Headstock resonance can be a problem

[charangohabsburg]

As many of us already have experienced chasing down the culprit of buzzing strings can sometimes be a bit of a challenge. This classical guitar is quite comfortable to play, but the not fretted strings 4 through 6 (G to low E string) were buzzing quite badly when played loud. I first thought it could be a lose string end or a lose part of the tuning machines. I finalyl found out that the buzz stopped when gripping with my fingers just any of the tuning gear buttons, it did not matter which one. This made me think that the problem might be the headstock itself, respectively one of its resonances causing the strings to do strange things. I found out that the problem also disappeared by firmly clamping additional weight to the headstock. In the following video you can appreciate the difference a 17 gram plastic clamp makes:


youtu.be/

If you didn't hear the difference you most likely will do when using headphones.

I have to say that the neck at the nut is rather thin for a classical guitar (19 mm opposed to more common 21 mm). Modifying the neck thickness, or even testing the difference neck thickness was making here was absolutely out of consideration, so I proceeded to add some weight to, or should I say into the headstock. A brace and bit is a wonderful tool when it comes to drill a hole in exactly the direction you want, when mounting the work piece beneath a drillpress bit would be a bit too time consuming:



Then I buried two pieces of 35 mm long M8 threaded rod in the two holes, which made an additional weight of 20 grams. I used epoxy to glue them tight, but oiled the threads so that I could get them out again in case the result would not be satisfying:



Next I cut some plugs to give the upper machine plate screws a grip. Getting the plug's grain orientation "correct" is not necessary as the plug will be completely hidden by the machine plate, but it was a good exercise:



Plug is glued in and gets trimmed level:



It worked just fine, problem solved, and it was much cheaper than buying heavier tuning machines (Sloane 300 USD, Alessi over 1k I believe, and so on) .

[johnparchem]

Interesting post, I understand that altering the head stock resonance stopped the buzzing, did you ever figure out what was buzzing? I just wondered if the original resonance got some other component buzzing.

I just racked down some string buzzing on my re-topped 8 string. In my case I was using the original saddle in a new bridge and it was a little loose.

[charangohabsburg]

Hi John,

Sorry, I forgot to mention here what actually was buzzing (I only wrote it in the YT video comment). It was the string(s) that hit the second, and plucking harder also the third fret. Upon my suspicion I sprinkled a bit of bone powder (remains from nut and saddle shaping) over the first few frets to make nicely visible what happens there. with the plastic clamp on, the strings stopped touching the second and third fret, and the noise had gone as well.

II just racked down some string buzzing on my re-topped 8 string. In my case I was using the original saddle in a new bridge and it was a little loose.

Yes there's a myriad of possible reasons for string buzzing. Checking for tightness of the nut and saddle fit was one of the first things I did. Then checking for evenly seated frets, and so on. I was quite lucky in the process of tracking down the problem I'd say.

[kiwigeo]

Markus,

Did you manage to measure the frequency of the buzz?

When tap testing a classical some time back I noticed some really low frequency peaks on the plots which disappeared when I clamped the neck to the bench so it couldn't vibrate.

[charangohabsburg]

Martin,

To be honest, I didn't bother at all measuring or tracking down the resonance frequency that was responsible for the buzzing of the four lowest not fretted strings. I just thought "great, problem solved".

However, I have the spectrogram of the finished guitar before I even discovered that plucking those strings very hard was a problem, and I can of course now record another spectrogram of the fixed guitar. Like you I also believe that the "headstock and/or neck resonance" must be found somewhere amongst those peaks below the main air resonance frequency. I'll have a look.

[seeaxe]

Thanks Markus
Very interesting. I still have my buzz so I will try this.
Cheers

[charangohabsburg]

However, I have the spectrogram of the finished guitar before I even discovered that plucking those strings very hard was a problem, and I can of course now record another spectrogram of the fixed guitar. Like you I also believe that the "headstock and/or neck resonance" must be found somewhere amongst those peaks below the main air resonance frequency. I'll have a look.

Here: