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Turntable Resonance Fix

I've been investigating different materials of turntable mats in hopes that I can find one that will help tame a -30dB rumble centered around the 20 Hz region that I fear is affecting the rest of the audio spectrum to some degree. I'm guessing that either platter bearing noise is to blame, or possibly vibrations from the motor creeping into the tonearm. Ultimately I would like to take steps to eliminate the source of the rumble, but I fear that will involve several thousands of dollars (a different turntable). With the vast amount of experience and knowledge out there, can any of you share an example where a particular mat helped with this sort of issue? Baring that, do any of you have advice for altering or upgrading the Pro-ject turntable to eliminate this problem? 

For reference, the setup is as follows:

- Pro-ject 2Xperience turntable (stock)
- Soundsmith Aida cartridge
- PS Audio NuWave phono preamp (digital measurements were taken from the USB output of this unit)

The well-isolated and -damped audio rack sits 25 feet from the speakers. But regardless of that, measurements were taken with the speaker output at a whisper. 

I have taken screen shots of the analyzer that I will post to my profile page. 
sixfour3
millercarbon's avatar
millercarbon
12,531 posts
 
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. 
lewm
12,562 posts
 
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.
sixfour3 OP
21 posts
 
@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. 
millercarbon's avatar
millercarbon
12,531 posts
 
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.
lewm
12,562 posts
 
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???
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