Upon completion, I conducted a frequency response analysis. For this, I used a speaker’s oscillator, placed at the position of the bridge on the soundboard to amplify its vibrations. I played sine waves of various frequencies and then used software to analyse the sound captured by the microphone.
The results indicated a significant vibration peak around 190 Hz, which is close to the note D#3. Observing the frequency spectrum, there were a few overtones present. I wasn't entirely satisfied with these findings.
The test results revealed that the soundboard produced more high-frequency overtones, resulting in a more balanced frequency response overall. There were no excessively dominant resonance peaks, and there was an increase in overtones across multiple frequencies
Additionally, when applying traditional tap toning techniques, I noticed a richer presence of high frequencies and overtones, with the tapped tones resembling the sound of a struck bronze bell. I am quite satisfied with these outcomes, but I still need to slightly thin down the ends of the added braces into an arc shape. Without this adjustment, the soundboard would be too rigid, potentially compromising the volume of the played notes.
Another reason for adding horizontal bracing was to address the issue of feedback, particularly at lower frequencies, when the classical guitar is amplified. This addition should mitigate the overwhelming low-frequency sound waves and the troublesome feedback often encountered with amplified classical guitars. This aspect, however, can only be conclusively tested once the guitar is complete.
Updates after the guitar is strung:
After stringing and playing it, I found the A string to be noticeably louder than the others, confirming my test results. However, this resulted in an uneven volume on each string, with the E string being on the weak side. Due to the increased frequency of the soundboard this resulted in a lack of bass and the low E string was not full sounding. After connecting the amp, I found that there was no lack of bass, but it was noticeable that unlike the classical guitars I had been using, there was too much low end when amplified. The sound of this soundboard through the speakers (fender 65 deluxe reverb, tone settings are all set to half) sound balanced, this is my first impression.