@mijostyn : This was what I posted a few months ago in other thread and was not the first time on that issue:
and this related in other " diferent " thread:
Today on those issues is my overall " take ".
R.
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.
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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) |
Is there any scientific data that indicates how a person with "normal" listening abilities perceives audio distortions? What are the lower limits or perception? Is there an emotional reaction to different frequencies? The commonly accepted sating that "even order sounds "good" and odd order sounds bad" is ubiquitous. Is there scientific data to back that saying up? If there are studies of this perception, I would really like to read references to that data. I have difficulty accepting commonly asserted "facts" unless there is data that has been peer reviewed. Pleas note that I am not bashing anyone. I am looking for explanations that are based on studies not commonly accepted sayings. |
@mijostyn : I don't know where you want to arrive. The power is just intrinsical in a live MUSIC event ( no one is preaching there and certainly not the Orchestra Director. ) and I thiink that any one but you already understood what I posted and the links I posted. For your " 20 + " latest posts in the thread you are living inside that imagin that according with what you already posted in the threads is a main characteristic for any room/system I don't know know if you attend to live events to enjoy the imagin. Not me. Anyway please tell me what can you appreciate in a single horn player at live SPL if you are seated nearfield say 2m.?. Maybe you know something that I just missed or we are talking of different " things ".
R. |
Dear @kevemaher : Obviously that you are not bashing anyone but instead of all those questions where you already have the answers then why not really enhance or apport something where all of us could be beneficiated for example: that you take your knowledge levels and make a mathematic model with measurements with the explanations of : what to measure, where to measure, how to measure and what all those makes sense to you and to any one of us. Scientifics along neurologists already made some research with measures how the brain and which brain parts react to some sounds and not specific on sounds of the ones in our audio hobby. In the mid-time you can google for those studies that even in Agon ( somewhere ) were posted and again with no relationship with the audio hobby.
You can start with your self at the end you are an audio hobbyst. R.
R.
R. |
- 76 posts total