Replace the belt on the wow and measure again. Let us know what happens.
A Few Turntable Measurements using the RPM Android App
I found this Android phone app for TT rotation. Phone is Pixel 4a. Thought I'd try this app out. I'm skeptical of these phone apps. Accuracy is always an issue.
I have four tables. I took 5 readings for the first table in order to see what the repeatability is. The "absolute" RPM, RPM peak to peak, and 2 sigma range readings were very, very repeatable. Consequtive RPM readings differed by a max of 0.01 RPM. Two sigma varied by 0.01% ( 2 sigma means that 86% of the readings were within the stated value). I personally would use 3 sigma, but that's a personal quibble.
I've measured all four of my tables. I am very certain that the results are very repeatable. I measured with no LP, LP rotating, LP on and Stylus engaged, and phone offset from center. RPM was the same for all cases, The 2 sigma showed a 0.01% rise (really small). The reading at the edge of the LP was different. And scary to do!
Here's the results:
1. DD-40 #1, RPM = 33.32, 2 sigma = 0.07% (63 dB)
2. DD-40 #2, RPM = 33.27, 2 sigma = 0.09% (61 dB)
3. Acoustic Signature WOW XXL, RPM = 33.17, 2 sigma = 0.10% (60 dB). This varied 0.02% from reading to reading (after running the table for 10 minutes, this noise diminishes), but the 2 sigma stayed the same.
4. Denon DP-57L, RPM = 33.25, 2 sigma = 0.02% (74 dB).
I then went back to DD-40 #1. Using the RPM app, I set the mean speed to be 33.25. The strobe on the table was slowly moving! I checked against the strobe on the Cardas test LP and yes, the RPM speed accuracy was wrong. I reset TT speed using the strobe. The RPM app measured 33.23 again. I must conclude that although the RPM app is very repeatable, the absolute accuracy is not. The wow result (2 sigma variation) remains the same.
I measured the 45 RPM on DD-40 #1. RPM = 44.91, 2 sigma = 0.05%, so the 45 RPM is fairly accurate and the 2 sigma is lower.
This app makes no distinction between wow and flutter. It's all reported in the wow reading (wow and flutter are the same thing by nature, the only difference is the frequency range).
I'm surprised by the poor performance of the WOW XXL table. This a modern, belt driven table, with a massive platter. It is 5 years old. There's no way for the user to adjust the RPM. The variation in the speed is similar or slightly higher than the 40+ years old Micro Seiki DD-40 tables, which don't have crystal oscillator driven speed control. The WOW XXL takes about 10 minutes before the very high frequency variations settle. Now, I don't know much about the internal workings of the app. Helpful would be better accuracy (or the AC frequency in my house is not 60 Hz). Bandwidth is not reported.
The DP-57L performance is outstanding!. This TT was made in the 80s. And the DD-40 tables are not bad, but are as good as or better than the WOW XXL.
In summary, in my opinion, the RPM Android App is very useful. The absolute accuracy is a bit off, but the repeatability is very good The wow measurement is also quite good.
