Billie Jean dance

[Thomas_A]

That resonance looks particularly massive.

btw, my RIAA has 1 uF at output; corner f at 3.4 Hz. When I measured I got -1.4 dB at 8 Hz.

 

[Thomas_A]

The Billie Jean dance is probably only one of many examples of horisontal stylus movement. I looked at another record (Fleetwood Mac - rumours), and there is an increase in LF content, in-phase, during a bass transient. The filtering of the "arm-pickup" resonance is just a 12 dB filter (I believe), so it would be -24 dB at a resonance of 10 Hz when hitting 40 Hz. Adding resonance it could be multiplied with 5-10 dB getting -15 to -20 dB signal. I start to believe that high inertia and damping in the lateral plane a la DP-8 is beneficial.

Below is an amplified signal of the LF content showing increases every beat, in-phase signal.

 

[MaxwellsEq]

Which track on rumors?

 

[Thomas_A]

Which track on rumors?

Just one track on side 1 with some bass beats, don’t have ithe system up right now so I cannot be more specific. But the effect is expected as long as you have a significant lateral arm-cartr. resonance peak. The bass roll-off from the music is never infinitely steep and will add to the arm-cartridge resonance peak. So the resonance peak level will vary up and down dynamically with the bass peaks of the music

One question is if and how audible this is. Cartridge movement means intermodulation distortion. A high lateral inertia and damping will reduce this ”problem”.

 

[antcollinet]

I have the album. I'm gonna fire up the old CD player and see if the laser dances.


OK - I'll scrap that idea and get the vinyl out on the Rega P3, Rb330 arm with ATVM95ML. Away from home right now so it won't be until next week sometime.

 

[MAB]

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

I'm pretty sure those are the resonance frequency of the tonearm cartridge. The intro to Billie Jean is like a delta-function, like a plucked string. As @mhardy6647 pointed out, you can measure this on the blank regions. If you use the outside blank-space on a record, you likely have to deal with some record warp issues (like the original video). You can also use the inner. A 45 that isn't too badly warped can help. Also 36% higher 45 RPM pushes the frequency components of a warp higher. Let me see if I can show that.

I have a moderately high mass tonearm (~23 gram effective mass unloaded). I can change the effective mass of the tonearm with the position of the tonearm weight from 23 grams to a bit higher. I have a Grace F-10L mounted on it for these measurements, dynamic compliance is said to be 20 x 10^-6 cm/Dyne.

I recorded Billie Jean with the tonearm weight close to the pivot (lowest effective mass configuration), and repeated the recording with tonearm weight at the far end of the tonearm from the pivot (highest effective mass configuration). The tracking force was set to 2.0 grams in each setup.

Comparing the digital copy to the vinyl rips of the song intro, and to the silent lead-in groove:

The tonearm/cartridge resonance is ~6Hz. You can see the first and third harmonic peak of the tonearm/cartridge at 12Hz and 18Hz. The black trace is the silent section before the song starts, same which shows the same 6Hz resonance. Changing the effective mass has little effect on this setup.

I have a Supex SD900 cartridge as well, which is lower compliance than the F10L, about 10 x 10^-6 cm/Dyne, about the lowest I have. I did the same test. I come to realize that the arm weight has only a small impact on the overall effective mass of the tonearm. So I also did a run with coins stacked (again at 2.0 grams tracking force). I didn't want to fuss around with actual cartridge weights, this non-approved method should do!

Here are the 3 recordings of the SD900 with different effective mass, with the first ~4 seconds highlighted:

The spectra of the first 4 seconds, compared to previous recordings:

That built-in arm-weight has almost no change to the effective mass of the SD900 measurement, like seen on the F10L. That's fine since it means as I use it to balance cartridges, the position on the arm is not so important. The coins do change the effective mass quite a bit, lowering the resonance from 11 Hz to 7.7 Hz. No surprise since they are far away from the pivot. I can see the arm is not well-damped for resonance below ~10Hz. Not bad though since I notice most arms are not well-behaved at low frequency.

I think Fleetwood Mac also came up. Looking at Dreams, which has the simple kick drum to act as a forcing function, you can see the resonance. And even see it in the silent gap.

