There was a theory, abaout wood from trees from glassial era, and the wood from those trees would be harder than noprmal wood.
The borax treatment it's today considered the main reason of Stradivairus quality. Stradivarius violins, made after wood practices with borax changed, are no so big deal.
Funny, Stradivarius hinself apparently didn't know that the borax was what gave his violins such good quality.
After a few years the seasonal changes were not nearly as bad and after four or five years they were not noticeable at all.
Now for a parallel (if you can follow a bit of structural engineering). Roof trusses are made from so-called kiln dried lumber (less than 19%). During the winter in northern climates, the exterior air is very dry and doesn't hold much moisture, so the potential for drying shrinkage is high. Ordinarily all member of the truss would shrink similarly, and the truss would be stable.
However in cold climates, while the top chord is above the ceiling insulation and remains cold, the bottom chord is at the bottom of the insulation, and is thus very warm. Note that the humidity of the bottom chord is very low because although it is warmed by the warm interior ceiling, it is effectively "outside" where the air is very dry.
As a result, the bottom chord dries out much more than the bottom chord in the winter, and this causes the trusses to arch upward in the midspan (note - when the bottom chord shortens, the truss arches).
In the spring, moist air returns with higher temperatures, and the bottom chord regains moisture and the truss settles back down.
This wouldn't be a problem if there were no interior partitions in the building, but when the truss moves upwards by two inches or so (50 mm), it raises havoc with the partitions.
After two sometimes three) seasons of cycling, the trusses finally stabilize and there is no more movement. The similarity to the piano soundboard is striking. Incidentally, they are both made of spruce.
It is my contention that when young, wood will take on and release moisture with seasonal humidity changes, but in time this decreases and is not a problem. I call this curing or aging, not drying. The cell walls harden, and simply won't take up moisture.
Perhaps our illustrious Guillaume can make comments on piano soundboards. Incidentally some researchers believe that the difference between the great violins (Stradivarius etc), and well made modern ones is that Strads used very old wood.
Glenn
]]>Entitled "Detune Test Rendered"
It is pretty much the same as the previous one.
Glenn
]]>Then played the file in Pianoteq with Unison settings of 0.0, 1,0 2,0 and 4.0.
I recorded the sound in my wave editor (Goldwave) into one wave file which was converted to an mp3. In order to shorten the time that the file would play, I removed any portion of the space between the sounds that was below about -90dB.
There are two ways to judge the four variations - by listening, and by observing the waves in a wave editor (which provides some interesting information).
I have uploaded the file "Detune Test 0.0 1.0 2.0 4.0"
Comments would be appreciated.
It seems to me that the note that is detuned to 4.0 has a quicker decay than the others.
I will repeat the test, this time rendering to wave in Pianoteq.
Glenn
]]>But I didn't until now see why it sometimes extended the length of the decay and sometimes abbreviated it.
]]>I've uploaded corrected versions of both fxps. Sorry...)
]]>...I'm still struggling to understand it fully.
You're not alone. I've tried playing with the "direct sound duration" before without _truly_ understanding what it does -- this particular iteration of the explanation does substantial justice to the concept.
Just be glad we can't futz with the deeper parameters behind this concept just yet -- you wanna talk about getting lost in a labyrinth...
Excellent explanation, Philippe! Spoken like a true mathemusician. ;^)
]]>Greg.
]]>"...seems like when I NAIL a unison in the high treble the note can become lower in volume and sustain and less interesting in content. I was in a class given by Don Manino once ("The Sound of Your Tuning") where he suggested and demonstrated SLIGHTLY detuning one of the strings of the unison up there to attempt to increase the sustain. There were two same-model pianos in the room and he did a direct A-B comparison. I was sold. Sustain was noticeably increased with the detuned unison. And it had a little "shimmer" to it - not really an objectionable beat, just a "shimmer", maybe a slow vibrato or slow-rolling beat, though the length of the sustain wasn't long enough to make the slow-rolling "shimmer"/vibrato/beat at all unmusical."
So the post at Northernsounds must be correct after all!
]]>For simplicity, let’s suppose there are 2 strings and let's talk only about the fundamental frequency. The strings are coupled by the soundboard, so you shouldn’t think about them separately but together. There are 2 modes of vibration, lets call them D and R:
- D is the direct sound, it is a mode in which the strings are almost in phase,
- R is the remanent sound, it is a mode in which the strings are almost in opposite phase.
How do D and R behave with unison tuning? This is the core of Weinreich’s “coupled piano strings” article: the more in tune, the faster is D and the slower is R. D gets faster because the more the strings cooperate (being more and more in phase), the more efficient is the energy transmission to the soundboard, thus the faster is the sound decay (and also the louder is the sound). For the same reason, R gets slower because the more in opposite phase, the less energy is transmitted, thus the slower is the sound decay.
So, when you have both modes in the sound (aD+bR), what will you hear when reducing the unison width?
Case 1) If D is prominent (a/b is big), then the total sound will get shorter. This is particularly the case with very well regulated hammers because in that case, the hammer being very parallel to the strings, R is almost zero.
Case 2) If R is prominent (b/a is big), then the total sound will get longer!
As you see, both cases - and of course all intermediate situations - are possible when reducing the unison width.
In Pianoteq, you can control the ratio a/b with the direct sound duration slider: the more you push it to the right (case of perfectly parallel hammers), the greater is a/b. Hope that helps!
]]>In the fifth try, I got the midrange too soft, but it may have possibilities for some types of things. (The mp3 gets LOUD near the end. Just two chords while exploring the sound.) Remember that it's based on the Chamber preset:
http://www.forum-pianoteq.com/uploads.p...20Time.mp3
Here's the fxp:
http://www.forum-pianoteq.com/uploads.p...20Bass.fxp
This is the latest (sixth) fxp, with the midrange hammers set a little harder, so the notes have more definition:
]]>Greg.
]]>From physics, unisons in tune should sustain longer - if two strings are vibrating at exactly the same frequency, they will excite the bridge/soundboard to vibrate at this frequency (in other words they work together). If they are slightly out, with frequencies that are very close, then these frequencies are "competing" for the resonance of the bridge/soundboard. This would result in an inefficient transmission of energy from the strings to the soundboard (less energy to the soundboard and the surrounding air). So the result should be a sound with less energy (that decays faster).
Glenn
]]>