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Hello Bernhard,
Thanks a lot for the analysis.
I'll try to get more accurate measurement for the string. I'll try to =
find out a micrometer tool, or may be
I'll ask my Kawai tech if he can provide us with precise numbers.
I would be interested to look at the graphics for the diameters you are =
recommending for comparison.
Actually, the parasitic noise is clearly a whistling, as you pointed =
out.
I think it is worth to go deeper in the study, although I would be =
surprised that Kawai made such a
design flaw, but who knows.... If this is the case, I can predict that =
this subject might make some "noise" !
Greetings,
Stephane
----- Original Message -----=20
From: Bernhard Stopper=20
To: St=E9phane Hanriat ; Pianotech ; oleg-i@noos.fr=20
Sent: Monday, April 19, 2004 12:21 AM
Subject: Re: Analysis of plain wire string/wound wire break on =
aSteinwayModel Bwith MiniMens 1.0.6
Dear Stephane,
After i entered the string measures that you sent me, MiniMens reports =
clearly that this a problematic string length/diameter setting. The =
Longitudinal wave matches very close the 13. transversal partial, what =
results in a strong resonance effect. (speaking length 1058 mm, 0,975, =
plain wire, copper 0,5 mm)
The three pointers in the "Longitudinal Freq." meter representing the =
first 3 longitudinal partials in the transversal partial spectrum =
(represented by the meters scale, transversal partials reported from =
partial Nr. 12-48, the first longitudinal partial has a frequency of =
1290 Hz.=20
The meter indicates, that the longitudinal partial matches slightly =
above the 13. transversal partial.
Physically, longitudinal partials near to Odd transversal partials =
produce a strong resonance with 2 times the frequency of the odd =
transversal partial, what means in this example, the 1. longitudinal =
partial has a resonance with the 26. transversal partial. Due to =
inharmonicity of the 26. partial, this occurs if the frequency of the =
longitdunal partial is slightly above the 13. transversal partial.
In the sound simulation produced by the MiniMens Simulator one can =
clearly here the whistling produced by the longitudinal resonance.
listen to the sound by clicking the link:
http://www.piano-stopper.de/dl/Kawai_G23_0,975_0,5.wav
a solution would be to change the diameters to 1,0 mm for the core =
wire and 0,475 mm for the copper diameter.
(inharmonicity must be checked with the neighbour keys)
what would sound like this:
http://www.piano-stopper.de/dl/Kawai_G23_1,0_0,475.wav
Regards,
Bernhard Stopper
info about the MiniMens Simulator:
www.piano-stopper.de
----- Original Message -----=20
From: St=E9phane Hanriat=20
To: Bernhard Stopper ; Isaac Oleg=20
Sent: Sunday, April 18, 2004 9:15 PM
Subject: Re: Analysis of plain wire string/wound wire break on =
aSteinwayModel Bwith MiniMens 1.0.6
Hello Bernhard,
Please find hereafter the measurements I made for the note G23 (the =
note for which the kissing noise is the most audible):
- speaking length : 1058 mm
- steel diameter : between 0.9 & 1.0 mm (may be 0.95 mm) - section =
looks square where covered with copper.
- total wire diameter (includin copper wraping) : 1.9 mm (copper =
should then be around 0.5 mm diameter)
- strike point : 133 mm from the agraffe.
Hope you'll be able to sdo something with those information.
All the best,
Stephane
----- Original Message -----=20
From: Bernhard Stopper=20
To: Pianotech=20
Sent: Friday, April 09, 2004 10:06 PM
Subject: Re: Analysis of plain wire string/wound wire break on =
aSteinwayModel Bwith MiniMens 1.0.6
Hello Stephane,
is it possible for you to send me length and diameters for the =
keys that causing the problems?
I will do a dynamic simulation and a sound simulation with the =
Minimens to find out what might be the case. Please let me know also =
what kind of steel wire Kawai is using. MiniMens can do a sound =
simulation that reports also the longitudinal waves. I rather think it =
is a problem caused by the longitudinal waves (as Isaac Oleg metioned =
also earlier), but to do an exact simulation, it is necessary to know =
the value of youngs modulus of the core wire. (I actually only have it =
for R=F6slau steel, it varies from 201 to 207 kN/mm=B2 depending on the =
diameter). I "measured" youngs modulus of R=F6slau steel by simulating =
different diameters with the Minimens Simulator and measured =
inharmonicity on real instruments with same settings until the spectra =
fit.
I don=B4t think that the problems are caused by the multiple =
contacts, because they are normal for the lower keys. on the lowest =
octave the hammer does bouncing with the string up to 3 or 4 times, =
thats normal.
Best regards,
Bernhard
----- Original Message -----=20
From: St=E9phane Hanriat=20
To: Pianotech=20
Sent: Friday, April 09, 2004 8:21 PM
Subject: Re: Analysis of plain wire string/wound wire break on a =
SteinwayModel Bwith MiniMens 1.0.6
Hello Bernhard,
Very interesting post. I'm wondering if the "contact ratio" has =
something related to the "kissing noise" effect I've observed on most of =
the Kawai piano I've played. Please see below the post I sent to the =
list on the subject. I've working with Kawai Europe & Japan to try =
understanding the root cause, but they were not able to explain this =
parasitic noise to me, just saying that this is well known and likely =
due to hammer condition ??? I've never been convinced about that =
explanation, since only very few notes are impacted (few first notes =
below the break tri-cord/bi-cord) and only on the 1.78m and 1.86m =
piano...
Personnally, as an engineer, I already made the hypothesis of =
multiple contacts with the strings in that range, creating this =
parasitic noise (see below)...
I would be very much interested to have your feedback on this =
point.
Cheers,
Stephane Hanriat - Owner of Shigeru Kawai SK3
______________________________________________
Hello List,
I'm back with another topic I would like to share with you.
During the process of selecting my Shigeru piano, I played a lot =
of Kawai instruments, and I found a strange noise impacting very few =
notes, but always the same notes : 23, 24 and 25. The noise looks like a =
whistling appearing at the attack, and is very easy to ear when playing =
a non legato trill at pianissimo. This noise is clearly audible on most =
of RX-2, SK2 (1.78 m), RX-3 and SK3 (1.86 m). Very difficult to ear it =
on larger instrument. RX-6 or SK6 (2.12 m) do not have it. - sorry for =
the metric unit -:)
I had extensive discussions on that with our french MPA who is =
now an expert to determine whether an instrument is having the noise or =
not. We have contacted Kawai in Japan. They replied that this is well =
known as "kissing noise" and that mostly all prestigious brands are =
facing this problem that originates from hammer conditions. Kawai also =
told us that Steinway has extensively studied the topic without =
identifying the root cause ; and when the problem is creating =
inconvenience at playing, Steinway is replacing the hammers...
We made some experiments at the french Kawai show room on some =
RX, without being capable to find a reliable fix. Some pianos were not =
having this kissing noise, but most of them had it in the showroom.
When I play grand pianos in this size range, I always discreetly =
check the stuff... but I've not seen this kissing noise as present as on =
the Kawai. I can tell you I've been cautious when selecting my Shigeru, =
so it took me 2 years to find an SK3 almost free from kissing noise (but =
not completely free).
If some of you have an explanation and/or a fix, I would be very =
excited to learn this (and lot of MPAs too, believe me).
Cheers,
Stephane Hanriat, the french guy who loves the Shigeru's.
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