Spikes don't drain all of a cabinet's vibration and it's a mistake to dismiss concrete floorborne vibrations as nonexistent, miniscule or inconsequential. Though concrete floors vary in their capacity to convey micro-vibrations, they are structures of steel/concrete that transmit aggressive, acute micro-vibrations readily, as most rigid materials do. Concrete floors all have a natural frequency and reverberant tendencies. Simply walking on a concrete floor induces vibration. Hospitals know this, and that is why they must specially treat concrete floors to minimize vibrations in labs where sensitive equipment like optical scanners are used. At least several optical scanning laboratories use Herbie's Audio Lab products to isolate (and decouple) equipment from vibration, including concrete floorborne vibrations. These products (Extra-Thick grungebuster Dots, Fat Dots, Tenderfoot isolation feet and Soft Fat Dots) do not isolate equipment from gravity and the whole physical world--they isolate and decouple just in the vibrational environment they are dealing with. These are largely vibrations you cannot feel or readily detect, yet like ants at a picnic are virtually everywhere.
I believe most loudspeakers are every bit as sensitive as optical scanning equipment. Floorborne vibrations do not have the inertia necessary to cause a dead-still loudspeaker driver to exert an audible sound. Though miniscule compared to the energies a loudspeaker driver generates, floorborne micro-vibrations have plenty of acute energy to affect the movement of moving drivers. Speaker drivers produce myriad musical frequencies simultaneously, some extremely low-amplitude and nuanced, some having less inertia than external vibrations they are competing with, many below the RFI noise level. Most of these extremely low-amplitude musical signals help to define the ambience and real-life presence of the original recorded event. Though it's perhaps David versus Goliath, floorborne vibrations cause audible anomalies in the music.
Even mega powerful bass frequencies can be affected by tiny floorborne vibrations. Scoping a single wave form will reveal nothing out of kilter, but by superimposing in real-time, the effects of micro-vibrations can be seen by the wave forms jittering, bending or wavering. Seems that battering a mighty, 40 Hz wavelength 40,000 times a second with an itty-bitty 40 kHz vibration can take an audible toll.
Loudspeakers spiked to the floor, whether hardwood or concrete, generate floorborne vibrations, some of which will reverberate right back up the spikes and cabinet the way they came. This is a measurable phenomenon. Speakers are also subject to floorborne vibrations from a multitude of other sources. You don't want your speakers coupled to these vibrations. Subwoofers coupled to the floor generate floorborne vibrations detrimental to floorstanding full-range speakers, and vice-versa.
Spiking to the floor is of course better than nothing. A loudspeaker cabinet just sitting on a bare floor or carpet with nothing in-between is relatively unconstrained, free to wobble and vibrate from its own energies. Placing speakers on rubbery resonating materials causes all kinds of anomalies like loss of dynamics and linearity. Spiking, even with its drawbacks, holds the speaker more firmly and more stable. A resonance-controlled compliant material with an intimate grip on the cabinet bottom--or, something like ISO-L8R--can do even better. This has been accomplished thousands of times with dBNeutralizer-based products replacing spikes for an audibly superior result--scarcely ever the other way around.
I think for the majority of audio systems and music lovers, spikes are fine and more than sufficient. Upgrading some of the components' interconnects might be all that's needed to achieve a decent quality of listening. For the more discerning listener, however, you can do better. You don't need "golden ears" or anything to appreciate a higher-level listening experience.
Whatever the method applied, minimizing the effects of floorborne vibrations on loudspeakers and subwoofers is audibly beneficial and substantially worthwhile.
Steve
Herbie's Audio Lab
