The Art & Science of Audio Tuning: Part Four
|The Art & Science of Audio Tuning: Part Four|
|Mike Vans Evers|
|1 August 2000|
"…check out the directionality of your digital cables, as its direction will also affect the bass. Additionally, the polarity of two-prong AC cords will affect the bass of an audio system. Getting the orientation of your cables optimized for your system can be a fun and rewarding way to get more enjoyment from your system."
The first step is to work with the energy storage of the room/speaker combination. You start by moving the speaker and/or listening position around in order to get the least lumpy bass. This step costs nothing, but does take up some of your time. There are many articles and speaker reviews, which spell out how to get the linear bass response from a set of speakers in a listening, room. There are even several computer programs available to guide you in this task.
To perform a quick test for evaluating your need for room tuning, pick a CD track with many bass frequencies, play it several times to familiarize yourself with it, and then pile some couch pillows on the floor in the corners of your room. You will definitely lose some bass. Whether or not this is a positive step depends on your taste and your system's needs. For those who aren't allowed pillows in the ceiling corners, this might open other avenues for room tuning. (Note for the do-it-yourself types: Fabric stores have a large selection of pillows and foam and enough fabric styles to match any decor.)
The second step deals with the bass characteristics of the system's cables and also costs nothing. The manufacturer's recommended directionality of a cable is not cast in stone. The manufacturer's system is almost certainly different from yours. The direction of the arrow may be the opposite of what will be best in your system. In for a penny, in for a pound. While you're at it, check out the directionality of your digital cables, as its direction will also affect the bass. Additionally, the polarity of two-prong AC cords will affect the bass of an audio system. Getting the orientation of your cables optimized for your system can be a fun and rewarding way to get more enjoyment from your system.
Here we will be working with the energy storage of the equipment; i.e. the panel resonance’s and sprung weight of the electronics. Our goal is to reduce the amount of "lumpy" bass at the listening position by using a combination of coupling-type and de-coupling-type feet. An examination of how coupling-type feet work will be helpful in understanding this step:
To recap: Audio equipment usually contains wire and PC boards. These act like mechanical tone controls (Axiom #1). Most decoupling-type feet cause bass energy to be stored. These spring-like feet, together with the weight of the equipment, form a bass energy storage mechanism (resonance) which enhances those same bass harmonics in the music that coincide with the frequency of this resonance. If this bass-energy storage in the equipment coincides with a gap in the room's resonant signature or the speaker's frequency response, it smoothes the resonance response of the system resulting in a positive change. However, if it coincides with a clump or a balanced area in the room's resonant signature, it makes the resonance response (and the sound) worse. (See Axiom #2.) (In any case, personal preferences will usually determine what sounds "right", smooth or accentuated bass.)
By placing a set of energy transmitting (coupling-type) feet under a piece of equipment, an audiophile is exchanging one bass bump for another. The compliance (springiness) of shelves is much lower than that of rubber feet; the amount of energy that can be stored will be reduced. The mass of the component will be free to interact with the stand in a more direct manner, and the resulting bass bump will be lower in magnitude. The new bass bump will also be lower in frequency if, and only if, the stand's bass resonance is lower in frequency.
PLEASE NOTE: Solid coupling-type feet DO NOT ISOLATE! This statement is true for all cone type feet from all manufacturers. Remember this: if it is Rigid, it Resonates [RIGID RESONATES]. Because cone-type feet are made from a rigid material, they must resonate, usually at an audio frequency. On the other hand, cone-type feet can have some areas of the audio frequency response where they will dampen transmission of mechanical vibrations. The resulting new distribution of resonance and absorption will change the resonance response of the system and therefore its sound. However, this modification of the transmission response does NOT make a cone-type foot an isolation device. A serendipitous change in sound is all that is often necessary for many people to believe whatever claims a manufacturer may make. (This statement is not meant to call into question the veracity of any manufacturer. It is, however, meant to set straight the actual working nature of the device.)
Procedure for Using Coupling and Decoupling Feet
"The placement of the Tuning Block affects the vibration pattern of a chassis bottom panel or top cover. This affects the harmonic balance of the mids and highs in the sound of your music."
Some systems will need every component coupled; some systems will need its components DE-coupled only. Most will need a mix of the two techniques. It is also possible to partially couple the chassis by placing a coupling foot under, for example, just the front, and by leaving the back half on its rubber feet. This gives an effect in between that of coupling and decoupling.
