Michael wonders why the choice between the standard wide -bandwidth RIAA or the 1976 IEC curve which rolls of the response below 50 Hz and is (only ?) useful for rumbly turntables.
I think Aalt Jouk van de Hul gives an excellent answer (http://www.vandenhul.com/userfiles/docs/Phono_FAQ.pdf)
A: There are several reasons for this effect (woofers constantly moving in and out with a big amplitude):
1. The bottom end of the frequency range of your phono amplifier is not limited to say 10 Hz, but runs deeper to e.g. 1
Hz or less. So here an internal modification is necessary to produce a stop at around 15 Hz. There is no music
around 15 Hz and an extended frequency response only produces problems for the rest of the equipment. Here a
subsonic/rumble filter is the correct message for your technician.
2. Your phono amplifier does not produce this 2 - 5 Hz by itself, but gets the signal from your cartridge/arm
combination. So the first question here is: Is the cartridge/arm resonance frequency to low? Normally the value is
around 10 Hz (see Appendix 2). When the cartridge has a too high compliance and/or the arm is too heavy (effective
mass around 20 grams and more) then the resonance frequency drops from around 10 Hz (which is standard) to 5
Hz or less (also see 36). So remove weight from your arm by e.g. taking a lower weight headshell or by removing
weight as much as you can. You can also ask your friend if you can try his cartridge in your arm to see if the same
happens again. Assuming that your friend has a different brand of cartridge.
3. What also helps to produce an unhealthy subsonic output is the uneven surface of your records. With uneven and/or
unpolished stampers (see 164), the vinyl pressing result is also uneven. When you still like to listen to such records,
use your pre-amplifier