As mentioned in the above posting, eliminating resonance due to motor vibration for many Pro-ject turntables is a two-step process. The first relates to the resonance onto the plinth caused by the vibrating motor and the second relates to the resonance on the subplatter caused by the vibrating motor and transferred by the belt. In my system, installing the grommets into the suspension and replacing the belt has made a significant improvement. I ordered the rubber belt from Turntableneedles.com. The part number is RBM19.5 and is identified as a medium round belt measuring 19.5 inches selling for $16.95+shipping. The drive belt arrived today and I installed it on the RM6 SB. Unlike the Pro-ject OEM belt which is loosey goosey and flat, this one is more rigid and round. The new belt did not fit any tighter and being round should equate to less surface area on the vibrating motor pulley and the subplatter.
In my system I can confirm that the improvements were dramatic and well worth the $28 investment (grommets and belt).
I’m not a journalist, but I can describe the soundstage as having even greater clarity with the new belt. The instrument placement across the soundstage is more solid and stable. I did not notice any more bass, but what bass there is has become more articulate. The background noise has become darker during low- level passages. And what sticks out the most are the little details in the music being clearer and more noticeable now.
Good luck and happy listening
regarding the position of the o-ring in relation to the grommets, I found placing it above the grommet below the screw head gave me better clearance from the plinth. Either way is OK so choose what works for you best. This fix is as much art as science so play with some of the options if you don't immediately get the improvement in sound you are looking for.
The key is definitely the new belt. This really brings the improvement to life.
FYI keep an eye on the blog on my site (www.TheAppleChap.com) as the official fix is nearing completion and I should be posting a review in a few weeks time as soon as it is ready.
All the best
I've been reading your previous postings. Excellent job! Has Pro-ject ever admitted that that they have a design flaw?
I've seen the charts and listened to the before and after on my turntable and it is evident that the changes are profound and necessary to transform the turntable.
I believe that every Pro-ject table with the the O-ring suspension suffers from the low-level rumble problem, not just a few. It may not be detectable in all systems as they may not produce soundwaves as low as 50hz., and it may be too sublte for others (or those unaware) to even notice, but unless these turntables are made by hand then every one should have the same anamoly.
Regarding the placement of the suspension o-ring directly attached to each screw, it seems that the vibration would channel into the plinth through the screw. Wouldn't a rubber grommet with LIPS decouple the suspension from the screw and plinth? Wait I'm not an engineer so I'm guessing.
Show me the charts!
Thank you! Thank you! I will do the grommets and belt upgrade to my RM6... can't wait.
The suspension design is inherently flawed. All they've done is shift the vibration directly to the platter... instead of moving the vibration into the plinth. Bad design. My workaround was to screw down the motor with the shipping transport screws... which really helped reduce the rumble... but added some other slight resonances.. but not bad compared to Pro-ject's intended design. What were they thinking? "Let's float a buzzing motor and connect it to the platter!" That maximizes the buzzing to the needle. Maybe next year they will put the motor into the tonearm... haha.. I'm a little irritated that such a nice table has such a bad design for vibration control... from a leader in the industry. And the solution isn't expensive... so why aren't they at least offering an upgrade kit? Just weird.
Regardless, thanks for the fix idea. :) :)
My Pro-ject Xpression III started with the rumble (or recently got worse). Cinellipro and I have talked before and he has been very helpful with info, time and more! :) Hopefully this solves my problem. Otherwise, my table is still under warranty. And a "to the top" action for this thread for anyone else that is experiencing this problem with the Pro-ject turntable.
The 4 additional rubber grommets problem did not fix my problem of excessive woofer movement at volumes at close to double normal listening levels (party mode I guess you can call it). I am lucky I am not getting this at normal or just above normal levels and I will have to keep an eye on the volume level. Hopefully it does not get worse.
Here is a link to a thread on what some people might think is going on:resonant frequency
Discovered one more effective resonance reducing method for the RM or RPM 6 series turntable. As you know the plinth transmits vibration to the tonearm from the motor. The tonearm assembly is connected to a recessed section of the the plinth with only three screws. You can remove the screws and install a square piece of rubber that fits into the recessed area, or use the grommets to isolate the tonearm plinth. The rubber square I used was 2 1/2 x 2 1/2 by 1/8 thick. Be careful holding the tonearm at the removal of the last screw as the cartridge will be exposed.
You will need to adjust the VTF and the tonearm lift the same height as the thickness of the rubber square. Easy to do with two smaller allen wrenches. Installing the rubber square was less than 10 minutes and getting the VTF and tonearm hold adjusted was another 10 minutes. In my system, it continued to significantly improve all the elements of the soundstage already mentioned.
Thank you so much Cinellipro for bumping this thread. I have a RM5.1 SE with a Sumiko Blackbird cartridge, and the rumble has irritated me since the day I got it. It seems to disappear once the music starts, but I knew it was lurking in the background, mucking things up. I saw Applechap's blog a long time ago and contacted Sumiko about a USA version of the fix, but could not get a response. I gave up and decided to live with it until I could afford a table upgrade. Anyway, after seeing this thread I ordered the grommets from Grainger, installed them with no problem, and the difference was like night and day! Amazing improvement. The new belt arrived today and after a quick listen, I think it helps too, although the fit seems looser than the old one.
I have 96 extra grommets if anybody needs any!
A little off topic but I was intrigued by Carlmans suggestion to screw down the motor with the transport screw. I recently purchased a Perspective and I'm having quite a bit of trouble stabilizing the platter to the plinth. It's reacting to every step I make. I set my tracking force to the recommended settings, set the deck up as instructed and the platter just won't cooperate. Is this the solution? Unfortunately I don't have the set-up screw, does anyone know the thread/length size? Also does this grommet issue reflect in the Perspective's design as well? Finally, I tried putting my round VPI belt on the platter prior to reading this thread an had no luck making it work. It seems the flat platter rim is to small for the belt.
Dreadhead, I think your turntable has the isolated motor which is mostly immune from vibrations being transmitted to the plinth and tonearm. You've got something else going on. Please describe in detail what you mean by reacting and not cooperating.
The platter rests on 3 isolated springs. Any walking in the area causes the needle to jump grooves. Either I need to try an affixed wall shelf or pursue Carlmans suggestion and use the transport screw to secure the platter. If you have time google the images.
Just discovered applechaps fix and semi official upgrade kit, was curious if anyone has some grommits left over they could send my way for a small fee, as the going price for the upgrade kit is kinda steep for what it is. What do those whove tried it think of the round belt, and is there any significant difference between it and the Henleys upgrade kit w round pulley? Thanks a lot,
Also, is the new pulley w the rounded channel needed if I want to use a round belt? Cinellipro, have you had any problems using yours that way? Do you place the rubber grommits around the four screws holding the suspension rubber band or under the motor where the transport screws go? Thanks!
I haven't check lately but the Henley upgrade refers to European models and the pulley will not work with North American Pro-jects. I use the OEM pulley and have had no problems. Since the surgery, everything continues to run quiet and smooth and resonance free. If you send me your e-mail Ill forward the pictures so you can see where I placed the grommets.
Picture of grommets in place.
Im actualy in Europe, so curious why youd need a different pulley over here for the round belt. Turntableneedles are unfortunately out of the belts, any other place you know of? How do I message you directly w my email? Thanks,
Also, would you be willing to send me some grommets, Id be happy to pay shipping plus whatever you think is fair. Thanks again.
Did you get my pm? Never heard back,