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Does box ornamentation effect resonance?

Hi guys,

I'm starting a new build, and was thinking of going to town and add brass corners and grommets. The question I have is, does the clutter glued, screwed or bolted to the lid of a box cause a noticeable change in the box's volume?

Also, I get the idea of a sound hole allowing the sound to escape from the box, but any cutting to the box's lid would cause the quality of the resonance to dip. Is there an optimum sound hole size to get the best of both worlds?

(I've added a photo of the box I'll be using, just for a point of reference.)

Cheers

Hedley

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Permalink Reply by Sharecropper on August 17, 2012 at 11:28am

Edit : ...... groment covered sound holes, one on each side of the front of the box .

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Permalink Reply by Thomas "Duck" Petry on August 17, 2012 at 6:06pm

I don't know anything about the science, (or science fiction) of acoustics. I built this box as an art exercise to a theme with the sound holes cut in the shape of oak leaves and placed them towards opposite corners because I liked the look. The build is pure acoustic and has great sound as far as I'm concerned and quite a bit of volume for a small box. Remember that it's a cigar box, not a vintage Martin. I believe the saying is "there are no rules". Experiment with your ideas, have fun with the build and post pictures of the results.

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Permalink Reply by wormil on August 17, 2012 at 9:50pm

A couple considerations: I don't know much about the science of sound but physics tells us that the more mass you have, the more energy it takes to create vibration (movement). The energy for a guitar is provided by the player strumming the strings and on a CBG there may only be 3 or 4 so you have less energy to transfer than a 6 string. This is why (I'm guessing) guitars are made of very thin materials, one to preserve interior volume but also so there is less mass to get vibrating (although early luthiers probably didn't think of it in those terms). On the other hand, getting 'good' sound is more complicated than simply reducing mass as demonstrated by bracing and soundposts. So do whatever the heck you want and it'll either sound okay or not. :)

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Permalink Reply by Bad Finger (Eric) on August 20, 2012 at 10:00am

Since we are spreaking about resonance, I wonder what Kasha would do with a CBG? He did put the sound hole in the deadest spot of the sound board.

http://www.jthbass.com/kasha.html

I only know about this because one of my best mentors was one of Kasha's PhD students at FSU.

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Permalink Reply by chris koh on August 20, 2012 at 10:13am

Hi I personally find that I dont notice the difference in sound when my CBG's has sound hole's keeping in mind Im talking about electric CBG's when just played acoustically Yes slight difference in tone change nothing Huge............ I have just started a group on Facebook for CBG's were same as here but MUCH smaller people can show the build's & vids discuss techniques and ideas etc etc here's the link if any interested http://www.facebook.com/groups/345844995503402/ :-))

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Permalink Reply by BUGGY (C) on August 20, 2012 at 11:37am

This one sounds ok and has no holes and loads of ornamentation and a funny bridge tail thingy

for the wood to resonate I would imagine less is more...I have a strange double resonance on a Dingly dog with no holes

but its still works well and is quite loud considering. I had just some tiny holes on a resonator toilet seat i built and was amazed how loud that was too.. maybe we need to look at how the frequency works and escapes.

Thin strong and under tension, less paper and metal clutter....struts on a guitar the wrong way kill the sound quality

diagonal one best...so the wood needs to flex in the rioght way to create the right resonance..

But why do carrier bags inside a biscuit tin guitar improve the sound, as they do?

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Permalink Reply by BUGGY (C) on August 20, 2012 at 11:52am

http://www.youtube.com/watch?v=hS8L7xPmtP0

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Permalink Reply by ron carlson on August 20, 2012 at 11:55am

Not initially taking into consideration that the top acts as a resonating soundboard. Ron's correct I would have to believe. A cigar box would act no different than a speaker enclosure, albeit a small one. In Thiele Small Parameter terms, it would have a particular Fc (if sealed) or Fb (if bass reflex/ported) using "sound holes". Most often in a speaker design, internal bracing would be added to reduce box vibration to a minimum to avoid cancellation or oddities at particular frequencies but in a guitar, a resonating component is desirable.

I dabble in speaker building and am a little more familiar with what is desirable in that application. CBG's, not so much yet ;)

Based on this conversation, I'm wondering if there may be something to be gained by mounting a pickup (humbucker for example) so it doesn't mount to the top other than the cut outs for the Pup to project through the top. Meaning, widening the neck inside the box to allow for all the fastening to be done there instead of the top itself. No sound holes at all. Just rough calc. the gap created by any cutout would be the equivalent of your @1"-1 1/2" sound hole.

Not sure how a guy could effectively accomplish the same with the bridge and other than cutout's, have nothing coming in contact with the top to effect it at all.

That said, I've hardly seen it all so it's probably been done a million times before. Also, there is always a possibility that I've been just smok'in too much crack.