I've created an app to measure turntabl speed and "wow"

snap, crackle and pop
knifeedge
member
member
Posts: 67
Joined: 08 Jan 2015 18:05

I've created an app to measure turntabl speed and "wow"

Post by knifeedge » 19 Sep 2018 13:22

Hi all!

I always appreciated RPM Calculator for the easy was to visualize turntable's speed, but I wish it could measure and calculate also the variations. I didn't find an app for Android that was able to do it, so... I've written one by myself!
And I managed to publish it. It's free.

It can visualize RPM turntable speed, or measure the speed for 10 seconds and visualize min/max variations.

Here it is if you want to try (and give me feedback):

https://play.google.com/store/apps/deta ... M.RPMSpeed

Image

Andrea

MRL_LPLvr
member
member
Posts: 40
Joined: 26 Jun 2010 14:30
Location: STL

Re: I've created an app to measure turntabl speed and "wow"

Post by MRL_LPLvr » 19 Sep 2018 14:50

Love to try it but I am an Apple user... porting it to iOS?

knifeedge
member
member
Posts: 67
Joined: 08 Jan 2015 18:05

Re: I've created an app to measure turntabl speed and "wow"

Post by knifeedge » 19 Sep 2018 14:53

MRL_LPLvr wrote:Love to try it but I am an Apple user... porting it to iOS?
I'm sorry but I don't have Apple devices so porting to iOS is far away in the to do list. :(

Solist
senior member
senior member
Posts: 265
Joined: 08 May 2017 18:49
Location: Ljubljana

Re: I've created an app to measure turntabl speed and "wow"

Post by Solist » 19 Sep 2018 19:29

How is the accuracy?

I use my ears and then a strobe light to check the speed, must admit I dont trust my smartphone being enough accurate.

knifeedge
member
member
Posts: 67
Joined: 08 Jan 2015 18:05

Re: I've created an app to measure turntabl speed and "wow"

Post by knifeedge » 19 Sep 2018 21:58

It gives the same values of RPM Calculator, and it's on pair with Dr.Fleickert's Platterspeed app measurements and my Pro-ject strobe disc (my turntable runs a bit high). It seems quite accurate to me. I was really interested in variations, and it seems very precise. (again, I obtained same values as Platterspeed).
It depends on the smartphone, but I think it can be useful as a quick evaluation tool, especially for variations drifts (loose belt etc.). Well, it's free, so enjoy to try it and verify by yourself with your references if you want.

ChrisfromRI
member
member
Posts: 197
Joined: 13 May 2004 04:17
Location: New England

Re: I've created an app to measure turntabl speed and "wow"

Post by ChrisfromRI » 20 Sep 2018 01:05

Can somebody make a turntable speed measuring system that tracks dynamic versus static speed accuracy? I believe it would require a known record containing say 5 seconds of heavy groove modulation alternating with say 5 seconds of little groove modulation, repeatedly. Then the known length bands could be sync'd at demodulation and you could see the effect of heavy groove modulation on speed accuracy with different turntables and drive systems...

knifeedge
member
member
Posts: 67
Joined: 08 Jan 2015 18:05

Re: I've created an app to measure turntabl speed and "wow"

Post by knifeedge » 20 Sep 2018 05:44

Btw, the app uses the gyroscope sensor. Your phone needs to have it. No GPS needed unless we want to put the turntable on road tour.

kingbender
Posts: 2
Joined: 01 Dec 2015 21:15

Re: I've created an app to measure turntabl speed and "wow"

Post by kingbender » 20 Sep 2018 06:17

Many thanks Andrea. I think this is a great little app that does what it promises with no fuss. This is my sl-120 MK2.
Attachments
Screenshot_20180920-055908.jpg

knifeedge
member
member
Posts: 67
Joined: 08 Jan 2015 18:05

Re: I've created an app to measure turntabl speed and "wow"

Post by knifeedge » 20 Sep 2018 06:37

kingbender wrote:Many thanks Andrea. I think this is a great little app that does what it promises with no fuss. This is my sl-120 MK2.
Thank you! Wow, this is steady speed!! :shock:

MikeyB456
member
member
Posts: 102
Joined: 24 Jan 2017 20:53

Re: I've created an app to measure turntabl speed and "wow"

Post by MikeyB456 » 20 Sep 2018 09:08

I tried it, and it seems to work pretty well :-)
However, I presume the W&F reading is simply the peak (ie worst-case) value recorded? It would be very handy to be able to apply DIN or JIS weighting to the results, so you could compare them to the spec of your TT. Also, my HFS75 test disc has 'built-in' Wow, thanks to the hole being slightly off-centre (LOL). Could your app be provided with a filter to take out this once-per-revolution component?
Last edited by MikeyB456 on 20 Sep 2018 09:09, edited 1 time in total.

chiz
senior member
senior member
Posts: 524
Joined: 16 Oct 2009 23:05
Location: London

Re: I've created an app to measure turntabl speed and "wow"

Post by chiz » 20 Sep 2018 09:08

knifeedge wrote:Ps. the gold standard for these measurements is test record with 3150 Hz track
If you can find a test record which is perfectly centred.

Otherwise the results will represent imperfections in the test record as well as the turntable.

MikeyB456
member
member
Posts: 102
Joined: 24 Jan 2017 20:53

Re: I've created an app to measure turntabl speed and "wow"

Post by MikeyB456 » 20 Sep 2018 09:09

Thanks, chiz - exactly!

knifeedge
member
member
Posts: 67
Joined: 08 Jan 2015 18:05

Re: I've created an app to measure turntabl speed and "wow"

Post by knifeedge » 20 Sep 2018 09:17

MikeyB456 wrote:I tried it, and it seems to work pretty well :-)
However, I presume the W&F reading is simply the peak (ie worst-case) value recorded? It would be very handy to be able to apply DIN or JIS weighting to the results, so you could compare them to the spec of your TT. Also, my HFS75 test disc has 'built-in' Wow, thanks to the hole being slightly off-centre (LOL). Could your app be provided with a filter to take out this once-per-revolution component?
Thanks MikeyB456! Yes you're right, as written when the app the displays the results, those are max and min (worst case) values (hence the "wow" between commas in the thread title :p). Many turntable makers give also max and min variations in the specs (i.e. Pro-Ject).
DIN weighting is not straightforward and anyway not "DIN guideline correct" if applied to angular speed measurement, because DIN weighting applies to spectrum analysis of frequency track.
Nevertheless I hope to be able to put in a future release of the app an "DIN-Wow-alike" feature .

knifeedge
member
member
Posts: 67
Joined: 08 Jan 2015 18:05

Re: I've created an app to measure turntabl speed and "wow"

Post by knifeedge » 20 Sep 2018 09:56

chiz wrote:
knifeedge wrote:Ps. the gold standard for these measurements is test record with 3150 Hz track
If you can find a test record which is perfectly centred.

Otherwise the results will represent imperfections in the test record as well as the turntable.
Indeed!
Also the measurement with the app is prone to interact with the system. With very lightweight and low-torque turntable, the off-axis weight of the phone can induce periodical variations to the measurement. (but with my Thorens TD-190, not the most heavy and powerful off the turntables, the problem is not present). In the case, you have to manage to put the phone exactly at the center, above the spindle (two cd cases can usually do the trick).

MikeyB456
member
member
Posts: 102
Joined: 24 Jan 2017 20:53

Re: I've created an app to measure turntabl speed and "wow"

Post by MikeyB456 » 20 Sep 2018 12:07

I use an upturned china ramekin type of pot, centred over the spindle. So then I can place my phone on it, symmetrically over the centre and avoid the wobble-factor.

Knifedge, thanks for the info. And good luck with the app development!

Post Reply