Isolation
Noun – the fact that something is separate and not connected to other things
Other than cabling there’s little the drives audiophile conversation quite like isolation.
Isolation of the speakers from the floor.
Isolation of the turntable from vibration.
Isolation of the motor to prevent “microphonic effects”.
Isolation, isolation, isolation and then, just for good luck, some more isolation!
Perfect isolation is total and utter codswallop!
The only way to truly isolate audio equipment is for it to be levitated in a controlled magnetic forcefield and shielded from any interference. The instant you, or anything else, touches it, a connection is created, there is no isolation anymore.
You couldn’t actually play a record in a perfectly isolated context: putting the needle on the record creates an energy transfer at miniscule levels; connecting cables, like power and interconnects will also break isolation. The only option left would be for you to just look at your possessions,which seems to be the primary aim of a lot of audio equipment for a lot of people!
The truth is that perfect isolation isn’t going to happen in your living room, or any other environment any time soon. You don’t want it anyway.
What is acoustic isolation?
Acoustic isolation is dealing with the effects of acoustic transmission, which is the transmission of sounds through and between materials, like air, walls, water and any other things. It really isn’t isolation at all, it is controlling transmission. We can do that in any number of ways, by damping (absorbing) or attenuating (deflection or reflection), or a combination of both.
Transmission of sound and vibration is correctly expressed in Pascals and is a measure of acoustic impedance. This article isn’t going to delve deeply into Pascals and impedance, but what you should understand is that:
Sound or acoustic transmission and propagation is directly related to the medium it is attempting to excite or pass through (which is still excitation of molecules).
Materials with closely matched acoustic impedances transfer those excitations with less loss and therefore more energy.
Also remember:
Nothing is lost, nothing is created, everything is transformed.
Antoine Lavoisier
This concerns energy too:
The total energy of an isolated system is constant; energy can be transformed from one form to another but can be neither created nor destroyed.
First law of thermodynamics
Consider your listening room as the isolated system.
Do we really need to prevent acoustic transmissions?
In short: no!
We are trying to promote acoustic transmission starting with the electrical energy out of your speakers, into the air, to your ears, by converting one type of energy (electrical) to another (kinetic). Note that this is why cables on their own really do not and cannot make any difference! Sorry haters, please read on if you want to understand why.
However, there are times when we want to prevent acoustic transmission. Some examples of that include the following:
- where vibration (kinetic energy) may cause a turntable or CD player to “skip”,
- where vibration may be transferred from a motor to a pickup mechanism as “noise” (microphonics),
- where vibration may be transferred to other materials such as floorboards or walls.
Let’s look at these three examples.
Vibrations causing a turntable or CD player to “skip”
It’s well known that excessive vibration can make turntables or CD players jump or skip. This happens when the internal mechanism cannot cope with an excessive vibrations. The result is that the reading mechanism cannot effectively read the source causing the tracking to fail and making the needle or laser unable to read the encoded signal.
This is indeed a real thing; some very bouncy floors and heavy-footed people do exist. Intense road traffic can shake entire buildings. In those cases, it may be a good idea to isolate the offending turntable or CD player from the external vibration sources. We are, however, talking about very large amounts of energy or a constant, but smaller, energy transference causing issues. These cases are usually fairly rare in your average house, especially if it has been built away from a main road, railway, or in the last 100 years or so.
Where vibration may be transferred from a motor to a pickup mechanism (microphonics)
Microphonics, microphony, or microphonism describes the phenomenon wherein certain components in electronic devices transform mechanical vibrations into an undesired electrical signal in the shape of noise. The term comes from the analogy with a microphone, which is intentionally designed to convert vibrations to electrical signals.
Wiring, cables and even PCBs can exhibit microphonics as charged conductors move around, and various materials can develop triboelectric (static) charges that couple with the electronic circuits.
The best way to explain microphonics to the ordinary person is to use in-ear-canal headphones as an example, when microphonics the cables transfer vibrations due to movement directly to the wearer’s ears. You get an uncomfortable encroachment into your listening pleasure by the appearance of crackles and loud bangs.
Microphonics are a real phenomenon. They particularly used to affect valves and could cause issues. However, and this is like many things in the audiophile world, it has often been blown up out of proportions.
Where vibration may be transferred to other materials such as floorboards or walls
The very act of playing music causes this phenomenon; it’s a by-product of what we are all seeking to do. However, remember: energy can neither be created or destroyed, only converted, stored or released (potential).
This is what we aim to do by setting up an energy transfer chain, using electrical energy from the source, passing it through an amplifier and onward to loudspeakers, which, hopefully, are efficient at converting it into kinetic energy, creating changes in air pressure. Your ears use reflections from your pinna, focusing kinetic energy into your ear canals, drums, etc. until your brain decodes all this as sound. Sound perception is different for everyone, it’s a uniquely and entirely un-shareable experience that is yours and yours alone.
