Billie Jean dance

[antcollinet]

many others have quite a steep filter in the bass

Good point. Just looked at my waxwing settings. Derumble filter is on which sets <150Hz to mono. There is also a 25Hz low cut filter.

I'll try again tomorrow with these turned off.

 

[antcollinet]

Good point. Just looked at my waxwing settings. Derumble filter is on which sets <150Hz to mono. There is also a 25Hz low cut filter.

I'll try again tomorrow with these turned off.

Decided to do it now. All filters off. That oscillation is 8Hz.

EDIT: Derumble as expected balanced it across the two tracks, then the 25Hz low cut eliminates it.

 

[Thomas_A]

It seems as if the 8 Hz component is present before the first beat but at a much lower level. Still it is unknown whether the beat is inducing the stronger resonance or if this is in the groove. Someone with a heavy linear tracker or a Moerch DP-8 could solve the mystery. Or perhapa a Dynavector DV-507?

If it is cut into the grroove, an arm that moves with the groove at 8 Hz signal should give no signal at the stylus. Most combinations have their resonance 6-12 Hz and this will instead cause some amplification and oscillation.

The Billie Jean LP track might to be an extreme example of what happens during bass beats with conventional tonearms. Korf audio have some results as well regarding resonances which I do not understand fully. I do not understand the results of Moerch either where the lateral response basically act as an HP filter at 20 Hz with no peaking (damped resonance). A high lateral mass should lower the resonance frequency, which seems to be the opposite in the lateral direction. The vertical resonance is elevated which is along with the theory though, since the vertical mass is very close to the pivot point, lowering the effective mass.

 

[Thomas_A]

I might have some new results within a couple of weeks. Stay tuned.

 

[Thomas_A]

This is the beginning of Billie Jean. It seems that a LF around 8 Hz, in phase (lateral) comes after the large beat. It is in the region of resonance (11 Hz) and also higher in level compared to the song before. It does not seem to bleed from the music signal, and it is still possible that this is cut into the record. There is no way to know unless there is another forum member that could test the same using an arm with high mass in the lateral direction.

View attachment 377882

And spectrum:
View attachment 377883

Spectrum for the song before:

View attachment 377884

Better now with a DP-8, even though not perfect...