Turntable Resonance Fix

MC is correct. And for an extra 200 you get the platform in addition to the Pods. Took care of my concrete bunker ringing problem. Completely.

"Which reminds me, in 1978 I lived in an apartment building in down town Miami on the top floor. The Mechanicals were on the roof"

The Mechanicals played a rooftop show in 1978 Miami? How did I miss that one...Darn!

What are you talking about? What Minus K? Pods for that are like $500 for a set of four.   https://www.audiogon.com/products/townshend-audio-seismic-isolation-pods

I started looking at the Townshend Pods, too.  Problem is cost, not much less than a good used Minus K shelf, for a Pod suitable in size and weight bearing capacity to suit one of my heavy turntables (typically 60 lbs and up).

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.

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.

@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. 

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.

@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. 

Which reminds me, in 1978 I lived in an apartment building in down town Miami on the top floor. The Mechanicals were on the roof and I could hear all of it on a Micro Seiki turntable I had for a short period. I realized it was not the turntable because the noise would change and sometimes disappear. Finally the light turned on. I pulled the carpet away at its edge and listened to the floor with a stethoscope. Sure enough the noise was coming from the building and the special feet on the bottom of the turntable were doing not much of anything. I had an LP 12 several months later which solved that problem. 

Then the noise is extrinsic to the turntable and a correctly isolated turntable will get rid of it completely.

Time to revisit the experiences with the Different Platter Mat Materials.
The results might prove interesting ? 

This is a follow-up on the latest development in this continuing saga to rid my turntable of low-frequency resonances. The latest results are nothing short of incredible. The turntable is still limited, but it has just taken a very large jump in value. I’m going to describe the original configuration and the changes made in detail just in case someone else can either learn from this situation, or better yet, provide insight as to the reason for the results. 

Two sets of Nobsound springs arrived at my doorstep this week. Per @millercarbon’s suggestion, these were purchased as a possible way to push the -30dB resonance measured at 20 Hz further down the scale. 

I removed the original metal, conical feet from the turntable’s levelers. The rubber bumpers to which the conical feet were attached are still present. In the original configuration the conical feet had been sitting on Vibrapod pads. 

So, conical feet now removed, I arranged three Nobsound springs beneath each of the turntable’s levelers. I put the test record on and started measuring with a track playing a 0 dB reference tone at 1 kHz. And not believing what I was seeing, I started running through the settings on my software to ensure that I hadn’t changed something. I hadn’t. All the settings were exactly the same as when I measured the previous configuration. 

This turntable is now emitting a resonance at 20 Hz down near the area of -70dB. 

The resonance rises slightly towards 16 Hz (the lowest frequency I can measure), but even that isn’t much more than -65dB.  By comparison, the second- and third-order harmonics from a 1 kHz sine wave and also random surface noises register higher than that as measured by my equipment. 

This hasn’t been a purely scientific test; there are flaws in my process. And I’m using software (Logic Pro 10.5.1) that isn’t strictly meant for this purpose, not to mention the fact that I don’t know the tolerances of its measurements.

While I cannot draw the conclusion that the Nobsound springs are entirely responsible for the dramatic drop in resonance (the removal of the Vibrapods and the turntable’s metal coned feet are both included in a list of variables that may have contributed), they should almost certainly be given the lion’s share of the credit. Furthermore, I cannot state definitively that the Vibrapods are ineffective in every application, but they don’t seem to offer any reduction of resonances in this frequency range. 

But why was I originally seeing such a high reading at 20 Hz? 

It would appear that a rotation-related noise from the bearing is creating a resonance that was traveling through the plinth, through the feet, possibly through the Vibrapods and into the shelf, and then back up through the feet and plinth, into the tonearm and, finally, into the stylus. At some point along that path the resonance was being excited by a still-unknown factor (determining this is what I still need help with). If not for this, the resonance from the bearing would simply travel directly through the plinth and into the tonearm. Since I no longer have a resonance as nearly as high as previously measured, the excitation of the original resonance is no longer occurring (or at least not to the same degree). And since I have done no further work on the bearing, the original root cause of the resonance has not been eliminated. But the Nobsound springs seem to be extremely effective at nullifying that problem or at least not amplifying the problem as the previous configuration did.    

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. 

Appendix

The turntable sits upon a shelf which “floats” above the audio rack’s superstructure (“floats” in that it sits on another set of Vibrapod pads). It’s a very heavy rack and has proved to be quite effective at reducing the impacts of footfalls. But I have yet to measure its sympathy to other types of vibrations. 

After the application of Nobsound springs to the turntable, I installed the second set of Nobsound springs underneath the shelf upon which the turntable sits. These replaced the aforementioned Vibrapods. I did not observe any measurable changes to the noise floor of the turntable spinning the same track on the same test record. It may be possible that the noise floor may now be low enough that no further reductions should be expected with the associated equipment. 