Most of the energy broadcast by loudspeakers will be transferred to walls, floors and then converted to other forms of energy. That is what sound does, regardless of whether you are playing Iron Maiden at full throttle at 2am in a morning, rattling the neighbourhood, or playing the gentlest of string ensembles at 6pm, accompanying your evening meal, gently vibrating your best crystal glasses. Sound is kinetic energy, of which the causal pathway is vibration.
Do we really want to isolate then?
In short: no!
What we want to do is manage that kinetic energy by converting it in a very controlled way, according to acoustic objectives.
Enough science! Those of you still reading may have noticed we’ve returned to science, and in particular, physics. There is a very good reason for this. Physics play the major part in audio, with a little biology and chemistry thrown in. It’s an impossible task to separate physics from audio. The scientific laws we exist by have been theorised, then proved and confirmed. There are few grey or unknown areas left.
The golden rule of isolation
There is, like many things in science a golden rule, one that is, and has proven to be, the best way forward. Just like the golden rule of never arguing with fools (they just take you down to their level, then beat you with experience), the golden rules are often ignored. The golden rule of isolation is often broken because people don’t truly understand its grounding. The golden rule of isolating kinetic energy is simple:
Isolate ONCE
“What?” I hear you say. I’ll say it again: isolate once, and once only.
But surely if you isolate twice, its better?
No, you can’t isolate twice.
All attempting to isolate more than once does, is set up a crazy sequence of events that can only go one way. A bit like an upside-down pyramid, it’ll stand on its point for a while, but you know that when it comes crashing down, it will make a hell of a mess.
OK, explain!
Trying to isolate more than once sets up more problems because you cannot destroy energy.
With regards to energy, you can only either
- convert,
- store or
- release.
You cannot do all three or only two, you can only do one at a time. Once one is achieved you can repeat the process and continue along the way. However, you cannot convert, store or release indefinitely because it is cyclic. By isolating multiple times, you would be required to convert across every individual frequency at its precise point to store or release energy.
Audio frequencies are generally accepted to be in the frequency range of 16 cycles per second (16 Hz), to 20,000 cycles per second (20 kHz). We can however perceive frequency way below this level, we stop being quite so susceptible to it at around 6 cycles per second (6 Hz). The earth itself has a resonant frequency of around 1 cycle per second (1 Hz), but we cannot discern it.
I’m not going to delve into the lengths and applied physics of power and wavelengths, there are plenty of far more intelligent people than me that have and can. Needless to say, it would have to be a seriously large and unwieldy isolation device to perfectly isolate something; let’s for simplicities sake say that you would have to have another earth or similar kicking about in your back yard before you can achieve anything reasonable.
What can we do then, Einstein?
We can selectively isolate a specific frequency. We can also isolate across a range of frequencies. We cannot perfectly isolate all of them.
Let’s go back to our three examples and see what we can do about them:
- where vibration (kinetic energy) may cause a turntable or CD player to “skip”,
- where vibration may be transferred from a motor to a pickup mechanism as “noise” (microphonics),
- where vibration may be transferred to other materials such as floorboards or walls.
The first and last examples on the list are closely related. We are dealing with relatively large amounts of kinetic energy. We will deal with them similarly.
Let’s first get microphonics out of the way. Many things exhibit microphonic tendencies. Valve sets were notorious for it for many years, as were many electronic items. Note the use of the past tense. While there definitely are items in the modern audio world which can exhibit microphonics, the list has shrunk considerably and even valves now tend to be mounted on or in boards which have a degree of flexibility to them. This means that microphonics are mostly confined to the realms of older HiFi equipment. Modern solid-state electronics are mostly immune from these effects. Manufacturers of components and equipment, know how to effectively deal with microphonics.
Because they are a predominantly electrical issues, as opposed to physical issues, we intend to get someone suitably qualified to write a short article on this. Watch this space…
But what about wire?
“You already said that cables can be susceptible to microphonics. It must make a difference!”
Yes, it can, if it’s moved, quite a lot and quite specifically, while electrical energy is being passed through it. Do you move your speaker cables quite a lot around while they are playing?
Back to the job at hand!
As we keep saying, energy cannot be created or destroyed. Only converted, stored or released.
When we set kinetic energy into rhythmic motion by whatever means, one of the effects is that vibrations are created. We most easily deal with vibrations with damping. However, there are few perfect dampers available to us in Hi-Fi. We could use a bath of viscous liquid or the previously mentioned levitation, but ultimately neither are particularly practical or free of issues.
