How to check resonance on Tonearm....

[pdm4606]

I think the best way is to connect a scope or maybe a analog meter to the pre out and play a sweep LP from under 20 hz to 100 hz and watch the result.
Is that a good method?

I don't know of any LP that goes under 20 hz.

If a resonance is present I would expect to see a very pronounced increase in wave form/signal or possibly a distortion at the resonance point.

Is there any other method?

Has anyone done something like this?

Paul

 

[gusten]

I think the best way is to connect a scope or maybe a analog meter to the pre out and play a sweep LP from under 20 hz to 100 hz and watch the result.
Is that a good method?

I don't know of any LP that goes under 20 hz.

If a resonance is present I would expect to see a very pronounced increase in wave form/signal or possibly a distortion at the resonance point.

Is there any other method?

Has anyone done something like this?

Paul

A resonance is always present when playing an Lp, especially at most outer grooves. Usually with most arm/cartridge combinations it will be between 5-10Hz. If You do a recording and look at it in an FFT software it will be easy to see.

 

[gusten]

Thanks gusten.

 

[marcmorin]

Thanks gusten.

He might not have been back to the board(s) yet. if so, I agree with you.

 

[hirscwi]

Excuse my lack of knowledge, but what is FFT software? Thanks.

A resonance is always present when playing an Lp, especially at most outer grooves. Usually with most arm/cartridge combinations it will be between 5-10Hz. If You do a recording and look at it in an FFT software it will be easy to see.

 

[Qilin]

FFT = Fast Fourier Transform. Search for the wikipedia article. Converts time-domain signal to frequency domain. Audacity can make these plots.
DM

 

[gusten]

Excuse my lack of knowledge, but what is FFT software? Thanks.

Like Qilin already wrote. One needs to see the output related to frequency. There are free softwares like Audacity and others that can do this, both record in time domain and convert to frequency domain.

 

[pdm4606]

Thanks gusten...

Always learning from AK and it's generous members. Your comments are worth a world of trial and error.

Paul

 

[pdm4606]

LP under 20 Hz....

I think the best way is to connect a scope or maybe a analog meter to the pre out and play a sweep LP from under 20 hz to 100 hz and watch the result.
Is that a good method?

I don't know of any LP that goes under 20 hz.

If a resonance is present I would expect to see a very pronounced increase in wave form/signal or possibly a distortion at the resonance point.

Is there any other method?

Has anyone done something like this?

Paul

A smart alek friend of mine came up with a great idea. If the sweep on an LP starts at 20 Hz, why not slow the Lp down to go lower.
If, let's say go 1/2 speed, it would be at 10 hz. Maybe huh??
All I gotta do now is figure a 1/2 speed setup for my old ROK TT.

Paul

 

[hirscwi]

Thanks to Qilin and Gusten for answering my question. It sounds like the Audacity software is freeware - even better.

 

[Willeve146]

If you check the graphs at the link below I think you will see that getting a tonearm to go into resonance above 16Hz is a challenge. You'll also see that the acceptable high limit is 12Hz. Resonance in these frequency ranges is can be seen by the naked eye very easily if you use a trackability test album containing a tonearm resonance test track. Shure's "An Audio Obstetrical Course" is an example of this type of test album. All tonearm/cartridge combinations have a characteristic resonance frequency and the link provides the general guidelines to use to avoid resonance issues. You can setup the equipment to do the resonance measurements, but like I say you will see the tonearm move when it's in resonance. As long as this occurs between 7 and 12 hz you should not have any issues (well below the audible range, but above the frequencies typically generated by warping.)

http://ortofon.com/hifi/support/cartridge-tonearm-resonance-frequency

Just another point; when a tonearm is in resonance the movement can be quite severe and there is a risk of damage to your cartridge. Careful monitoring of the cartridge during these tests is strongly advised.

 

[jk0592]

With HiFiNews record, the check for resonance is very easy to see, as the arm vibrates left to right in quite obvious fashion.
However, there is a vertical resonance check, and I can not identify the vertical movement with clearcut accuracy.

 

[pdm4606]

Home made tonearm setup...

