{"id":1571,"date":"2011-10-10T09:01:56","date_gmt":"2011-10-10T12:01:56","guid":{"rendered":"http:\/\/hifiplanet.com.br\/blog\/?p=1571"},"modified":"2016-01-03T12:58:50","modified_gmt":"2016-01-03T15:58:50","slug":"spikes-and-cones-%e2%80%93-what%e2%80%99s-the-point","status":"publish","type":"post","link":"http:\/\/www.hifiplanet.com.br\/blog\/spikes-and-cones-%e2%80%93-what%e2%80%99s-the-point\/","title":{"rendered":"Spikes and Cones \u2013 What\u2019s the point?"},"content":{"rendered":"<p>Um texto bem interessante sobre a utiliza\u00e7\u00e3o de <em>spikes<\/em> e cones.<\/p>\n<p style=\"text-align: center;\"><a href=\"http:\/\/hifiplanet.com.br\/blog\/wp-content\/uploads\/2011\/10\/spike.jpg\"><img decoding=\"async\" loading=\"lazy\" class=\"alignnone size-full wp-image-2122\" title=\"spike\" src=\"http:\/\/hifiplanet.com.br\/blog\/wp-content\/uploads\/2011\/10\/spike.jpg\" alt=\"\" width=\"95\" height=\"170\" \/><\/a><\/p>\n<p><!--more--><\/p>\n<p>Conforme prometido, durante os coment\u00e1rios surgidos no artigo <strong>&#8220;Projeto \u201cA Caixa\u201d \u2013 Parte II \u2013 A sele\u00e7\u00e3o dos componentes&#8221;<\/strong>, publicados aqui na categoria Espa\u00e7o DIY\/ Projeto &#8220;A Caixa&#8221;, e diante de alguns testes de equipamentos e acess\u00f3rios que recentemente tomei conhecimento por terem sido publicados por alguns ve\u00edculos de &#8220;desinforma\u00e7\u00e3o&#8221;, estou incluindo aqui este interessante texto que, apesar de estar em ingl\u00eas e eu n\u00e3o ter tempo de traduz\u00ed-lo (se algu\u00e9m desejar faz\u00ea-lo, agradeceremos por isso), \u00e9 bastante completo e esclarecedor.<\/p>\n<p>Esse artigo desmistifica as &#8220;lendas&#8221; sobre a utiliza\u00e7\u00e3o dos<em> spikes<\/em> e cones, e esclarece sobre suas verdadeiras caracter\u00edsticas, mostrando que s\u00e3o \u00fateis, mas n\u00e3o da forma como algumas publica\u00e7\u00f5es ou outros &#8220;interessados&#8221; tentam sugerir.<\/p>\n<p><strong><span style=\"color: #ff0000;\">Tradu\u00e7\u00e3o livre para o portugu\u00eas ao final do original em ingl\u00eas.<\/span><\/strong><\/p>\n<h2><span style=\"color: #0000ff;\"><strong>Spikes and Cones \u2013 What\u2019s the point?<\/strong><\/span><\/h2>\n<p><span style=\"color: #0000ff;\">by Jim Lesurf \u2014 last modified September 18, 2007<\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong>In recent years it has become common for items of audio equipment to be mounted using \u201cspikes\u201d or \u201ccones\u201d. These come in all sorts of shapes, sizes, and materials, at all kinds of prices. The Hi-Fi magazines sometimes \u2018review\u2019 these accessories, and recommend their use. However, are they worth buying and using? On this page I\u2019ll consider their use with loudspeakers, and discuss some alternatives.<\/strong><\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong><a href=\"http:\/\/hifiplanet.com.br\/blog\/wp-content\/uploads\/2011\/04\/fig1.gif\"><img decoding=\"async\" loading=\"lazy\" class=\"alignnone size-medium wp-image-1572\" title=\"fig1\" src=\"http:\/\/hifiplanet.com.br\/blog\/wp-content\/uploads\/2011\/04\/fig1-249x300.gif\" alt=\"\" width=\"249\" height=\"300\" srcset=\"http:\/\/www.hifiplanet.com.br\/blog\/wp-content\/uploads\/2011\/04\/fig1-249x300.gif 249w, http:\/\/www.hifiplanet.com.br\/blog\/wp-content\/uploads\/2011\/04\/fig1.gif 505w\" sizes=\"(max-width: 249px) 100vw, 249px\" \/><\/a><br \/>\n<\/strong><\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong>The above diagram shows a typical arrangement. In this case there are a set of cones between the actual loudspeaker and its stand. (In some cases these cones are placed \u2018point upwards\u2019 rather than as shown here.) The base of the stand also has spikes fitted \u2013 i.e. long thin cones. These can penetrate the carpet, and if you have a wooden floor, they may then stick into the floorboards through the carpet.<\/strong><\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong>In some cases, people use such spikes with some form of washer or coin so that the points sit on a small \u2018puck\u2019 rather than dig into the floor. Also, sometimes the spikes do not penetrate the carpet or flooring. To start with, I&#8217;ll ignore these possibilities, and return to them later on.<\/strong> <\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong>In general, Hi-Fi magazines claim that using cones and spikes like this will improve the sound. They also sometimes tend to describe the action of the cones or spikes as providing \u201cvibration isolation\u201d. Indeed, cones are sometimes also recommended for use under CD players, amplifiers, etc, and it is sometimes claimed that this can improve the sound by \u201cisolating\u201d the units from vibrations. This leads to two questions:<\/strong><\/span><\/p>\n<ul>\n<li><span style=\"color: #0000ff;\"><strong>Do these cones or spikes actually <em>do<\/em> anything worthwhile? <\/strong><\/span><\/li>\n<li><span style=\"color: #0000ff;\"><strong>If so, <em>what<\/em> do they do, and how do they work? <\/strong><\/span><\/li>\n<\/ul>\n<p><span style=\"color: #0000ff;\"><strong><br \/>\nAt first appearance, it seems plausible that cones under a loudspeaker should reduce the amount of sound energy transmitted between speaker and stand because they reduce the area of contact between the speaker and the stand. In the same way, we might expect spikes at the base of the stand to provide isolation. The basis of this idea seems to be that if the contact area was zero (i.e. no contact at all!) then no solid vibrations could pass. Hence if we make the contact area tiny, this approaches zero, so should only allow a small amount of vibration through. Unfortunately, although plausible, this idea may simply be incorrect.<\/strong><\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong>We can understand how the above idea might be wrong by considering another example of the use of \u201cspikes\u201d \u2013 a running shoe. Here the purpose is to <\/strong><strong><em>increase<\/em> the grip between two objects (shoe and ground) and hence transmit forces more efficiently. This example instantly shows that a cone or spike might not reduce the amount of actual force transmission, but actually help <em>ensure<\/em> effective transmission. Hence spikes and cones \u2013 far from \u201cisolating\u201d \u2013 might sometimes give a more effective link for vibrations to pass though.