Arm resonance

[borchee]

Hi Vince,

there is a hidden agenda on my behalf; hopefully, the discussion goes the desired direction....examples:

1) cartridge specs - the right way...see attachment - relates to 2)
2) g...well, the gravitational acceleration on face of the Earth is not constant, but varies within ~1%. That is negligible, I agree. The reason for bringing it up is that folks discuss - for what now?...a half a century at least! - the resonant frequency to decimals, and not just the first one. Let's say the desired resonant frequency is in the range 8-12 Hz, the "optimum" being 10 Hz, meaning a +- tolerance of 20%...but decimals are "important".
Not all turntables relly on g...vertical ones or the ones with spring-loaded tonearms - both will work on the International Space Station, oppose to conventional ones.
3) depends on how the discussion evolves.

The 64.000 smackaroones question: What weighs more; a 1 kg solid chunk of aluminum or of gold? - talking planet Earth...hint: same location, same athmospherics. Answers/thoughts greatly appreciated.

Perhaps the discussion, I'm heading to, deserves a thread of its own?

 

[marcok]

https://en.wikipedia.org/wiki/Mass_versus_weight
Read carefully this article , if you want .
It's not simple , but the mass is not the weight !
In the trade , however , for simplicity you can say that the mass is the weight .
Ciao
Marco

 

[borchee]

https://en.wikipedia.org/wiki/Mass_versus_weight
...the mass is not the weight !
In the trade , however , for simplicity you can say that the mass is the weight .

This is exactly my point! Simplicity/everyday use is fine, but I'm talking the ad nauseam (non-)sense regarding turntables adjustment.

 

[marcok]

In Carver C4000 service manual you can find the electric diagram for a subsonic filter .
It's an active filter . Download it from HiFi engine .
Ciao
Marco

 

[Makymak]

For simplicity of measurement we have adopted the kilogram (and it's subs) as a force unit taking the equation 1 kilo = 10 Newton, rounding g at 10m/s². See the car engines specs of torque. Since the force of the stylus is vertical it is very easy to measure it with a scale.

The 64.000 smackaroones question: What weighs more; a 1 kg solid chunk of aluminum or of gold? - talking planet Earth...hint: same location, same athmospherics. Answers/thoughts greatly appreciated.

Regarding where each chunk is standing and if it has air beneath it and what shape it has it is possible the one kg of aluminum to be lighter than the one kg of gold since the aluminum has grater volume (has lower specific weight). It's all about aerostatics/hydrostatics and levitation. The simple answer that both bodies would weigh exactly the same stands only in vacuum.

 

[vince666]

But I never said that weight and mass are the same thing.
I stated that they are proportional through the g constant. (the point that the g might vary a small bit can be ignored, otherwise the whole matter would become a lot more complex)... and measurement units for the weight and for the mass are different, of course.

Not all turntables relly on g...vertical ones or the ones with spring-loaded tonearms - both will work on the International Space Station, oppose to conventional ones.
3) depends on how the discussion evolves.

ah yes... forgot about those TTs!

The 64.000 smackaroones question: What weighs more; a 1 kg solid chunk of aluminum or of gold?

a similar question we use to ask here is: "what weights more, half chicken alive or half chicken dead?"

 

[borchee]

Makymak,

shape has no influence whatsoever - i said: solid chunk, Earth, same location, same athmospherics. Other than that...you nailed it! ...buoyancy (displacement of gas/air or liquid/water) is what makes the chunk of aluminum lighter.

Vince, my point is that laws of physics seem to have no place in HiFi. Just look with what a TT newbie asking about a turntable set-up is usually tortured with. This area is so full of variables and unknowns, that anyone stating he's got his TT set up perfectly is dillusional. Example: The consensus about setting the anti-skate force is that there is no consensus. I'm working towards your thesis.

 

[Makymak]

Buoyancy, yes that's the word I was looking for. Levitation is the result of the buoyancy.

Shape matters: if flat underside and standing on a flat surface, no levitation exists as no fluid can put pressure underside upwards.

 

[borchee]

No, shape doesn't matter - take, for example, window-glass; it'll weigh the same regardless if it's laying flat, on one of the sides or corners. The object/glass has a given volume and it displaces the exact same volume of, let's stick with it, air. Hence the weight of it is: (mass of glass - mass of displaced air) x acceleration.

 

[Makymak]

For an object to be lighter it needs a force pushing it upwards underneath. Since the displaced fluid is what pushes the object upwards (and makes it weighing lighter) it needs this fluid to reach underneath the object. If no fluid is underneath then no pressure is transferred underneath so no force upwards. To be more specific under such conditions, the chunk of aluminum will weight more!

Do an experiment. Sink a piece of flat glass on a flat surfaced sink. Try to raise it and you find it's too hard. As long as a tiny movement is done and water gets underneath then the piece of glass will be easily raised.

