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alex_holden

Making Quieter Reeds for a Drone Button

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Posted (edited)
6 hours ago, Dana Johnson said:

    The low D in my old duet was in the range where the chambers were getting longer than the reeds.  By the time you got to the low G it was half again as long as the reed shoe.  It will better support the low fundamental..

 

Thanks. This photo is from the previous instrument I mentioned. It's a 6" wide C/G Anglo with long scale reeds, 31 buttons + a low D drone.

 

14.jpg

 

My next client doesn't want the 31st button on the left hand, which happens to be connected to the chamber next to the drone, so theoretically I will have spare room to do something unusual with the shape of the chamber. I'm now thinking that the approximately L shaped arrangement in the final picture could be worth a try. I'll do some experiments and get back eventually.

 

14_mod.jpg

14_mod2.jpg

14_mod3.jpg

 

I do put tapered pans in the duets I build, but it's trickier to implement variable chamber depth on an anglo and leads to some other compromises (I did it on the first anglo I made). Theoretically for the drone chamber you could glue an extra deep section on the bottom of the pan, but I'm not sure it would be worth the effort.

Edited by alex_holden
Rearranged pictures

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Posted (edited)

Not mentioned so far; make the clearance between reed and frame wider. Yes, it costs air but should be quieter. Also I would endorse using a larger draught angle. 

Edited by Chris Ghent
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On 6/3/2020 at 6:31 AM, alex_holden said:

 

Thanks. I did experiment with the valves a bit on the previous one. Gluing them down part way had some muffling effect but I didn't like the result and returned them to normal. There wasn't enough space to try lining the walls on that one, but it could be worth experimenting with in the future. Maybe cover them with chamois: Using foam inside an instrument makes me a little nervous because some types break down and crumble over time.

 

I have some self adhesive Eva foam that’s 0.5mm thick if you could use some.  It’s super thin.

 

i like the idea of this discussion.  I put a D-17 drone button on the 5” mini Anglo I recently finished and it’s pretty loud, not quite overpowering, but very present.

 

Seth

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I thought I’d better check out my suggestions rather than just  propounding on them.  Here are results for a D3 reed:  I did three different reed shoes and two reeds.  The first reed/shoe combination was my normal low D but with zero relief angle.  The reed is .123 x 1.525 inches.  The reed shoe is .063 inches thick.  I used this as a base line.  The second reed shoe had the same size window and I used the same reed swapped out from the first one.  The difference was that on this shoe I used an end mill to relieve the back of the window so it was only .025 inches thick.  The relieved area was.215 x 1.525.   The third reed / shoe  was also .063 inches thick  and the window was also 1.525 inches long. But this combination used a reed that had the identical profile, but filed to a width of .093” or a little more than 2/3rds as wide.  The window also had zero back relief.  Clearance and set was identical.  I did two comparisons, one at 1 inch wc which is my normal tuning pressure, and one at 1.75 inches wc, which is the maximum my tuning blower will deliver at that reed’s flow rate.  
I arbitrarily chose to call my first reed as zero dB  with the 1 inch wc, to make comparison easier.  All the reeds were mounted the same way in the same chamber on the test reed pan.  
The results of the 1’wc test were:  (Reed 1) 0 dB.  (Reed 2)  -4 dB  (Reed 3) -2 dB.

The results of the 1.75” wc test were. (Reed 1) +4 dB  (Reed 2)  -1 dB   (Reed 3) +1 dB.

the net change from 1” wc to 1.75” wc was:  (Reed1) +4 dB  (Reed 2)  +3 dB   (Reed 3) +3 dB.

Both reed 1 and 3 managed to increase output above  Reed 1’s  1” wc level at the higher pressure. Reed 2 increased its output but even at the higher pressure couldn’t get to Reed 1’s low pressure output.  
the reeds all sounded clear and not dulled in any way though I was only interested in volume this time.

my conclusions are that the reed with the back relief leaving a window .025” thick reduced the volume most, being 4 dB quieter from #1 at low pressure and 5 dB quieter At high pressure.

The narrow reed worked well, but was 2db quieter than #1 at low pressure and 3 dB quieter at high pressure.  
So far it looks like the reed shoe with the cut out back is most effective in reducing volume, and might be even more so if I had cut deeper leaving a thinner window.  The narrower reed also had a reasonable effect,  but wasn’t as pronounced.  I found it interesting that the back relieved #2 couldn’t get up to #1’s low pressure output, suggesting that it was close to maxing out.  I don’t know if a 4-5 dB reduction would be sufficient to better work as a drone or if some other way of dealing with it would be needed. ( or you could make a narrow reed with the back relief cut out I suppose )

Dana

 

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When I think about it, a 4 dB difference isn’t a lot.  I do think you may get a decent reduction with a long  sound path, but I don’t know how that might effect the reed response.  It does make a mellower tone.

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Thanks Dana! It sounds like it could be worth combining multiple strategies.

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