Subsonics with Grado & Rega Arm

I get massive amounts of subsonics with my Rega arm and Grado Reference cartridge.

Anyone else have the same problem? What arms would be a better match for the Grado Ref?
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.