Resonance in the range up to 20Hz

[Erogen]

This plays the test signal used on this forum to measure phono cartridges.
As a reminder for those unaware, every turntable constantly adds a high-amplitude signal to the music, up to 20 Hz.
All the time.
Big problem.

 

[MaxwellsEq]

This plays the test signal used on this forum to measure phono cartridges.
As a reminder for those unaware, every turntable constantly adds a high-amplitude signal to the music, up to 20 Hz.
All the time.
Big problem.

That's slightly true, but a bit simplified.

No LP has a perfectly drilled centre hole and so off-centre resonance associated with 33.3 rpm are unavoidable. No LP is perfectly flat, so you also have warp resonances associated with multiples of 33.3 rpm. Clearly these two resonances are not "music" and not on the original master tape so we must filter them out.

Every stylus assembly in a cartridge must move to a) capture the groove modulation and b) stay in the groove even with warps and off-centre LPs. The cantilever can't just flop around, so has to be mounted in a flexible (often rubber-like) suspension. This suspension has a certain rigidity (often defined as a value of compliance). A tonearm has an effective mass (even the lightest tonearms weigh something). When you combine the cantilever-mount compliance with a tonearm effective mass, you get a resonance.

If you miss-match the compliance and mass, 1) the resonance is at warp frequencies meaning the playback is unstable on real-world disks OR 2) the resonance is in the audio band.

Where your statement is imprecise is attributing the this "additional signal" to the turntable. Assuming the bearing is good and motor noise is isolated, the turntable is not really the primary contributor, it's mostly off-centre LPs, warps and arm-cartridge resonance.

 

[Balle Clorin]

That is why any property designed RIAA have a subsonic filter. A RIAA without is simply not acceptable.

 

[FrantzM]

hope this is not crapping on this thread

One has to wonder, why the bother? Dealing with Vinyl?

… perhaps because of unavailability of specific musical pieces or performance? Outlier cases but … to each its own, I guess

 

[Erogen]

If you miss-match the compliance and mass, 1) the resonance is at warp frequencies meaning the playback is unstable on real-world disks OR 2) the resonance is in the audio band.

High-amplitude resonance up to 20 Hz always occurs; it's unavoidable.
What matters is how high this amplitude is, and it's usually very high.
If we significantly increase the effective mass, we reduce the amplitude of this resonance, but this will place greater strain on the stylus cantilever suspension and, consequently, accelerate the degradation of its technical parameters.

Vinyl records and turntables are an outdated technology for recording and reading sound; they should be available only in museums.

 

[Redacted]

Can't this all be handled by filters? What could be recorded on vinyl under 20Hz that matters?
Just to be able to play vinyl properly, you must go through a filter (RIAA) to remove the pre-emphasis, so it's not as if filters are that scary.

 

[MaxwellsEq]

If we significantly increase the effective mass, we reduce the amplitude of this resonance,

With a different effective mass you principally change the frequency of the resonance, assuming cartridge compliance is unchanged.

Increased system damping can reduce the Q (and hence the resonant peak) at the cost of moving it to a wider frequency range.

In reality a turntable+arm+cartridge+LP in a room is a complex dynamic mechanical system as @Frank Dernie rightly points out.

 

[Thomas_A]

High-amplitude resonance up to 20 Hz always occurs; it's unavoidable.
What matters is how high this amplitude is, and it's usually very high.
If we significantly increase the effective mass, we reduce the amplitude of this resonance, but this will place greater strain on the stylus cantilever suspension and, consequently, accelerate the degradation of its technical parameters.

Vinyl records and turntables are an outdated technology for recording and reading sound; they should be available only in museums.

Reducing the peak s possible.

 

[Balle Clorin]

An Denon electronic Q-damping arm helps too

 

[Erogen]

Reducing the peak s possible.

View attachment 533647

-20 dB, good result

Of course, you can reduce this amplitude. The entire history of turntable development is a constant battle against this undesirable phenomenon. A losing battle.

The problem with the average vinyl enthusiast is that they almost never measure this amplitude level for their system.
They measure the cartridge, not the level of unwanted resonance. It's ridiculous.
Some vinyl enthusiasts calculate effective mass, compliance, etc., as if it had any significant impact on this amplitude level. Changing the effective mass by a few grams won't change much.

