Official Luthiers Forum!

Y'all,
I haven't submitted for awhile.
I thought I'd show you what I've been up to lately.


The Heresy1 (#4) - Spruce front, followed by hard maple, followed by torrified oak, with a mahogany back.


Pinless bridge design.


I added the 2 large "crescent holes" to the front, to allow more of the high-freq energy to escape.
I think on the next one, I'll get rid of the bottom one (on the right), and migrate the left one to be more of a sound port for the player's ear.


I'm pretty excited about this one - The VooDoo Child (#1).
Figured maple in the center, followed by 2 strips of torrified maple, with swamp ash in the outer areas.
Perhaps the most heretical feature of this guitar is the modified hardtail bridge. (Photo of bridge at end of thread)
Not only does it eliminate the need to machine parts of dead animals, but you can easily intonate, and height-adjust each string!


Side view of the VooDoo Child.


Here's a look at the insides of the VooDoo Child #2.
Doug fir front, followed by a ring of hard maple.
This one will get a set of K&K Pure Mini piezos.


A close-up of the modified hardtail bridge and East Indian rosewood base.

More photos and information can be found at KOZM Guitars.

All comments, questions and critiques encouraged!

Thanks for taking a look,

Jeff Kosmoski

NEAT!
I wanna do one!

_________________
"Act your age, not your shoe size" - Prince

Very cool.

_________________
guitarsbygiltzow.com

I thought I replied last night, I must've closed the window before pressing send...

That VooDoo child is seriously cool!

So many questions but one leads to three more!

Does it work like an archtop or a chambered electric? It doesn't quite look like it works like any guitar I've seen... If it's archtoppish (:lol:), how does the hardtail bridge affect the string energy transfer? My ignorance knows no bounds, now I think about it... Could an archtop take the tension of all the strings in the way a flattop (or the VooDoo child) does? Or is the VooDoo child distinct from an archtop in that respect?

Have you done Chladni patterns to see how the top vibrates? Or recorded a frequency response curve? It's so intriguing!

Also, what goes into those position pin holes?

I'll probably have loads more questions!

Awesome work!

I'd say it works more like an acoustic guitar - an acoustic guitar with a small body. I removed some of the material from the brass hardtail bridge, and overall I'm pretty pleased with the amount of tonal volume it produces.


Y'know, I guess the "urban legend" going around is that the main reason acoustic guitars don't use hardtail bridges, is because they restrict the acoustic energy flowing into the body and soundboard. That MAY be true for an un-modified hardtail, but as I said above, it's really not bad at all. I actually made 2 VDCs during the last batch, as well as the Heresy 1 that appears in the post. The Heresy 1, with its bone saddle, is a little louder, but not by much.


I'd say so - only because I'm not aware of any hardtail archtops.


I guess I wouldn't be able to do Chladni patterns, cuz all the sand would just fall off the curved surfaces. Haven't done a freq response curve yet. I DO plan to make a demo video pretty soon.


If you're referring to the ones that are spaced around the perimeter, in both halves... they're used to align the 2 halves during gluing. I put .125" dowel pins in the holes in one half, and mate them with the corresponding holes in the other half. [/quote]

Thanks for the questions.
Let me know if I misunderstood any of them.

Cheers!

Jeff

all i'm seeing is tremendous wood waste for something that likely sounds like an Ovation...and definite splitting in the future

I think it is pretty cool. Nice work.

_________________
Ken

And exactly why Jeff uses inexpensive, plentiful wood that most others will not use! I have observed this project from the beginning due to the fact I was intrigued by his cad and cnc work.

https://www.youtube.com/watch?v=A5rqW4RbLg0

Watch and decide for yourself! I rather like the sound!

Mike

It sounds beautiful! I'd be really interested to hear what the scientists think about how it works... It seems to have a lot of the qualities of Clapton's 000 in that sample. I'd love to see a video where the two go head to head.

Thanks for the answers Jeff! Interesting stuff regarding the hardtail bridge.

I assumed the pin holes were just for positioning but thought I'd ask... It would be interesting to know how thick the top is, etc. Another measurement I'd love to know... Monopole mobility! And just stiffness in general and how it compares to a thin braced spruce top. Of course, I'm only newbie speculating (and learning whilst doing so I hope) but the VooDoo Child seems to break rules and sound great, so it seems like a great opportunity to do some science!

Seems like an excellent thing to do with CNC! Congratulations on a fine instrument!

I do CNC work - mostly 2D+. I am trying to figure out 3D CNC but the cuts take a long time! How long was this guitar 'on the machine'?

CBRviking,

I don't have all the numbers handy, but I'll tell you that the body consists of a front and back, and each of these has front ops and back ops. Typical time for the one side of one side is about 1.3 hours of actual machining time. This doesn't account for setup time and tool-changes (I don't have an ATC).

Hope this helps.

Jeff

Jeff when are we gonna hear a clip of the VooDoo Child? How does it compare to the guitar I linked the youtube vid to?

Mike

What software do you use? I am using Rhino3D and CamBam and I'm having a lot of troubles.

Here's a link to the YouTube video:



Cheers,

Jeff
KOZM Guitars

Jeff, I think you are on to something with the bridge, wood choice etc in the VooDoo#1

The sustain in that one was far greater than the others, plus to me it is the one that sounded the best overall as well.

Mike

ps, just for curiosity sake, do you cut your wing pieces as semi profiled flat sawn that when glued together, make it quartered and use less wood? If you prefer not to answer, I understand, then again a pm would be nice in that case!!!

What kind of troubles are you having?

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

I posted it on CNCZone and the CamBam forum, and I hate to take over this thread. Simply, I only want to cut the back of a neck, not the heel or headstock. CamBam puts a trough around the edges of the cut so it messes up the front edge of the heel.

Some really cool work there!