Earthquakes on hifi
Effect- Vibrations on Audio
Any group of components brought together with the aim of accurately reproducing music or a film soundtrack is at the mercy of our planet, and the consequences truly are seismic.
Every moment of the day and night, global activity is occurring, mostly manifested as a phenomenon known as microtremors. These ground-borne seismic vibrations are always present, everywhere, all the time.
They are Mother Earth’s never-ending backing track, the residual noise recorded on seismographs between earthquakes. Unless filtered out, the microtremors join in and wash away crucial fine detail.
So how come we can’t feel them?
Their amplitude is very low, measuring between force -1 and force 2 on The Richter Scale, shown in any seismograph reading. No, you can’t feel them and the only way you can see them is as a graphic trace. But you can hear their degrading influence.
The presence of low-level seismic activity 24/7 is responsible for undermining your hi-fi’s potential to give true musical satisfaction and ultimately
compromises your financial investment in whatever hardware you choose to own.
Townshend Audio is the world’s only manufacturer of isolation systems that protect hi-fi and AV equipment from seismic microtremors. The first line of defence is the Seismic Podium. Designed as a range to accommodate any size and weight of speaker – stand-mount plus stand, floor-stander or subwoofer – the Seismic Podium breaks the acoustic connection between the floor and the speaker, preventing the passage of deleterious vibrations both to
and from the speaker cabinets.
For a detailed explanation of why this is an absolute necessity before any speaker can perform to its true potential, read ‘Earthquakes on hi-fi’
Floated on Seismic Isolation Podiums, speakers are freed from the ever-present seismic activity and room/floor interactions that seriously degrade sound quality. The result is simply magical, allowing listeners to hear into their favourite music in a way they were never able to previously. When under your speakers, they will give you immediate improvements in overall sound by preventing speaker generated vibration from entering the floor and
sound from entering your speakers. By eliminating the resonance between the speaker-cabinet mass and the floor, the sound will be noticeably clearer, much more tuneful, controlled and natural.
Bass boom is significantly reduced and there will be a far larger, much deeper and wider sound stage. The sound becomes natural and more enjoyable.
As many have already witnessed, the improvements are a revelation and a true pleasure – not least because
severing the acoustic link between the speaker and the floor allows playback at more realistic volume levels
without annoying the neighbours!
There is an earthquake under our feet 24/7. The amplitude is very low, measuring between force -1 and force 2 on The Richter Scale, as shown (fig. 1)
Fig 1)
Fig 2)
This means that most living room floors will be vibrating with an amplitude of about 10 microns (force 1) with a frequency range from 1—500 Hz.from the US Geological Survey. These tremors are the result of myriad worldwide earthquakes shaking the ground at such low amplitude, they are not felt. The amplitude of these earthquakes in built up areas varies through the day due to man-made disturbances and natural phenomena, such as wind and tide. For example, The Houses of Parliament rise and fall 11” twice a day due to the rise and fall of the Thames. The result of these vibrations is shown in the Seismograph read-out (fig. 2), which is from The British Geological Survey
Seismograph, measured in Swindon, England, on the 27 January 2015.
Notice how quiet things are between 8PM and 5AM. Then the increase in amplitude,
commencing at around 5.30 AM, caused by the build-up of traffic on the nearby M4 motorway. As the traffic builds and human activity increases, the noise increases quite dramatically.
The range is from force 0 to force 2 and is typical of most built up areas throughout the world. Clock the force 3 natural earthquake at 6.30PM! To see more of these read-outs, look up “live seismograph data”.
This means that most living room floors will be vibrating with an amplitude of about 10 microns (force 1) with a frequency range from 1—500 Hz. The closer noise sources result in higher frequency vibration.
The speaker (fig. 3) has an upper mid-band 5kHz signal, level 40dB at 1 metre applied. This is representative of the level of sound from a decaying cymbal note. The resultant cone move- ment of a 100mm diameter driver, is about 0.01 microns. If the speaker is coupled rigidly to the floor with spikes, the 10 micron earthquake floor vibration will travel up the spikes, into the cabinet, into the basket and onto the magnet plate. As the magnet plate is the “launch-pad” of your audio signal, this seismic movement will be superimposed onto your music (10/0.01=1000 times greater!) inevitably contaminating it.