 

[Redacted]

But blu-tacking a penny onto the headshell did make some records less prone to jumping for me.

 

[MAB]

-20 dB, good result

Of course, you can reduce this amplitude. The entire history of turntable development is a constant battle against this undesirable phenomenon. A losing battle.

The problem with the average vinyl enthusiast is that they almost never measure this amplitude level for their system.
They measure the cartridge, not the level of unwanted resonance. It's ridiculous.
Some vinyl enthusiasts calculate effective mass, compliance, etc., as if it had any significant impact on this amplitude level. Changing the effective mass by a few grams won't change much.

Effective mass and cartridge compliance both have a large impact on the frequency of the resonance, and the amplitude.
Not quite sure why you are claiming 20Hz is the frequency, it depends on sqrt(k/m) since the system is a harmonic oscillator. Also, damping affects the amplitude, something you haven't mentioned. There are multiple threads with these measurements and discussion.

Do you have data to share?

 

[Thomas_A]

-20 dB, good result

Of course, you can reduce this amplitude. The entire history of turntable development is a constant battle against this undesirable phenomenon. A losing battle.

The problem with the average vinyl enthusiast is that they almost never measure this amplitude level for their system.
They measure the cartridge, not the level of unwanted resonance. It's ridiculous.
Some vinyl enthusiasts calculate effective mass, compliance, etc., as if it had any significant impact on this amplitude level. Changing the effective mass by a few grams won't change much.

Well, you are on ASR, and we all know this. We strive for good technical setups and what matters. You could buy the laser turntable if you want to or use clever damping, like the Shure cartridges did. And horizontal damping for the arm. Flat LPs helps. As a last step one can add subsonic and elliptical filters in the RIAA to save headroom in amps and speakers. The measurement I showed is without such filters, and you save up to 20 dB more with those.

 

[Erogen]

Well, you are on ASR, and we all know this.

Yes.
The average vinyl fan doesn't know this.

 

[EJ3]

Reducing the peak s possible.

View attachment 533647

Yes, it was quite possible to reduce the peaks earlier than 1977 (APT/Holman PreAmp):
Filters measurements top

Frequency Response, Normal (left) and 15 Hz filter (right), Apt Holman Preamplifier.

​

Same as above, different vertical scale.

​

15 Hz filter (only) response.​

The low-frequency response is the same with the tone controls either defeated or engaged, for all inputs and all outputs.

The 15 Hz filter is selected with a rear-panel switch.

It's -1/2 dB at 20 Hz, -1 dB at 17.5 Hz, -2 dB at 15 Hz, -3 dB at 14 Hz, - 5 dB at 12 Hz and -10 dB at 10 Hz.

 

[Erogen]

Please describe how the average vinyl enthusiast should measure the level of unwanted resonance in their turntable system up to 20 Hz.
What level can they consider good, and what level is bad and needs improvement?
What should they do if the level is too high?
Please remember that the average vinyl enthusiast is not an ASR forum user; their technical knowledge is much lower, so they expect simple, understandable advice.

 

[sergeauckland]

Please describe how the average vinyl enthusiast should measure the level of unwanted resonance in their turntable system up to 20 Hz.
What level can they consider good, and what level is bad and needs improvement?
What should they do if the level is too high?
Please remember that the average vinyl enthusiast is not an ASR forum user; their technical knowledge is much lower, so they expect simple, understandable advice.

Use any of the several test LPs with resonance bands. The resonant frequency can be observed visually, by watching the cartridge moving, up and down, or side to side depending on the modulation. No need for test equipment. Ideally, this unavoidable resonance should be at around 11Hz, above warp frequencies and below lowest audio frequencies. If too high, mass can be added to the headshell, if too low, more difficult to fix, but a lighter headshell if removable can help, otherwise a change of cartridge to one less compliant may help.

S

 

[Frank Dernie]

A pickup cartridge is one type of seismic transducer.
This type in effect it means that it is only accurately transducing above the influence of its fundamental resonance, which is usually around 2x the Fn, though damping and its type influence this. So typically a record player is capable of being reasonably accurate from around 26Hz and up but never lower.

