Turntable Resonance Fix

@mijostyn, I’m not sure the problem is extrinsic. I conducted these measurements with either no speaker output or extremely low speaker output. I considered noise from mechanicals as a potential source of vibration early on in this process, so I made sure the air conditioning system wasn’t running nor were either of the refrigerator compressors in the nearby bar nor the water heater in the adjacent utility room. This doesn’t exclude sub-sonic vibrations (with associated harmonics that could creep into the audible range) occurring from outside the house, so I confirmed the integrity of the system’s isolated state by keeping the motor drive off, placing the needle on the non-turning record and observing the results on the analyzer. For an extra degree of thoroughness, I took readings both with the drive belt taken off the platter as well as installed normally. No measurable noise occurred in either of these configurations with the drive motor off. To eliminate the possibility that the drive motor itself was the culprit, I kept the motor and belt off while hand-turning the platter to a slightly faster rate than normal and allowed its inertia to slowly dissipate. The original resonance problem was observed using this method. 

If I understand you correctly, your experiments suggest the resonance comes from the bearing but the successful addition of the springs leads you to propose that to achieve its original magnitude the resonant energy must be traveling into the shelf then back up into the turntable/tonearm. Yes?

Usually you don’t want to spring load something that is already spring loaded. You probably don’t need the second set of springs under the shelf.

@lewm This is correct. However, it still seems implausible that an amplification of that magnitude is possible through the bearing/plinth/feet/shelf and back up to the tonearm. I'm trying to account for other possibilities, but I'm just not sure where to look. Is it possible that the tonearm itself is contributing to the resonance? And furthermore, that the tonearm's resonance is somehow being amplified as it travels down to the shelf and back? 

I'm considering reversing the configuration, measuring again, and then reconfiguring with the Nobsound springs and re-measuring just to be sure. 

Good advice re: spring-loading the shelf that holds an already spring-loaded turntable. Those will be coming out. 

sixfour3:

Thanks again to @millercarbon for his advice. This has to be simultaneously the cheapest and most effective fix for an audio problem that I’ve yet come across. 

You're welcome. Happy to have helped. You have a really good handle on the situation, too. The vast majority of vibration control problems are generated within the component itself. A lot of guys miss this so congratulations are in order for figuring it out all by yourself. 

What is always happening, not just with turntables but with everything, the component generates its own vibrations. They travel down the feet into the shelf or rack or floor or whatever. What exactly it is really does not matter. Some find magical properties in concrete. Sorry, no. Carbon fiber is way better but even that has been demonstrated nowhere near as effective as isolation- and springs are the best isolation. 

All these different things, none of them eliminate vibrations. Every time we try and do that all we wind up doing is having a different set of vibration characteristics. We shift the energy around the spectrum. Ultimately it remains and colors the sound until finally it dissipates.   

What you have just measured then is this: In the beginning you had a tiny little bearing rumble that would have been inaudible, but for the sad fact it was at just the right frequency to excite sympathetic resonant vibrations in the shelf and rack and everything else around the turntable. All of it, and you could knock yourself out trying one thing after another in search of the culprit. If even it was just one thing. Probably not. Now the bearing is making just as much vibration, but being on springs this stays within the turntable which has been designed (we hope!) specifically to dissipate and attenuate exactly this sort of noise. 

This same principle applies to every single component. Every single one. Tube amp, DAC, speaker- speaker cables and power cords, even! Think about it. Think about the tremendous improvement you can see and hear just from this one thing. Now imagine doing your whole entire system. That is what I have done. Now I bet you can understand why.

I should probably add, the general term for this is ringing. One thing excites another until the whole mess is ringing. The best demonstration of this I know is this one by Max Townshend. https://youtu.be/BOPXJDdwtk4?t=5 The demo is a speaker but the same applies to everything else as well. The main difference between his Pods and Podiums and your Nobsound springs is damping. Nobsound has none and so allows resonance, and this colors the sound. Townshend eliminates this with an ingenious air damping valve. It is hard to notice the resonance you are hearing now with Nobsound. I know because I had them, everywhere. Moving to Pods however, when it is gone the improvement in authentic tone and timbre is impressive.