<\/strong><\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong>In some recent issues of the audio magazine, \u2018Hi Fi News\u2019 [ref 1], Keith Howard used an accelerometer to measure the levels of vibration in various objects. When he tried measuring the vibrations produced in a loudspeaker stand by playing the speaker he found a result that surprised him. With the speaker unit sitting on cones the level of vibration of the stand was over one hundred times greater than if the cones were replaced with small rubbery feet. This indicates that cones are of doubtful use if the intention is to stop vibrations passing from the speaker to the stand, or to any other solid objects against which the speaker may sit. <\/strong><\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong>In fact, this result is also consistent with the predictions you can get by looking into the theory of vibrations in solid structures and objects. [ref 2] (Although such predictions sometimes need to be treated with care as the results depend upon the assumptions made when doing an analysis!) The theory and actual measurements seem to agree that hard cones and spikes are not necessarily a sensible choice if vibration isolation is what you require. An air gap or soft rubbery feet would probably be much better. <\/strong><\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong>So do cones and spikes do anything useful, and are they worthwhile?<\/strong><\/span><\/p>\n<h2><span style=\"color: #0000ff;\"><strong>Spikes into the floor.<\/strong><\/span><\/h2>\n<p><span style=\"color: #0000ff;\"><strong>Despite the above, there may be cases where the use of cones or spikes <em>do<\/em> have an effect \u2013 although probably not for the reasons often given in audio magazines. In some cases the effects may be unwanted, though, so beware. To illustrate this we can use two examples.<\/strong><\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong><br \/>\n<\/strong><\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong><a href=\"http:\/\/hifiplanet.com.br\/blog\/wp-content\/uploads\/2011\/04\/fig2.gif\"><img decoding=\"async\" loading=\"lazy\" class=\"alignnone size-medium wp-image-1573\" title=\"fig2\" src=\"http:\/\/hifiplanet.com.br\/blog\/wp-content\/uploads\/2011\/04\/fig2-234x300.gif\" alt=\"\" width=\"234\" height=\"300\" srcset=\"http:\/\/www.hifiplanet.com.br\/blog\/wp-content\/uploads\/2011\/04\/fig2-234x300.gif 234w, http:\/\/www.hifiplanet.com.br\/blog\/wp-content\/uploads\/2011\/04\/fig2.gif 449w\" sizes=\"(max-width: 234px) 100vw, 234px\" \/><\/a><br \/>\n<\/strong><\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong>The first example is shown in diagram 2. This shows a side-view of a speaker on a stand without cones or spikes. The stand rests on the carpet. When we play music the speaker cones vibrate backwards and forwards. This produces the sound we want. However by Newton\u2019s Laws of motion it also shakes the speaker and the stand. The result, especially at low frequencies is a tendency for the speaker and stand to \u2018rock\u2019 back and forth. Compared with solid materials like metal or wood, the carpet is quite soft and spongy. Thus it can act like a spring and allow the base of the stand (or the legs) to move, and the whole system wobble.<\/strong><\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong>This behaviour may have various effects. One is that vibrational energy now finds it more difficult to \u2018escape\u2019 from the speaker and stand into the floor. In this case, it is the carpet that is providing some \u201cvibration isolation\u201d. Another possible result is that, by allowing the speaker to \u2018recoil\u2019, we may be influencing how easily the speaker can produce low-frequency sounds. Hence we may find this alters the bass response. It may also be worth noting that when the floor does vibrate at low frequencies we may sense or hear these vibrations. Hence isolating the speaker from the floor might mean some other changes in the sound due to reducing the floor vibrations. <\/strong> <\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong>By having spikes on the base of the stand (as illustrated in diagram 1) we allow the speaker stand to \u2018grip\u2019 the floor under the carpet. As a result, we can expect the spikes to reduce how much the speaker and stand wobble around, particularly at low frequencies. Unwanted vibrations or shaking of the speaker box and stand at low frequencies could then be reduced. By holding the speaker more firmly we may alter or assist its ability to radiate low frequencies. In addition, the floor may now act as a secondary radiator or medium to convey sound vibrations to the listener. Hence spikes under a stand may well have an effect we can sense, not because they \u201cisolate\u201d vibrations, but for precisely the opposite reason! To do so, however, they need to effectively penetrate through the carpet so the stand can grip the floor underneath. <\/strong><\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong>What the above <\/strong><strong><em>can\u2019t<\/em> tell us, of course, is whether any changes produced by such spikes will be judged to make the resulting sound \u201cbetter\u201d or \u201cworse\u201d \u2013 or even if the changes will be noticeable. That will be a matter of individual circumstances and the personal preferences of the listener. There are various reasons for this. One example is that, in some cases, the movement on the springy carpet might help damp out higher-frequency resonances in the stand more effectively than being gripped by the floor. Matter of circumstances which might be judged \u2018best\u2019 for changing the performance in the way the individual user might prefer.<\/strong><\/span><\/p>\n<h2><span style=\"color: #0000ff;\"><strong>Cones between speaker and stand.<\/strong><\/span><\/h2>\n<p><span style=\"color: #0000ff;\"><strong><br \/>\n<\/strong><\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong><a href=\"http:\/\/hifiplanet.com.br\/blog\/wp-content\/uploads\/2011\/04\/fig3.gif\"><img decoding=\"async\" loading=\"lazy\" class=\"alignnone size-medium wp-image-1574\" title=\"fig3\" src=\"http:\/\/hifiplanet.com.br\/blog\/wp-content\/uploads\/2011\/04\/fig3-300x173.gif\" alt=\"\" width=\"300\" height=\"173\" srcset=\"http:\/\/www.hifiplanet.com.br\/blog\/wp-content\/uploads\/2011\/04\/fig3-300x173.gif 300w, http:\/\/www.hifiplanet.com.br\/blog\/wp-content\/uploads\/2011\/04\/fig3.gif 756w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><\/strong><\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong>From the explanations given above it seems reasonable to expect spikes on a speaker stand to be capable of having an effect. So what about cones between a speaker and its supporting stand? For our second example, lets look at diagram 3.