Showing 8 responses by mijostyn
I was never an AS fan. I do not care for units that go out of their way to look flashy without obvious benefit. Having said that there are four sources of noise when playing vinyl, the turntable, the record, the environment and lastly electronic. I assume you used the same record for all measurements. The environment is basically the same for each table and to my knowledge none of them have isolating suspensions. Electric noise would also be the same for each table. The conclusion you came to is correct. The AS has a Rumble issue. Rumble is a problem if you can hear it or if it affects the performance of speakers particularly subwoofers. I also think it is a significant marker of overall quality. It is also possible this turntable was damaged. I had an 80s era MS turntable which was wonderful. Its only failure was lack of a suspension. The apartment building I lived in had the worst environmental rumble problem I have ever lived in. The AC compressors were clearly audible in spite of concrete floors, all 19 stories. Because of this I returned to the Linn LP12 which was much quieter as long as you tip - toed around it. Measuring is always the best way to confirm anything. You also discover that “ears” have limited sensitivity when dealing with certain things as it sounds you only identified the problem by measuring. Measuring is also a great way to train your ears. If you really want to have fun get yourself a Dayton Omnimic V2. They are about $300 and worth every cent. You need a PC. The program is free but you need to have a serial # to access it. In the process you download the calibration file for your microphone. You will find it essential for possitioning loudspeakers, adjusting room treatments and writing target curves if you ever get into digital signal processing. |
I read that review back in the day and It's positivity over vacuum clamping remained lodged in my neurons. The comments about the turntable sounding "dull" only for everyone to decide that the reference system was too bright is a characteristic that is legion in high fidelity systems. There is a tendency for us to prefer brighter reproduction, brighter is better. There are many problems that will cause high frequency aberrations. In this review it is the high frequency resonance of underdamped records. But this problem also occurs with digital sources. It manifests itself as sibilance and poor imaging. Sibilance is obvious but the effect on imaging is more insidious. I "look" for it by listening to cymbals. The entire frequency palate should emanate directly from the cymbal. The cymbal should be in focus. Instead the cymbal will have a glow of high frequency. At its worst you can not define the cymbal at all. It is smeared across the stage. The usual cause of this is poor room control with omnidirectional loudspeakers. With a system that seems to sound dull listen carefully to the cymbals. If the cymbal is sharply defined and all the high frequencies are present and sibilance is totally absent you listening to an accurate system in a well managed room.....with vacuum clamping:-) |
I think your preaching to the choir. Perhaps a better way of putting it would be transient power. It is not just enough to be fast but a system must be powerfully fast. This is one of the characteristics of sound quality. Imaging exists as its own category with a different set of determinants. A system can have the right balance of frequency ( amplitude response) and be powerfully fast but still not image well. A system can image beautifully yet lack realistic transient power and not have the right balancer of frequencies. A great system will line up all these factors, have lifelike transient power, the right balance of frequencies and image correctly. Any variation from the ideal are what Raul characterises as distortions (of reality) |
Trying to do anything over the internet is folly at best. There are way to many uncontrolled variables. Most of what people say they hear is imagined which is why rigidly controlled studies with a cooperative panel are necessary to say anything. All audio is personal. We all expect something out of our systems. I want to feel as if I am at a live venue. Needless to say I have never gotten exactly what I expect, close maybe, but not good enough which is why I am still at it. I am a lot closer than I was 25 years ago. This has nothing to do with the enjoyment of music. Most of my listening is done on an inferior workshop system. This is only about the potential performance achievable with todays tech at a less than ridiculous price, We seem to be like ships passing in the night. Are you saying that you can only achieve a satisfactory level of performance at a live performance and that this is not achievable with a residential system? I attend a live performance about every other month. The last was Nickle Creek at the State Theater in Portland Maine about one month ago and it was killer. Chris Thile is a major talent. Their recordings are also stellar. Putting them in the media room is easy. Black Midi, not so much. All I care about is feeling like I am at a live venue. Many recordings make this impossible but that does not mean that I can not appreciate the voices of Billy Holiday or Enrico Caruso. With many recordings it is. System (includes the room) errors like sibilance and exaggerated high frequencies destroy any possibility. Amplitude errors are far more pervasive then either IM or Harmonic distortion. What seems to bother me most with turntables is problems that interfere with pitch, more wow than flutter, things like offset spindle holes and warped records. |
@rauliruegas , Only in instances of unamplified acoustic instruments are you going to perceive a real image at a concert. Many larger concerts have no image at all, they are mono. This does not mean that a stereo system can not create the illusion of real instruments before you. |
Dolby Atmos? Come on Raul, that stuff is for Mexicans:-) What I am saying Raul is only unamplified acoustic instruments present us with a realistic sound field. Everything else is compromised to one degree or another. A great home system is more capable of presenting a realistic impression than the majority of amplified venues. |