Edit: as long as no fluid is underneath the object, the surrounding fluid will pressure the object downwards making weight more.

 

[8991XJ]

I thought I had finished my engineering degree years ago. I don't know if I have the text books but the web probably has some answers.

I did give all my math books to my brother who has decided he wants to learn calculus since university courses are free to him.

as to the 64 question the Fidelity Research FR-64s uses a spring to apply tracking force. What did I win?

 

[borchee]

No, the mass of the glass is given, the gravitational pull/acceleration is given - its weight is the same! I don't need to sink the glass, it's enough to lean another piece of flat glass at it (both standing vertical), and I will not be able to pull them appart perpendicually - well, depends on the square footage of the glass. But here are other forces at work, not gravitation/weight.

 

[borchee]

What did I win?

A golden shower...not of the naughty kind, though.

 

[Makymak]

I don't disagree with that!

No, the mass of the glass is given, the gravitational pull/acceleration is given - its weight is the same! I don't need to sink the glass, it's enough to lean another piece of flat glass at it (both standing vertical), and I will not be able to pull them appart perpendicually - well, depends on the square footage of the glass. But here are other forces at work, not gravitation/weight.

Exactly! The same applies to your example of aluminum and gold. They both have the same gravitational pull. This pull is a force that depends on the mass and the g. Since both bodies locate at the same point and have the same mass then the gravitational pull/force will be the same. What will be different is the buoyancy since the bodies have different volume. The buoyancy can produce lift, a force that is applied under the body and pushing it upwards. Lift is produced because the pressure that acts on the bottom of the body is grater to the force that acts on the upper side of the body due to hydrostatic (air is considered fluid so hydrostatic applies here, too). Since gravitational pull is a force and lift is also a force on the same system, the actual downwards force will be equal with the sum of the two forces. And since they have opposite direction, the actual downwards force will be the difference of the two forces. So, the aluminum will be pulled downwards with smaller total force than the gold since the aluminum has grater lift. Till now we agree, I guess. The difference comes when there is nothing underneath to push the body upwards, producing lift. Then the body will be pulled downwards from it's weight plus the hydrostatic pressure that acts on it's surroundings except the bottom. And since the total force that acts on it's sides is equal to 0 (what pushes it's one side, the exact same thing pushes the other) then the only side that has no opposite force is the force that pushes the upper side downwards. Then and only then, the total downwards force will be grater than the gravitational pull alone, since it will be the sum of two forces on the same direction.

Sorry for my huge post and the out of topic but can't explain it simpler!

 

[Makymak]

The above post of mine proves how physics has impact on sound reproduction. Even hydrostatic gets involved!!!




Truly sorry for the off topic!

@borchee mate thanks for the conversation. I don't disagree with you, I just stand on details.

 

[borchee]

We see eye to eye. My goal in a debate is for me to learn something - I'm right until I'm proven wrong, which I can happily accept.

And...if one has to feel sorry for off topic...well, I blame the bastard in my mirror.

Best regards...from the bastard also.
Borut

 

[J!m]

VTF is always stated as a range anyway, so the minutiae of the actual downforce gets lost in the tolerance.

VTA on the fly is real; VTF on the fly would be cool too (not quite sure how to implement that) Then you tune by ear.

And really the test records are great for identifying the resonance. I actually took a short video of my arm resonating at ten hertz last time I checked it. Very easy to identify it when the whole thing is wagging like a happy puppy!

 

[J!m]

In Carver C4000 service manual you can find the electric diagram for a subsonic filter .
It's an active filter . Download it from HiFi engine .
Ciao
Marco

Hi Marco. The Elliptic filter is not a subsonic filter, nor is it a traditional hi-pass filter (text from the designer):

" Phono Warp first order "elliptic" filter with vertical (L-R) rejection of c. 3dB at 140Hz and c. 36dB at 2Hz. Nominally 0dB rejection of horizontal (L+R) rejection. "

It is only active on vertical input (L-R) and not on horizontal (L+R), so it literally removes "warp" signal (record pushing cartridge up) without effecting recorded musical information, even if it's very low frequency. Above 150Hz it is essentially non-existent as well, but it really doesn't matter- it is completely inaudible. It's an excellent design and I am looking into have a stand-alone right now. It won't be before Christmas, but soon...

Completely by-passable as well but I could have hard-wired it into my preamp. You don't know it's working!

 

[laatsch55]

DAYAM!!!!!!!!!! This thread got deep in a hurry!! Well done gentlemen!!

 

[laatsch55]

We see eye to eye. My goal in a debate is for me to learn something - I'm right until I'm proven wrong, which I can happily accept.

And...if one has to feel sorry for off topic...well, I blame the bastard in my mirror.

Best regards...from the bastard also.
Borut

Borut, from the beginning of Phoenix, and after the point I acquired it from The Larrt, I have encouraged off-topic meanderings for precisely this reason....ya never know where ya gonna end up, and many times those places are priceless....thank you....