Quote:
Originally Posted by
KevWind
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So what were the measured differences in decoupling between 1/2 tennis balls and ISO acoustic stands ?
At constant load (speaker weight) Tennis balls will have a higher deflection (softness) and better bounce up = better performance. So I already know who's winning.
But let's do a rough run of the numbers so you have a better idea of what's going on.
First you must calculate the stiffness of the decoupling (elastic) layer. For that you use the equation
s= ES/d where
E is the elasticity modulus (Young's modulus)
S the surface and
d the thickness.
Half A tennis ball being fairly softer/ more elastic than the Iso Acoustics stand with less contact surface (just tip of the half balls) and the interface can be considered to have more more thickness you necessarily get
s (tennis ball) < s (Iso Acoustics stand).
Which means the 3 half tennis balls are less stiff than one ISO Acoustics stand. That's a clear hint at better performance already.
From there we can calculate the resonant (or natural) frequency of the system which is:
f(0)= (1/2Pi)sqrt(ES/Md) with M the total mass (here, speakers).
The Mass M being a constant (speakers) only the stiffness s we calculated higher matters.
Since we know the factor
s for the half tennis balls was lower, it mathematically implies that the natural frequency for the tennis ball will be lower.
Which means the half tennis balls start decoupling from a lower frequency, calculated at f(e)=sqrt(2)xf(0).
Tennis balls are more efficient.
I'll happily run an accelerometer test if any ISO Acoustics stands user can lend me stands for a couple days. But I have little doubt as to the outcome.
One of the other factors that also must be taken in account in calculating such systems is called "Foundation Compliance" (Impedance, mass, spring characteristics, insertion loss etc) and will dictate if the support on which the decoupling interface is resting (stands or a table top / furniture) will in fact increase or decrease performance of the decoupling system itself.
Ideally you want your support/foundation as heavy and stiff as possible.