<\/strong><\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong>Engineers are often asked to produce flat surfaces. Alas, \u2018flat\u2019 is a nice theoretical ideal, but can sometimes be awkward to obtain in practice, especially when objects are being subjected to various forces which have the effect of bending or distorting their shapes. Diagram 3 illustrates this by considering what happens when the bottom of a loudspeaker unit isn\u2019t actually flat, but bulges downwards in the middle.<\/strong><\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong>Ideally, if both the bottom of the speaker and the top of the stand are flat, they will make firm contact over a large area. The system would then be fairly stable, and would efficiently link forces and vibrations between the two. However if the bottom of the loudspeaker is curved then it might not remain stable on the stand. The curvature shown on the diagram is exaggerated for the sake of clarity, but should indicate what would then happen. With a curved base, any sideways forces would cause the speaker to wobble back and forth on top of the stand. However if we place some cones in between the speaker they act as \u2018legs\u2019 to support the speaker in a few locations. This means we can now remove the effect of the underside of the speaker not being flat, and the result may be stable again. Hence cones may improve the stability of the speaker-stand combination by removing any problems due to the surfaces not being flat. <\/strong><\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong>As with the spikes on the base of the stand the cones would, in principle, act here by giving a firmer and better-defined mechanical link, so do not \u201cisolate\u201d the speaker when behaving as described. In <\/strong><strong><em>practice<\/em>, however they may not always be required when used with decent loudspeakers and stands. The reason for this is that \u2013 although not perfectly flat \u2013 the surfaces of the speaker and stand may be flat enough that when they press together their elasticity allows them to deform and come into contact over most of the surfaces. Hence in practice, the surfaces may often be flat enough for any imperfections not to matter.<\/strong><\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong>In principle, when vibrating hard objects are resting upon each other, the surfaces may vibrate enough to keep \u2018bouncing\u2019 in and out of contact. The result then might be some unwanted distortion due to the non-linearity of the contact forces. (i.e. the surfaces might \u2018rattle\u2019 together.) If this occurs, then compliant feet of some kind (or a layer of soft material in between the two objects) may be desirable to help ensure a more enduring contact. However having said this I\u2019ve have not encountered any measurements or observations which show this is a real problem in most practical cases with domestic audio speakers. I therefore have no reason at present to think that this problem does occur in practice, so no \u2018solution\u2019 may be required.<\/strong><\/span><\/p>\n<h2><span style=\"color: #0000ff;\"><strong>Not making holes in the carpet!<\/strong><\/span><\/h2>\n<p><span style=\"color: #0000ff;\"><strong>An obvious problem with using spikes as considered above is that we end up with holes in the carpet and floorboards! The good news is that with narrow spikes, the holes in carpet tend to close up and become invisible when the stand is moved. However, wooden floors are less forgiving, and there is an obvious risk of damage that might sometimes be unacceptable. Hence we may allow the spikes to press onto the carpet but avoid pushing them hard enough so they drive through onto or into the floor. When the weight of the speaker and stand is high people can choose to place the spikes on coins, or washers that act as a supporting \u2018puck\u2019 and prevent damage to carpet or floor.<\/strong><\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong>By placing the spike on a small puck we make it impossible for the spike to contact the carpet or floor. This means we can&#8217;t expect the combination to dig in as effectively as the spike would do by itself. The combined spike and puck then will tend to act as a narrow hard foot. For much the same theoretical reasons [ref 2] as before, the result is unlikely to effectively isolate or damp any vibrations, although the stand may be held less firmly than if the spikes can grip the floor. Having said the above, using narrow feet might be useful in some cases. The weight and vibrational forces of the speaker will then be pressed onto a much smaller area of carpet (assuming the pucks are above the carpet) than if no feet or spikes are used. This may alter the effective stiffness of the carpet, and alter the ease with which the speaker may wobble, or lose vibrational energy. The resulting changes may be less when using a puck than when the spike is allowed to \u2018dig in\u2019, but may be useful in some cases.<\/strong> <\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong>When sitting on a concrete or stone floor it is unclear if a puck should be expected to do much in terms of vibrations. It may just prevent the spikes from blunting themselves digging small holes in the floor. However, either way, this arrangement will lack the grip we might get with spikes driven into a wooden floor. In general, therefore, we should perhaps view pucks or washers with caution as their benefits may be cosmetic rather than acoustic. Indeed, they may tend to defeat the purpose of fitting spikes at all. As usual, though, the results may depend upon the detailed circumstances!<\/strong> <\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong>The effect of using spikes which do not penetrate the carpet even without a puck can, again, be expected to be much like using narrow feet. It seems doubtful that they will isolate the stand from the floor. The results will depend upon how well (if at all) the spikes can grip the carpet without making holes. They may, however, act like the cones under a speaker and provide a more stable seating when the surfaces are not flat.