We usually resort to wideband damping by using an elastomer. It converts kinetic energy into heat and releases the remaining energy to lower intensities, resulting in dissipation, at least in the common sense.
Elastomers work by connecting (not isolating!) one mass to another mass via a spring. That spring in this case is the elastomeric compound. Its composition, shape and quantity is calculated to adapt both to the mass of the item we are trying to isolate and the frequencies of vibrations that we are trying to deal with. The elastomer will release the energy into the mass of the ground (or a substantially large mass such as a building) in a controlled way, at different frequencies, below the audio range. The rest of the energy is converted into heat. Elastomers work best for frequencies below 120 Hz but are also effective up to around 800 Hz, depending on the “shore” or hardness of the compound. However, there are harmonics to consider; elastomers will play a part well into the thousands of cycles per second frequencies (kHz) range.
Such systems are called “Mass Spring Mass” (MSM) systems and are a well-defined and proven solution to vibratory issues. They are employed in many places, from train lines (to make them less noisy and more comfortable) to entire buildings and delicate measurement systems so immune to most vibration that they are effectively totally efficient. The spring can be created using many materials, including gases, solids,or liquids. The key to using that spring is to place it under an initial pressure; an uncompressed spring will do nothing. The need for this pre-compression state is the main reason why knowing what the exact mass of the equipment is, so that we can adapt the spring to suit.
There are some very good elastomers out there. Many years ago, I developed one of my own in conjunction with Getzner (who make Sylomer), specifically for use in audio applications (there is no magic involved, it’s simply a little softer and spongier than many industrial elastomers!).
There are many commercial products on the market advertising their capacity in preventing CD player and turntable skips and jumps. They mostly attempt to use the theory that we have just explained, applied to shelves and feet. However, they pretend to be universal, usable for any equipment, regardless of their mass. This is a problem… For such system to work anywhere close to any fruitful level, the springs must be adapted to the specific mass of the equipment, within 0.3%. You can now understand why most of those products can’t really do what they should be doing in any efficient way!
Compounds sold by the likes of Sorbothane (which is a brand, not a specific elastomer) will give you a weight range you can support. In many cases this will do a reasonable job. However, it is extremely unlikely to be perfect. More dangerously, if the calculations are wrong, these things can give worse results compared to doing nothing.
Many people think that manufacturers don’t consider vibrations and start adding third-party feet, attempting to isolate their turntables and CD players a bit more. In fact, what they are doing is usually making the situation far worse and amplifying vibrations into the audible range.
My advice? Leave well alone; the feet installed on your equipment are probably far more effective than you think. Despite what you may think you hear, you’re unlikely to be making any worthwhile additions.
Well, what about equipment racks?
Equipment racks serve a purpose, usually to support your equipment safely and solidly in the best possible way. They have a purely psychoacoustic effect. In other words, they mostly do nothing other than display your audio jewellery to the best effect.
There are good and valid reasons for having a solid equipment rack but balancing each shelf on top of little spikes and the whole lot on other spikes is pure unadulterated rubbish! There are limited reasons for isolating some items from the floor: turntables and some valve amps and rarely, (possibly), a CD transport. But unless each of those shelves is precisely tuned to the weight of your equipment, it’s a vanity project. Sorry not sorry, it’s the truth!
Let’s now turn our attention to isolating speakers from the substrate they are stood on
Many years ago, I developed an acoustic support called AcoustInert™. It is an elastomeric compound that is designed specifically for audio application with quick and easy calculations available for a usage as the spring in an MSM system. It was designed to support large speaker stacks and other heavy objects while avoiding transmissions into the surrounding floor. They are proven to work; I sold thousands into clubs around the world and despite the fact they are extremely simple devices, they were manufactured to order, because you must measure the mass of the object you are supporting to very fine tolerances to manufacture the right shape and quantity for the required result. For example, getting the specifications wrong in the context of a nightclub can result in closure of the venue because of energy transmission issues. You really do not want a legal case that could run into hundreds of thousands of your local currency worth of damages and legal fees, ultimately resulting in the closure of a venue for months to years.
While this is large scale use, the principles remain the same for the Hi-Fi loudspeakers used in your home. You must support the weight of your speaker effectively, properly and securely while precisely matching the calculated spring to the supported weight.
Great speaker designers go to extreme lengths to design cabinets that resonate very little, with low residual energy that could transfer into the floor. Are your speakers from great speaker designers?
In most cases, speakers that are well braced and solidly manufactured will not transfer enough energy into your floor to create a real problem that you will need to solve. What energy is transmitted is so minute as to be literally inaudible, almost unmeasurable without specialist equipment. Your iPhone certainly isn’t going to be good enough!
