Earthquakes on hifi
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.
The solution is to isolate your speakers from the building structure using a low-pass filter, in other words to let them ‘float’ throughout the audio waveband. This can be achieved by using Townshend Seismic Load Cells.
They work by coupling the mass of the speaker cabinet to the building structure, usually the floor, via a spring. At very low frequencies, the supported mass (speaker cabinet) follows the (slow) movement of the floor with a transmissibility of 1, just as with the rigid coupling. As the frequency of movement of the speaker cabinet (caused by reaction to the movement of the speech coil as it plays music) rises, a point of resonance is reached where it oscillates a large amount for a small input, 3.5Hz in the example in the graph. This large resonant oscillation can be tamed by damping.
As the frequency rises further, the movement of the speaker cabinet reduces, ultimately at a rate of 12dB per octave, the orange line in the transmissibility graph. For audio systems, this reduction in coupling between the speaker cabinet and the building structure should start at about 5Hz. This resonant frequency of oscillation depends on the mass and spring rate, but it can be shown to be 3.5Hz if the compression of the spring when loaded is about 30mm.
In this way a spring can be selected for any speaker cabinet to give a resonant frequency of 3.5Hz.
Since Seismic Load Cells are bi-directional they also reduce the effects of building structure vibration from entering your speakers. Furthermore, they act equally in all three planes, thus counteracting all aspects of building structure vibration.
For large displacements and without any damping, the speaker cabinet would oscillate for quite a long period, as is common with undamped sprung turntables. In the Seismic Load Cell this oscillation is rapidly damped by the turbulence of the air passing through the hole in the bellows/small-hole resistive damping arrangement, as shown by the dotted orange line. When at rest there is no resistance, and full isolation performance is realized. The orange shaded area in the graph shows the high level of isolation achieved by using Seismic Load Cells, compared with that from spikes and cones.
As a listener, you experience the Townshend Floating Effect – the sound improves dramatically and becomes independent of the speakers, providing wider stage width and greater depth, together with tighter and more realistic bass, thuddy boom now eliminated. You will be able to enjoy your music at its natural volume level – as if you were listening to a live performance – without annoying the neighbours!
For a more detailed explanation of this phenomenon, see the article “Bad Vibes” Stereophile…..
Rigid devices such as cones and spikes do not isolate, they couple. Springs made of rubber compounds, such as sorbothane, are partially successful, but they don’t act as springs at frequencies below about 50Hz, and much of the musical energy which can stimulate vibration of the building structure is contained at lower frequencies, at which these compound springs act effectively as couplings with a transmissibility of 1, as shown by the green line on the transmissibility graph. The effectiveness of sorbothane speaker mounts, shown as the green dotted area on the graph, is thus severely limited. Magnetic repulsion ‘spring’ mounts are only partly successful because they cannot operate in all three planes without some form of mechanical restraint (Earnshaw’s theorem), which detracts from their effectiveness. Unlike these, and all spikes and cones, Townshend Seismic Load Cells act equally in all three planes.
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Splendid Isolation
With every component you isolate with Townshend Isolation the sound will become progressively clearer and enjoyable
Isolation for source components
Seismic Pods, Platforms
Isolation for speakers
Seismic Podium and Bars
Isolation for audio racks and consoles
Seismic Corners
Hear more detail in every note
- The Townshend floating effect
- Harmonic synergy with Maximum supertweeters
- colourless preampfification
- Transparent speaker-cable
- Detail within detail with Fractal technology
Townshend products aim to enable enthusiasts to better appreciate and enjoy music in high fidelity.
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