For tuning the bass, the type of material used is as important as the fact that a hard material is being substituted for a soft material. Coupling feet made from small blocks of wood such as oak (7/16" × 3/4" × 1") can be made and used for bass tuning.
However, it's always better to have several materials and/or types of wood available when it comes to tuning the bass, midrange, or treble of your system. There are many tuning devices currently available. Rather than debate which ones are the best, we recommend a different approach: use anything that makes your audio system sound better to YOU. The VansEvers Company makes different and sometimes unique tuning products. We feel that our Tuning Blocks offer the most flexibility because they are offered in many different types of wood (and each type of wood has its own unique sound). In addition, for those of you so inclined and equipped, give us a call and we'll tell you where to get the wood so that you can make your own tuning blocks. However, anywhere in the text that it says to use a VansEvers "Tuning Block" feel free to substitute a Tip Toe* or any other product that you may prefer. The mechanism will still hold true: the resonance response of the new object will alter the harmonic balance of your system. The positive or negative response this will elicit is not tied to the superiority of the theory that has been used to validate this product. The concept that should hold the most value to you is your reaction to the change in the sound of your system: is the sound better or worse? If the sound is better, keep the change. If the sound is worse, put the tweak back in your cache of tuning products until another time when it may be perfectly suited for correcting a problem in your system's resonance response caused by a new component or some other changed factor.
Step I. Select a piece of music or test disc that has a range of music or notes that cover the bass spectrum. Play it several times until you are familiar with the strong notes and the weak notes.
Step II. Place coupling type feet under the heaviest component in your system that doesn't already use them. Play the same music again. If the bass is more even, leave the feet there. If the bass isn't more even, remove the feet and move to the next heaviest component.
Step III. Repeat Step II with each piece of equipment in your system. Include transports, power conditioners, and other things you may feel cannot possibly make a difference. Components sitting atop isolation platforms are also candidates for this procedure. The isolation of these platforms only reduces vibrations transmitted through the shelf. Vibrations will still travel through the air and connecting cables.
Step IV. Start over: experiment with the heaviest component first as in Step I, but use your aftermarket decoupling feet this time. (Yes, this section IS about coupling type feet. However! No one concept works 100% of the time. That's the reason there are so many competing concepts/products out there, each with its own legion of supporters. The idea is to mix these concepts to your advantage.)
Step V. To add another, and lower, dimension, place heavy objects on top of a component to change its bass resonance frequency. The heavier the object, the lower the resulting resonance and therefore the lower the bass "bump" in the sound of your system. This technique will broaden the effectiveness of coupling and decoupling methods.
There are a number of audiophile-approved "heavy objects" on the market. They work well. It helps to have several objects with differing weights to work with, though. Heavy books and leftover barbell weights can be very useful. Just remember that with barbell weights, the metal, or plastic they're made from or covered with will also become part of the sound. Wrapping the object with several layers of a suitable dampening material, such as soft cloth, may be able to tame objectionable mid and high frequency resonances. Lead diver's weights are inexpensive and also very useful. (To keep from getting lead residue all over you and your equipment, a layer or two of cloth or cloth tape should be considered mandatory.)
At this point, your bass should be a lot less lumpy. For those really serious about getting the best sound possible, it may prove beneficial to go back and repeat at least the first three steps.
To continue this discussion, I will concentrate on the characteristics of a product that I know very well: the VansEvers Tuning Block. The resonant signature of a VansEvers Tuning Block, or any other resonance control device, affects the energy it transmits or absorbs. The placement of the Tuning Block affects the vibration pattern of a chassis bottom panel or top cover. This affects the harmonic balance of the mids and highs in the sound of your music.
Wood has obvious influences on the sound of musical instruments. The same style of instrument made from another type of wood will create sounds with a different harmonic balance. Each distinct variety of wood has its own set of frequencies that will be absorbed because of internal friction. Other frequencies will resonate because of that wood's elastic properties. Still other frequencies will be transmitted without attenuation. This adds up to a characteristic sound for each particular wood.
The VansEvers coupling-type feet are made out of many different types of wood, from Amarello to Zebrawood. (Many of them are quite beautiful.) Our goal is to make the resonance response of the system more of a level playing field and thus more dynamically neutral. It is necessary to have a variety of materials from which to choose, because each system will have a unique set of strengths and weaknesses.