<\/strong><\/span><\/p>\n<h2><span style=\"color: #0000ff;\"><strong>Softly softly&#8230;<\/strong><\/span><\/h2>\n<p><span style=\"color: #0000ff;\"><strong>For what it is worth, my own experience is that spiking the loudspeaker\/stand through the carpet to \u2018grip\u2019 a wooden floor seems to have a noticeable effect when I have tried it, and I think I prefer it in the main audio system I use. However there is no guarantee this impression would be the same in every case, or that you would agree with my preference, or indeed that I am not imagining the change it made! I can&#8217;t say that I have ever had the feeling that spikes which do <em>not<\/em> drive through the carpet had any audible effect. Where genuine vibration isolation or vibration absorption <em>are<\/em> required my experience (plus the analysis and measurements I have mentioned) make me doubt that cones\/spikes of hard material are a good bet. My own experience is that something like soft rubber feet (bumper buttons), or felt feet are more effective for isolation purposes.<\/strong><\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong>Some people have experimented with cutting squash-balls in half, then using the resulting hemispheres of soft rubbery material as \u2018feet\u2019 under loudspeakers or other units. I don\u2019t know of any measurements upon the effects of their use, however it seems quite possible that this arrangement would be better at isolating vibrations that hard cones or spikes. An alternative that was once popular was using a layer \u2013 or blobs \u2013 of \u2018Blu-tack\u2019. This is quite soft and squidgy when you apply a steady pressure. However it is more elastic and springy when vibrated. A potential problem with Blu-tack is that it contains a solvent which may discolour or mark other materials if held in contact with them for a long time. The material may also \u2018creep\u2019 or dry out, and its behaviour change with time. Hence it may not be suitable for long term use. <\/strong><\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong>Another alternative I have not seen suggested or recommended anywhere is the use of cut-up pieces of carpet tile. This tends to be a composite of a layer of a soft rubbery material with a fibrous layer. An advantage of these tiles is that they are cheap to buy, and easy to cut up into shapes. You can also stack them into piles of a few layers if you wish. Hence they are very convenient to experiment with if you wish explore any effects they may have. Another advantage is that they are available in a variety of thicknesses, colours, and patterns. <\/strong> <\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong>I don\u2019t know of any reliable measurements of the possible effects of Blu-tack or bits of carpet tiles used as \u2018feet\u2019. Hence if you try them you may decide that do nothing much, or you may find you dislike them. However if you are interested in damping or isolating, they seem worth considering as an alternative to the now-conventional hard spikes and cones. <\/strong> <\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong>The real difficulty with trying to deal with vibration and acoustics to \u2018improve\u2019 a domestic audio system is that the circumstances vary a great deal from one system and room to another, and the preferences of the user also varies. My own experience is that the choice of loudspeakers, their location, and the listening position generally have a larger effect upon the sound quality than the use of spikes, etc. In some cases cones or spikes may be desired to give a better \u2018grip\u2019. In other cases some damping or isolation may be desired, so soft inelastic materials may be preferred. Hence when it comes to loudspeakers and stands, any specific recommendation may be fine in some cases, and poor in others. The best bet is therefore simply to experiment. I hope the above gives some food for thought if you are interested in doing so! <\/strong><\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong>[1] Articles on vibration by Keith Howard in the July and August 2002 issues of Hi Fi News <\/strong> <\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong>[2] Textbook:<\/strong> <strong><em> Structure-borne sound<\/em>, by Cremer, Heckl, and Ungar, published by Springer-Verlag.<\/strong><\/span><\/p>\n<p><strong>(Clique nas fotos acima se desejar ampli\u00e1-las)<br \/>\n<\/strong><\/p>\n<p><span style=\"color: #0000ff;\"><span style=\"color: #000000;\"><strong>Uma discuss\u00e3o interessante, em portugu\u00eas, sobre este tema:<\/strong><br \/>\n<\/span><\/span><a href=\"http:\/\/www.audiomania.com.pt\/index.php?topic=3450.0\" target=\"_blank\">www.audiomania.com.pt\/index.php?topic=3450.0<\/a><\/p>\n<p><span style=\"color: #ff0000;\"><strong>Recebemos uma tradu\u00e7\u00e3o do texto do leitor Andr\u00e9 Luis Dias, a quem agradecemos muito pela colabora\u00e7\u00e3o.<br \/>\nSegue a vers\u00e3o traduzida.<\/strong><\/span><\/p>\n<h2><strong><span style=\"color: #008000;\">Spikes\u00a0e Cones \u2013 Valem a pena ?<\/span><\/strong><\/h2>\n<h2><\/h2>\n<p><span style=\"color: #008000;\">por\u00a0Jim Lesurf\u00a0\u2014 tradu\u00e7\u00e3o de Andr\u00e9 Luis Dias<br \/>\n<\/span><\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify;\"><span style=\"color: #008000;\"><strong>Nos \u00faltimos anos tornou-se comum montar equipamentos de \u00e1udio em \u00b4spikes\u00b4 ou \u00b4cones\u00b4. Estes\u00a0est\u00e3o\u00a0dispon\u00edveis em diversos formatos, tamanhos, materiais e em diferentes n\u00edveis de\u00a0pre\u00e7os. As revistas de HI-FI por vezes publicam \u00b4reviews\u00b4para esses acess\u00f3rios, inclusive recomendando seu uso. Mas, vale a pena compr\u00e1-los e utiliz\u00e1-los ? Nesta p\u00e1gina vou tratar o uso desses acess\u00f3rios com caixas ac\u00fasticas, e\u00a0discutir\u00a0algumas alternativas. <\/strong><\/span><\/p>\n<p><span style=\"color: #0000ff;\"><strong><a href=\"http:\/\/hifiplanet.com.br\/blog\/wp-content\/uploads\/2011\/04\/fig1.gif\"><img decoding=\"async\" loading=\"lazy\" class=\"alignnone size-medium wp-image-1572\" title=\"fig1\" src=\"http:\/\/hifiplanet.com.br\/blog\/wp-content\/uploads\/2011\/04\/fig1-249x300.gif\" alt=\"\" width=\"249\" height=\"300\" srcset=\"http:\/\/www.hifiplanet.com.br\/blog\/wp-content\/uploads\/2011\/04\/fig1-249x300.gif 249w, http:\/\/www.hifiplanet.com.br\/blog\/wp-content\/uploads\/2011\/04\/fig1.gif 505w\" sizes=\"(max-width: 249px) 100vw, 249px\" \/><\/a><br \/>\n<\/strong><\/span><\/p>\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">O diagrama acima mostra um t\u00edpico \u00b4set-up\u00b4. Neste caso, existe um conjunto de cones entre a caixa ac\u00fastica e seu pedestal. Em\u00a0alguns\u00a0casos, estes cones\u00a0s\u00e3o\u00a0posicionados com a ponto para o lado de cima em forma inversa a mostrada no esquema acima. A base do pedestal tamb\u00e9m tem\u00a0spikes. Estes podem penetrar o carpete ou tapete e, se\u00a0voc\u00ea\u00a0tiver um\u00a0assoalho\u00a0de madeira sob o tapete, eles podem at\u00e9 se fixar no\u00a0assoalho (perfurando-o).