So why bother? Isolating speakers is something that very few people need to do, and to do it properly you need to take the speaker weight, centre of gravity, and have a custom-made matched plinth. Trust me, none of the “pods” on the market work properly, unless they are exactly matched to your speakers.
There is an exception to this rule, but it has certain caveats. First, you must be placing high energy speakers on a desk or similar light furniture, then you also must have an item on the same surface that can be shown to be susceptible to kinetic energy (such as a CD player. Precision in the specification of the isolation compound still stands. Solutions to that particular use case are not and will never be as simple as buying something that promises to do the job, because from an isolation point of view, it can’t and it won’t.
My advice is to put a layer of felt down on a hard floor to stop marking your speakers and floor, or maybe some thin semi-sticky rubber feet. A spot of BluTack does a wonderful job for not much money!
The case of the misunderstood spikes
Spikes as an isolation solution… It’s a bit of a folly!
Spikes are not there to isolate your speakers from your floor (although they do an adequate job)!
Spikes have a single use: keep your speakers in one place and provide a decent platform for your loudspeakers when placed on carpets… That’s it! Any other reason proposed out there is futile.
Spikes were seized upon by an industry desperate to sell you more utter rubbish at inflated prices! (A bit like other parts of the industry really.)
Many speaker manufacturers now fit or supply spikes. Our advice is to either remove them or use spike cups if you have a solid floor. If you have carpets, use them, of course. Don’t attempt to push your speakers through the floor to the depths of Hades, just push the spikes through the carpet, down to the hard surface below, so they don’t move around and are stable.
You can mark your hard floor with a bit of masking tape, so you know where your speakers go if you move them around. You can also put a small screw into the floor to act as a cup.
Let me make it clear that, spikes are not going to hurt anything, they will present some isolating properties, they will ensure your speakers stay still, in place, and do their job. They will not set up weird artefacts in the audio responses you hear.
Speaker Stands
Speaker stands need to be relatively heavy and inert. If you tap them, they shouldn’t ring or respond with anything other than a dull sound. They should bring the tweeters up to around ear level as their primary job. Floor contact and should follow the same rules as a floor standing loudspeaker. Push spikes through carpets to keep them stable and fixed in one place. If you have a solid floor (concrete, wood, laminate, etc) then either cup the spikes or remove them.
Regarding the interface between the speakers and the stand, you only want to provide something that is purely preventing movement and falls. We’re not trying to isolate in any way, we just want to hold the speakers firmly in the correct position. Spikes or other esoteric systems have no role to play up there! The best solution is to use a thin rubberised mat. They usually have a tacky texture that does an admirable job. An easy and cheap alternative is to place a few blobs of Blu Tack under each speaker.
We’re aware that this isn’t what many people have been told, it flies in the face of many of the accepted Hi-Fi “rules”. But from an acoustical point of view, it’s correct and based on science.
Stone slabs and chopping boards between floors and loudspeakers really don’t make a difference to the physics at play. Hi-Fi speakers are rarely specifically optimised for solid floors or for carpets, so they’re designed to handle pretty much whatever situation they are put in. We’re certainly not going to say “don’t do that” about any solution put out there; if it sounds good to you then the psychoacoustics have done their job. Most of the time, that is all that matters.
Literally, the elephant in the room!
Walls interact with speakers and should be considered as a single system. Loudspeakers will hit walls with energy at audible wavelengths. Walls reflect and diffuse and, in some cases, also absorb that energy. There are no two ways about this, walls can be a problem.
Walls and your entire room in general are probably the most important elements in your system. With good room acoustics comes good audio; the two go hand in hand. If you can get the base room acoustics correct, then the rest usually falls into place. That doesn’t mean you can call a company and expect them to magically and remotely deliver a perfect way to make your room sound good. They can’t. No one can. They can give you approximations and a whole boat load of psychoacoustic-heavy kit.
We cannot deal with this effectively in this article because we are dealing with transmission. Walls and room treatments are pure acoustics science. You may wish to read the article on “How to improve your room without spending anything” and other articles which will give you some good pointers. We’ll be dealing with acoustics in another article or more likely series of articles.
Parting words
Finally, enjoy your music. The audiophile world is full of rubbish, utter rubbish, and, quite often, complete and utter rubbish with a cherry on top. Some things out there use grains of truth, but in many, there are unfortunately none. They are nearly all designed to part you from your hard-earned money without making much effort in delivering much benefit. Forget most of it and love the music, not the equipment. We all like a bit of jewellery, nothing wrong with that, but never forget that the true purpose of our hobby is enjoyment. Avoid stress, vanity projects and the constant seeking of perfection, which you almost certainly can never attain.