Resonance is an inevitable consequence of physics, and messing with it in a record player is pointless IMO. More damping reduces accuracy at audio frequency, less damping increases amplitude at resonance but that is rarely a problem in playing a flat record. The worst case is obviously if the Fn is at a harmonic of warp frequency.

In normal use the resonance is unlikely to be excited but correct engineering includes a high pass filter on the phono stage so if a warp does excite it it doesn't overload amps etc downstream. There is a lot of incorrect engineering and misinformation in the record player community these days.

Seismic transducers work either below resonance or above. The most commonly used traditional accelerometers (at least when I was designing transducers) use a high stiffness (usually the actual piezo sensing element) and lower mass in their seismic layout and they are accurate below the Fn of the mass on its compliance, which allows them to measure down to DC, but limits the highest frequency they can measure.

 

[EJ3]

Please describe how the average vinyl enthusiast should measure the level of unwanted resonance in their turntable system up to 20 Hz.
What level can they consider good, and what level is bad and needs improvement?
What should they do if the level is too high?
Please remember that the average vinyl enthusiast is not an ASR forum user; their technical knowledge is much lower, so they expect simple, understandable advice.

I do not know, I have been analog since the mid 70's (when I started this journey, there were Audio/Video clubs. I started working at Radio stations were it was really important that the cartridge did not jump out of the groove).
Though the Audio/Video club, we got this Society of Audio Engineers White Paper "NEW FACTORS IN PHONOGRAPHPREAMPLIFIER DESIGN by Tomlinson Holman Chief of Phono Preamp Design ADVENT Corporation; Henry Kloss, the owner of ADVENT, hired Tom straight out of M.I.T.(the eventual inventor of 5.1 sound, The man that George Lucas hired for Lucas Film (and a whole lot more).
It is well broken down so that a layman can understand it (IMHO):
Here is the link:
https://hifisonix.com/wp-content/uploads/2019/06/Tomlinson-Holman-phono-pre-research.pdf
hifisonixhttps://hifisonix.com › wp-content › uploads › 2019 › 06 › Tomlinson-Holman-phono-pre-research.pdf
NEW FACTORS IN PHONOGRAPH PREAMPLIFIER DESIGN

Vintage Apt Corporation Holman // Solid-State Preamplifier​

SOLD , now part of a Private Collection
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Called "the best preamplifier ever designed" by Ken Rockwell, the Apt/Holman preamplifier is a HiFi legend. Imperceptible noise and distortion. Designed by the brilliant Tom Holman, who invented both 5.1 audio and THX motion picture sound, this preamplifier even has a patented variable stereo expansion circuit. The Holman preamp is so well thought out that its precise bandlimiting not only prevents distortion in other components, it sandboxes inactive signals coming into the unit, making the active signal the only signal. If you are serious about sound, you simply must audition the Apt/Holman.

Production1978-85 APT-1 Orig. MSRP$447

1 of my 2 was tested here, by Amirm in 2020. It had a couple of issues that were easy to adjust and one resistor was missing, which was replaced.
Find it in the search mode on this site: APT/Holman vintage review.

There is a lot of TT info in these forums on this ASR site:
To me, the MM version of this is the current top of the line (with how you can do blending and filtering [I own one]) and it is reviewed (the MC version) on our ASR site:

Classic Audio MC Pro Phonostage Review​

I hope that this helps

 

[Frank Dernie]

Please describe how the average vinyl enthusiast should measure the level of unwanted resonance in their turntable system up to 20 Hz.
What level can they consider good, and what level is bad and needs improvement?
What should they do if the level is too high?
Please remember that the average vinyl enthusiast is not an ASR forum user; their technical knowledge is much lower, so they expect simple, understandable advice.

My advice would be not to bother to measure it.
It is the inevitable consequence of physics and should have been set by the manufacturer to be at a frequency minimising its influence of the playing of records.

The most common misunderstanding these days is not using a high pass filter in the phono stage to get rid of the inevitably inaccurate amplitude and phase response it generates that may in rare circumstances get to the amplifier.

All this has been well known and documented for almost a century but the internet has encouraged the spread of misinformation and speculation as usual