Re: [Harp-L] Reed design question.

[Zombor Kovacs <zrkovacs@xxxxxxxxx>]

I am wondering what is the point making high pitched reeds narrower. I understand that if you increase the circumference at the same length it will increase flow cross section area, but at high pitched reeds much less air passes through anyway. While you can blow your lungs into a low reed, you can only blow a fraction into a high reed which - according to me - is not that comfortable. Why is it a good idea to reduce air quantity for high holes even more when it should actually be increased? 
 
 
Another thing  what I experienced is response, which I put in relation with material properties. Sometimes I replace reeds for thicker reeds without knowing it. I only see it is the same length, so it will be fine. But what happens before I start tuning it is that suddenly the replaced reed has a much higher pitch than I expected and I have to put a lot of solder on it. Then after tuning it will have the right pitch but it will sound flat and unresponsive. My feeling is that it is the hysteresis what you get between a loading and unloading cycle. If you have a thick reed the thicker it is the more it will behave like a plastic material, which means that there will be a loss of energy inside the reed material. I don't know if anybody can confirm this theory. 
 
Zombor
 


________________________________
From: Vern <jevern@xxxxxxx>
To: pneupco@xxxxxxxxxxxx 
Cc: harp-l@xxxxxxxxxx 
Sent: Friday, April 20, 2012 7:41 AM
Subject: Re: [Harp-L] Reed design question.

Length and width are only two of the design parameters of a reed.  The thickness profile, the modulus of elasticity and density of the material are also important.

If you merely shortened a reed, its pitch would go up and if you merely lengthened it, its pitch would go down.  Then to restore it to the proper pitch, you could retune it by adding or removing material at different places...changing its thickness profile.  Then you would have a reed of a different design.  It is possible to make the reed of the new design behave as the "old" one did but it would have differences in the other parameters.  This is presumably what the manufacturers do.  Generally, you won't perceive any difference in the way they sound and respond to the player.  However, it is also possible that the pitch can be correct but the stiffness could change....making the reed respond differently to the player.

These types of geometry changes do not substantially alter the basic mechanism by which a reed makes the sound that you hear.  This is the way the flow area changes as the reed swings through the slot.  This is the reason that all reeds sound pretty much alike.

The pitch is determined by the ratio of the mass near the tip to the restoring force as the tip deflects.  In a stiff reed, both of these values could be high and in a limber reed, they could both be low.  The reeds in a Hering may be a bit more limber than those in a Hohner... accounting for their easy responsiveness and very slightly diminished power. Because they are more limber, they require less breath power/pressure and may make a tiny bit less sound.  

If you increased the width, the pitch would remain the same but the reed would require more air to play and it might be a bit louder.  You wouldn't like it! 
Hohner has reduced the width of the high-pitched reeds in its Chromatics 10% from .080" to .072".  (They may have done the same in diatonics but I haven't bought any of those.)  This frustrates technicians looking for replacement reeds but hasn't much changed the sound of the harp.    Think of two identical reeds vibrating in sync alongside each other.  Their deflections are the same at every instant.  If they were joined, one would not influence the other so the pitch would not change.  However the opening around them would be larger admitting more air.

Vern

2012, at 6:21 PM, pneupco@xxxxxxxxxxxx wrote:

> What does the length and/or width of a reed do to the playing characteristics of a reed? Say, for example, that I had three reeds all tuned to the same note and the middle one was of the "normal" size. One of the others was the same width as the normal but a mm or so longer and the other reed was the same length as the normal one, but a mm  wider. How much different would their playing characteristics be?
> Thanks,
> Paul N.
> Tonawanda, NY
> Sent from my Verizon Wireless BlackBerry