracting resonances, you are changing the system's tonality and harmonic balance...as well as its imaging specificity and sound staging capabilities. Tonality is the starting point for all sonic qualities.
The-sound-of-an-audio-system-playing-a-piece-of-music is a sonic-portrait of that piece of music. The canvas for this music is your listening room, its acoustics create a sonic-canvas, and the harmonic balance of the system creates a tone painting on your sonic canvas. The tweakable nature of an audio system provides a great opportunity for you, the listener, to achieve a more musical perspective through this process of adding and subtracting the right resonances for your system. This process is called tone balancing.
Tone Balancing Your System
OUR GOAL: to increase our enjoyment level when listening to music. Our means are the application of Axioms 1 and 2.
Envision a three-legged table with a bowling ball balanced on its top. The bowling ball represents musical enjoyment. By keeping the ball at its highest level, i.e., off the floor, we achieve the maximum level of enjoyment with our system. The three legs represent the three major factors we have to balance in order to keep the tabletop level and the bowling ball off the floor.
These three major factors are as follows:
Acousticians design recording studios utilizing scientific principles which allow them to design OUT many of the flaws that most of us have to live with in our listening rooms. Standing waves (room resonances) are an unavoidable consequence of having a roof, walls, and a floor. The dimensions of your listening room determine the distribution of its standing waves. Because most of our listening rooms aren't designed by acousticians, our standing wave (room resonance) distribution will probably in no way resemble the ideal.
Because of this, the listening room is a MAJOR factor in the sound of our systems. The same system will sound different in different rooms. Just ask any died-in-the-wool audiophile who has moved. Equipment resonances that complemented the previous room's resonance modes often conflict in the new room. In addition, power in different cities, or even different parts of the same city, cannot sound exactly the same. (See Appendix E.)
2. The Static Neutrality of the Components
The equipment we buy should utilize the highest level of engineering and technology that we can afford. It's true that superior specifications have not always been a key factor in the best sounding equipment. However, superior measured (static) neutrality can be sonically obscured by an irritating resonance response. (It's always best to compare apples to apples. For example, don't compare single-ended tube amp harmonic distortion specifications with those from a conventional solid state amp and expect to draw a valid conclusion.)
3. The Dynamic Neutrality of the System
There are thousands of manufacturers, brand names, and models of equipment; consequently, there are billions of possible combinations. The manufacturer that designed the equipment, the reviewer who wrote about it for your favorite magazine and your dealer ALL have different systems. Each of these systems will sound different. Each system's owner will feel that he has THE correct idea about the sound of any given piece of equipment. However, your room, your mix of equipment, stands, cables, etc. WILL be different. If a particular piece of equipment makes the resonance response of your SYSTEM more even, you will probably like it. If not, you probably won't. This is because your ear will be drawn to the colorations caused by a more uneven resonance response, distracting you from enjoying the music. (Tone-balancing the system in order to even out the resonance response irregularities can often cure these distractions. This will increase the system's level of Dynamic Neutrality, produce a more pleasant sonic-portrait, and increase your level of enjoyment.)
Tone Balancing the Bass Response of the System
"The whole is greater than the sum of its parts" is a phrase that can be used to describe an in-tune audio system's bass response.
It is important to note that our focus is the bass response of the system, rather than the bass of any one component. This is called a "systems approach". Even though we will be working with only one component at a time, we are interested only in how well its bass integrates with the bass of the SYSTEM. Individual components by themselves cannot make sound, much less music.
It is usually best to get the bass as even as possible before tuning the midrange and the treble. While the following methods of tone balancing the bass also affect both the midrange and the highs, for this step, we should only be paying attention to how they affect the bass.
[However, if the highs are brash and annoying, it might be best to first tame the highs to at least a minor degree, by one of several methods: 1) Place heavy or dampening-type objects (rubber pucks, MDF or Teak blocks, sand or lead-shot filled bags, a phone book, etc.) on top of front-end components. 2) Remove metal type spikes or cones from under components, one component at a time, until the highs are more balanced. 3) Fill lightweight metal equipment stands with playground-sand (available from home improvement or other such stores) so as to dampen the upper harmonics of the stand's resonance response.]
There are 3 elements involved in tuning the bass response:
1. The frequency response of the speaker
How low it goes and how flat it is in the bass region.
2. The energy storage of the room
Standing waves are unavoidable. Very few listening rooms are designed by acousticians. Because of this, you will almost certainly experience an uneven bass response at your listening position, even with perfect speakers.
3. The energy storage of the equipment and cables
Mechanical resonances are also unavoidable. The weight of the component together with the spring-like rubber feet forms an energy storage mechanism (resonance). This mechanical energy storage affects the electrical properties of the wire in the equipment, thus affecting its sound. The directionality of the power cords and connecting cables in your system also play an important factor in the smoothness of the bass response of your system.
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