Preview - Koa tricone

A discussion of techniques, and equipment for guitar. Fretted, bottleneck or slide, acoustic or electric, this is the place.

Re: Preview - Koa tricone

Postby ricochet » Tue Mar 23, 2010 9:02 pm

Both the spider and the biscuit types usually have relatively small soundholes, either the screened ports of the Dobro (those screens were originally foundation vents to let moist air out of crawl spaces) or F-holes, and their relatively small area makes the body into a Helmholtz resonator with a lower resonant frequency than the tricone. Spiders and biscuits have their own unique sounds, (Tricones do too), and I think there's more to choose from than just which has the strongest bass. But IMO the biscuit's probably got the most bass, followed closely by the spider, and the tricone's got less.
User avatar
ricochet
Regular
 
Posts: 10256
Joined: Thu Jan 01, 1970 12:00 am
Location: Bristol, Tennessee, USA

Re: Preview - Koa tricone

Postby Buffalo_Bill » Tue Mar 23, 2010 9:23 pm

I converted a Drednaut into a biscuit type and I dig it lots, 8) then I also added a humbucker and dig it on steroids mucho. 8) 8)
Just for speculation, do you think a jumbo size converted to biscuit would have a stronger bass sound? :roll:
Bill
Buffalo_Bill
Regular
 
Posts: 495
Joined: Sun Dec 13, 2009 1:52 pm
Location: New Buffalo, Michigan, USA

Re: Preview - Koa tricone

Postby ricochet » Tue Mar 23, 2010 9:37 pm

Might. I think the body volume's a little bigger in the jumbo than the dread. I like jumbos.

Sorry for hijacking the thread, Freeman.
User avatar
ricochet
Regular
 
Posts: 10256
Joined: Thu Jan 01, 1970 12:00 am
Location: Bristol, Tennessee, USA

Re: Preview - Koa tricone

Postby kiwiblues » Wed Mar 24, 2010 1:24 am

With my skills my only option would be to buy a second hand 12 string dreadnought and convert it into a reso. This wouldn't be so difficult would it?
After all everything except the top and reso set up is already there.
It would surely only be a matter of carving the required hole in the top , making the sound well and lining evrything up accordingly.
This would be well within the capabilities of someone like Bottleneck John after seeing what he did with his Amistar peghead!? :) :wha: :wink:
User avatar
kiwiblues
Regular
 
Posts: 934
Joined: Tue Apr 29, 2008 5:59 am
Location: Aotearoa (New Zealand) - Shaky Ground!

Re: Preview - Koa tricone

Postby ricochet » Wed Mar 24, 2010 2:24 am

Depends on your skill level. I wouldn't start on it myself.
User avatar
ricochet
Regular
 
Posts: 10256
Joined: Thu Jan 01, 1970 12:00 am
Location: Bristol, Tennessee, USA

Re: Preview - Koa tricone

Postby Freeman » Thu Mar 25, 2010 4:20 pm

ricochet wrote:Sorry for hijacking the thread, Freeman.


Not a hijack at all. As an engineer I am quite fascinated with the workings of the guitars that I build and on other luthier forums sometimes get involved in discussion about bracing and tuning plates and glitter patterns and body size, sound hole size and placement, yadda yadda. Lots of theory and opinions and its rather fun to talk about.

In the case of resonators, I'll bet the Dopreya brothers didn't give a lot of thought to either the size of soundholes or for that matter, the size of the air box. After all they made single and double holed guitars, round holes, f-holes, some with the little holes inbetween. I think the tricone hole were mostly asthetic - they really fit the shape of the coverplate. Most of the reso's that I've seen (my Type 27 spider and Duolian biscuit) are shallow bodies with more or less an OM size (again, I think that is dictated by the size of the cone and cover plate - but NRP's wooden El Trovador is a deeper body, as are many squareneck spiders.

I used a template from an old (11-1/2 fret) tricone to cut out my sound holes, mostly trying to stay with tradition. Because of the lovely figure in this koa it was very hard to cut away anymore wood than necessary (its all there in the back). However I did make the body deeper than the measurements of the old ones for three reasons - (1) I like deep bodied guitars and think that the additional air volume does in fact lower the bass resonance, (2) that koa was just too pretty to cut off, and (3) this is a bolt on neck and I need to be able to get my hand thru a sound hole and turn the bolts (always the practical engineer). We'll see how it works.

