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Hello Everybody! I'm new here and I just finished my first build that I like for the most part but I've got some issues with wolf notes/tones. The open A string seems to be a bit louder than the rest with less sustain but the G-string at the 2nd fret (A one octave higher) is even more loud and with less sustain and a little tendency to ring with the pitch harmonic. Here's the guitar:

Here's the top:


It was built using a Blues Creek Guitars 000-18 12-fret kit with Adirondack top. I modified it a little: the upper bout and waist are about 3/8" smaller and the body is about 3/8" shorter than original. The top bracing is 1/4" wide and about 5/8" high at the X-crossing. The scale is 24.9". The fretboard and bridge are madagascar rosewood and the string height at the bridge is a bit high, about 9/16".

Here's a sound sample in open-D:
http://www.soundclick.com/player/single ... i&newref=1

So, overall I'm really happy with the guitar but I would like to hear some ideas what to do with the wolf note? I remember that the Gibson L-00 reissue from 1991 had the exact same wolf-notes and the Recording King Maple Nick Lucas copy had them even worse. I didn't want to start messing with them but sold them but this one is going to stay so I need to find some way how to kill those wolf-notes. They are most noticeable when played with bare fingers and probably least noticeable with fingerpicks.

did you check that the top and back were a semi tone apart

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Nope. How do I that? Tap the back and soundboard and record the sound? With or without strings and the soundhole open or covered?

Stevie: The Gore -Gilet books cover this problem. Both the measuring of resonances and cures for the problems found.
Tom

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A person who has never made a mistake has never made anything!!!

If it's new, play it a lot for a few months. It will change.

Pat

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formerly known around here as burbank
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Sounds as though you've got the 'main air' resonance at the low A, and the 'main top' at the higher one. Those are pretty normal pitches for those resonances, although a bit higher than I usually see on my 000-12 frets. It's not too hard to make some measurements, and then you'll know for sure. With some data to go on you can make some decisions as to possible remedies.

To find the 'main air' resonance (close enough):

Lay the guitar down on your lap. Pinch the low E string between your left thumb and finger down near the nut, while plucking the string with your right hand. You should get a dull pitched 'thunk'. Move the pinch point up the string while plucking it as uniformly as possible, and listen for the loudest tone. That's the 'main air' resonant pitch.

To find the 'main top' pitch:

Your ear usually assigns the energy of a higher resonance to a lower one if the pitch is pretty close, one sort of tone 'masking', so to hear the 'top' pitch clearly you'll have to cut down on the lower 'air' pitch. You can do that by holding the guitar up with your thumb on the end of the fingerboard and your fingers between the strings on the upper transverse brace. you hand blocks the hole pretty much, but try to avoid touching the edges of the hole. Now tap on the bridge in the center with a finger tip. You should be able to pick out a pitch, which will probably be somewhere near the troublesome note.

As John says, sometimes getting the 'back' pitch down close to the 'top' pitch can help these sorts of problems. Try tapping in the center of the back while holding the guitar up with the hole blocked, and see if you can isolate a pitch there as well. Depending on the back bracing pattern there can be more than one; try to find the lowest pitched one, which is usually also the loudest (but maybe not).

Strange as it may seem, sometimes lowering the back pitch can drop the pitch of the 'main air' resonance. The strongest effect will happen when the two are exactly the same, but you don't want to do that! This will give generally give you a major wolf problem. A semitone separation is close enough to couple strongly, and far enough apart to avoid troubles (usually). Given my druthers, I'd make the back a semitone higher than the top: in some cases I've seen the 'top' pitch drop over time, and you don't want it parachuting in on the back's terrain. Shaving the center of the back brace that's nearest to the active (loudest) area of the 'main back' mode will usually have the biggest effect. To be sure, you can add some temporary mass (such as poster putty) to the back over the brace. This will drop the resonant pitch, and you can play the guitar to hear the result. If you don't like it, remove the putty and no harm done.

Getting the top and back working together in this way can also help with the high A problem. This gets to be a complicated problem in coupled oscillators, and you can look up the math(s) in Trevor's books. The bottom line is that all the parts of the guitar work together to make the sound, and changing one can often change most of the others. Sometimes it doesn't take much of a change to remedy a wolf problem.

Note:
Trevor responded while I was editing this post. I'm adding another edit to say that he may not agree with everything in this now, but I hope won't be too offended...

What Al said.

It would appear to be a classic example of why you should not stack the main resonances an octave apart and on a scale tone. The data will confirm (or not!)

There are lots of potential fixes, but if you have small hands I'd be taking some beef out of the braces, but make sure you know how to measure the main resonances before you start and keep measuring them as you go.

_________________
Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Aside from the wolf note, great looking first build. I think a 000 is next on my list. Welcome to the zoo!!!

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Wisdom is justified by her children

That's good stuff, thanks! Seems like I've got homework to do, I guess I'll start with a few coins and double-sided tape to see how adding mass affects the tone. I've got a feeling that my main top resonance is a bit higher than usual, at least I recall that m Martin 000-16SGT had considerably lower note when tapped on the top. Then again it had a 3/8" richlite belly bridge that probably weighs 3 times as much as this straight rosewood bridge.

I'll try to do some measuring before I take out my sanding blocks and planes but how would you attack the top? I'm pretty sure the top is stiffer than needs but what's the best place to start working? Scalloping the X-brace and tone-bars or cutting down the finger-braces?

To my untutored eye, the lower transverse braces look way big.....I think I'd try to reduce them a bit, but maybe not until some playing in, as Todd says.....

I did some tapping and found 2 frequencies: The main air resonance was the easiest, it's between A and A sharp, quite in the middle. I found that by holding the guitar from the neck, muting the strings and tapping with the soft part of the fingers on the bridge. Really loud and clear "Duuummmm". That was really easy to find and I'm quite sure I got it right. On the back I can hear A sharp (octave higher than the main air), maybe a bit over so between A sharp and B. I hold the guitar on my lap with a pillow covering the soundhole and bridge while tapping on the back. Also on the back I can hear B pretty strong while tapping the back near the end-block.

I just seem to find the main top resonance? The main top just seems to be changing depending on how my hand covers the sound hole. Really easy to hear how the main air goes down as I cover the soundhole but I just can't get a clear note on the main top. I'll keep-a-knocking..

From what I read about the main air frequency on the net I think it makes sense. I think this guitar is lacking a little bass but the mid-frequencies are really cutting and powerful, however I would be willing to trade some of the mids for good bass.

You need to get a program that can plot the FFT graphs of the taps so you can see the actual frequencies and figure out which to change. I use Audacity others use Visual analyzer tap the top with the strings dampened and post a screen capture of the waveform on the forum. You will get lots of ideas and it will create an interesting discussion.

From looking at your top its bracing can be worked on quite a bit to lower the top frequency but get some readings before you start.

Fred

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I can't get any graphs out of my Audacity? It's got a "analyze" button but it doesn't work, I guess that's because I've got the freeware version.

Anyway, I got the main air recorded and the signal stretched out on Audacity I can measure peak-to-peak 88ms which is 113,6hz and that is between A and A sharp so my ears seem to function

For main top I get 44 or 45ms = 222-227hz

For the back I see 40 or 41ms so 243 to 250hz

These are measured without strings. The main top resonance was measured with the sound hole covered with a newspaper. I tapped on the middle of the bridge and placed the microphone about 3 inches back from the bridge towards the end-block.

Does this sound right?

Do a series of taps and select the area then chose plot spectrum in the analyze pull down menu, and the graph will be displayed. To display here do a print screen with it displayed to capture the spectrum to the clipboard then paste the clipboard image into a photo program and save the image. It can then be attached to a post on the forum and will look like this one which is what you also see in Audacity.

This one is a display of a series of taps on my fan fret Baritone jumbo that I also had resonance problems on that shifted the intonation of the G2 notes this was controlled by shifting some of the frequencies.

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Fred Tellier
http://www.fetellierguitars.com
Facebook page http://www.facebook.com/pages/FE-Tellier-Guitars/163451547003866

When you tap for resonances, have it strung up and in playing position without damping the back or covering the soundhole.
Just tap at the bridge location (not the back) and that will give you the "COUPLED" resonances which are what matters.

I'll do some more tapping tonight with the strings tuned to EADGBE. I know I should just play the guitar and see how it changes but still I just got a feeling that I need to shave down the braces..

My mind says that I should get the main air down to about 105-107hz, the main top to 205-210hz (I guess it's safe to assume that it's going to go down a bit as it ages?) and main back to 225-230hz? I'm looking for powerful mid-rangy cutting tone sort of like the vintage Gibson L-00:s so I think I don't want to start scalloping the braces but I could taper them a bit more on the top? I guess the back braces should come down pretty easy with a sanding block?

Wait for it to settle in. It is much harder to put back wood than to take it out.

I made a new nut for the guitar and I was looking at the sound hole without the strings and I just couldn't help it.. I took out a sanding block and tried how it feels to shape the braces through the soundhole and found it pretty painful.. I took away about one millimeter of the 2 back braces on the lower bout so now they are about 14-15mm high (9/16"). I also took some material off the peak on the fingerbraces but really only scored the surface.

Anyway here are the measurements with strings tuned to EADGBE, the soundhole not covered. The main air is really easy to plot, really nice sine-wave and the main back is pretty clear too but the main top has more distortion on it but unfortunately I still can't make the analyze function work on Audacity.

109hz main air
229hz main top
236hz main back

So it became pretty clear to me that 2 tea-spoons of sanding dust is about 4hz in main air resonance frequency=)

I'll play it for a week now and do the measurements again, let's see what happens. BTW this guitar has now been stringed for about 10 days total.

Record a series of taps as an mp3 and email them to me and I will get you a graph.

Fred

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Fred Tellier
http://www.fetellierguitars.com
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I can pretty well guarantee that the work you described, producing 2 teaspoons of sanding dust, won't drop the main air resonance by 4Hz. So I think you need to get your resonance measuring process under control before you decide what to do next.

_________________
Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

If you're interested in building more guitars, and putting some science into the builds, learning to measure the
guitar frequencies is very helpful. Here are two files I pulled off OLF and ANZLF for using Audacity and Visual
Analyzer. I like Visual Analyzer because it's easy to set it up to collect an average of 10 taps. If you do searches
on these two sites on Tap Tuning or on the program names, you'll find lots of information. I use an old laptop
and with a Behringer ECM8000 mic, and EURORACK UB1002 mixer in my workshop, about $130 from the web.
It's best to use a firm rubber "hammer" to generate the taps. I made one by cutting a 3/8" slice off the rubber
bar I use to clean the drum sander paper, then cutting that in half so I had a triangular piece, and gluing that
to an 8" or so stick (not my original idea, came from OLF, but I can't remember who. A firm gum eraser would
also work, I'd think. You don't want it to be so hard it'll dent the wood, but not doughy soft either.

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David Malicky Post subject: Re: Looking for an FFT software package
Posted: 18 Nov 2009 03:59
Cocobolo
Joined: 21 Jun 2009 19:40
Posts: 373
First name: David
Last Name: Malicky
City: San Diego
State: CA
Zip/Postal Code: 92111
Country: USA
Focus: Build
Status: Amateur

One more: Audacity. It's not nearly as flexible as Wavesurfer (which I also like) but if you're mainly looking for the peak frequencies, I find Audacity is less quirky and easier to use.

My main problem with Wavesurfer is that I can't get it to do the FFT on the selected signal. That is, if I click and drag to create a dotted yellow selection, the Spectrum Section plot doesn't account for the full selected region, even if I click the "Average of selection" box. It only analyzes from where my selection starts (the vertical yellow line on left) to the ~0.5 seconds afterwards to get enough data for the 8192 FFT points (what I use, with 16k samples/sec).

A quick-start on Audacity:
- Install as usual. http://audacity.sourceforge.net
- In Audacity: Edit > Preferences > Audio I/O > Select your recording device > OK.
- Record the taps.
- Select the tap(s) signal with the mouse
- Analyze > Plot Spectrum
-- Change 512 to 16384
-- Change Linear Frequency to Log Frequency
-- Drag the right window edge to make it a *lot* wider
-- Hover the cursor near the peaks... Audacity will automatically lock onto the peak frequencies! Numbers are in the lower left. I've found it's within 1 Hz of Wavesurfer for the air, top, and back modes.

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David Malicky (david82282)

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http://www.anzlf.com/viewtopic.php?f=1& ... lot#p44370
Post subject: Setting up Visual Analyser and capturing a frequency plot

Capturing a frequency plot

A few people have asked me how to set up Visual Analyser and then how to capture data. I am by no means an expert as I only worked out how to get good results a few days ago. So if you see anything wrong and there is abetter way of doing it please us all know. But here is how I have done it to get decent consistent results.

First we need to set up VA. Click on ‘setting’ at top left.

Under the ‘main’ menu
1. set your FFT rate to 16384
2. set your frequency sampling to 11025
3. click confirm and the spectra line resolution should change to 0.67Hz
4. Next go to the 'capture' tab and set the capture spectrum - spectrum average buffer to 10. There is capture scope window on this page as well so make sure you set capture spectrum.
5. save your settings. Apparently you can save these setting as default but I have to redo them every time I open VA so check before you start a new session.

Next test your mic
6. turn VA on with the button at top left.
Now check you are getting decent sound levels. The lines on the charts should be jumping all over the place from you voice. If you make a noise into the mic you should see it spike on the charts. If so all is good but if not you need to go to your sound card settings in windows. Set your mic boost higher until you get a decent response on the main chart.

You are now ready to capture data but first do a dry run so you can practice your taps. Nice consistent force and nicely timed taps are best and avoid the centre line. There are spots that sound louder for a given tap force so I try to tap on those spots.

7. Get your guitar ready with your tapping stick and the mic pointing at the soundhole. Trevor mentioned sitting on a chair with the guitar or just the body on your knee and I found this the easiest. Don’t damp the back of the guitar with your beer guts. I held the body by the neck mortise.

8. When you are ready, with VA still on, click the capture spectrum button at the right centre of the screen and start tapping your 10 taps with about 1.6 seconds between. Don't do it faster or you will get weird results. Going slower seems to be OK.

9. Keep tapping and when VA has recorded 10 buffers of data it will pop up the spectrum window with your completed frequency spectrum. You can then select the range up to 500Hz and it will zoom in.

10. You can save this as a text file then copy and paste it from there into excel for further analysis if you want.

You are done.

As I said, please correct me if I am wrong anywhere but I am getting consistent results using this method.

Hope this helps all you budding scientists.
Cheers
Dom

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but you can't bomb the world to peace!

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Gene

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Thanks for the comments and advice everyone!

Fred, I'll send you the files later today so we'll see if my math correlates to real world. And thanks for all the help so far.

Trevor, this time I did the measurements with strings tuned to pitch and I guess some of that 4hz might come from that. Also this time I did my measurements a bit different compared to the first time. The first measurements were done from one sine-wave peak-to-peak and I tried to estimate the duration time as accurately as possible but that leaves too much room for error so now I took 10 sine-waves and measured from peak 1 to peak 10 and divided the time by 10. I took 3 taps for air, top and back and from all signals I get my measurements within +-1 hz so I'm pretty comfortable with them. Anyway, we'll see as soon as Fred gets Audacity to do the math.

gozierdt: I'll download the latest version of Audacity and try your instructions. I haven't used Audacity in anything except raising the level of some home recordings so again I've got homework to do.

Todd: I don't need ToneRite, I'll grab the guitar and play "Drunken Lullabies" by Flogging Molly. As soon as I start playing that the kids start running around the house like crazy and I'll start chasing them while playing the guitar. They can do it all night long but I need to change the pick every 5 minutes because the small-size Fender tortoise picks start to smell funny =)

- Ville

Here are the taps:
https://docs.google.com/file/d/0BzCR9Aa ... sp=sharing
https://docs.google.com/file/d/0BzCR9Aa ... sp=sharing

The first file "Main Air" has just that, 2 taps on the bridge and the mic above the soundhole, nice and clean sinewave
The second file "Main Top + Back" has first 3 taps on the bridge with the mic about 3 inches back from the bridge and then 3 taps on the back with the mic about 3 inches off the back. Hope these are good for better analysis than just counting waves.

I looked at your files and I think that you need to try doing this. Hold the guitar with the mic at least a foot from it and tap on the bridge recording at least 6 or 8 taps. It will show what the guitar is doing as for as coupled resonances. I let the guitar rest on its butt with the soundboard facing the mic and tap with the strings damped. On what I could see from what you recorded the main air is fine and depending on which waveform I look at the top is 196 hz which is exactly G3 and the back is around 235 which is real close to A#3 ( 2 hz away). I will look at what you have when you do the taps I suggested above.

It looks like the top is the problem from what you provided so far which goes with the comments several people stated from just looking at the braces in the picture. A few hz lower would probably ease your problem.

Fred

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Allrighty, I'll tap some more tonight even though my wife is looking at me in a strange way when I do that, she probably thinks I'm trying to communicate with the guitar?