Fiddlerman said
Wow Dennis, You've learned so much in such a short period of time.
I guess I need to download a spectrum analyzer now. LOL
Very interesting stuff.
Thanks.....

I have learned a lot but mostly just using what I already knew in so many areas, physics, mechanics, computers, research & testing, analysis, general life and have just applied it to the old violin...  

I think you were joking but just in case you weren't,  here's why a spectrum analyzer on the Internet wouldn't work. Feedback... The microphones on peoples computer systems are pretty varied, and their phones are sitting right there without delay, or connection issues or transmission issues.

Sending the sound of a violin would be like trying to talk with Skype. You can see from that example alone why it wouldn't work too well if at all. Good idea though...

In the realm of star trek maybe, but then you'd just beam over, use it in person and beam back. LOL

wow, that thing is pretty complex, almost too much and too fast on the display.

Hard to see what's going on there... guess you'll have to get a new phone. LOL 

You can see though the mid and high freq response of what you make the sound with are totally different in amplitude.

Try bowing when you make recording on open strings. 

Oliver said

@cdennyb

Just a little uncertainty about the spectrum:

1  Have you adopted a spectral criteria for a preferred sound post location ?  What should the individual note spectra look like ?

2  I am assuming that your signal transducer is a microphone ?

3  I believe that the standard sound post location is 3 mm behind the bridge.  Are you finding that to be true ?

IMHO I think the location of a sound post by frequency response is a great idea if one is set up for that and I would expect that such a systematic approach would far exceed the accuracy of a human operator.

Well Mr. Oliver...

[some comments below are directed at others but included for the general information of all]

...as you might guess this is just for curiosity mostly but I think if Antonius had one, he would've used one. I wonder how many luthiers who turn there nose up at using one, have even considered the scientific aspect of post placement and whether their ear was as good as using a tool to get close in a short amount of time and then fine tuning that location after achieving decent results. Can you do it without technical equipt...(?) well of course. and like you said, scientific equipment is far more accurate than the human ear in general.

I have no preconceived notion of what is and what isn't a good readout on the analyzer but in MY situation, achieving a flat across the top series of peaks from as low as I could see to as high as I could see made the nicest sound. Lacking any scientific or testing to prove otherwise, I'm happy with that.

The signal transducer is a simple cell phone microphone of an android phone. Not some sophisticated laboratory device worth thousands and this test was in my living room with many other device running at the same time (e.g. fan on the fireplace, computers, the TV/Stereo turned down low, etc.) so it was hardly the holy grail of discovery. LOL It was for fun and to peak peoples interest in the subject.

I don't know what the accepted location is from the "experts", but my expert whom I work for part time working on violins now, has actually voiced an interest in me using this little 'novelty' to 'see' the sound from other violins in his shop that are there for new strings, peg work, etc. I find his interest refreshing rather than turning a deaf ear to technology. The location I have ended up with is about 6-7mm behind the bridge foot and almost directly behind the bridge. (I have set a half-dozen posts and reamed peg holes and pegs and made 4-5 bridges since I have been there) ...and under his watchful eye, he made the remark... "you are a natural at this".

I originally set the post 'somewhere', when I first put it in (it was a tiny bit tight) and from the sound I achieved, only the E and A strings really had any voice to them. The others were muffled a touch and as such I was disappointed in the result of my hard efforts to bring this violin back to life. I sat at the bench and tuned it numerous times trying to change the bridge position forward and back and get that perfect sound from all 4 strings. No luck. I chatted with a fellow named Neil Ertz who makes violins in Scotland and we discussed the "tightness" of a post inside an instrument. I then proceeded to copy his instructions to make it loose enough that even a slight tap to the side would dislodge the post without a string or two holding the bridge up. I was amazed at the result.. the first time I trimmed off about .2 mm in total length, worked on the angles a bit and then after careful placement re-tuned and played the thing. Each time I moved it a little further back away from the fingerboard the sound began to improve. I started about 1 post dia from the ff hole notches and moved it about 1/2 post dia each time. Now I'm about a full post dia or a touch more back from the ff hole notches and I'm not touching it! It's perfect sounding in all strings. They jumped to life when I moved the bridge up even with the notches and left the post away. The sound projected instantly and even the low freq of the G string were vibrating the body like nothin' I had held nor heard before.

It felt almost the same as the $20K violin I briefly played in his shop. Is mine worth $20K, hell no... but the feeling it makes when played is very similar.

Consider this a scientific fun experiment in acoustics to better understand how the strings make sound...good sound that your ear likes, that's all. 

It isn't all that hard to place one and if anyone thinks professional players all wait to get their posts moved by some 'professional luthier', well think again. Many players and some very famous ones move their own and many do it far more than they should. Once you have achieved the perfect spot, leave it alone and enjoy it is my opinion. It isn't rocket science... it's a lot of luck and a little skill.