Fig 3)
Fig 4)
Replacing spikes with Townshend Audio (TA) Seismic Isolation, dramatically reduces the ground borne vibration entering the speaker, so that only the music is heard (fig. 4) Seismic Isolation will break the connection between your speaker and the floor with a subsequent increase in clarity, depth and soundstage.
Seismic Isolation will break the connection between your speaker and the floor with a subsequent increase in clarity, depth and soundstage.
Fig 5)
When the cabinet is Seismically suspended, at the lower end of the spectrum, a bass note of 41Hz (E1) at 80dB level, at 1m is reproduced by a 300 mm (12”) driver, the cone movement will be 4mm. If the mass of the cone is 40g and the mass of the cabinet is 40kg, the cabinet movement will be 4 microns. (fig. 5)
By Newton’s Third Law, the 4 micron cabinet movement will be linearly related to the 4mm cone movement, causing no distortion. This will only decrease the bass output by a miniscule 0.01%. If the speaker is rigidly spiked to the floor, then the 10 micron floor noise will be added to the 4 micron driver movement, causing more problems than it solves! Further, the resultant bass noise (boom) will be transmitted into the floor, where it will re-radiates into the listening room and all adjacent rooms. (fig. 6)
By Newton’s Third Law, the 4 micron cabinet movement will be linearly related to the 4mm cone movement, causing no distortion. This will only decrease the bass output by a miniscule 0.01%.
If the speaker is rigidly spiked to the floor, then the 10 micron floor noise will be added to the 4 micron driver movement, causing more problems
than it solves! Further, the resultant bass noise (boom) will be transmitted into the floor,
where it will re-radiates into the listening room and all adjacent rooms.
(fig. 6)
With Seismic Speaker Isolation this insidious path is blocked, so you can enjoy your much more musical system without disturbing the neighbours. For the last 25 years, TA has promoted the radical concept of very low frequency vibration Isolation of all hi-fi components, including speakers. With the extensive experience gained and the in-depth understanding of real life situations, TA has engineered a compre- hensive range of products to ensure the optimum performance and enjoyment of any hi-fi system.
Fig 6)
The Townshend ‘Floating Effect’ will free every note allowing accurate attack and decay of each musical note- simply magical
vs Resonant frequency vs Deflection
Assertions about using spikes.
By Jack Dinsdale, Professor of Mechatronics
If, and this is a very big IF because it is impossible practically, every item in the sound reproducing chain from front end to speakers was connected (spiked) by infinitely stiff means to an infinitely stiff, perfectly (100%) damped, infinitely stiff infinite mass which was perfectly (100%) damped and not vibrating in any way, then spiking would work. This is clearly impossible, but it might explain how spiking came into vogue in the 1950s, when folk had no idea about stiffness (lack of), damping (lack of) and how buildings and the earth itself are anything but perfect.
The only logical practical alternative is to isolate each item, which is what we do with your various mounts. It could be argued that our system ‘spikes each item to the atmosphere (void)’ which is effectively perfectly (100%) damped and (almost) perfectly isolates them from each other
Jack on Transmissibility
Ideally you would like to enjoy your music at its natural volume level– as if you were listening to a live performance – without being irritated by vibrations caused by other equipment in the building and without annoying the neighbours!
Conventional so-called rigid supports (spikes or cones) aim to hold the speaker cabinet ‘still’ at audio frequencies. However there will be a resonance set up by the mass of the cabinet reacting with the unavoidable springiness of the floor, even concrete floors. This can cause vibration of the whole building structure in the audio band, which can be very audible to your neighbours. This ‘rigid coupling’ is shown by the black line in the transmissibility graph – a transmissibility of 1. Rigid coupling also transmits building-borne vibration back into the speaker cabinet and thence to the speaker driver baskets where it is superimposed onto your own music and also into other components in your audio system.
Level of isolation achieved by Seismic and other approaches
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