The reason I ask about checking resonance is that I built a home made tonearm. It sounds very good and is over 18" from stylus to fish line pivot.
I am using a Shure cart. now (35c or something) and it sounds clean, clear but lifeless. Very few ticks & pops come through.
My old Pickerings have more life(dynamics). I don't see how I could lose so many dynamics changing cartridges. But it happened.
My best guess is that the tonearm setup is giving me a truer cartridge playing that previous tonearms(Old ROK and a no-name).
Is that possible?

Paul

 

[gusten]

The reason I ask about checking resonance is that I built a home made tonearm. It sounds very good and is over 18" from stylus to fish line pivot.
I am using a Shure cart. now (35c or something) and it sounds clean, clear but lifeless. Very few ticks & pops come through.
My old Pickerings have more life(dynamics). I don't see how I could lose so many dynamics changing cartridges. But it happened.
My best guess is that the tonearm setup is giving me a truer cartridge playing that previous tonearms(Old ROK and a no-name).
Is that possible?

Paul

What You can do, also without using any test record, is to drop the arm at a flat record surface. Let´s say from about 3mm height. The arm will then bounce up and down with exactly the resonance frequency. If one record these amplitudes one can also at the same time look at how damped the arm is by looking at how the amplitudes deminish.

 

[gusten]

An extraterrestrial audio course.:thmbsp:

 

[Willeve146]

obstacle[/b] course, but the suggestion does sound fascinating.

Curse you auto-spell checker! Also brings to mind the birth of my last child:scratch2:

 

[Catcher10]

Is this need to know just a "curiosity killed the cat"? I mean as stated all tonearm setups have a resonance, why put your cartridge thru that stress just to say.."yup it has resonance..ok"
If it is really bad you don't need a test record, you will hear it and see it in your woofer movement I would think.

 

[gusten]

Is this need to know just a "curiosity killed the cat"? I mean as stated all tonearm setups have a resonance, why put your cartridge thru that stress just to say.."yup it has resonance..ok"
If it is really bad you don't need a test record, you will hear it and see it in your woofer movement I would think.

Tonearm resonance and damping thereof is fundamental in vinyl playback, as they largely effect VTF and SRA. There are always small resonances present when playing. Depending on at what frequencies and how damped the arm is, the amplitudes varies. But these amplitudes will effect the VTF to a smaller or larger degree. And when doing so the SRA will continuously also vary, as will the frequency modulations.
So as a whole, the resonances from tonearm and cantilever suspension are really fundamental parameters to look into if one wants to learn more about how vinyl playback works, and how is should be optimized.

 

[ripblade]

A resonance is always present when playing an Lp, especially at most outer grooves. Usually with most arm/cartridge combinations it will be between 5-10Hz. If You do a recording and look at it in an FFT software it will be easy to see.

This is a reliable method, provided the spectrum analyzer has a high enough number of FFT points for good resolution.

I recently compared a time-frequency resonance sweep of a CBS STR-100 test record against the spectrum of a silent portion in between tracks using Izotope Rx and the results differed by only 0.2Hz. Furthermore, comparing this against other records played with the same arm/cart yielded closely matching results.

Unlike a proper resonance sweep, using a silent portion requires more samples to be measured as there are a number of peak amplitudes occurring at different frequencies around the fundamental resonance, so an average needs to be taken for truly reliable results.

Nonetheless, it does work, indicating that a dedicated test record isn't absolutely necessary to measure arm resonance.

 

[gusten]

This is a reliable method, provided the spectrum analyzer has a high enough number of FFT points for good resolution.

I recently compared a time-frequency resonance sweep of a CBS STR-100 test record against the spectrum of a silent portion in between tracks using Izotope Rx and the results differed by only 0.2Hz. Furthermore, comparing this against other records played with the same arm/cart yielded closely matching results.

Unlike a proper resonance sweep, using a silent portion requires more samples to be measured as there are a number of peak amplitudes occurring at different frequencies around the fundamental resonance, so an average needs to be taken for truly reliable results.

Nonetheless, it does work, indicating that a dedicated test record isn't absolutely necessary to measure arm resonance.

No a test record is not needed at all. It is also so there is at least two fundamental resonances going on when playing a normal record, one vertical and one lateral. These can be rather mixed depending on resolution and record, and can be seen as one rather wide resonance, but in fact there are normally two.

A good method is also dropping the arm and look at the resonances like this: