Here's the issue from my view. I wanted to run certified vibration tests on a Black Platinum filter sitting on a PXK frame, so I took it to a certified testing facility. For reference, I brought the test results and test set up parameters another highly reputable manufacturer published on their website. I handed the printed materials to the technician and told him that I wanted to duplicate the experiment. As he read he began shaking his head. He said he didn’t have any devices that were that low powered. He said he couldn’t do it.
The product ended up on the surface of a large square metal plate that sat level with the floor. The plate was separated from the floor by a 2” gap all around its perimeter. The plate sat on top of a huge hydraulic piston that was hooked to a 200,000-watt diesel engine. We ran several tests over a period of 3 hours, mostly in low frequencies. When the table started it moved upward several inches and then fell an equal distance below the floor. This was much more intense than the minimal shaking described in the reference material I brought. As the frequency progressed upward, the plate moved up and down faster but the distance of the movement decreased. I hope you get the picture because it is a fascinating thing to watch. When the tests were completed, we had flattened the spike tips.
So, here’s what bothered me. Of course, the results of a “self-administered” test could be shaped by the strength of the input signal, but let’s put this aside. In this case, the shaker table was essentially delivering a single, time-controlled, “fundamental tone” to the filter directly from the floor. No harmonics. Music is scored to deliver (I’m thinking about classical music) many fundamental tones with broad harmonic contrasts at varied dynamic levels by instruments of wide ranging timbre, bandwidth and tone, the time lapse of each note often highly varied and precisely specified. Even more complicated, these “vibrations” aren’t just delivered from the floor, they are also delivered through the air by loudspeakers positioned vertically in space in close proximity to electrical circuits that produced them. To my mind, the filter system had to handle all of this at the same time.
The problem became much more complex. It begged the question, “What am I trying to measure and how/where do I measure it?” One could put an accelerometer on the floor to establish a baseline, but where to attach another for comparison. The top of the filter didn’t seem right because this supposes that the filter surface is more important than the component producing the signal. One could attach the accelerometer to the bottom of the component or to the top, but the signal is produced elsewhere. More important, it’s not the signal in the component that is most important, it’s the sound that comes out of the loudspeaker. So how, at the location of the transducer, to measure the difference between a signal produced by a component that it is and is not subjected to vibration. The first condition requires the component to be turned on whereas the latter requires it to be turned off and this isn’t practical for obvious reasons.