<\/span><\/strong><\/p>\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">Em\u00a0alguns\u00a0casos, estes\u00a0spikes s\u00e3o\u00a0utilizados com\u00a0algum\u00a0tipo de\u00a0prote\u00e7\u00e3o\u00a0met\u00e1lica (em forma de moeda ou pequeno disco) de forma que as pontas dos\u00a0spikes\u00a0fiquem posicionadas sobre estas pecas. Tamb\u00e9m, as vezes\u00a0n\u00e3o\u00a0penetram o tapete ou\u00a0assoalho. Mas para\u00a0come\u00e7ar, vamos ignorar estas possibilidades e retornaremos a\u00a0elas\u00a0mais a frente.<\/span><\/strong><\/p>\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">Em geral, as revistas HI-FI atestam que a\u00a0utiliza\u00e7\u00e3o\u00a0de cones e\u00a0spikes\u00a0como estes, melhoram a qualidade de som. Estas revistas tamb\u00e9m descrevem a\u00a0a\u00e7\u00e3o\u00a0dos cones ou\u00a0spikes\u00a0como\u00a0itens\u00a0que\u00a0proporcionam\u00a0\u201cisola\u00e7\u00e3o\u00a0de\u00a0vibra\u00e7\u00e3o\u201d. De fato, os cones\u00a0s\u00e3o\u00a0tamb\u00e9m eventualmente recomendados para\u00a0utiliza\u00e7\u00e3o\u00a0sob CD\u00a0players, amplificadores, etc. , e tamb\u00e9m afirmam que isso pode melhorar a qualidade de som atrav\u00e9s da\u00a0isola\u00e7\u00e3o\u00a0de\u00a0vibra\u00e7\u00e3o\u00a0dos componentes. Isso nos remete \u00e0 2\u00a0quest\u00f5es:<\/span><\/strong><\/p>\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">\u2022 Ser\u00e1 que estes cones ou\u00a0spikes\u00a0realmente resultam em melhora?<br \/>\n\u2022 Em caso positivo, o que eles melhoram, e de que forma ?<\/span><\/strong><\/p>\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">Numa an\u00e1lise superficial, parece plaus\u00edvel que cones sob uma caixa ac\u00fastica reduzam a quantidade de energia sonora (ou\u00a0vibra\u00e7\u00e3o) transmitida entre as caixas e o pedestal, porque os cones reduzem a \u00e1rea de\u00a0contato\u00a0entre eles. Da mesma forma,\u00a0poder\u00edamos\u00a0presumir que\u00a0spikes\u00a0na base da caixa resultariam em\u00a0melhor isola\u00e7\u00e3o. A base desta\u00a0id\u00e9ia\u00a0parece ser de que se \u00e1rea de\u00a0contato\u00a0fosse \u201czero\u201d (nenhum contato), ent\u00e3o nenhuma vibra\u00e7\u00e3o\u00a0s\u00f3lida poderia ser transmitida. Portanto, se fizermos a \u00e1rea de\u00a0contato\u00a0bem pequena (restrita), isto chega perto de zero e deveria permitir somente uma pequena\u00a0transmiss\u00e3o\u00a0de\u00a0vibra\u00e7\u00e3o. Infelizmente, apesar de plaus\u00edvel, este ideia pode estar simplesmente\u00a0incorreta.<\/span><\/strong><\/p>\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">Podemos entender como a\u00a0id\u00e9ia\u00a0acima pode estar equivocada em considerando outro exemplo de uso de\u00a0spikes; num\u00a0tenis\u00a0para\u00a0jogging\u00a0ou corrida. Neste caso, o prop\u00f3sito dos\u00a0spikes\u00a0\u00e9 aumentar o \u00b4grip\u00b4 (agarramento) entre o\u00a0tenis\u00a0e o solo e portanto, transmitir forcas mais eficientemente. Este exemplo mostra que cones ou\u00a0spikes\u00a0podem\u00a0n\u00e3o\u00a0reduzir o\u00a0montante\u00a0de forca transmitida, mas sim assegurar uma transmiss\u00e3o mais eficiente. Desta\u00a0forma, cones e\u00a0spikes, ao inv\u00e9s de isolar, podem resultar num \u00b4link\u00b4 (contato) e\u00a0vibra\u00e7\u00e3o\u00a0mais eficiente.<\/span><\/strong><\/p>\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">Em\u00a0edicoes\u00a0recentes da revista de\u00a0audio\u00a0\u00b4HI-FI\u00a0News\u00b4\u00a0(Ref\u00a01),\u00a0Keith\u00a0Howard usou um medidor de\u00a0acelera\u00e7\u00e3o\u00a0para medir n\u00edveis de\u00a0vibra\u00e7\u00e3o\u00a0em v\u00e1rios\u00a0objetos. Ao tentar medir a\u00a0vibra\u00e7\u00e3o\u00a0produzida num pedestal\u00a0enquando\u00a0a caixa `tocava`, ele chegou a um resultado que o\u00a0surpreendeu. Com as caixas posicionadas sobre cones, o n\u00edvel de\u00a0vibra\u00e7\u00e3o\u00a0do pedestal foi mais de 100 vezes maior do que se os cones fossem trocados por pequenos \u00b4p\u00e9s\u00b4 de borracha. Isto indica que os cones\u00a0sao\u00a0de uso duvidoso caso a\u00a0inten\u00e7\u00e3o\u00a0seja de evitar a\u00a0transmiss\u00e3o\u00a0de\u00a0vibra\u00e7\u00e3o\u00a0da caixa para o pedestal ou qualquer outro\u00a0objeto\u00a0s\u00f3lido sobre o qual a caixa esteja posicionada.<\/span> <\/strong><\/p>\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">De fato, este resultado \u00e9 tamb\u00e9m consistente com as\u00a0conclus\u00f5es\u00a0que\u00a0voc\u00ea\u00a0pode chegar quando analisando as teorias de\u00a0vibra\u00e7\u00e3o\u00a0em estruturas e\u00a0objetos\u00a0s\u00f3lidos. [ref\u00a02] (Apesar de tais\u00a0conclus\u00f5es\u00a0deverem ser tratadas com cuidado porque os\u00a0resultados\u00a0dependem das\u00a0concepcoes\u00a0tomadas\u00a0enquanto\u00a0realizando a an\u00e1lise!). A teoria e\u00a0medicoes\u00a0reais parecem concordar que cones r\u00edgidos\u00a0n\u00e3o s\u00e3o\u00a0necessariamente uma escolha precisa se o que\u00a0voc\u00ea\u00a0procura \u00e9\u00a0isola\u00e7\u00e3o\u00a0de\u00a0vibra\u00e7\u00e3o. Um\u00a0espa\u00e7amento\u00a0de ar ou p\u00e9s de borracha macia, seriam provavelmente bem melhores.<\/span><\/strong><\/p>\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">Afinal, os cones e spikes resultam em algo \u00fatil; valem a pena ?<\/span><\/strong><\/p>\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\">\n<h2 style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">Spikes no assoalho.