I know that generally speaking all acoustic guitars need sound holes and solid body guitars don't. But I am starting to question how bad CBG's need them. I think they look better without them and if the guitar has an electronic pick up then that is the way the guitar is intended to be played and the sound hole is unnecessary. I recently built a 3 string fretless with a piezo pick up and because the box was on the small side, I opted for no sound hole. What I found out was this guitar will handle loud volume with a lot of gain without a lot of feedback issues. When I play this unplugged while it isn't loud it plays about the same as my builds with sound holes. If I wanted to build an acoustic only then I would opt for a bigger box and a non through neck design, BUT I would put the sound hole in the back, My reasoning is this. It is my understanding that the sound hole only functions to allow for air flow. This air flow allows the top to vibrate more freely, thus producing more sound. If that is the sound holes only function, then it doesn't matter where the hole is. I think by leaving the top with no holes would allow more material to vibrate and create more volume. This also makes me wonder if acoustic guitars would benefit from a "sound peg" like a violin has. A peg that is wedged from under the bridge to the back to allow additional vibration from the back. Let me know what you think.
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Hi Mick, thanks for getting back and letting us know your findings, that's always helpful.
If I may make a few constructive comments that may help your future builds.
First a question, you said the box is 12mm ply, is that the top too?
I just played the guitar shown above with a piezo pickup, with no mechanical noise at all. I had the amp on 10 and the guitar volume on 10, I then tapped all over the guitar, and no mechanical noise at all. Why? My piezo pickup is under the saddle, a strip piezo, not fitted to the top.
Piezo transducers react to the vibration of whatever they are attached to, in my case [under the saddle]the strings mainly, and in your case the top mainly. It could be, that the reason your piezo pickup sounded lacking is that it was mainly reacting [picking up the vibrations] of only half of the top. Not a very big soundboard. If the top was 12mm thick, it would not be very responsive to the string input as the strings appear to be attached to the neck only, and not to the top.
Your idea is sound, I have used piezo and magnetic pickups many times, as you have, with great results. But sorry to say, there are rules to getting good sound. Hahaha.
Cheers Taff
Thank you Taffy for your detailed comments.
My answers and next experiments on this prototyping CBG platform ?;
- 12 mm Plywood was used also for the top. i will continue with thinner upper and bottom decks later to compare response. Just looking for material.
- piezo was located on the back side of neck, just behind the low bridge, this location gives better balance of low and high strings loudness.
- the bad noise from piezo, which I mentioned - was the noise when metal slide touches the strings. With Inductive pick-up these ugly sounds are missing.
- optimal locations of pick-up’s installation were chosen experimentally both for Inductive and Piezo cases.
For info: I used Piezo taken from the kit Belcat Iris-1. Piezo looks like a 10 cm long rigid piece of cable 2 mm in diameter, - as I understand: for installation close to the low bridge of acoustic guitar. In my case the piezo was tightly fixed (pressed) to the neck wood with a plastic plate on screws. Next I will try traditional Piezo Discs. Though I do not expect much from this replacement.
and of cause - drill the holes ?
my kind Regards
Hi Mick,
Hi, I have found that for me, the ideal size box is one I build myself. Its size came about for two reasons.
One, I experimented and found that this size suited the scale length I was using [ put the bridge in the sweet spot on the top], gave me the best, volume, and tone [depending on the materials used], and could give me consistent outcomes if that was what I wanted.
And two, it is pretty close to the Golden Ratio. [I’ll leave you to check that one out.
The size is 300 mm x 200 mm x 60mm. Scale 25” mainly. Sides around 3/16” – 1/4” thick tops and backs depending on materials used 1/8” thick. Braced as required.
This is the all pine model.
The size of the box is only part of the sound story, the materials are also very important, especially the top. The same size boxes in my shop have different sound quality depending on the materials used.
I use mainly three different timbers for three different models. Rosewood/hardwood back and sides and cedar or pine top, Pine [fence palings] Top back and sides, and plywood Top back and sides.
This difference is noticeable when demonstrating a guitar to a customer. Customers, as I seem to do, go for the best guitar first, but I have learned that it’s best to work up to the best ones by playing the others first. By doing this they hear how much better the expensive ones sound when I get to them, so they are easier to sell. I would agree that in some cases you can get away without a sound hole in an actual cigar box as those boxes come in so many different shapes and sizes and materials, the sound you get is what you get.
If the top is not responsive enough to create sound waves in the box, [either too thick or unsuitable materials] then a soundhole is not much benefit.
The CBG could be seen as a different animal to a full guitar, but we are trying to get it to do the same thing as a guitar, I like to help it along.
Oops too much rambling.
Taff
Dear Taff,
appreciate your detailed story. Will use your findings in my future works!
Your CBG looks great and iconic!
Thank you!
So my conclusions.
Also, pls, see my blog,
Metal sheet (I wrote about earlier) gave no visible sound effect. But it increased weight of CBS. So I rejected this concept.
Seems Inductive Pick-up sounds better than Piezo. Slide on Inductive pick-up has less mechanical noises than Piezo.
I'm planning to write a new song with this CBG. So it will give impression of how it sounds.
All the best.
Inside the box. To the left - Piezo channel, Right - Inductive part. Each has own output socket. Foil used for shielding and fixing cables.
In my experience CBG's and an acoustic guitar are two different animals. I have found that sound holes on a CBG are for looks only, as the entire cigar box is resonating to produce acoustic sound. A guitar is designed to have a vibrating top mounted on the body. Yes, a sound hole might change the timbre or tone a little, and sometimes one in the side pointed at the player is nice, but I no longer use sound holes except for the "bling" effect. That being said, there are no rules.
One of the very loudest acoustic builds I did used a tiny little Presado box, had no sound holes, and it was a "cannon". ;^)
Thank You.
What do you think about size and depth of Cigar Box? What sizes would you recommend?
Hi Slow Mick, it’s good to see somebody trying to improve the sound from a basic box guitar.
Let us know either way, your findings. Good or not so.
The bottom line is that soundholes do improve the sound of a guitar. It’s an interesting subject, and a lengthy one to go into.
The main things that come together to produce sound in a guitar are, strings, soundboard, and air. There are a few other things that contribute to the quality of that sound.
This may help you in your endeavours.
The energy from the plucked strings vibration is transferred to the top, which in turn vibrates (if sensitive enough). The vibrating top then excites the air in the box causing sound waves that carry’s what we hear as the different frequencies of music. (A layman’s explanation here).
Keep in mind that a very small % of the energy of the string is available to excite the top, the rest is lost.
Only a small % of the sound produced comes off the surface of the top.
The majority of the sound is bouncing around in the box as sound waves, hence the use of soundholes.
As an experiment I made a cbg, in a way that that I could remove the box/air chamber. Withe strings attached to the top only…very little sound. Attach the box and loud sound.
Sorry to ramble on.
Taff
Agree with you.
Thank you.
Now I have a CBG in manufacturing, based a box made of plywood. Earlier I was making 3-string guitars with Inductive pick-up and solid body. But now the question of making holes in the box of guitar or not - became interesting to me.
As experiment, I decided to put a sheet of thin metal inside box, fixed in one point to the neck. I was thinking that vibrations from neck to metal sheet will give some additional overtones to the sound.
At this moment works are in progress. One thing is clear: box makes sound of guitar louder. But no resonating noticed (added by metal sheet).
Guitar is not finished yet.
Picture with current status attached.
If any interesting results, I will report.
Slow Mick
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