The following properties are those that we have observed for unfinished (other than smooth-sanded) wood blocks approximately 3/4" × 1" × 1.5" in dimension:
Basswood: This light-weight softwood sounds thin when replacing wood types with the same mid-bass emphasis (a size phenomenon). It resonates (enhances) in the upper treble area; it sounds recessed in the lower and upper mids. (Basswood: Tilia Americana)
Bloodwood: This is a reddish straight grained, fine textured hardwood that has a high frequency resonance in the mid-treble. It also resonates slightly the lower midrange and has a lack of energy in the middle and upper midrange. (Bloodwood, Brosimum paraense, has a wonderful smell when freshly sawn.)
Bocote: This can be quite beautiful wood. It has good extension in the highs and sounds quite "solid" because of a slight emphasis in the lower midrange/upper bass. It also has a slight emphasis in the mid treble. (Bocote, Cordia gerascanthus, which is native to Costa Rica, is considered an endangered species, and therefore will not be offered by the VansEvers Co.)
Cherry: This American hardwood has more mass than Basswood and therefore resonates at a lower frequency. Its area of enhancement is in the upper midrange; its peak is lower and broader than Basswood. Cherry (Prunus serotina) is not distinctive in its looks, and can easily be mistaken for other woods such as maple.
Cocobolo: This imported hardwood has one enhancement area in the lower and mid-treble, another in the upper bass. This size block also sounds recessed in the lower midrange. Cocobolo (Dalbergia retusa) has an alternating color scheme. The thin dark brown bands are from the dense winter growth. The lighter summer growth's color can vary from golden orange-red to a reddish dark brown. The grain ranges from straight to wavy, and the texture is usually fine. Some individuals will have allergic reactions similar to those from poison ivy upon exposure to sawdust from cocobolo.
Ebony: This is an African hardwood. Some of the darkest black varieties (Gaboon) are almost unobtainable (in large quantities) today. Its emphasis range is in the upper treble and top octave. (Gaboon ebony: Diospyros mespiliformis)
Lignum Vitae: This is a medium to dark-colored (brown or black) hardwood whose grain is often strongly interlocked, very irregular, and "roe"y; the sapwood is pale yellow or cream colored. Its upper resonant peak is a narrow band in the upper treble; the lower resonant peaks are in the middle midrange and middle bass. Correspondingly, it sounds weak in the lower mids and the upper midrange. It has less top octave than amarello. Lignum Vitae (Guaiacum officinale) is very waxy, up to 30% by weight, and has growth rings that are very thin; the resulting wood is so dense and heavy that it will not float. It is, however, compared to some other woods like Pernambuco -- seemingly -- relatively soft. This is an interesting paradox in the light of its use as ship's propeller shaft bearings...where it lasts as much as three times longer than steel or bronze bearings.
Mahogany: This wood is imported from many different countries, and even continents, as there are some 40 species. The darker (denser) varieties enhance the lower mids and the upper mids. The sound will become warmer with more midrange presence. There is also a lack of support from the mid treble up. The lighter varieties shift the enhancement up, and sound less "lumpy"; the highs are not quite as extended as zebra's. (Mahogany dust can be toxic.)
Maple: This is an American even-grained wood, and there are over 20 native species. It can be either hard or soft. Rock maple is the hard variety. Our sample had emphasis in the mid-bass, upper-treble, and top octave; there was a loss in lower midrange and upper bass presence.
MDF: Medium Density Fiberboard. This is a manufactured material made from fine sawdust. The MDF at our disposal absorbed lower treble and upper midrange energy . This makes the treble sound thin even though it is not accentuated. There is also a slight emphasis in the lower midrange. (Formaldehyde is used in MDF's manufacture; cutting and sanding MDF will liberate this pungent gas.)
Oak: This popular American coarse-textured wood is available at most large lumber stores; it is available in both red and white varieties. The enhancement area of common Home Depot red oak is in the upper midrange. There is a de-emphasis in the upper-bass/lower-midrange, and the highs are extended and smooth. Southern oak trees are faster growing than their northern counterparts, which accounts for their coarser texture. (Quercus alba: white; Quercus rubra: red)
Olivewood: This wood is indigenous to the Mediterranean area, and has a nice full middle and lower midrange; it rolls off high frequencies starting at the upper midrange. Its sonics are similar to cypress. Olive (Olea europaea) is light tan with greenish/grayish darker brown stripes.