<\/span><\/strong><\/h2>\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">Podem haver casos em que o uso de cones ou\u00a0spikes\u00a0tem sim um efeito (provavelmente\u00a0n\u00e3o\u00a0pelas razoes normalmente apontadas nas revistas de\u00a0audio). Em\u00a0alguns\u00a0casos, o efeito pode ser at\u00e9 indesej\u00e1vel,\u00a0ent\u00e3o, fique atento. Para ilustrar esta\u00a0situa\u00e7\u00e3o, podemos usar dois exemplos:<\/span><\/strong><\/p>\n<p><span style=\"color: #0000ff;\"><strong><a href=\"http:\/\/hifiplanet.com.br\/blog\/wp-content\/uploads\/2011\/04\/fig2.gif\"><img decoding=\"async\" loading=\"lazy\" class=\"alignnone size-medium wp-image-1573\" title=\"fig2\" src=\"http:\/\/hifiplanet.com.br\/blog\/wp-content\/uploads\/2011\/04\/fig2-234x300.gif\" alt=\"\" width=\"234\" height=\"300\" srcset=\"http:\/\/www.hifiplanet.com.br\/blog\/wp-content\/uploads\/2011\/04\/fig2-234x300.gif 234w, http:\/\/www.hifiplanet.com.br\/blog\/wp-content\/uploads\/2011\/04\/fig2.gif 449w\" sizes=\"(max-width: 234px) 100vw, 234px\" \/><\/a><br \/>\n<\/strong><\/span><\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">Este primeiro exemplo \u00e9 mostrado no\u00a0diagrama\u00a02 (acima). Trata-se de uma\u00a0vis\u00e3o\u00a0lateral de uma caixa num pedestal \u201csem\u201d cones ou\u00a0spikes. O pedestal est\u00e1 situado sobre um tapete ou carpete. Quando a m\u00fasica \u00e9 reproduzida, os cones do auto-falante da caixa vibram para frente para tr\u00e1s. Isto produz o som. Mas, de acordo com a lei de Newton, essa\u00a0a\u00e7\u00e3o\u00a0dos cones tamb\u00e9m vibram a caixa e o pedestal. O resultado,\u00a0especialmente\u00a0em baixas\u00a0frequ\u00eancias, \u00e9 uma\u00a0tend\u00eancia\u00a0da caixa e pedestal\u00a0balan\u00e7arem\u00a0para frente e para tr\u00e1s. Comparado a materiais s\u00f3lidos como metal e madeira, o carpete \u00e9 macio e esponjoso. Por isso, o carpete pode agir como uma mola e permitir que a base do pedestal se mova e todo os sistema balance.<\/span><\/strong><\/p>\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">Este comportamento pode ter v\u00e1rios efeitos. Um \u00e9 que a energia de\u00a0vibra\u00e7\u00e3o\u00a0para \u00b4escapar\u00b4 da caixa e pedestal para o\u00a0assoalho. Neste caso, \u00e9 o carpete que est\u00e1\u00a0proporcionando\u00a0a \u201cisola\u00e7\u00e3o\u00a0de\u00a0vibra\u00e7\u00e3o\u201d. Outro poss\u00edvel resultado \u00e9 que, em permitindo que a caixa \u00b4recue\u00b4, podemos estar influenciando a forma como a caixa reproduz baixas\u00a0frequ\u00eancias. Portanto, podemos constatar que isto altera a resposta ou\u00a0reprodu\u00e7\u00e3o\u00a0dos \u00b4graves\u00b4 (sons de baixa\u00a0frequ\u00eancia). \u00a0Ent\u00e3o, isolar a caixa em\u00a0rela\u00e7\u00e3o\u00a0ao\u00a0assoalho\u00a0pode resultar em outras\u00a0alteracoes\u00a0sonoras por estarmos reduzindo as\u00a0fibracoes\u00a0do\u00a0assoalho.<\/span><\/strong><\/p>\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">Utilizando\u00a0spikes\u00a0na base do pedestal (como ilustrado no\u00a0diagrama\u00a01), permitimos que as caixas se \u201cfixem\u201d no\u00a0assoalho\u00a0sob o carpete. Como resultado, podemos esperar que os\u00a0spikes\u00a0reduzam o quando a caixa e o pedestal\u00a0v\u00e3o\u00a0\u00b4balan\u00e7ar`, particularmente em baixas\u00a0frequ\u00eancias\u00a0(graves).\u00a0Vibra\u00e7oes indesejadas\u00a0ou\u00a0balan\u00e7o\u00a0das caixas poderiam ser\u00a0ent\u00e3o\u00a0reduzidos. Em mantendo a caixa mais\u00a0firmemente\u00a0posicionada, podemos alterar ou auxiliar sua capacidade de radiar baixas\u00a0frequ\u00eancias. Al\u00e9m disso, o\u00a0assoalho\u00a0pode desta forma agir como um ou condutor (ou meio) secund\u00e1rio de\u00a0condu\u00e7\u00e3o\u00a0de\u00a0vibra\u00e7oes\u00a0de som ao ouvinte. Portanto,\u00a0spikes\u00a0sob um pedestal podem at\u00e9 resultar num efeito que se note,\u00a0n\u00e3o\u00a0porque isolam as\u00a0vibra\u00e7oes, mas precisamente pelo contr\u00e1rio, porque as transmitem. Mas para isso, os\u00a0spikes\u00a0precisam penetrar o carpete e se fixar no\u00a0assoalho\u00a0sob ele.<\/span><\/strong><\/p>\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">O que o exposto acima NAO pode nos dizer, \u00e9 claro, \u00e9 se quaisquer\u00a0mudan\u00e7as\u00a0produzidas por esses\u00a0spikes terao\u00a0um resultado\u00a0efetivo\u00a0na \u201cmelhora\u201d ou \u201cpiora\u201d da qualidade do som \u2013 ou at\u00e9 se haver\u00e1\u00a0altera\u00e7\u00e3o\u00a0not\u00e1veis (percept\u00edveis). Isto ser\u00e1 uma questao de circunst\u00e2ncias individuais e tamb\u00e9m das\u00a0prefer\u00eancias\u00a0do ouvinte em\u00a0quest\u00e3o.<br \/>\nH\u00e1 v\u00e1rias razoes para isso. Um exemplo \u00e9 que, em alguns casos, o movimento no carpete pode ajudar a amortecer as\u00a0resson\u00e2ncias\u00a0de alta requ\u00eancia no pedestal mais efetivamente do que no caso do pedestal bem fixo ao\u00a0assoalho. Uma\u00a0quest\u00e3o\u00a0de\u00a0circunstancias\u00a0que podem ser consideradas `ideiais` por alterar a performance da forma que o usu\u00e1rio prefira.<\/span><\/strong><\/p>\n<p style=\"text-align: justify;\">\n<h2 style=\"text-align: justify;\"><span style=\"color: #008000;\"><strong>Cones entre caixa e pedestal <\/strong><\/span><\/h2>\n<p><span style=\"color: #0000ff;\"><strong><a href=\"http:\/\/hifiplanet.com.br\/blog\/wp-content\/uploads\/2011\/04\/fig3.gif\"><img decoding=\"async\" loading=\"lazy\" class=\"alignnone size-medium wp-image-1574\" title=\"fig3\" src=\"http:\/\/hifiplanet.com.br\/blog\/wp-content\/uploads\/2011\/04\/fig3-300x173.gif\" alt=\"\" width=\"300\" height=\"173\" srcset=\"http:\/\/www.hifiplanet.com.br\/blog\/wp-content\/uploads\/2011\/04\/fig3-300x173.gif 300w, http:\/\/www.hifiplanet.com.br\/blog\/wp-content\/uploads\/2011\/04\/fig3.gif 756w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><\/strong><\/span><\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">\u00c0\u00a0partir\u00a0das\u00a0explicacoes\u00a0dadas acima, parece razo\u00e1vel que\u00a0spikes\u00a0num pedestal possam ser capazes de causar algum efeito.\u00a0Ent\u00e3o, o que podemos dizer de cones entre as caixas e os\u00a0pedestais? Para nosso segundo exemplo, vamos observar o diagrama 3.<\/span><\/strong><\/p>\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">Engenheiros\u00a0s\u00e3o\u00a0frequentemente solicitados a conceber\u00a0superf\u00edcies\u00a0planas. A verdade \u00e9 que \u201cplano\u201d \u00e9 mais uma\u00a0quest\u00e3o\u00a0te\u00f3rica que muitas vezes se torna\u00a0dif\u00edcil\u00a0de obter na pr\u00e1tica, especialmente quando os\u00a0objetos est\u00e3o\u00a0sujeitos \u00e0 v\u00e1rias for\u00e7as que tem o efeito de causar\u00a0distorcoes\u00a0nas formas dos materiais. O diagrama 3 ilustra isto considerando o que acontece quando a parte de baixo (superf\u00edcie inferior) de uma caixa ac\u00fastica nao \u00e9 exatamente plana e apresenta uma \u00e1rea de\u00a0contato\u00a0saliente na parte central.