Making a Loud CBG

While planning to build a CBG I am reading a lot of theory and I came across a MIT paper about sound hole shapes ( The paper is for violins, but I think the same principles stand for a guitar. Apparently the more perimeter (edges) a hole is having, the louder sound. Thus the the area of the sound hole does not matter much as the air is hardly moving in the center of it. Long narrow holes takes less space than a round but adds more air speed (louder).

Besides the obvious heavier strings, what other simple things could be done while building a CBG if you plan to play without a pickup and you want it to be loud enough for that?

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  • Electricly ! i say Buy a BIG AMP ! acousticly ! i say use a Big Body ! the rest is up to You ! Good luck! & Greeeeettsszz A.D.

  • "The loudest build I ever built used a small cigar box that was all wood, but only about 2 ounces in weight.

    No sound holes."

    Pretty sure it would be louder with sound holes.  That has been my before & after experience.

  • The 2 loudest I've built acoustically were.

    A build where I substituted an old steel cake pan for the cigarbox, and use high action on a fretless build.

    The loudest build I ever built used a small cigar box that was all wood, but only about 2 ounces in weight.

    No sound holes.

    Once the CBG was done the whole box resonated well, the the volume was noticeably louder thatn all the others. 

  • My loudest acoustic build used a box that weighed only 2 ounces, and had no sound holes. A slider. The whole box resonated well, resulting in max volume.

  • Hi Carl, you lost me with your descriptions of the word concrete, ha-ha, but you nailed what I meant.

    Hi Engblom, ok I got ya. If you look into my earlier post, the bit – The areas I focus on -, mentioned are the Real and Practical areas to investigate. Read different accounts by different builders, see what works for you and change it if it does not work for you.

    Hi Mr. I C President, interesting ideas, are you going to do the top testing suggestion? if so it would be very interesting to hear back.
    I do a similar thing when tuning guitar tops, that is attach the top to a solid form and record the changes as I work on the bracing. See photo…

    I’m not so confident regarding the idea of holes in a resonator cone. I would imagine it would have a similar outcome to a speaker cone with a hole in it. It’s been many years since the Dopera Brothers developed the resonator guitar and if there was a benefit in having holes I feel it would be in use already. But I could be wrong, let us know what you find.
    Cheers Taff

  • "Regarding concrete, I was a bit tired and by mistake in my head I translated the Swedish word "konkreta" to "concrete". It should have been translated like "real" or "practical"."

    No foul.  :)

    As you used the word concrete as an adjective instead of a noun, it is a synonym for real.

    I am sure Taff means the recipes will vary, nothing is set in stone.  ;) :)

  • I wonder about the effect of back angle, depth of box, and internal volume

    it would be interesting to score a pile of identical drop in lid boxes and make one body with interchangeable lids.

    it would be interesting to experiment with a plain resonator cone, a cone with many small holes, and a cone with a few large holes.

  • Hi, I think that Chicken bone John gave much good information, and I thought my account of the areas of importance to me would get you headed in the right direction.
    As soundholes do not a guitar make, neither does any other one component n isolation. If I advise someone that the sound I get is such and such due to this component or material, they may not get the same result as me ‘cos I have only shared one part of what I do or the materials I use.

    As I mentioned earlier tone is important to me, so I do not want volume at the cost of losing a balanced tone. Your question about bolts or timber use is a question of what tone you want [and other qualities], the bolt may sound louder but that could be due to the higher treble tone that the material creates. It carries better than bass tones, as already mentioned.

    Concrete made me chuckle, I think I can safely say that nothing is concrete in our line of endeavor as we are working with wood, air, and metal. All these components come together in different quantities, qualities, and workshops, by different people.

    It sounds like you are seeking to build good quality CBGs, and I commend you for that, but I think the best teacher experiences as Chicken Bone John alluded to. Learning for oneself the whys and what-ifs. I think you are on the right track, it's easy to build anything, but it's harder to do it well and it takes time.

    Short story: Talking to a group of student guitar builders one day, their instructor was a guy who visited my workshop years earlier and asked to take photos and asked lots of questions. He ordered two guitars from me and now builds his own fine guitars. At this meeting, he told the group – “I learned a lot from Taff, but he never told me the complete story, always left me hanging”. My reason for that was I did not want him to think my way was the best or only way but go and think and research about the issue. He did.

    Gee is that the time…

    Oh, bridge height question, the Break angle of the strings over the bridge is important, it also “loads” the top, and creates good downward pressure aiding in better sound creation. That includes volume.

    • Regarding concrete, I was a bit tired and by mistake in my head I translated the Swedish word "konkreta" to "concrete". It should have been translated like "real" or "practical".

  • My purpose with this topic was not to get a full complete guide to making a loud and perfect sounding CBG. More to gather pointers for what could contribute to a louder sound and still be fairly simple to do at the building stage.

    I am interested what in your experience brings out more sound of the guitar. For example the bridge was mentioned, but what kind of bridge do in your opinion contribute to louder and better sound? For example, which one is more loud between a hardwood bridge or a "bolt and nut" bridge? How is the height affecting? How is the weight of the bridge affecting the sound?

    Please give some concrete examples of what has given you better sound!

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