Pro-ject RM RPM 5 5.1 6 6.1etc. Owners Fixed

I own a Pro-ject RM6 SB turntable and love the turntable. However, it has always had a low end rumble once the needle hits the record. I tried ignoring it attributing the issue to record surface noise or one of the other compromises of living with vinyl. I recently discovered that this is a common problem with many Pro-ject models. At the urging of my not-so-local dealer I replaced the OEM footers with a set of threaded Edensound brass footers which yielded a dramatic improvement in everything except the rumble (I consider THREADED brass footers a mandatory investment). I then placed a cork mat between the subplatter and platter and silicone between the cartridge and headshell, minimal improvement if any on those two. The low end rumble continued and it really wasn’t that noticeable or intrusive once the music started, or so I thought.
I started my internet search and found a bunch of postings about the rumble problem inherent with certain Pro-ject TTs. There’s even a youtube video on the problem. I then came across a site from an RPM5 owner who claimed to have resolved the rumble problem found in Pro-ject turntables. He shows the before and after effects graphically on a spectrum analyzer identifying the low-end rumble with peaks at 50 and 100hz before and after his method of fixing it. Go here if you want to read more.

http://www.theapplechap.com/TheAppleChap/Blog/Entries/2011/5/24_Enhancing_the_sound_from_Pro-ject_turntables_by_removing_rumble.html

He provides a beautiful narrative on the fix and his science seems solid, but obtaining the parts needed seems a little complicated and he is waiting for Pro-ject to come up with a retrofit solution. Anyway, I discovered the repair can be done easily, for cheap, and now. Using his method, kind of, the fix is to install four rubber grommets (I’m not saying or recommending that you should do this, I just want to share my story). Based on the AppleChap’s approach, I went to Grainger.com and ordered a package of 1/8” ID 3/16”OD rubber grommets part number 3MRT4. They don’t sell them individually so I had to purchase a packet of 100 for an astounding $4.20 plus shipping.
The grommets arrived 3 days later. I then removed the platter, located the 4 screws that hold the rubber suspension (rubber band) in place. I removed one screw, inserted the grommet around the washer surrounding the screw and re-screwed it in place. It might be a little tricky at first as the suspension is tightly fit. I did this three more times, and four minutes later I was done. An important note the rubber band fits between the lips of each grommet, not above or below, unlike the pictures shown in AppleChap’s method. This isolates and decouples the rubber band from the screw and plinth. Also, I had to make sure that the screws were placed back correctly because any shift in the motor’s original position may cause the edges of the motor to touch the rubber grommet. If that would have happened I could have shaved the side of the lip of each grommet that faces the motor.
I returned the platter to its home and played a record. The second the needle hit the record, there was no rumble. It had disappeared, like magic. The grommets not only eliminated the rumble, but it cleaned up the soundstage and things that were previously masked were revealed. An amazing transformation! AppleChap also recommends changing the belt to a round instead of flat belt; less surface area to transfer resonance. I ordered a belt but it had not arrived yet.