"Jim Lesurf" wrote

My speakers have four spikes beneath them which makes it a pain to
move the speakers even slightly as the length of at least one
spike has to be adjusted to make all four rest on/in the floor.
(The floor is solid - maybe concrete - and not wood.)

"concrete"... is a very good vibration sink compared to wood, for
example.

What size/shape/structure/type of "concrete" do you have in mind, and
what do you mean by "sink"? Can you point pun me at measurements to
support what you say?

In theory, all things being equal (concrete's mass will convert more
sound energy to heat more efficiently as compared to wood which tends to
resonate.

Afraid that reads like a rather muddled set of assertions to me. Which
"all
things" are you setting "equal"? What do you mean by "concrete's mass"? Do
you mean 'density', or what?

How does 'concrete' having 'mass' mean it disspates vibration more easily
than the same 'mass' of wood?

What about the question of coupling between the different mechanical
impedances which may mean that less energy transfers? etc, etc.

All solid structures have a tendency to 'resonate'. But since you still
say
nothing about the structral sizes and shapes, nor the internal wave
impedances, velocities, or dissipation factors, nor how the coupling
depends on many factors, your assertion isn't one you have actually
explained.

The spiked speaker act as a spring component (albeit a rather stiff one).
The potential positive effect of spikes is related to the speaker-floor
coupling this spring component causes.

The speaker-floor coupling is a (more or less damped) resonnant system.
Below the resonnance frequency, the speaker & floor acts as one solid unit.
If you have a rigid, heavy floor (concrete etc), you might experience clean
bass with maximum attack. Hi-fi bass at it's best? With a lively (wooden
etc.) floor, the floor - and maybe even the walls - may act as passive
transducers totally out of control. If you can feel the bass coming through
your feet or your chair (as opposed to hitting your stomach & chest) this is
probably what caused it. Hi-fi bass at it's worst!

Above the resonnance frequency, the speaker is practically decoupled from
the floor. Whether this causes "the tail wagging the dog" in an audible
sense depends on speaker mass, cone mass, speaker center of inertia and cone
location on speaker. In most cases this effect will be neglible. But if the
resonnance frequency is very low (say, 15 Hz) - and if the speaker is
lightweight (30-40 Lbs) - you may get compressed transient response,
particularly from the bass element.

What's now left is the region around the resonnance frequency. A lot of
unwanted things may happen here. The speaker-floor coupling will have a Q
value, determining how well-damped the resonnance is. Poor damping may cause
significant problem in this region - due to speaker vibration.

For a given speaker, the speaker-floor coupling (be it spikes, squash balls,
rubber wheels, MDF etc), defines the resonnant frequency and the Q value of
the coupling. Spikes will typically move the resonnant frequency up somwhere
in the midrange , and the system will have a relatively high Q-value. While
(in some cases) improving bass performance, this may create audible problems
in the midrange. Remove the spikes and you may replace midrange problems
with similar (but not neccessarily similar sounding) problems in the bass
region. You cannot move the resonnance frequency above audible range (20
kHz) - which is why you might have to compromise.

Another strategy is to move the resonnance down in frequency with silent
feet, rubber weels etc. With heavy speakers you can move the resonnance
frequency well below 20 Hz - out of audible range. In addition the bass
output will be as clean as you've ever heard, but you might be loosing some
attack due to the decoupling from the floor (or maybe you're just addicted
to "hi-fi bass"). Compromise here too? Maybe not.

Allthough the sonic effects of spikes may vary from speaker to speaker and
from room to room, they do move the resonnance of the speaker-floor combo up
in frequency. Sometimes it improves overall sound, sometimes it doesn't. But
the effects have a very natural explanation.



Many high end speaker manufactures like Wilson Audio, B&W,
Egglestonworks and others construct speaker cabinets out of synthetic
compounds, stone, or aluminum for this reason., for example. Of course
in practice it is more a complicated subject because of Q value effects.

Meausrements... yes, I have data. What is your specific question?

Provide the specific measurements (and how you did them) that back up the
specific assertions you make above. We could then decide if your views are
supported by measurements you (or others) have made, nor not.

Who is "we"? You don't speak for anyone but yourself, Lesurf.


Since my background is in science and engineering,

There are ZERO qualifications, not even a Drivers License,
for someone to call themselves a "Engineer". What kind of
formal education in engineering do you have...
undergraduate/graduate and in what field?


I do tend to prefer to base my own conclusions on being able
to assess measured evidence, and the details of how those
measurements were obtained.

I understand. I've run about 23 batches of tests, as I recall, several
years back. If I have time I'll post something.


Given that consumer audio is awash with 'technobabble' I tend to
place more reliance on that than on simply accepting assertions.

You enjoy intellectualizing but it would behoove you to get off your
penguin butt and do the work yourself.