soundboard driver: tool or toy?

[Bob Hammond]

Hi,

Here's a pic of a modern gadget that my daughter-artist gave me, and I put it on a soundboard. It's basically a self-amplified speaker-driver element without the cone and framework. It is meant to drive a planar surface to act as a soundboard, and it sticks onto the surface by means of a 'Gecko-foot' micro-adhesive that leaves no residue. It couples amazingly well and drives the soundboard to a realistic volume.

I put it on the soundboard to see if I could detect loose braces on this abused body that is under repair. The gadget is driven by the smartphone using the Android 'gStrings' app, and it is tunable. I also tried out some symphonic music featuring different instruments (e.g. oboe, horns, piano, etc.) from the smartphone's music library. Interesting....

[Bob Hammond]

Hmm, I can imagine a guitar that is equipped with a 'booster' amp that is affixed to the underside of the soundboard. Well, heck. Why not the whole shebang? The driver-amp, and a smartphone with scrolling music/or tabs, and an equalizer, and recorder? And also an 'Intermission' looper feature that plays on while the guitarist goes on break?

[Michael Lewis]

Bob, is this item for frequency testing or for loosening up the structure, as in 'playing it in' ? There are some devices on the market for de-damping of the soundboard and the rest of the structure to hasten the playing in period. They can be effective but usually require many hours or days to do the job.

How long will your battery last?

[Bob Hammond]

Michael, I don't really know what to make of this thing yet. The advertised use is as a "Portable Vibration Speaker" for the iPod crowd to stick it onto to any hollow object.
.
If so far as uses for lutherie, I don't think that I understand the technical engineering aspects well enough to offer intelligent commentary. Let's just say that I find it intriguing. It certainly could be used for the purposes that you suggest, and maybe for making tea leaves dance in Chladni patterns. Last night, I poked around the web and found several frequency generator apps that could be used as a sound source, or maybe I could dig out an old computer that has CoolEdit on it, or maybe Audacity could be used to generate sweeps/samples. I was planning to use it with a stethoscope (medical or mechanic's?) to try to localize any strange sounds that may occur.

Below is a link to manufacturer. The most current version has a rechargeable batter with 10hrs life. If I were going to use it to 'break in' an instrument, then I'd hook up a battery eliminator. I see on the webpage that they can be daisy-chained to increase power output.

http://www.origaudio.com

[David King]

It's basically a miniature car audio "shaker". I have some other ones that can handle up to 20 W if you aren't afraid of annoying your neighbors. Mine were designed to work with empty cardboard boxes and actually sound pretty good at "party" levels.

[Nicholas Blanton]

David, what "other ones" are you talking about? Do you have a manufacturer? A 20 w transducer would be something to see, that's a lot of current.

Of course, it might crack the harpsichord, making those Chladni patterns.

[David King]

SI or Sonic Impact, they were available a few years back from Amazon and Target but I haven't checked recently. The 20W T-path amp they sold with the transducers worked quite well on 8 AA cells

[Jason Rodgers]

If you found the right surface to stick this thing on - to get the best response - it could do away with the various iPod dock speaker units. What does it sound like when you stick it on a hollow-core interior door, for example?

[Chuck Tweedy]

Off topic, but...

My daughter has one of these little horns for her iPhone, and it works amazingly well. Just goes to show what a little impedance balancing can do.
http://www.jamesbom.com/battery-amplifi ... eaker.html

[Bob Hammond]

Jason, it's a little hard to predict. A masonite clipboard worked well, but a cabinet door didn't. A computer case was so-so. But I can tell you that when it is stuck to a guitar, a recording of guitar music sounds better than other instruments (who'd a thunk that?). It's kinda fun to hear your favorite artists 'play' your own guitar.

[Bob Hammond]

Hmm, it could be fun to play a duet, too. Or trio, quartet,...

[Bob Hammond]

Hmmph.

This thing is FUN. It''s >Flavorful<. It's a 'Reverse Stethoscope'', when held gently under the fingertips as if the box is a Ouija Board.

It allows one to drive the soundbox with favorite music that the Mind's Ear recognizes and can compare to memory. It' doesn't reproduce the music exactly, but it is a tool that lets one explore the acoustics of the box, using the Mind's Ear as a Discriminator. I can also locate the effective dampening range of the soundboard braces. It''s inexact, but then again the phenomenon of audition is too.