- Mar 24, 2016
That defies the laws of physics.The concern with the cutoff frequency was phase shift at 20Hz. The ear interprets phase shift in the bass (generally speaking) as a loss of impact. I've no doubt that low frequency noise and abituary cutoff frequencies would explain why so many people think that digital somehow has more bass extension and impact than LP (and certainly if low frequency noise is goobling up amplifier power, digital would be obviously perceived as 'better'). IME there isn't any difference at all, but only if the analog playback is designed and set up properly.
By its very nature a seismic transducer is not capable of operating to DC, and if it did the groove wouldn’t be able to move it so it would be useless for a record player.
The effective low limit of a seismic sensor is 2x its mechanical natural frequency. Lower than that and the part that is supposed to be the stator in the transducer isn’t “stationary”, so the output from the cartridge, which we want to be movement of the groove relative to “earth”, no longer is that.
If your arm/cartridge resonance is 12 Hz, for example, the lowest frequency you can accurately transcribe is 24Hz. Yes there will be output below this - lots of it if there isn’t much damping - but it is not an accurate analog representation of the groove so IMO it is best be filtered out. It is almost spurious, so poor is any relation to any actual music on the disc since it is effectively outside the usable bandwidth of the transducer assembly, wastes power and moves the bass driver into non-linear areas.Yes, there is still phase shift probably going on, but not much and it is the least of the shortcomings of this sort of transducer.
I have designed seismic vibration sensors for many uses, not just record players, and it is possible to get them to work reasonably well down to their natural frequency but the damping required to achieve it shunts higher frequencies so it is inaccurate at higher frequencies and it is a poor choice of transducer for a music application.