Lastly, checking the CD rip I have of Dreams, also see nothing below 30 Hz as I kind of expected:

None of this explains why the original video is so jumpy, just perhaps explains how to get the resonance frequency of the jumps, which is really just the resonance of the cartridge/tonearm. Some tonearms have moderately different horizontal vs. vertical effective compliance, often through viscosity, still shouldn't be jumping around like that. I tend to think something was wrong with the setup in the original video, and the record was also very uneven, but difficult to diagnose from so far away!

 

[Thomas_A]

From the original CD it seems to have a peak around 8 Hz at the first beat. This is analyzed by Ior, a member of another forum:

faktiskt.io • Visa tråd - Mørch DP-8 tonarm någon?

Looking at the LP version there is a clear 8 Hz peak that is added to the typical arm-cart resonance peak. The 45 version might not have that.

 

[MAB]

From the original CD it seems to have a peak around 8 Hz at the first beat. This is analyzed by Ior, a member of another forum:

View attachment 379506

faktiskt.io • Visa tråd - Mørch DP-8 tonarm någon?

Looking at the LP version there is a clear 8 Hz peak that is added to the typical arm-cart resonance peak. The 45 version might not have that.

See above post.
The arm/cartridge resonance doesn't depend on the rotation. The arm-cartridge resonance shows up on every record I have, at any speed. If the record is warped, it exacerbates the resonance. But it doesn't depend at all on the speed, or the song being played.

 

[MaxwellsEq]

There seems to be conflicting evidence of the Billie Jean infrasonic resonance on the digital versions. in your graphs, @MAB you show a flat line below 20Hz, whereas the graph you quote, @Thomas_A has the resonance, but a long way down. Are these different releases, I wonder, e.g. the first CD releases may be derived from a version of the LP master, but subsequent releases are taken from a normal studio master. Perhaps this resonance was an error that crept in during the vinyl cutting stage.

 

[Thomas_A]

See above post.
The arm/cartridge resonance doesn't depend on the rotation. The arm-cartridge resonance shows up on every record I have, at any speed. If the record is warped, it exacerbates the resonance. But it doesn't depend at all on the speed, or the song being played.

YesI am aware of the system resonance. The 8 Hz peak seen in my and MaxwellsEqs spectrum however indicates another resonant peak that adds to the system resonance. (I have 11 Hz system resonance peak laterally and vertically. )

 

[MAB]

YesI am aware of the system resonance. The 8 Hz peak seen in my and MaxwellsEqs spectrum however indicates another resonant peak that adds to the system resonance. (I have 11 Hz system resonance peak laterally and vertically. )

I think you are measuring your tonearm cartridge resonance.
I did the same on my copy of Billie Jean, and the resonance moved with changes in effective mass and cartridge compliance. I see the resonance on the silent lead-in and gap tracks on all of my records, at both 33 and 45 RPM, also as expected for a resonance. Records don't typically have 8Hz content, unless warped and even that is unusual. I'm not aware of pop songs mixed with subsonic back in the day either, unless there is an artifact embedded in the track or pressing, which is totally possible.

The subsonic content isn't in any of the digital copies I can find. For instance the first four seconds of my CD from the '80s:

I have a HiRes copy as well and I found a few versions on Spotify. Here are the first four seconds compared:

I just found my other 45 of Billie Jean. I also have a full copy of Thriller somewhere in the bookshelves. I will measure them both when found. It occurs to me one thing I don't miss about vinyl is sifting through the collection looking for an item.

 

[Thomas_A]

I think you are measuring your tonearm cartridge resonance.
I did the same on my copy of Billie Jean, and the resonance moved with changes in effective mass and cartridge compliance. I see the resonance on the silent lead-in and gap tracks on all of my records, at both 33 and 45 RPM, also as expected for a resonance. Records don't typically have 8Hz content, unless warped and even that is unusual. I'm not aware of pop songs mixed with subsonic back in the day either, unless there is an artifact embedded in the track or pressing, which is totally possible.

The subsonic content isn't in any of the digital copies I can find. For instance the first four seconds of my CD from the '80s:
View attachment 379581

I have a HiRes copy as well and I found a few versions on Spotify. Here are the first four seconds compared:
View attachment 379582

I just found my other 45 of Billie Jean. I also have a full copy of Thriller somewhere in the bookshelves. I will measure them both when found. It occurs to me one thing I don't miss about vinyl is sifting through the collection looking for an item.

Your CD version look clipped?

