ETD comparison

[Mike and Jane Spalding]

Ron et al,

Here's some numbers generated with RCT Mac and Tunelab Pocket.  I set the Tunelab partials to match the RCT default partials, then simultaneously sampled A1 thru A6  with both programs.  Tunelab curve was adjusted for 6:3 in the bass and 4:1 in the treble.  RCT was set to OTS4.  Then I tuned all of the A's using Tunelab, and measured the offset using RCT.    I was too lazy to do all 88 notes, but you get a pretty good idea just from 7 octaves of A.

Note    Partial    TuneLab    RCT    Offset
A0        6                -10.46    -13.93    0.8
A1        6                -7.39        -3.28    -1.69
A2        3                -7.48        -3.58    -1.70
A3        3                -0.79        2.15    -1.14
A4        2                2.75        2.46        0.42
A5        1                4.56        4.13        0.49
A6        1                12.32        12.37    0.70
A7        1                30.45        29.73        N/A

The piano is "difficult" - Gulbransen spinet, hammers in pretty good shape but plenty of scaling and termination problems.   RCT didn't want to believe what it was hearing, "either A4 or A5 was not in the expected range for a piano...."   It took several tries to get acceptable samples.   When measuring the offsets with RCT, I saw up to a cent variation, so I averaged 3 readings.   When tuning with TuneLab, it was difficult to tell when the phase display was really stopped, easily +/- 0.5 cent error in the tuning.

The "Offset" number should equal the difference between the "RCT" number and the "TuneLab" number, but it's not, by up to 4 cents.  Some of that could be inaccuracy in my tuning, but hopefully not more than a cent even on this piano.  Any thoughts on why the numbers don't add up?


Mike Spalding