Re: XB-40 in C has this squeal problem

[Pat Missin <pat@xxxxxxxxxxxxx>]

Jr Bliggins wrote:
>
>About six months ago I hand built my own XB-40 because I just couldn't 
>wait any longer for distribution.  I experienced the same problem.  Does 
>the squeal sound like two notes beating slightly out of phase? It isn't 
>really the same single reed cross tensional squeal we sometimes hear 
>when learning overblown notes.

I think the noise described recently on harp-l is precisely that - the
same noise that you get from a badly poorly adjusted reed when you
overblow it, or use bad bending technique. Certainly this what I found
on my own XB-40. 

The problem can be reduced by various methods (both tweaking the harp
and tweaking the playing technique), but to be honest I think it will
generally need to be accepted as a limitation of the instrument, in
the same way that players currently accept that it is tough to get a
decent 10 blow bend out of an F harp, or a decent 1 draw bend from a
low C harp.

>  I believe it is caused by the enabler reed in the adjacent hole 
>vibrating in sympathy with your target note when it is bent. 

No. I know the problem you mean (having built my own harps that employ
auxiliary reeds), but that is an entirely different thing. The final
version of the XB-40 employs a valving system that prevents this from
happening. On your home-made XB-40 (assuming you are using a standard
comb and standard reedplates), you would need to have reverse valves
on your auxiliary reeds to prevent the sympathetic vibration.

>For Example:
>
>I have the problem in the high notes but I also experienced the problem 
>on the 3 and 4 draw.  My "C" XB-40 Harp was set up with one step bends 
>on each hole, not the two step bends that Rick's design has.  Hence the 
>enabler reed for th hole 4 blow was tuned to "B". 

In order to get a semitone bend from a C, you would have to tune the
auxiliary to Bb, or thereabouts. If you paired a C reed with a B
auxiliary, you would only be able to bend it by the same amount that
you can bend 5 draw on a standard Richter.

 -- Pat.