At what vol level do you get rumble / flutter?

Adding mass to the cartridge/tonearm will lower the resonant frequency. Note that warp induced signals are in the 0.5 - 7Hz region, so you don't want to drop the cartridge resonant frequency too low if your cartridge/arm/table already has a problem in this area.

FWIW, I can't recall any cartridges I've used that have fallen outside the broad ideals for cartridge resonance, say 8-14Hz, when a test record is used. However there have been large differences in the amplitude behavior at resonance - no doubt due to the different construction methods of the particular cartridges and arms. For instance I'd expect a rigidly constructed Lyra cartridge to produce a higher Q resonance that a cartridge built on a plastic frame/body. The latter type of cartridge will probably be easier to accommodate, though of course that doesn't make it better.

07-04-12: Tobes
Adding mass to the cartridge/tonearm will lower the resonant frequency. Note that warp induced signals are in the 0.5 - 7Hz region, so you don't want to drop the cartridge resonant frequency too low if your cartridge/arm/table already has a problem in this area.

FWIW, I can't recall any cartridges I've used that have fallen outside the broad ideals for cartridge resonance, say 8-14Hz, when a test record is used. However there have been large differences in the amplitude behavior at resonance - no doubt due to the different construction methods of the particular cartridges and arms. ...

Right, but 10-11 Hz is considered more ideal than 13-14 Hz or 5-8 Hz. Adding 4-5 g of effective mass to the OP's rig will lower the resonant frequency from 13-14 Hz to a more ideal 10. However, as you mention, there's the resonant frequency and then there's the amplitude of that frequency. The OP noticed the increased pumping after changing from the stock cartridge on the Xpression (Sumiko Pearl) to the Ortofon, so it seems that there's something in the cartridge swap that increased the pumping. The Pearl weighs 2g more than the Ortofon and is a little more compliant as well at 15 vs. the Ortofon's 13. I don't know enough about the Turbo's housing to form an opinion on its damping, but when you combine a very light arm (8.7 eff mass) with light cartridge (4.1g) and stiffer compliance, you're raising the resonant frequency, and with the lower mass the amplitude would be higher too.

Fortunately the OP's tonearm has a fluid damper, so he may be able to add fluid to lower the amplitude of the resonance. Increasing the effective mass with headshell weights should not only lower both the resonant frequency and amplitude as well.Wrapping the tonearm in PFTE pipe thread tape might help a bit too, both in damping and effective mass. It sure made my Technics tonearm sound better and more linear.

@johnny, never had the factory cartridge on my Xpression. Had two mc-3 turbos on it and recently had the ortofon mc 25 fl with the heavier counterweight and it did the same thing (the 25 fl is about 10g). How do I add fluid? Is the tape u mention for my tone arm easily removeable if it does not work out?

There is rumble recorded in about 50%+ of the records I own, and it has NOTHING to do with set-up or placement or arm/cart matching. When I go to the audio shows I always notice woofer pumping, even on super $$$ set-ups. On a lot of LP's it is unavoidable. KAB's rumble filter is a God-Send and seemingly transparent, at least in my system. When I play LP's, I flip on the KAB.

07-06-12: Sbrownnw
@johnny, never had the factory cartridge on my Xpression. Had two mc-3 turbos on it and recently had the ortofon mc 25 fl with the heavier counterweight and it did the same thing (the 25 fl is about 10g). How do I add fluid? Is the tape u mention for my tone arm easily removeable if it does not work out?

Well, it looks like I shot my mouth off without paying closer attention. I realize now that the earlier post about adding damping fluid was contributed by someone else who has a tonearm that uses it. So never mind about that.

Second, one thing that makes this difficult is that what may be a normal amount of pumping for one person may be alarming or excessive to someone else. Third, pumping can come from record warps, how the bass groove was mastered, and tonearm/cart resonance. How bad the speakers pump is relative to the amplitude of the resonance.

If you tape your tonearm, it's reversible. There is no adhesive on the tape; it is very thin and stretchy. However, since you have a carbon fiber tonearm, the effect of an arm wrap is probably minimal. My tonearm is undamped hollow aluminum, so the arm wrap made a significant audible difference. With a more modern carbon fiber arm, probably not so much, but it's only a $1 experiment. We're talking about Teflon pipe thread tape, which should be a buck or two at Walgreen's or Home Depot.

After looking over the entire thread and getting a better feel for your rig, it looks like the KAB RF1 Rumble Filter addresses the various problem sources most directly.