Can you be more specific about what you mean by "sub-sonics"? Are you hearing turntable rumble? acoustic feedback? too much very deep bass? And, by the way, what turntable do you have, and how is the turntable mounted?
I also have an analog front end that uses a Rega RB-900 arm and a Grado Reference cartridge, and have had no problems with this system once I got the turntable absolutely level. In the early stages of use, I was getting a bit of the "Grado dance", but two actions corrected the problem:
1. I made sure the turntable / platter was dead level (this essentially eliminated the "Grado dance");
2. I replaced the spring suspension in my VPI HW-19 Mk4 with sorbothane pucks which eliminated vibration feedback from the floor.
(I'm assuming that you have verified that the stylus tracking force is correct.)
There is a remote possibility that the suspension in your cartridge may have been damaged, but the only way to assess that is to send the cartridge back to Grado for a check-up. |
Hi There
The table is a spring suspended Logic DM101 similar to a Linn. It rests on the cement floor on cement blocks with inverted cones underneath.
I've checked tracking force, cartridge alignment and table levelling many times.
When I say subsonics I mean woofer bounce to the point it's ridiculous I get it on every LP I play.
I'd also like to point out I've had the same problem with the Platinum and Sonata on this table/arm and other tables so I know it isn't my cartridge.
I know it isn't vibrations because the woofers go nuts even on silent passages even on relatively flat LPs with record clamp.
So I'm down to looking at the arm and it's compatibilty with the wooden Grados. Some people say the Rega/Grado combo is great and other get subsonics big time.
I love the Grado sound and don't want to change cartridges so I'm looking for a more compatible tonearm but don't know what. |
The revised description you've provided is a bit different problem than your original post suggested. Woofer-flexing due to infrasonic signals can, as you imply, be caused by warped records, and may also be caused by a cartridge/tonearm mismatch that causes the tonearm resonance to fall below 8-9 Hz. Since neither of these seem to be the cause of your problem, I'm inclined to think that you have some sort of low-frequency feedback loop somewhere in the amplification chain, but that's outside my technical expertise. You might try dropping a note to our resident tech guru, Sean, and see what he says. You might also try replacing the spring suspension in your turntable with the same kind of Sorbothane pucks that cured the acoustic feedback problems I experienced with VPI turntable. |
I do not know about the Logic tt, but on some Rega turntables, hum from the motor is picked up by Grado cartridges. If that is what you are hearing, a sheet of mu-metal from the Magnetic Shield corporation will solve that problem. It seems unlikely that the arm is the problem. |
I don't get hum it's definetly subsonic vibration which is why I'm inquiring about tonearms that are compatable with the wooden grados and perform as good or better than my modded RB300 |
I got around to looking at your post again, and a detail that I missed in your comments jumped out at me. You state that your turntable is on a cement floor, on top of cement blocks. It is possible that this location is exposing the turntable to a lot of airborne low frequency acoustic resonance, particularly if the turntable is also located close to a wall. Intersections where the floor and wall(s) or ceiling and wall(s) intersect create a lot of bass reinforcement, which is why subwoofers are often placed in the corners of rooms (where there are 3 intersecting surfaces).
You might try mounting your turntable on either a good isolation rack, or a turntable shelf mounted to the wall, and see if that helps to reduce the infrasonic overload. |
Hi SdCampbell
Thanks for your reply. I did consider that as a possiblity but quickly changed my mind.
I get serious woofer bounce even at the start or end of a record when no music is playing and thus no vibrations could be affecting the table.
There seems to be a compatabilty issue with the RB300 and Grado which is why I'm looking for a suitable replacement.
However my knowledge of tonearms is limited and I don't know what to buy. Perhaps I should get a different cartridge but I really like the Grado sound. |
You probably do have a compatability issue with the Rega RB 300 and the Grado Ref.The cartridge resonance for this combination is about 8Hz which is below what is considered the ideal today,around 11-12Hz.I would consider a new cartridge and if you still want to use a Grado your going to have to go for a more lightweight arm(9gms?) than the Rega(11gms) which is considered a mid-mass arm.You can find a lot of info in the archives about the issues involved. |
I had the same result with my Reference Platinum on a suspended Thorens TD147 with a TP16III arm of 7,5 eff. weight.
I ruined the stylus and experiment with a Denon DL301 MC cart right now.
Strange thing is: with the Grado the woofer extention didn't affect the sound audible.., with the Denon the woofer is thight and controled but the sub-bass is to much to bear.
Because sound was good I never realy bothered about the woofer extension but now I wonder if a thighter suspension may cure the problem.
Maybe a subsonic filter may do some good.
Good luck..! |
Thanks Stefanl
Thats exactly what I was thinking a Haddcock or Morch with interchangable arms wands could be ideal.
What about a used SME such as the 3009.
anyone? |
The SME 3009 has many different gradations or varying models(?)but one figure I did find that indicates about what it could be,is that the effective mass for a fixed headshell version 3009(?)is 6.5gms and if it has a removable heashell 9.5gms.So with the Grado Ref. cartridge you would be better off with the fixed headshell version with a cartridge resonance near 10Hz which is o.k.Sorry I can't be of more help. |
After doing some calculations the Grado cartridge resonance with the Rega arm is 8.4Hz.
When one takes into consideration the heavier after market counterweight I use the Frequency will drop even lower beacuse the arms effective mass will increase from 11 to lets say 13 or 14g.
What baffles me is that Grado suggested to me that effective mass arms between 12-16g are good with 14g being optimium.
One would think that a lighter arm would be a better match say around 9g and thus raising the frequency to between 11-12hz.
Bottom line Grado and Rega don't match on my table and I'll be trying another cartridge perhaps a Benz H2.
If anyone would like to comment further please do. |
I am currently using a Grado Gold with a Expressimo modded
RB-300 on a Thorens 320 suspended turntable with very good
results.I'm suspicious that there is something else that
has not been investigated.Have you verified that all of your
wiring(low volt. vs. 120V) is truly isolated ? |
Not sure I understand what you mean |
I was having a similar problem. I have been using a Grado Reference Sonata with my Rega RB300 Origin Modified arm on a Sota Star Saphire table with the Sota Reflex clamp. I sent my arm to an Audiogoner (Michael Wharton - teatime66@hotmail.com) for rewiring the arm in Cardas and installing a Cardas 5 pin DIN termination. I purchased a custom tonearm cable from a terrific fellow in China that incorporates twisted pair construction of LC-OFC wiring with braided copper shielding, hermetically sealed insulation and an RF stopper - all for a very fair price and QUICK turnaround). The problem is completely resolved. I am hearing much deeper into the vinyl now even before any meaningful time for burn-in has occurred. I could not be more pleased. Actually, this is one time I can be the guy to say that he cannot believe the magnitude of improvement a tweek made. |
Would a phono stage with subsonic filter help?
Grado dance and woofer pump when used on an old Thornes. I dont think Grados like suspension turntables. No dance on rega table but hum increases nearer to motor. I think Grado on Rega is very musical regardless of how the numbers crunch out.
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A tonearm rewire would probably remedy this situation. A typical 3 wire set up is required for a Grado. Without a dedicated ground wire problems like those posted happen. |
Rega and Grado don't like each other.....heard of these problems with this combo before.
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