I'll also add that I think the mechanism of the cone(s) and bridge is what really determines the way a reso sounds - whether it is the sweet singing sustained note of a spider or the brash nasty chopped note of a biscuit, or the tricone, which seems to be somewhere inbetween. Basic body material (wood vs metal) probably colors the sound a lot - the type of wood or metal probably has a much smaller effect. Again, look at all the different woods used for spiders - most of them selected for appearance.

I had never heard a wooden tricone until just recently (Mike Dowlings Youtube) and originally I had been thinking of building this critter out of titanium (one of my buddies is a ti welder for Moots cycles). I suppose you would call that a TiCone? However I had the koa and the cones, was bored one day and.....
User avatar
Freeman
Regular
 
Posts: 126
Joined: Thu Feb 25, 2010 10:53 pm

Re: Preview - Koa tricone

Postby Freeman » Thu Mar 25, 2010 4:38 pm

kiwiblues wrote:With my skills my only option would be to buy a second hand 12 string dreadnought and convert it into a reso. This wouldn't be so difficult would it?
After all everything except the top and reso set up is already there.
It would surely only be a matter of carving the required hole in the top , making the sound well and lining evrything up accordingly.
This would be well within the capabilities of someone like Bottleneck John after seeing what he did with his Amistar peghead!? :) :wha: :wink:


It is not that hard a conversion and is pretty well documented in the archives at MIMF (I can find the links for you if you get interested). There are some issues - you need to accurately locate the soundhole and route it, you need to deal with bracing the remaining portions of the top (reso tops are usually thicker and often even plywood). Most people build a ring type of sound well like a standard biscuit and glue it into the top. Getting it in is a bit of a problem (it will be bigger that the hole in the top, duh). One trick is to make the ring, then make a vertical cut thru it. You can twist it and put one side into your hole, then kind of "screw" it in. Clamp and glue it up, do any final routing for the cone. The tops on resos are flat - your acoustic will be slightly domed but once the X brace is hogged out you should be able to flatten it to the sound well.

Six string tailpieces are easy to find, getting one for a twelve is problematic. When I made my Stella-clone (another tread) NRP sold me one of theirs (about 80 bucks if I recall), Todd at Fraulini is another possibility or maybe an old Harmony 12. Shop for the widest biscuit you can find - you are going to need a bit more string spacing than a sixer. I would consider a Paul Norman CF biscuit - he routinely builds 12 string resonators.

Depending on how accurately you measure and build your sound well you might actually have to reset the neck to get the geometry right. If you want slide only you can be sloppy on the high side, but if you expect to fret it you want to get the angle pretty good to start with (I'm dealing with that now - I've got the cones in place and I'm setting the neck angle in the traditional fashion).

None of those are big issues, but they do need to be considered. Let me know if you want any references to people who have done it.
User avatar
Freeman
Regular
 
Posts: 126
Joined: Thu Feb 25, 2010 10:53 pm

Re: Preview - Koa tricone

Postby ricochet » Thu Mar 25, 2010 5:17 pm

I don't think the Dopyeras were into acoustic theory at all, they worked on the "cut and try" principle. Came up with some good stuff that way, didn't they? I quite agree that the bridge and cone setup is the main determinant of tone, and body material and construction is rather secondary. I was discussing body Helmholtz resonance mainly as an effect on the bass output.
User avatar
ricochet
Regular
 
Posts: 10256
Joined: Thu Jan 01, 1970 12:00 am
Location: Bristol, Tennessee, USA

Re: Preview - Koa tricone

Postby Freeman » Thu Mar 25, 2010 6:39 pm

It goes againt my logic to think that a larger soundhole raises the resonant frequency...
User avatar
Freeman
Regular
 
Posts: 126
Joined: Thu Feb 25, 2010 10:53 pm

Re: Preview - Koa tricone

Postby ricochet » Thu Mar 25, 2010 6:45 pm

But it does. Google up "Helmholtz resonator."

The way to rationalize it is that if you have a fixed air volume and something (like those moving cones) raises the air pressure inside it by a fixed amount, it takes longer for the air to flow out and equilibrate with outside air pressure with a small outlet hole than with a larger one. Same when those moving cones drop the pressure by an equal amount. That longer time to move the air equates to a lower resonant frequancy with the smaller hole.
User avatar
ricochet
Regular
 
Posts: 10256
Joined: Thu Jan 01, 1970 12:00 am
Location: Bristol, Tennessee, USA

Re: Preview - Koa tricone

Postby Freeman » Thu Mar 25, 2010 9:12 pm

No need, I've blown across enough bottles and I'm actually an engineer by training. I've built bass reflex speaker enclosures and guitars with small air boxes and sound holes ("parlor" or 0 sized) and I've listened to the arguements about Tony Rice's D28. Wasn't it Allan Carruth who built the "corker" - the guitar with all the holes in the side that he could plug with corks to experiment with sound ports and locations. Bind the f-holes on a mando to lower the resonance... I know all the theory, it just seems like a bigger hole ought to sound lower LOL

This tricone thing might be a complete disaster but I'm having fun making sawdust. I'll report back in a month or so.
User avatar
Freeman
Regular
 
Posts: 126
Joined: Thu Feb 25, 2010 10:53 pm

Re: Preview - Koa tricone

Postby ricochet » Fri Mar 26, 2010 5:26 am

I hope you're having fun with it. It's beautiful!
User avatar
ricochet
Regular
 
Posts: 10256
Joined: Thu Jan 01, 1970 12:00 am
Location: Bristol, Tennessee, USA

Re: Preview - Koa tricone

Postby B-dub » Fri Mar 26, 2010 11:09 am

That's really cool. I'd like to see more pics when it's finished . . . or along the way too! I've been looking at that new National M-1 wood body tricone, although I think I might prefer the nasally tone of a spider bridge (model D). Going to test drive the M-1 soon...
User avatar
B-dub
Regular
 
Posts: 12
Joined: Mon Jul 06, 2009 3:07 pm
Location: Detroit Burb

Re: Preview - Koa tricone

Postby ricochet » Fri Mar 26, 2010 3:43 pm

I've never been able to fit that spider tone with the word "nasal," but it's a really cool sound. The word that comes to my mind is "hollow." Anyway, I love it! It's got to come from an interference between the spider legs driving the edge of the cone and the tension screw driving the center. Loosen the screw and the signature spider tone fades out, along with a buzz developing when it's really loose. (I always wonder when someone talks about how a particular spider reso sounds great or lame just how that screw was adjusted.) I'd really like to see a physical analysis of the cone harmonics in spiders and biscuits. The tricones' individual cones ought to work just like the biscuits', but interference between the three cones' outputs within the guitar body comes into play, along with rocking movements of the T-bridge. It's been done all over the place with the vibrational modes of acoustic guitar tops, but if anybody's looked at the vibrational modes of center and edge driven reso cones, they're keeping quiet about it. Maybe speaker testing info could give some insights?
User avatar
ricochet
Regular
 
Posts: 10256
Joined: Thu Jan 01, 1970 12:00 am
Location: Bristol, Tennessee, USA

Re: Preview - Koa tricone

Postby Freeman » Fri Mar 26, 2010 4:15 pm

I've always wondered how the Dopyeras came up with the whole spider contraption in the first place - from a structural standpoint it makes a lot of sense but how would you figure out that tension screw and the whole idea of coupling the bridge and cone in that fashion. And yes, I know how the cone tension can affect the sound - I've done a lot of setup on my old Type 27.

When I finish this critter I will own one of each type of bridge/cone configuration. Maybe what I should do is find a nice graduate student who needs a thesis topic and do some Chlandi patterns of each one (I'll let her work out the details of how to get the glitter to stay on the cones). We can publish this in some scholarly work and become famous and rich.

Meanwhile I'm going back out to the shop and make some sawdust.
User avatar
Freeman
Regular
 
Posts: 126
Joined: Thu Feb 25, 2010 10:53 pm

PreviousNext

Return to Guitar

Who is online

Users browsing this forum: No registered users and 4 guests

cron