My first video showing off the app and the database: • This GREAT app will he... RPM, or speed apps for phones are an easy and convenient way to check your turntable's data. But are they accurate?
I had the same results when I didn't follow the App instructions properly , like you didn't , which was to position the phone disc in the centre - you would do this by raising the phone over the centre spindle by using a small selotape roll plastic center or similar. Position the phone so the circular info window is as central as possible and then calibrate as per instructions. I found that the slight difference 0.2% was caused by having the phone way off center like you show here. Once it was central, the readings were as accurate as the stroboscope disc I got from Audio Technica and also the 100 timed rotations (I also did 200 and 300 timed rotations). To put it simply, having the phone being rotated off center affects the gyroscope readings, even when calibrated as the phone is constantly having to adjust for the addition forces inflicted on it rather than just calculate perfectly central roatation. Try it, you'll see it checks out. I've checked over 40 turntables this way and all have provided near identical results.
thank you, random person who seems to be much smarter than the guy making this video, trashing an app he does not understand how to use. maybe Audioanus would be a better name for him.
Hello, I restore turntables and I compared my strobe discs with the app results and I get always the same speed on both of them. I only put my 2014 samsung in the center of the platter. When I put it off center, the result is off too and shows much more wow. Same for DD, belt drive, even idler drive. Excuse my english please and thank you for the nice video!
Doesn't the phone need to be in the exact center? Put it on a tape or upside down bowl or something. Anyway, speed is important but you probably may not hear it when it's 0.01 rpm off. It is far more important that the platter has a steady rotation to prevent any 'wow'. The app that I'm using shows me that I need another turntable. A belt replacement didn't help.
Indeed. Wow & flutter is more important than the actual speed itself +/- 0.5 %, nobody will notice. Though even wow & flutter can change if the record is pressed off-center.
Exactly. Centrifugal forces will fluctuate and induce W&F. Just think of the merry-go-round. It was always harder to sit at the outside while it was spinning whereas sitting in the center (or close) was easy (less outward force)
The first test is done with the stylus in the grove which properly introduces drag yet the second test is done without the drag of a stylus in the groove. Also as another member mentioned the weight of the phone should be placed symmetrically on the platter, not haphazardly to one side of the spindle. Both tests should be with the weight of an LP AND PHONE and with the stylus in play of the same cut of the same LP. [Large groove modulations from loud tracks have added drag.]
I've found that although these apps are always "off" and will show different speeds on different phones they are consistently "off" so if you have access to a TT that is known to be accurate and stable like a well serviced technics SL-XXXX or similar all you have to do is take note of the values on the "good" TT and then you can use your phone to set or check other TT's against those values. Also if you place a small bowl over the spindle and put the phone on top of it (so directly over the spindle) the results seem to be more stable, these apps are also the only cost effective way I know of measuring the "wow" (variations in the speed) and for that the speed measurement does not need to be correct only consistent.
One other problem: turntables aren't designed to be operated with an off-center weight, which may worsen wow especially if the table isn't *perfectly* level. You can test this by putting another phone (or similar counter-balance) on the other side and seeing if the wow and flutter figure goes down compared to just one phone on the table. My turntable is designed to operate within spec at any angle including upside down, but I guess I could try taping some phones to it if something possessed me to mount my turntable on the ceiling...
The problem is the weight of the phone causing offbalance and pertubulations in the speed, better way I did it was to blutack the middle of the phone to the spindle. That way I measured 0.18 wow which is the given spec of my turntable. You will get more accurate readings with lighter phones.
I don't think it's the app's fault, but perhaps is dependent on the phone . Even phones that are the same brand and model will measure differently, probably because of the tolerances of the quartz time bases within them (a guess) or maybe slight differences between accelerometers. My wife 's iPhone and my daughter's iPhone always show slightly different RPM measurements between each other, but consistently, for my Technics SL1200Mk2 turntable. Again, both are the same model iPhone. My Motorola phone running the Android version of the RPM app consistently measures between 33.32 to 33.34 RPM (within .09%) on the same turntable. I believe that phone to measure the RPM speed more accurately.
As suspected. Its a shame really, but still close I think. I dont remember if I wrote this on the previous video but Ive heard that some phones have more accurate gyro sensors. So maybe you might also just be unlucky with your phone. Although that still doesnt help the consistency of the data base numbers since you cant know what phone is used and if its properly working.
I have an android phone, so I don't have the same app but a similar one that only gives you the rpm. With my turntable it reads 33.3 and 33.4, that probably is the best precision it can get as I am pretty sure that it does exactly 33 and 1/3 rpm as it has quartz lock and the light always stays on for the whole reading. Another thing you may try is to place the phone on the dead center, to avoid having unbalanced loads on the motor. On paper it shouldn't affect the rpm reading that much (but probably it would affect wow and flutter), but with some quartz lock turntables maybe it can give you inaccuracies depending how it reads the rotations. I simply put a roll of scotch tape in the center so I can put the phone in the middle without interfere with the spindle.
Just for curiosity did you find differences in wow and flutter? At this point I think that those measurements are well outside the sensibility of the gyroscope (that can't even track accurately continuous rotating speed!), but if possible to have an empirical confirmation I would be more than happy! Also thank you for your videos, they are always helpful!
W&f went from 0.10 on the platter to 0.09 in the center. Not much of a difference. But like you, I don’t know if those results are accurate. Better to question at this point.
Given that from the data sheet of your turntable wow and flutter should be less than 0.025% I think we'll have to wait more precise sensors... I can understand some degradation with age, but 4 times more to me seems a little too much!
I found using the android version with the green numbers on my galaxy S6, placing it on the centre spindle went from 34 to 33.4rpm on a Pioneer PL12D with a new belt, I can't play test yet as I'm waiting on a stylus but I think it should be spinning properly
Don't you think the weight of the phone would count? Try to count the 100 turns again with the phone weight and see if it will show the same precision... 😉
How big is the influence of the accelerometer quality/accuracy? Or is it mostly caused by inaccurate software? In the first case, it would mean that it could be more accurate on certain smartphone models.
Really appreciate the video. I was thrown off throughout though by the visibly horrendous wobble. Seems like a pity to be as accurate and scientific as you are clearly being, yet getting your data from such a source..
Tried this, my Technics table was off by -0.18% consistently. Even if it's true and the app / gyro is 100% accurate, I firmly believe that 0.18% margin of error doesn't really matter. The
I'm curious why you assume that your strobe is firing at the correct speed. The accuracy of the strobe also has to be questioned. We didn't get to see how you started and stopped the 100 rotation test which is a pity because there is no way to assess the margin of error there.
This is a typical Apple philosophy: a lot of functions and features to amaze, but accuracy is not that important. RPM Speed & Wow for Android is free, does not load the measurements to a database (what is the use of it anyway...?) - but does what it is supposed to do. And does it accurately and measures much faster than this i-crap.
What accuracy did you expect for a gyro on a consumer device like this? Nothing is 100% accurate. 99.8% is pretty darn good and good enough for most consumer applications.
an imbecile if you think all android phones will be the same. from an app developer standpoint, using the standard hardware of the apple phones is going to make for a much more accurate experience overall, even if the program needs to correct for hardware error.
Your test is absolutely flawed: the phone should be IN THE CENTER, OVER THE SPINDLE!!! On a raised support, like a roll of masking tape. You can do everybody s favor and remove your video.