(I am using an unipivot with 4 g arm mass and cartridge of 6,5 g, compliance of 20 cu-= 11 Hz. Which also fits with sweep measurements. The 8 Hz component is an addition, as also seen in Maxwellseq spectrum. )

 

[Descartes]

I found a video on AK regarding arm/cartridge ”dance” while playing the highly modulated Billie Jean on M Jacksons album Thriller. I checked my own and it does the same. My guess is that this would be fixed if the horizontal Rf would be low, as would be expected if you use an arm with much higher horizontal mass. Eg the Moerch DP-8. Thoughts?

It’s Michael he is in the groove!

 

[MAB]

Your CD version look clipped?

(I am using an unipivot with 4 g arm mass and cartridge of 6,5 g, compliance of 20 cu-= 11 Hz. Which also fits with sweep measurements. The 8 Hz component is an addition, as also seen in Maxwellseq spectrum. )

Are these quoted specs or measured? Can you record a blank region? That will solve any confusion, and is why I included blank region recordings with spectra, even on different records and different RPM. Also, I don't typically trust manufacturer compliance and even effective mass.

Looking at the CD Rip of mine, I see it is actually 2001, so not an '80s release as I stated. I thought I had ripped my original copy. Maybe I omitted the original when I ripped my collection, likely believing it was somehow inferior!?! It would be nice to find a first edition and see if there are artifacts that they neglected to filter out.

I found another copy. A greatest hits collection, HIStory from 1995:

Here is the spectra of the first 4 seconds!

Now I have no idea of what I am looking at! The same subsonic is on the Spotify version of HIStory as well.

 

[Thomas_A]

Are these quoted specs or measured? Can you record a blank region? That will solve any confusion, and is why I included blank region recordings with spectra, even on different records and different RPM. Also, I don't typically trust manufacturer compliance and even effective mass.

Looking at the CD Rip of mine, I see it is actually 2001, so not an '80s release as I stated. I thought I had ripped my original copy. Maybe I omitted the original when I ripped my collection, likely believing it was somehow inferior!?! It would be nice to find a first edition and see if there are artifacts that they neglected to filter out.

I found another copy. A greatest hits collection, HIStory from 1995:
View attachment 379597
Here is the spectra of the first 4 seconds!
View attachment 379598
Now I have no idea of what I am looking at! The same subsonic is on the Spotify version of HIStory as well.

I can assure you that the resonance is around 11 Hz with the Moerch 4 g arm. Will be traveling now so any graphs will be presented later next week. With lateral and vertical sweeps.

With respect to different versions, it is a mess to compare.

 

[MAB]

I can assure you that the resonance is around 11 Hz with the Moerch 4 g arm. Will be traveling now so any graphs will be presented later next week. With lateral and vertical sweeps.

Cool. No rush.

With respect to different versions, it is a mess to compare.

Yes.

 

[MaxwellsEq]

Hi @MAB and @Thomas_A

Here's the frequency response of the "silent" lead in groove on side 2 of Thriller (the same side I sampled Billie Jean from) which is dominated by 10Hz:

Here, in contrast, is the frequency response I posted earlier of Billie Jean with its 8Hz infrasonic peak:

HTH

 

[Thomas_A]

So here is the resonance of a blank track; tonearm UP-4, 4 gram arm, V15Vx SAS_B with brush. The brush is very effective to damp vertical resonance, while not that effective of lateral resonance.

Red track = blank stereo track between tracks of 1 kHz reference tone.
Green track: the same track but made to mono = out of phase signals cancels out, in phase adds. About 6 dB lower signal.
Blue track: the same track, but one channel inverted, and then made to mono: out of phase signals adds together, in-phase signals cancel out. 11 Hz peak is dow 12 dB, but higher f are increased by about 6 dB.

This shows several things;
- a mono filter below 150 Hz is beneficial to lower the vertical LF noise (warp noise).
- the lateral resonance is significant between 5-20 Hz, while vertical LF noise is dominant > 20 Hz.
- The pattern could be an effect of the brush, so it should be repeated without brush.

 

[antcollinet]

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

So here is my video, and my recording.

I think there is a little dancing of the cartridge - but not sure it isn't just an effect of the off center.

I don't, however, seem to have your 8Hz oscillation.

Rega P3
RB330 tone arm. 2g. No idea of effective mass.
AT VM95 ML

 

[Thomas_A]

There is a clear dance there. Your lack of oscillation in the track picture might depend on your RIAA stage. I have -1.4 dB at 8 Hz, many others have quite a steep filter in the bass, so it is not as visible.