Altering the frequencies of the plates

[Herman]

On my latest guitars I measure the top and back frequencies. On some of them the top is quite close to the back resonance. What to do in such a situation?

Second thing: When a top resonance (with the top attached to the sides) is a bit too high, lets say 220 Hz. And I want it to get it below 200HZ, What do you do to lower that response?

Thanks
Herman

[John Parchem]

Some nylon string guitars are built with the top and back on top of each other. It could lead to a wolf note at the frequency as the low impedance quickly drains the energy in the sting. It is easier to lower a resonance than raise one.

For top not yet finish, thin the top or the parameter. Reach a hand in and lower the braces. Add some mass to the top, can try with blue tac putty under the bridge.

One way to separate the top and the back is lower the top if there is room.

[Herman]

Thanks mate, I already thought that, but it is always nice to have a second view.
Herman

[Herman]

I have this Triple 0, for 2 years now and it won't sell. Maybe because it developed a nasty wolf note on the G#. Before other guitars of mine sometimes had uneven notes, but this one was different and really unpleasant.
I measured the three basic resonances: Body 103 Hz, Top 209 Hz and the back 215 Hz. They all gathered around that G#.
And I think that is why the guitar performed its way and customers were reluctant.

Since I am peddling for two years I decided to dig in. The top needed to change.
The top finish was removed with paint remover. I took down the 2 inches of the lower bout edge to app. 0.9".
Guess what: It did not change the resonances at all. DANG!!

After that I taped a 15 gram (0,5 oz) ebony block to the bridge plate, and......................
Hallelujah, the resonances changed!! Body 105 Hz, Top 190 Hz, Back 220 Hz.

And even better: The guitar sounds great now. Nothing of a wolf note anywhere, clear rings and a very appealing overall sound.
It is not a very pretty solution, but I will glue that ebony block to the top. Someone is going to be happy with this guitar, even it is not pristine.
Herman

[Dave Bagwill]

Good for you, H! A very good solution that will make some player very happy, and taught us something also.
Dave

[Herman]

This is what changed:
The frequencies after completion in the first place:


It had a very strong body resonance on the 104 Hz G#. The top resonance goes along the 208 Hz. Also a G#!
That is why the low bass sounded awkward.

After the thinning the top and adding some mass to the top this is where I ended up:


The top stayd at the 104Hz. But the top dropped down to about 190 Hz. And the frequencies around are far more even. And that shows in the perfoming of the guitar. I'm happy with it.

Something to consider when you have a guiter that is not satisfying.
Herman