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View Full Version : Spikes vs Foam Floor Isolation



Megalomaniac
01-17-2009, 04:23 PM
Just found this article. It makes sense to me, but I would love it we could bump our heads together and expand more on this. Why? I love to hear others thoughts and learn more. I always thought spikes cause distortion, like a record player the needle transfers sound through bumps and valleys using a tiny needle tip. :)

If you want to read full article here:
SD damping feet for loudspeakers (http://www.sonicdesign.se/sdfeet.html)

key notes:



Every loudspeaker rests on a surface that can be compared to a spring, even though the surface may be quite hard. As a result, a resonance appears within or outside the loudspeaker's frequency range. Below this resonance frequency the loudspeaker is coupled to the floor, and above this resonance it will be more or less isolated from the floor.

The traditional approach has been to try to make the suspension so stiff that the resonance might be placed above the audible range. This is one of the basic ideas behind the use of "spikes". However, this approach does not work. The resonance between the cabinet and the floor will not be any higher than the upper bass range. Not even a concrete floor will do, as anyone who has drilled a hole in a concrete wall will be aware of after having experienced the resonances and sound transmission in this material.

The spokespersons for spikes also bring forward two more incompatible theories:

1. Spikes work as mechanical diodes, transmitting vibrations one way only.

2. Spikes rest on an infinitesimal area unable to transmit vibrations.

Regarding theory 1, Sir Isaac Newton has yet to be proven wrong. A force causes a counterforce. This is of course valid both ways.

Regarding theory 2, the tip of the spike may be very small, but not smaller than necessary to carry the weight of the speaker. In that way a force exists between the spike and the floor. This force will be modulated by vibrations and thus transmit them.



The conclusion that the resulting movement is small enough not to cause any trouble is surely correct. One could however get an implied conclusion that spikes could improve things ever so little. This is simply not so. A high Q resonance will multiply the movements until they become quite noticeable. The free floating approach should be the goal.

http://www.sonicdesign.se/bilder/osc1.gif
Sinus signal 125 Hz to the speaker (top),
floor movement below, using soft feet.
Floor signal magnified 2 x.

http://www.sonicdesign.se/bilder/osc2.gif
Sinus signal 125 Hz to the speaker (top),
floor movement below, using spikes.



Spikes can give an open but slightly hard and distorted sound, which some may say is more musical. But resonances and overtones in the floor are equivalent to harmonic distortion in the amplifier.

A soft overdamped support where the resonance frequency is a little too high seems to make the music sound dull.

The use of "Blue Tack" or damping feet with extremely high internal damping can be compared to a car with too hard shock absorbers, where much of the vibrations will pass through even if they are not amplified.


Serious turntables should already have an internal floating chassis with a resonance much lower than the already low resonance frequency of the tonearm/cartridge combination. The introduction of a third series decoupling resonance would fail unless it was lower than 1 or 2 Hz.