<\/span><\/strong><\/p>\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">O ideal, se tanto o lado inferior quanto o superior da caixa\u00a0s\u00e3o\u00a0planos, haver\u00e1 um firme\u00a0contato\u00a0sobre uma \u00e1rea mais\u00a0abrangente\u00a0(correspondente\u00a0\u00e1s\u00a0dimens\u00f5es\u00a0da caixa). O sistema se apresentaria\u00a0entao, razoavelmente est\u00e1vel, e haveria uma\u00a0conex\u00e3o\u00a0(ou\u00a0contato) eficiente de forcas e\u00a0vibra\u00e7oes\u00a0entre a caixa e o pedestal. No entanto, se a superf\u00edcie inferior da caixa for curvada, talvez a caixa\u00a0n\u00e3o permane\u00e7a\u00a0est\u00e1vel sobre o pedestal. A curvatura mostrada no diagrama \u00e9 exagerada propositadamente (somente para clareza da\u00a0ilustra\u00e7\u00e3o), mas indica o que aconteceria. Com uma base curvada, qualquer forma lateral faria a caixa\u00a0balan\u00e7ar\u00a0para frente e para tr\u00e1s sobre o pedestal. Se colocarmos cones entre as caixas e o pedestal, esses\u00a0servir\u00e3o\u00a0como suporte \u00e0 caixa em algumas\u00a0posicoes\u00a0espec\u00edficas. Isto significa, que podemos\u00a0ent\u00e3o\u00a0remover os efeitos por conta da superf\u00edcie da caixa\u00a0n\u00e3o\u00a0ser totalmente plana e o resultado pode ser novamente est\u00e1vel. Portanto, cones podem melhorar a estabilidade da\u00a0combina\u00e7\u00e3o\u00a0\u201ccaixa+pedestal\u201d atrav\u00e9s da\u00a0elimina\u00e7\u00e3o\u00a0de efeitos decorrentes da instabilidade da base da caixa, ou at\u00e9 da\u00a0superf\u00edcie\u00a0do pedestal.<\/span><\/strong><\/p>\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">Como no caso dos\u00a0spikes\u00a0na base do\u00a0pedestal, os cones iriam, em princ\u00edpio, agir como uma melhor\u00a0conex\u00e3o\u00a0(uni\u00e3o)\u00a0mec\u00e2nica\u00a0entra as superf\u00edcies, e\u00a0n\u00e3o\u00a0como\u00a0isola\u00e7\u00e3o\u00a0entre os meios. Na pr\u00e1tica, entretanto, os cones podem\u00a0n\u00e3o\u00a0ser necess\u00e1rios quanto se utiliza caixas e\u00a0pedestais\u00a0de razo\u00e1vel\u00a0padr\u00e3o\u00a0de qualidade. A\u00a0raz\u00e3o\u00a0para isso \u00e9 que, apesar de ser pouco prov\u00e1vel que qualquer caixa ou pedestal tenham superf\u00edcies totalmente planas, quanto se tratando de equipamentos de qualidade, dever\u00e1 haver uma poss\u00edvel acomoda\u00e7\u00e3o dos materiais que permita uma\u00a0uni\u00e3o\u00a0est\u00e1vel da caixa e do pedestal. Desta forma, o peso da caixa provocaria a\u00a0acomoda\u00e7\u00e3o\u00a0e as superf\u00edcies se tornariam planas o suficiente para que quaisquer\u00a0imperfei\u00e7oes\u00a0se tornassem irrelevantes.<\/span><\/strong><\/p>\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">A princ\u00edpio, quando\u00a0objetos\u00a0s\u00f3lidos e que vibram,\u00a0est\u00e3o\u00a0posicionados um sobre o outro, as superf\u00edcies podem vibrar o suficiente para manter os\u00a0objetos\u00a0se movendo (balan\u00e7ando) alterando os pontos de\u00a0contato. Isso pode ocasionar\u00a0distorces indesejadas\u00a0devido a falta de linearidade das forcas de\u00a0contato. (por exemplo, as superf\u00edcies podem bater uma na outra). Se isso ocorrer,\u00a0algum\u00a0tipo de suporte (p\u00e9s ou uma faixa de material macio entre as superf\u00edcies) pode ser aplic\u00e1vel afim de\u00a0proporcionar\u00a0um melhor\u00a0contato\u00a0entre as superf\u00edcies. De qualquer forma, em se levando em conta o acima exposto,\u00a0n\u00e3o\u00a0encontrei nenhum tipo de\u00a0avalia\u00e7\u00e3o\u00a0ou\u00a0mediacoes\u00a0que evidenciem o problema na maioria dos casos pr\u00e1ticos com caixas ac\u00fasticas de\u00a0utiliza\u00e7\u00e3o\u00a0dom\u00e9stica.<\/span><\/strong><\/p>\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">Desta forma,\u00a0n\u00e3o\u00a0tenho\u00a0raz\u00e3o\u00a0para acreditar que este problema ocorra na pr\u00e1tica, e talvez n\u00e3o\u00a0haja a necessidade de uma \u201csolu\u00e7\u00e3o\u201d.<\/span><\/strong><\/p>\n<p style=\"text-align: justify;\">\n<h2 style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">Cuidado com furos no carpete!<\/span><\/strong><\/h2>\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">Um dos problemas\u00a0obvios\u00a0na\u00a0utiliza\u00e7\u00e3o\u00a0de\u00a0spikes s\u00e3o\u00a0os furos nos carpetes ou no asolalho de madeira. A boa\u00a0not\u00edca\u00a0\u00e9 que se os\u00a0spikes\u00a0tiverem pontas bem finas, os pequenos furos no carpete tendem a se fechar quando o pedestal \u00e9 removido do local. No entanto, os asoalhos de madeira\u00a0nao proporcionam\u00a0a mesma\u00a0facanha\u00a0e existe o risco de danos permanentes, os quais podem ser vis\u00edveis e inaceit\u00e1veis. Ent\u00e3o, podemos permitir que os\u00a0spikes\u00a0sejam pressionados contra o carpete mas devemos evitar que o atravesse e danifique o piso abaixo (no caso do piso de madeira principalmente). Quando o peso da caixa somado ao do pedestal for relativamente alto, pode-se posicionar os spikes sobre protetores met\u00e1licos ou moedas que\u00a0agir\u00e3o\u00a0como suporte e\u00a0prote\u00e7\u00e3o\u00a0entre o\u00a0spike\u00a0e o asoalho.<\/span><\/strong><\/p>\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">Quando posicionamos os\u00a0spikes\u00a0sobre estes \u201cprotetores\u00a0met\u00e1licos\u201d, evitamos o contato entre o\u00a0spike\u00a0e o piso (asoalho\u00a0ou carpete). Isto significa que\u00a0nao\u00a0podemos esperar que o\u00a0spike\u00a0tenha uma\u00a0fixa\u00e7\u00e3o tao efetiva\u00a0quanto o desejado. Em combinando o\u00a0spike\u00a0com uma base de\u00a0prote\u00e7\u00e3o\u00a0met\u00e1lica, estes se comportaram como um fino \u201cp\u00e9\u201d met\u00e1lico (s\u00f3lido). Pelas mesmas razoes\u00a0teoricas\u00a0expostas anteriormente [ref\u00a02], o\u00a0resultado n\u00e3o\u00a0ser\u00e1 o de isola\u00e7\u00e3o ou amortecimento das\u00a0vibra\u00e7oes. De qualquer forma, a\u00a0utiliza\u00e7\u00e3o\u00a0de p\u00e9s com pontas pode ser \u00fatil em alguns casos. O peso e forcas de\u00a0vibra\u00e7\u00e3o\u00a0da caixa\u00a0estar\u00e3o\u00a0concentrados em pequenos pontos de\u00a0contato\u00a0no carpete.<\/span><\/strong><\/p>\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">Quando posicionados sobre piso duro (concreto, piso\u00a0cer\u00e2mico,\u00a0m\u00e1rmore, granito, etc), n\u00e3o\u00a0fica claro se estes \u201cacentos met\u00e1licos\u201d (pecas met\u00e1licas posicionadas sob os\u00a0spikes) possam ajudar em termos de\u00a0vibra\u00e7\u00e3o. Talvez evitem que os\u00a0spikes\u00a0criem pequenos buracos no piso devido ao peso das caixas somadas as forcas de\u00a0vibra\u00e7\u00e3o. Mas, de qualquer forma, esta\u00a0situa\u00e7\u00e3o\u00a0ocasionar\u00e1 falta de\u00a0contato\u00a0e \u201cfirmeza\u201d no posicionamento das caixas. O resultado de posicionamento e firmeza \u00e9 melhor atingido com\u00a0spikes\u00a0num piso de madeira. Por isso, devemos entender que o uso de pecas met\u00e1licas sob a ponta de\u00a0contato\u00a0dos\u00a0spikes\u00a0talvez\u00a0afete\u00a0apenas a\u00a0quest\u00e3o\u00a0cosm\u00e9tica (ou visual) mas\u00a0nao\u00a0a ac\u00fastica em si. Como j\u00e1 dito, o resultado depende das\u00a0circunstancias\u00a0espec\u00edficas.<\/span><\/strong><\/p>\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">Minha\u00a0experi\u00eancia\u00a0tem mostrado que\u00a0utilizar spikes\u00a0para atravessar o carpete e fixar firmemente as caixas no\u00a0assoalho\u00a0sob ele, parece resultar numa\u00a0diferen\u00e7a\u00a0percept\u00edvel.<\/span><\/strong><\/p>\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">Mas,\u00a0n\u00e3o\u00a0h\u00e1 evidencias de que esta \u201cmelhora\u201d v\u00e1 se repetir em todos os casos. J\u00e1 quando utilizando os\u00a0spikes\u00a0sobre o carpete, por\u00e9m, sem forc\u00e1-los para fixa\u00e7\u00e3o no assoalho, n\u00e3o notei nenhum efeito. Para\u00a0redu\u00e7\u00e3o\u00a0da\u00a0vibra\u00e7\u00e3o, acredito que\u00a0spikes\u00a0e cones feitos em materiais duros,\u00a0n\u00e3o\u00a0sejam a melhor escolha. No caso da\u00a0redu\u00e7\u00e3o\u00a0ou\u00a0isola\u00e7\u00e3o\u00a0de\u00a0vibra\u00e7\u00e3o, atingi melhores resultados com p\u00e9s de borracha ou materiais macios.<\/span><\/strong><\/p>\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">Algumas pessoas j\u00e1\u00a0experimentaram\u00a0cortar bolas de\u00a0aquash\u00a0(ou tenis) ao meio e\u00a0posicionadas\u00a0entre a caixa ac\u00fastica e o\u00a0assoalho. Aparentemente, esta\u00a0solu\u00e7\u00e3o\u00a0seria de melhor resultado para efeito de\u00a0redu\u00e7\u00e3o\u00a0de\u00a0vibra\u00e7oes\u00a0do que a\u00a0utiliza\u00e7\u00e3o\u00a0de\u00a0spikes\u00a0ou cones. Uma alternativa, que j\u00e1 foi popular, foi o uso de adesivos\u00a0emborrachados\u00a0(Blu-tack). Um problema com estes adesivos \u00e9 que eles podem exalar ou transpirar solventes que podem marcar ou\u00a0danificar\u00a0as superf\u00edcies com as quais\u00a0est\u00e3o\u00a0em\u00a0contato. Este material tamb\u00e9m pode se ressecar e alterar seu comportamento, deixando de ser \u00fatil ao longo do tempo.<\/span><\/strong><\/p>\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">N\u00e3o\u00a0conhe\u00e7o nenhuma\u00a0medi\u00e7\u00e3o\u00a0ou teste confi\u00e1vel que expliquem os poss\u00edveis efeitos da utiliza\u00e7\u00e3o\u00a0de \u201cselos emborrachados\u201d ou\u00a0peda\u00e7os\u00a0de carpete como p\u00e9s para caixas e pedestais. Portanto se\u00a0voc\u00ea\u00a0tentar utiliz\u00e1.los, talvez chegue a\u00a0conclus\u00e3o\u00a0que eles\u00a0n\u00e3o\u00a0lhe trazem o resultado esperado ou at\u00e9\u00a0n\u00e3o\u00a0lhe agradam. Mas caso\u00a0voc\u00ea\u00a0esteja\u00a0interessado\u00a0em provocar a\u00a0isola\u00e7\u00e3o\u00a0ou amortecimento das\u00a0vibra\u00e7oes, esses materiais macios podem ser uma boa alternativa aos cones e\u00a0spikes.<\/span><\/strong><\/p>\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">A real dificuldade em tentar lidar com\u00a0vibra\u00e7oes\u00a0e ac\u00fastica, com a finalidade de \u201cmelhorar\u201d o sistema de som dom\u00e9stico, \u00e9 que as\u00a0circunstancias\u00a0variam muito nos diferentes sistemas e ambientes onde\u00a0est\u00e3o\u00a0instalados. E as prefer\u00eancias de cada usu\u00e1rio tamb\u00e9m variam. Minha experi\u00eancia me diz que a escolha das caixas ac\u00fasticas, do posicionamento das mesmas no ambiente e o posicionamento do usu\u00e1rio, em geral,\u00a0s\u00e3o\u00a0muito mais relevantes a qualidade sonora do que em se utilizando\u00a0spikes. Em\u00a0alguns\u00a0casos, como j\u00e1 exposto, o uso de spikes e cones podem\u00a0proporcionar\u00a0uma melhor fixa\u00e7\u00e3o do pedestal (ou da caixa). Em outros casos, o\u00a0objetivo\u00a0pode ser a\u00a0isola\u00e7\u00e3o\u00a0ou amortecimento das\u00a0vibra\u00e7oes, onde materiais macios (n\u00e3o-el\u00e1sticos) podem ser uma melhor\u00a0op\u00e7\u00e3o. Portanto, quando se trata de caixas ac\u00fasticas e\u00a0pedestais, qualquer\u00a0recomenda\u00e7\u00e3o\u00a0espec\u00edfica pode ser \u00fatil a\u00a0alguns\u00a0casos e\u00a0inapropriada\u00a0a outros. A melhor\u00a0opaco\u00a0\u00e9 simplesmente\u00a0experimentar. Espero que o exposto neste texto lhes\u00a0proporcione id\u00e9ias\u00a0para que\u00a0voc\u00eas\u00a0possam\u00a0refletir, caso se interessem pelo assunto.<\/span><\/strong><\/p>\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">[1] Articles on vibration by Keith Howard in the July and August 2002 issues of Hi Fi News <\/span><\/strong><\/p>\n<p style=\"text-align: justify;\"><strong><span style=\"color: #008000;\">[2] Textbook: <em>Structure-borne sound<\/em>, by Cremer, Heckl, and Ungar, published by Springer-Verlag.<\/span><\/strong><\/p>\n","protected":false},"excerpt":{"rendered":"<div class=\"mh-excerpt\"><p>Um texto bem interessante sobre a utiliza\u00e7\u00e3o de spikes e cones.<\/p>\n<\/div>","protected":false},"author":1,"featured_media":2122,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[15],"tags":[],"_links":{"self":[{"href":"http:\/\/www.hifiplanet.com.br\/blog\/wp-json\/wp\/v2\/posts\/1571"}],"collection":[{"href":"http:\/\/www.hifiplanet.com.br\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.hifiplanet.com.br\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.hifiplanet.com.br\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.hifiplanet.com.br\/blog\/wp-json\/wp\/v2\/comments?post=1571"}],"version-history":[{"count":16,"href":"http:\/\/www.hifiplanet.com.br\/blog\/wp-json\/wp\/v2\/posts\/1571\/revisions"}],"predecessor-version":[{"id":3312,"href":"http:\/\/www.hifiplanet.com.br\/blog\/wp-json\/wp\/v2\/posts\/1571\/revisions\/3312"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/www.hifiplanet.com.br\/blog\/wp-json\/wp\/v2\/media\/2122"}],"wp:attachment":[{"href":"http:\/\/www.hifiplanet.com.br\/blog\/wp-json\/wp\/v2\/media?parent=1571"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.hifiplanet.com.br\/blog\/wp-json\/wp\/v2\/categories?post=1571"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.hifiplanet.com.br\/blog\/wp-json\/wp\/v2\/tags?post=1571"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}