Need input on a sonic response experiemnt.

[DanPanther]

I have a dual trace Oscilloscope, and I want to run some sonic vibration experiments covering Nuts, Saddles, strings, and bridge pins, and even some string, mainly for gauge comparisons.. I plane to take one guitar and change out all of the above with variations of each, one at a time.
This is what I need to know;
What type sensor would give the best results ?

Peizo under saddle
Soundhole Pickup
Soundhole microphone
External Microphone

OR suggestions.

I plan to use an Alvarez RD26SB, It's a new guitar. I understand Not top of the line, but using the same equipment will give accurate results rather than using two different guitars. UNLESS of course someone would volunteer to send me a Martin I can use.

Thanks in advance.

Dan

[Alan Carruth]

Almost any sensor can be used for this. It's more important to make sure the test is run exactly the same way every time. Thus, if you use a mic out in front of the guitar make sure that it's in exactly the same place every time, and that there have been no changes in the room. Even moving the mic by three inches can change the output: those things are so darn literal!

It's also important to get the same input every time. Since you're trying to find out stuff about the way the guitar responds to the strings, you'll want to pluck them. The best way to do that is the 'wire break' method. Get some fine (#43 or #44) copper magnet wire, say from a dead magnetic pickup. The quality control on this stuff is phenomenal: it always breaks at a certain force, plus or minus about 2% in my tests. Loop a length of it behind the string and pull upward until the wire breaks. You can always 'pluck' the string in the same place and even in the same direction if you're careful, so you know what the input is to a very nice tolerance. Just make sure the wire always breaks right where it goes around the string, and not someplace else. I actually set up a solenoid operated 'plucker' so that I can trigger it from a distance, eliminating the variable of me standing there in front of the guitar. This won't be a problem if you're using a UST or top transducer, of course.

Have fun! Tell us what you find out!