Accuracy of phone-based RPM apps for turntables

Has anyone been able to validate these vs. a more established method? Strobe etc?

I've set the adjustable power supply unit to a steady 33.3/45.0 via the RPM calculator app (on a Galaxy S7). It sounds fine in isolation, but can't help but wonder how accurate they really are.

Thanks.

 

I've used the RPM app as well as the Feickert App and test record and I found the RPM app close enough for my needs.

 

I trust the app but something to consider, what does your phone weigh vs what a record weighs and how that might affect the platter speed! I'm sure it's splitting hairs but still something that drives me nuts.

 

I just use the "Anti Gravity" app

 

You could test the potential phone weight issue with a TT that has a built in strobe. Set the phone on it and see if it changes the RPM. I doubt it would, perhaps on cheaper TTs.

I have used RPM and turn tabulator and they work fine for my purposes (though my TT does not have a strobe or speed box).

 

Pretty accurate I think.
I used one on my MMF-5 and it read 33.5, installed a Speed Box, and it now reads 33.4 using an RPM app for my Android phone.

 

The "Turntabulator" app on my iPhone does not agree with my strobe disk. I can get the strobe at a dead stop, while the app reads "33.2".

YMMV

 

Thanks.

Two things really:
1. The accuracy of the reading/app itself
2. Potential effect of the weight of the phone. If anything I'd guess this could be more of a factor; and perhaps hence why Sid's 0.1 slower vs. the strobe? Interesting if anyone else has found this.

Not sleep-losing stuff is it, but all the same...!

 

The test I referenced earlier was on my SP-15, which uses a closed-loop servo regulation. The strobe reads the same even if I stack several albums underneath, put the phone on with the disk... etc.

I consider the app useful for field testing, quick checks. Not for critical alignment.

 

OK, thanks for clarifying.

 

I tried both the Turntabulator app and the RPM app on my iPhone 5s.
My turntable is the Pro-Ject xtension 10. It has a built in speed box to set the speed exactly and a massive platter that I'm sure the relatively tiny weight of my iPhone won't affect. I checked it with a strobe, and it appears to be right on.
The Turntabulator app also says that it is right on. But the RPM app shows it fast by quite a bit (33.9 RPM).
I like the features of the RPM app (graph), but it appears its accuracy is suspect. If you go to the developer's web site, it even states that the accuracy is affected by the accuracy of the gyro in the phone you use, and you should calibrate it against a known good turntable.
The Turntabulator app claims it does not use the gyro and is accurate even if the phone isn't.
So unless you know the RPM app is accurate with the phone you use, I would stick with the Turntabulator app.

Terry

 

I have tested both Turntabulator and RPM on an iPhone 5s against my KAB Speedstrobe, which I believe is extremely accurate. Turntabulator in "Exact Mode" matches what I see with the KAB Speedstrobe very, very closely in terms of absolute speed. I would trust its accuracy in terms of giving an RPM reading. It does not tell you anything about wow and flutter however. The RPM app I found to be off from the reading of the strobe, reading about .2 slower than either the strobe or Turntabulator. It does give information about wow and flutter, but I don't know how much to trust it given that I believe its speed reading to be off.

Either app is worth a try, but I would trust Turntabulator more in terms of its speed reading.

 

I have verified the accuracy of the RPM Calculator android app, running on a Google Nexus 5X, against my AT-6 tachometer. If you want to use a tachometer to check the platter speed, affix a small square of white tape to the side of the platter (large enough for the tachometer to detect) and commence measuring. If anything, the app is more accurate because the phone remains still where the accuracy of the tachometer reading depends upon the steadiness of your hand.

 

Verified as in they read the same? Good if so (though as above I suppose different phones could be more or less accurate with the same app).

 

Yes

 

I've tested the RPM app on my iPhone and it matches the Thorens' integrated strobe exactly. So I'd say they're pretty accurate, at least when used with an iPhone.

 

It makes no difference unless you have a seriously cheap table. Turtabulator and Feickert app are consistent in their speed measurements.

 

If you want accuracy use the KAB SpeedStrobe. It uses a disc with playable track, so you can take into account your record clamp and outer ring (if you have them) and the drag and weight of your cartridge tracking a record.

 

Go onto Youtube. Tell youtube to give you a 3150 khz test tone.
Test your App against the tone.

The Feickert app for my samsung S9 by the way is dead on.

 

The RPM Calculator app on my old Samsung Galaxy phone is very inaccurate, showing something like 32.7 RPM even though a strobe disc, external tach, and platter rotation count shows it right on. Guess the accuracy heavily depends on the phone model for this android app, the iphone method seems to get much more accurate results, as do most new phones in general from what people say.

 

The problem with some of these apps is getting your phone centered on the spindle. A record weight or clamp may help with that but depending on the TT and clamp/weight, it could alter the playback speed slightly.

 

Davey, I had a similar reading from the Turntabulator app on my iPhone SE upon checking my now sold Marantz 6100. I printed out a strobe disc and from inference (the bars running backwards) seemed to feel it was correct. I tried the app on my Technics SL-QL1 (quartz locked direct drive) and got a reading of 33.4 from the platter with no record. I would guess some apps are more accurate than others as are the phone's capabilities.

 

The free Feickert app is no longer available for iOS. They never updated it, and it won't run or even install on the latest versions of iOS.

That 3150 test tone is recorded on the Analogue Productions test LP. That's what I used to use (when the Feickert app worked)

 

Well, the moral of the story is to put a sticky on the side of a record and put the stylus in the groove and take 3 minutes and count the rotations to find out how close to 100 it comes out. The vintage turntable speed app