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Diaphragm expertise needed!


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My name is Will and I live in Niagara-On-The-Lake, ON.

I am a banjo player who is obsessed with creating an acoustic phono-gizmo to razz up my banjo until it sounds like the “jungle sound” brass section of the 1920’s Ellington Orchestra.


My current vision is a small tin can sitting directly below the banjo bridge, underneath the plastic banjo head.


This tin can would contain two diaphragms…


—- an upper 2” metal phono-style acoustic diaphragm attached by a thin screw to a small metal footplate just beneath the bridge, mounted parallel with the banjo bridge, ie, horizontally.


—- a lower plastic/parchment diaphragm to deliberately distort the sound created by the upper diaphragm, imparting a kazoo -like buzzy sound… also mounted parallel with the banjo bridge ie, horizontally.




Given that I know little or nothing about diaphragms, I thought I would seek the guidance of some of the experts here who hopefully have lots of experience with various types of acoustic diaphragms.


I hope you may help answer questions, such as


- What kind of homemade or store-bought diaphragm would be loudest?


- What would be the best way to couple the diaphragm with the banjo brige’s vibrations?


- Would it be possible to impart a kind of “cracked” tonality to the sound, much like the “cracked” quality of Louis Armstrong’s voice?


I hope my description of my project is adequate to convey the idea. If not, please let me know and I can provide some drawings, assuming anyone is interested in corresponding about this.






Edited by Banj0Gizm0
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I think this would be a question best suited to musical instrument specialists. I used to play banjo and would not even know where to begin on this question.

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In 2015, I made a "Stroh Violin" replica from scratch.  I always wanted one, but couldn't find a four string model for sale, so I decided to build one.  A Stroh Violin is an acoustic violin made to record with.  It uses a reproducer and diaphragm connected to the bridge to amplify and direct the sound through a horn (either brass or aluminum) which could then be directed into a recording horn.  The sound needed to be focused instead of dispersed through the "F" holes.  So, the extent of my knowledge about these has only been gained from making a fully operational Stroh Violin from scratch using mahogany from a junk Edison upright cabinet, part of a wrecked German violin from eBay, a generic phonograph reproducer, a trumpet horn that someone converted to use on a cylinder machine and a lot of experimenting.

Curt's Stroh Violin-1.jpg

Curt's Stroh Violin-2.jpg

Curt's Stroh Violin-3.jpg

Curt's Stroh Violin-4.jpg

Curt's Stroh Violin-5.jpg

Curt's Stroh Violin-6.jpg


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The banjo effect you are trying to create would require a good amount of experimentation.  A diaphragm is basically an acoustic amplifier and without a horn or sound chamber I'm not sure what it would do.  I don't think it would do anything without being mounted in some type of reproducer which receives and transmits the sound waves.  The only way I can see connecting to the bridge on a banjo is internally, inside the body, but that would require a sacrificial banjo to experiment with...  It's easy to find cheap violins like mine was, but banjos are another story.

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There are many styles of banjoes, so basically which do you have?  A backless one or one with a resonator?  Actually the drum head on your banjo is a diaphragm, mounted with a tension ring to the pot and that converts the vibrations from the strings into sound...  In re-thinking your original question, I'm confused by what you are actually trying to accomplish...  You might want to pose your question to someone who works on banjoes.  You could probably mount an electric pickup and create the sound distortion digitally as an easier solution.

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