ETD question re: unisons

[jolly roger]

Hi Muray,
               The test was done on a newly strung and hammered piano,
regulation set with very close letoff. etc.    Each string was sampled 10
times on the spectrum analyser to ensure the partials on each string were
close. Also verified by ear. Each string was tuned several times for full
blush on RCT, .01cent.  The test was done with back and front duplex scales
muted.
The piano was a really nice Steinway O.  But I have have had similar
results from my SD10.
Several notes were done in this manner each showed a drop of 0.2 - 0.3 cents.
And yes you can just hear the shift when checking the octave. .3 cents is
very audible within the unison
To do this test all string temination points have to be in good condition.
Ron is slowly winning me over, re a connection to either impedence, or the
reverse, reactance.
Some serious study of the principals of reciprocity is badly needed before
we can begin to start to understand what is going on.
Traditional piano thinking has been to look at the effect of loading with
respect to the impedence of the board.  Mechanical reactance (I think )
will be looking at the boards effect on the strings.
They are not nessesarily the same.
The subject is so complex that it would make a great PhD project.
Good to hear from you.
roger


At 08:26 PM 2/14/01 -0700, you wrote:
>Hi Roger
>I'm really on a roll tonight , this is my 3rd reply.Correct me if I'm wrong
>,but are you saying that you tune each string a number of times with the
>RCT,then take a reading of the three together and have a pitch drop of .3
>cents.I have been using a Sat for a number of year sand I find that I cannot
>always use the lights to tune a unison.I do not have a RCT to do a real
>comparison but I find that when the lights stop there still is a "window ''
>to tune within.With my SAT a difference of .3 cents would be noticable to
>the ear.I would wonder if all that has happened is that one of the strings
>is not in unison.
>Regards
>Murray
>----- Original Message -----
>From: "jolly roger" <baldyam@sk.sympatico.ca>
>To: <pianotech@ptg.org>
>Sent: Wednesday, February 14, 2001 9:27 AM
>Subject: Re: ETD question re: unisons
>
>
>> Hi Howard,
>>                  Yes it is easy to confirm.  The test that I have done
>with
>> a RCT show about a 0.3 cent drop in octave 5/6. The test was performed by
>> tuning each string individually several times, to over come the
>> interaction. then the net 3 string unison was measured.
>> The effect is known as string coupling.
>> My own theory is that. as all strings start to increase the amount of
>> energy into the bridge, the board is moving through a greater excussion,
>> and hence dropping the frequency a tad.
>> Now I've been out to lunch before, and I could be off base on this one.
>> Regards Roger
>>
>>
>> At 10:47 AM 2/14/01 -0500, you wrote:
>> >Hi everyone,
>> >
>> >Since I know nothing about ETD's my question might be naive. Nevertheless
>> >here goes: I believe that Virgil's assertion that a 3 string unison is
>> >flatter than each of the single strings heard singly, is a bit
>questionable
>> >or should I say not fully accepted. Wouldn't it be easy and conclusive to
>> >check this thesis by using an ETD to measure this? Thanks!
>> >
>> >
>> >Howard S. Rosen, RPT
>> >7262 Angel Falls Ct.
>> >Boynton Beach, Fl  33437
>> >
>> >hsrosen@gate.net
>> >
>>
>>
>