Pequia Amarello: This hardwood is light yellow in color. The middle midrange is emphasized in comparison with the upper and lower midrange. Its upper enhancement range is the upper treble and top octave. Too much energy in this area will decrease depth of image. Its lower range of enhancement is in the middle bass. (If you're going to make blocks of Aspidosperma tomentosum yourself--always use a sharp blade...otherwise you'll generate an abominable smell, and even with a sharp blade, it can sometimes still smell bad...and, just wait till you sand it!!! To be truthful, it doesn't always smell bad when being worked, however, it does far too often for my olfactory nerves. )
Pernambuco: Another imported hardwood. The treble enhancement is nicely broad. Its main enhancement area is the middle midrange; it sounds quite even elsewhere. Its hue leans slightly toward orange. It is often used to make bows for violins, cellos, etc. Its species name is: Caesalpinia brasiliensis S.
Poplar: This readily available wood highlights the treble and lightens the lower midrange and bass, even more than Basswood. There is a slight emphasis in the lower treble and the middle midrange. The name is actually a misnomer. This greenish-gray hardwood which is commonly mistaken as poplar is really a member of the magnolia family of trees. Yellow poplar and Tuliptree are also common names for Liriodendron tulipifera.
Purpleheart: An imported hardwood whose name graces wood from approximately 20 species; it is dark in the upper-treble and top octave. Its resonant area is the lower and middle midrange. The grain is typically straight with medium to fine texture, and the color vividly purple (except when fresh-cut, when it is grayish to a dull brown). Peltogyne porphyrocardia is one of the species of purpleheart.
Teak: This wood is popular with the yachting crowd because it weathers well. If your middle midrange or top octave needs taming, this is a good one to use. Its resonance peak is in the lower midrange/upper bass. Burmese teak, Tectona grandis, is straight-grained with a coarse and uneven texture.
Zebrawood: This light golden-yellow to pale yellow-brown imported hardwood is striped like its namesake with narrow dark-brown to almost black veins or streaks. It has a smooth peak in the lower treble and does not roll-off the top octave. While it has an emphasis in the upper-bass, it has less upper bass/lower midrange energy than teak, and less top octave than amarello. The dust and odor from cutting or sanding Zebrawood (Microberlinia brazzavillensis) can smell unpleasant and even be an irritant.
Tuning Blocks or other coupling-type feet placed at the extreme outside edges of a chassis allow its bottom panel to vibrate freely. This enhances the highs of the system. If you need more "air," place the blocks near the edge, and use a suitable wood. To lessen the contribution to the highs, use a "darker" sounding wood and/or move the Tuning Blocks closer towards the center.
More highs: move feet toward outside edge of chassis
Less highs: move feet toward center of chassis
Step 1. Select a piece of music that you know well. It should be something that has a rich and well developed midrange.
Step 2. Start with the coupling feet nearest the source. Try different woods (or other materials) until the harmonic balance is closer to being correct. Once you get acquainted with the sound of several types of wood, experiment with combinations of wood types. This will broaden the effect.
Move the blocks closer to the outside edge of the chassis for more highs, further underneath for less.
(Note: Either select wood or other materials with the same general bass characteristics, or be aware that the bass of the system will also change and might need re-tuning.)
Step 3. Go to the next piece of equipment and, using tuning blocks, repeat step 2 as necessary.
As valuable as tuning blocks are underneath a component, they are just as valuable a tuning method (if not more so), atop audio components. Components that are sitting on original feet, aftermarket coupling/decoupling feet, or isolation shelves/platforms can all benefit from Tuning Blocks placed on that component's top cover. The effect is twofold: The cover's high frequency vibrations will be somewhat dampened, thus reducing their contribution to the sound of the system; the resonant signature of the wood or other material will be added to the sound of the component.
Two or more types of wood can be stacked, one atop the other, for a mixture of the sounds of the two woods. The relative position of the stacked wood is important. For example, Basswood on top of Lignum Vitae sounds different from Lignum Vitae atop Basswood.
Again, I will illustrate tuning principles with products whose properties I know very well. The reader is free to find equivalent products. There are two types of VansEvers Cable-Multi-Resonators:
1) The lighter treble versions are built around a plastic clothes pin and are very easy to use. Their intended purpose is to add or enhance treble resonances, thus providing a more even support for music's upper harmonics.
2) The heavier midrange CMR is built around two aluminum discs of different thickness’. It uses a wooden cable clamp and holds much heavier and larger resonant plates than the lighter version can. Because the diameter and mass of the plates can be larger, midrange frequency enhancement and/or treble dampening is the result.
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