Squealing 3 draw
Hiya Kinya,
Just sized up a brand new Lee Oskar Bb harp. All reeds plinking clean and .001 clearance between reed and slot sides.
Upon reassembly, the 3 draw has a squeal when played with very gentle breath force as the note is being bent.
Took the harp apart, double checked 3 blow & draw slots. No problems. Looked for imperfections under 10 & 20x magnification. Don't see any problems. Reassembled harp and it's still got this squeal, but again, only when very gently drawn and bent. The note sounds cleanly until it is bent.
I noticed that this set of reed plates have very tight tolerances between the free end/leading edge of the reed and the reed slot. Can't even size the end at all, there's just no room.
Hmmm...
Is this possibly torsion of the reed?
Any suggestions (besides don't play it so gently!)?
Thanks,
TomE
ps Been using your sizing technique and not rotating the reeds. It's faster and easier than how I was doing it before. Now I can see the side of the slot in relation to the reed as I work and I'm not over sizing. Nice to not have to spend any time freeing up stuck reeds.
Hey TomE, I believe you are correct with your hunch.
Also known as the reed "torsion" phenomena--the reed twists diagonally, and as the column of air passes in/out of the reed slot, a super annoying high frequency squeal (screech) can be heard.
My recommendation is try the solution that Prof. Antaki developed. He applied prox. 1/16"W x 1/8"L pieces of 3m Micropore medical tape (usually found securing IV needles to arms ;o) onto the backside of those draw reeds plagued by the squealing isse. Land the tape approximately 25% (of the reed length) up from the rivet. Note: this will de-tune the reed, so be prepared to retune the reed.
Your Harpsmith, Kinya
Hiya Kinya,
How do you feel about the idea of putting a drop of nail polish at the rivet end of the harp?
While I have heard of the Micropore tape fix I've also heard that the tape will suck up breath condensation and detune the reed as you play the harp.
Always learning,
TomE
Hi Tom, this is a terrific opportunity for you to try out both and choose the best that suit your playing style.
Your Harpsmith, Kinya
That's a fine idea!
Please don't forget to report your findings after conducting your experiments.
Your Harpsmith, Kinya
Hello guys This may be completely unrelated, but I have experienced a similar issue lately and it turned out to be because of the fact that I had over tightened the screws between the plates.
A recommendation I came upon is to tighten those screws just until they bite and then tighten them ever so slightly 1/4 of a turn more (or even less).
Then to achieve the so desired air tightness you tighten the cover plates screws as much as you want as that will not affect the plates' shape.
Well that did the trick for me, so I decided to share. :)
Thank you Angel!
The cause for this phenomenon is when the reed plate fasteners are over "torqued", they fold the reed plate slots inwards. For harmonicas with sized (burnished, embossed) reed plate slots, this means the vibrating reeds will make contact with the upper corners of the reed plate slots and make unwanted sound effects!
Please check out a past Forum on the subject:
https://www.bluesharmonica.com/how_tight_should_my_reed_plate_screws_be
Your Harpsmith, Kinya
Thank you so much Kinya!
A very usefull article!
You know Team bluesharmonica.com is here to help!
Your Harpsmith, Kinya
Hiya Kinya,
I applied nail polish to the reed slot sides and to the root of the reed at the rivet end.
I went up the sides of the reeds about 1/3 of their length too. After the polish had set up but before it totally cured I used a .001 shim secured in an Exato knife shaft to cut the malleable polish away from the reed. This gave me a built up side to my reed slot. I removed any trace nail polish from the reeds themselves.
Seems to have stopped the squeal and I now have something quite similar to your tape sizing going on. I had previously sized the reed slots but now they're sized AND built up. Make sense?
The harp is playing quite nicely now!
TomE
Well done Tom. Our friend Brendan Power is one of the earlier pioneers of this technique. In fact he uses Nail Art pens to dispense surgical amounts of nail polish (rather than brushing).
Your Harpsmith, Kinya
Yeah, I used the nail art pens. I must have seen a Powers article or video about the built up nail polish. Works well on a new, clean plate. Takes a bit of scuffing on an old, grungy retuned plate.
Good ideas abound in the innerwebs! I love it. Thanks for all your expertise Kinya. Now if I could just find some more time...
Ha! There is never enough sand in the hourglass ;o)
Your Harpsmith, Kinya
I looked for other posts here in the forum that might help and saw one that sounded like almost exactly the same issue. You had recommended setting the zero point to .002 and reducing the gap on the 3 blow reed. I have tried both those fixes and still get the squealing at very light draw pressure. My usual draw inhale force does not cause this squeal.