OP the bearing and the well are the turntable. Take it apart clean everything out and up. Polish everything with really REALLY fine steal wool and then polishing compound. CLEAN, CLEAN, CLEAN, then get a good oil. I use Rislone or a good gun oil and a black velvet or sapphire bearing.. Whop-te-do, Amigo... 10.00 dollars usd at the most.. As good as, if not better than, anything anyone else can do..

That's a tough one.. LOL 20 minutes and wait for the ball to show up..

Just get a tube and listen to the bearing base. IF it's noisy, it's noisy.. A long thin tune up screwdriver or a Stethoscope is even better. THINK....

Now if you want to see the failure take a few high res 12 mp or better macro pics.. of the old bearing.. A mag glass or good eyes..

Regards

I've spent the afternoon cleaning, re-lubing, re-instaling and re-measuring. Thick or thin, additives or none, synthetic or conventional, none of the different oils I tried had any effect on the results. 

What I did notice during measuring, however, is that there are amplitude fluctuations that are consistent with the rotation of the platter. It's obvious to me that the bearing is the cause of the rumble. But to the untrained eye (mine) there are no visible flaws in the bearing and no contaminate in the mechanism. 

I'm going to chalk this up to a poor bearing design that has reached the end of its useful life. I'll start by replacing the bearing. Then I'll work on replacing the table. Thanks, @mijostyn, for the recommendations. 

sixfour3, Not that oil! Too thin and too many additives. Single weight non detergent oil only. Compressor oil is perfect for this use. This may be your problem or part of it. No amount of damping or isolation is going to cure a rumble problem. 20 Hz is also quite high for rumble. You sure this is not feedback? Can you hear it at all volumes?
For turntable isolation these pods are next to worthless. MinusK makes the best isolation platform. Townsend makes a platform but I have no idea how well it works. None of these will address any intrinsic turntable noise only extrinsic environmental noise.
If the turntable is rumbling this bad it is more than likely time for a new one or a new bearing or motor. Don't buy crutches for a bad turntable, buy a better turntable instead. The Thorens 1600 is a great table for the money and completely isolated. Following this would be Sota turntables like the Sapphire, the Avid Acutus then Basis and SME models. If you have the bucks the Dohmann Helix is the last word. All of these tables are completely isolated and will not pass on any environmental noise of vibration over 3 Hz. 

Microfiber should be fine.  If you had already re-lubed the bearing before your OP, I apologize for being redundant.  However, if you have since done the lube, did it help???

Yeah, I had a Technics SL1700 I thought was dead quiet, until years later using it with my by then much improved system it was easy to hear bearing rumble. One way to tell, if it is bearing rumble it will be more audible at the outer edge because that is where the lever arm of the platter is longest, whatever wobble or vibration is coming from the center is amplified most at the outer edge.  

Even if this is the case it is better to let the turntable dissipate this energy itself on springs rather than energize the rack which then feeds this back into the turntable. 

You can also use stuff like fO.q tape, but it is not much good at low frequencies. It is great for cleaning up midrange and treble though.

@millercarbon, I have read your essay "Vibration Control and the Townshend Audio Seismic Pods," and your advice above. I believe that your approach is a good one. Two sets of Nobsound pods have been ordered. Wish me luck. But regardless of their effect on this issue, I'm looking forward to trying them out on other components as well as the turntable. Thank you for that. 

@lewm, I used Mobile1 0W-40 to re-lube the bearing. However, I did not consider using paper lens wipes. That's a good recommendation. Hopefully the microfiber cloth I did use did not impart any foreign debris into the bearing. I very well might repeat the exercise and re-measure per your recommendations. 

All this effort to push a slight rumble a little further down the scale. Mid-fi can be very frustrating. 

It doesn't cost thousands of dollars to check and possibly replenish the bearing lubricant, if indeed this is true rumble from a noisy bearing.  It costs nothing first of all to remove the platter and take a look inside the bearing well.  Once you've done that, I would advise you to clean out the residual lubricant.  I use photographic lens paper because it is less apt to leave any deposit of its own in the well, which should be kept scrupulously clean.  Also wipe the old lubricant off the spindle using similar paper.  After that, add a few drops of almost any good quality machine oil.  Many, including me, like to use a synthetic motor oil, single weight 20 is good.  THEN listen to determine whether that has any effect on your problem.

The first, simplest and cheapest thing to try is Nobsound springs. One set for $30 (or less, shop around) and if this doesn't eliminate your rumble then it is probably the bearing. Assuming it is not the bearing then this will work and when you hear how well it improves everything else the next logical step will be to upgrade to Townshend Pods and move the Nobsound to your other components. But first, the turntable.