Random idea: Has anyone tried using a mobile phone as an accelerometer to check turntable suspensions? Modern phones have these sensors built in, and they are pretty accurate too! at least enough for comparative measurements. There are many apps tbat work with this, and save a trace of accerlaertion vs time on three axes. We use this at work for investigating building vibrations.
I used the physics toolbox app on my phone to take the measurements I posted. In my case the mass of the phone is insignificant compared to the suspended mass and I am testing without the tonearm attached to keep the total suspended mass as close as possible. With lighter tables you could probably just calculate K based on the measured frequency with phone mass added and recalculate the natural frequency with the net mass.
Hi I have some experience with vibration dampening. I tested it with the smartphone and noticed that the sensitivity is far too low. I use a vibration meter. With steel springs, the swing out is actually quite long. but not that relevant in terms of hearing. Steel springs have another disadvantage, they only dampen up to about 800 Hz. If you put so much weight on springs that they are compressed 10 mm, this results in a resonant frequency of 5 Hz. As for the foam, there is an excellent product out there. Sylomer. This is significantly better than sorbothane, and inexpensive if you can buy small amounts. Unfortunately, this is usually not possible. However, Sylomer has a somewhat high resonance frequency. 25 mm thick / 13 Hz. It is particularly suitable under the electronics and under the loudspeakers. The effect is phenomenal!!! A lower resonance frequency should be aimed for in turntables. Still, Sylomer is better than no suspension at all. regards
^ The foam springs I used were cut from a material like sylomer but in my case it was manufactured by Fabreeka. I believe the data for natural frequency is based on a shape where length and width are considerably greater than depth. At least that would account for the differences I measured. The sampling rate of the app I use on my phone is 417 Hz so fine for low frequency resonance testing. I can see noise at about .03 M/S^2 so I would say sensitive enough for this work.
Hi, I don't want to argue about whether the smartphone is enough. That has nothing to do with the app, but with the sensors, which are not sensitive enough. A vibration meter must be handled with care or the sensor will be damaged. That's not really the case with smartphones. You can also use a smartphone to record a loudspeaker playback, but a good recorder is still much better. regards
Sorry if I gave the impression I wanted to argue. I was only pointing out that the sensor is accurate enough for this work. Specifically determining the natural frequency and relative damping of a turntable suspension. Once you are into the audio frequencies the turntable system comes with a built in transducer
I measured some sorbothane pucks. I could not get anything clean in the Z dimension by either pushing down or tapping the plinth. This was taken with (4) 1.5” duro 50 hemispheres under a 26 pound platter/ plinth combo. the maximum weight suggested by the seller was 30 LBs. I have no idea why one of the dimensions (Y = short way on the platter) shows a higher frequency but in multiple measurements, it all looked roughly the same. I see about 11.5 Hz in the X dimension and 20+ in Y.
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Wow that's a huge difference. There appears to be ~60Hz or so ripple on the spring and foam traces, which will be a source of audible colouration. That might be part of the Linn 'plum in mouth' sound character.
Marty, thanks for these informations, very interesting! (My td-125 may make good use of it 😊)
Question: how did you use the sorbothane, just like the foam-dampener? (Didn’t see it in the thread, sorry if it’s already there
Question: how did you use the sorbothane, just like the foam-dampener? (Didn’t see it in the thread, sorry if it’s already there
David, I used the sorbothane in lieu of springs, just sitting flat at the corners with plinth on top.
John, Yes that ripple showed up sometimes and I'm not sure if it is an artifact of the way I was releasing the plinth or something inherent in the springs themselves. I think I will measure the undamped springs again and check for ringing like that early in the trace. I was more focused on getting a good read on the frequency and damping rather than looking for anomalies
John, Yes that ripple showed up sometimes and I'm not sure if it is an artifact of the way I was releasing the plinth or something inherent in the springs themselves. I think I will measure the undamped springs again and check for ringing like that early in the trace. I was more focused on getting a good read on the frequency and damping rather than looking for anomalies
I have used Sorbothane hemispheres in place of the original springs for Thorens, Linn, Goldmund, Lenco, etc, turntables with very good results. For someone addicted to the Linn 'sound' it can be a bridge too far, but if it is the music on the record you want to hear without the syrupy flavour of an underdamped turntable on top, is a significant upgrade IMO.
Thank you. Cost me $3.13 to go to Pro which adds some comfort features (log freq in Spectrum, etc). Doesn't fix my bent compass or other shortcomings of a $39 phone.... hah! it will set sample rate far faster than my 13 cent microphone can make waves, showing the sharp cutoff at 21kHz. Thanks again.
https://play.google.com/store/apps/details?id=com.chrystianvieyra.physicstoolboxsuite
https://play.google.com/store/apps/details?id=net.vieyrasoftware.physicstoolboxsuitepro
https://www.vieyrasoftware.net/
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Hi johnmath,
I see that you’re familiar with Sorbothane suspension upgrades on Goldmund tables.
I just purchased a Goldmund Studio with an SME arm, and I’m very interested in swapping out the springs in favour of sorbothane.
I read various audio Forum posts from folks that said it’s a great upgrade, however I can’t seem to find any specifics on what folks have actually used in terms of parts for the upgrade.
I’ve also read that you’re supposed to use different stiffness sorbothane - just like the 3 different Springs they replace - but again no specific info on what parts would fit that requirement.
Any advice that you’d care to share would be immensely appreciated!
Thanks,
Mike
Hello. I am providing the isolation feet that I have built. Good results.
https://www.thingiverse.com/thing:5805205
Thanks for the message - the feet look great. Unfortunately it doesn’t pertain to my question, but thanks.
I'm confoosed. 🙁 (But I'm someone whose thinking is possibly constrained by owning a 'sprung' TT for 45 years.)
"Springs", to me ... are there to stop vibrations travelling up from a benchtop/rack etc. into a TT's structure.
Getting rid of motor vibrations ... is another thing entirely! 🙄 Preferably, I suggest ... motors should be mounted off the TT.