Why should it matter what you use to house or support the equipment in your Hi-Fi system? The reason is 'acoustic feedback' from loudspeakers which seriously degrades the sound quality a Hi-Fi system makes - regardless of how good or expensive that system is. The usual choice of high mass (usually metal and glass) stands, racks and cabinets makes the problem worse not better. To find out how and why, read on!
It's only electronics, how on earth can it tell the difference? Surely any possible difference would be too small to notice? Good questions and ones you can best answer for yourself by conducting a simple experiment: try the Cushion Test!
The Cushion Test
1. Slip a cushion between your CD player and the surface it stands on. Play a few seconds of music.
2. Take the cushion away and play the same music again.
You should hear a big difference between ‘cushion in’ and ‘cushion out’. (If you didn’t then this is your second opportunity to close this book and give it to a friend!) Don’t worry at this stage whether the sound is ‘better’ or ‘worse’, we’re just proving that there is a difference.
Try this experiment with your preamp, power amp or integrated amp, speaker, etc. You will find that every part of your system changes its performance depending on what it is standing on.
When I first heard the difference that a support made, two questions immediately demanded answers: why did the support make a difference? And consequently: what was the best support possible? I set about a period of R&D to find the answer.
All my early work was with turntables: the source component most sensitive to the support problems and therefore the most revealing of the differences. It made the development process quicker and easier being able to hear the differences in construction and materials so clearly.
It also allowed me to prove that I had a universal solution to the problem of supports rather than one limited to a particular product or situation. I found that it didn’t matter whether the turntable was cheap or expensive, heavy or light, belt drive or direct drive or any combination - the effect of the correct solution (my Torlyte® turntable stand) was totally beneficial and the same across the board. Subsequent work with CD players, preamps, power supplies, amps etc. proved the point and confirmed the ‘rightness’ of the solution.
Any discussion of the causes, effects and solution of the Hi-Fi system support problem must begin with a clear analysis of the mechanics involved. This is not rocket science but the simple mechanics (physics) everyone was taught at school. The effects those simple mechanics have are very interesting and lead to problems in the electrical or electronic domain.
Acoustic and Electrical Feedback
A Hi-Fi is not a simple chain of components with a source (e.g. turntable, CD player) at one end and a pair of loudspeakers at the other end. The two ends (and every point in between) are connected together acoustically by the sound from the loudspeakers passing through the air, the floor and, crucially, the system support stands - this is 'acoustic feedback'.
As the acoustic feedback enters each piece of equipment it becomes 'electrical feedback'. How? Well the electronic components inside your Hi-Fi equipment (e.g. capacitors, diodes and resistors) are 'microphonic'. That means that they produce small electrical signals in response to mechanical vibrations such as acoustic feedback. These electrical signals (electrical feedback) are not in themselves very large, but in relation to the audio signals being processed they are very significant indeed. They mix with the audio signal and pollute it audibly.
And to make matters worse, the feedback effect is cumulative. The energy content and frequency balance of the feedback signal is added to the music signal passing through the system and modifies it cumulatively. This cumulative effect is a classic vicious circle where the system sounds worse and worse as you play it louder and louder.
This acoustic and electrical feedback link seriously compromises the performance of your system by creating 'time smear' distortion and 'colouration'. The result is an increase in tonal colouration, loss of information and detail, a reduction in dynamic range and, worst of all, a marked reduction in musicality caused by time smear.
Colouration and Time Smear
The first thing you may notice is the effect feedback has on the tonal colour of the music (colouration). However, the worst and most destructive effect feedback has on the music is to cause 'time smear'.
The feedback signal is like an echo; it is a delayed repeat of an earlier sound.
The confusing effect of this can be heard in its most extreme form in a large church or cathedral. In this situation an experienced speaker will pace his delivery to allow for the echo and so maintain intelligibility.
In a Hi-Fi system however, even the small amount of echo visible is a very big problem because it causes 'timing smear' that destroys musicality. Timing is very important in this world; never more so than in music. After you learn to play the right notes in the right order - timing is everything. It conveys emotion and meaning. Timing is the difference between a good musician and a great one! Timing IS musicality. If timing is so important in the creation of music, then logically, timing must be equally important in a music reproduction system.
The time smearing that occurs in a Hi-Fi system 'bleaches out' the strength of the rhythm and destroys the timing subtlety of the playing. After taking steps to reduce timing smear in a system, listeners have made comments about the ability or talent of the musician: "I didn’t know he could play that well" and "I was bored by that piece of music before, but now I quite like it!"
This is what is so important about time smear (or more technically 'Time Domain Coherence'): it controls enjoyment of the music itself rather than just affecting the sound of the music.
The message I want to get across is the extent to which equipment supports affect rhythm, timing, bass depth and colouration; and the fact that the conventional Hi-Fi recommendation to use metal, glass and high mass (weight) is completely wrong. Not just a little bit 'off message' but wholly, totally and completely wrong!
I’m sure you find it difficult to believe that so many people can be so wrong. And I agree that it is difficult to believe. The problem is that people have a tendency to accept things that they have read or been told without questioning it or researching it for themselves. Because of this, inaccuracies and errors get repeated. If these inaccurate assumptions are then used as the basis for further research it is easy to see how we can be sent off course. If you do think about this problem of acoustic feedback and apply some very elementary physics to it, the real answer is staring you in the face!