My first build: Solid electric to electric resonator conversion

[Justin Pruitt]

Hi, all! This will be my first build, ever. I am also documenting this build on the ResoHangout forums but I think there are many more active users here so I thought to post my work here as well. I have good math skills and rudimentary (at best) wood working skills. I have never dared to do anything to any of my guitars for fear of destroying them. It took some time to get over the intimidation of ruining the guitar but I have already caused sawdust to fly and feel much more freedom and less pressure.

It's always nice to share but, more importantly, I can hopefully get some feedback on my methods and ideas as I go through this build. I will measure and cut to the best of my neophyte ability however I will be using the TLAR method often!

A quick and dirty rundown:

Guitar: Hondo II Les Paul Jr. (ish)
Year of production: No idea (stick with number on bolt plate "HD990AB" and a stick on the head that says "3021" then "Inspected by" then either "128" or "138")
Cone: National 9.5" biscuit
Neck: bolted
Pickups:

• GFS P90 (don't know which version),
  Piezo (undecided which or how)

To do (tentative):

• Route resonator well and pickup cavity
  route out the neck joint cavity so as to move the neck further down as the cone center is 1 3/8" below the original bridge location
  Drill out some hidden cavities in the body to enhance resonation, possibly add some air holes with fancy (cheap) speaker covers
  Install cone
  Figure out how the hell I'm going to wire this thing (so lost...)
  Solder fest
  String it
  Test electronics (also remind self that hair is thinning and ripping it out isn't going to help)
  Test intonation (and inevitably fix it)
  Strip it down
  Remove the paint and sand
  Lacquer it
  ????
  Profit (i.e. play it)

Questions:

• Better to put piezo under bridge or on cone? I want a good resonator sound
  Piezo: how the hell to do it (hand made with varitone or $10 Ebay preamp)
  Paint or clearcoat? The wood covers are pretty quilted, might go au natural
  Is the plane in the neck joint level with the top/back? If not how the hell will I replicate that angle (which I can't even measure)
  How moveable is the biscuit bridge? Since it's on a circular base I assume it can be rotated but can it be slid forward and backward?
  Need to see the shape of cone before routing to see which part is 9.5", the lip or the inside of the lip
  Should I route the cone well all the way through the body as Keith Hosterberg did on his "Black Cat Bone"? I don't much like the aesthetics of the back cover plate
  Can I adjust neck angle with shims?
  Should I sand the black paint off the fretboard?
  P90 pickup has 3 wires and I don't know which wire is which (red, white, bare copper)
  Can I strip the paint, use regular wood stain, and cover it with polyurethane rather than lacquer?

Notes:

• Entire guitar is beaten but sound; needs to be refinished
  Fretboard seems to have been painted black, assume is rosewood
  Neck binding isn't binding at all but instead just black paint
  The head is extremely heavy; balances about 2-3" below the nut, even though the rest of the neck is thicker and wider
  Body weighs a ton
  Don't know how to check if the P90 pickup is in working order: need to find multimeter

Inspiration:
http://youtu.be/J6XXFPvIU_M
http://youtu.be/v4uNHp-Lzl0
http://youtu.be/VTZw2v8hENc

My thread on Reso Hangout forums:
http://www.resohangout.com/topic/29602

Now, onward!

[Justin Pruitt]

Here's the body all marked up. I used a hobby knife to finely etch the lacquer on the body to find the center line, bridge placement, etc. I also marked the neck where it met the body.

[Justin Pruitt]

There's the neck right after I took it off of the guitar.

I needed to make a template for routing so I needed to find some way of getting what was on the guitar body onto a piece of plywood. Due to my laziness, I didn't really desire to painstakingly measure every component in relation to some arbitrary axis (which would also introduce a lot of error) so I decided to make the lines very deep and, using a piece of paper and a black crayon, make a rubbing of the guitar face. It worked perfectly.

[Justin Pruitt]

I didn't get any pictures but I was able to make the plywood template based upon the paper rubbing I made. I drilled out the holes for the bridge poles and used them, along with the hole for a switch/knob in the top left of the guitar body, to align the template correctly. The routing came out ok. The routing bit I used was cutting the same diameter as the rod that goes into the router so there was no washer. I don't know if this caused a bit of heat but for some reason, in one corner, it cut into the template leaving a dip. I plan to fill it with wood filler, later, and try to hide it.

You can see from the scratch I made earlier that the neck doesn't meet the body at the same angle it did before. I routed parallel to the guitar face at 9/16" deep but neglected to take into account that it was originally installed at an angle. Using this scratched line, I will measure the angle and put it into the new neck joint plane with a wood chisel.

The white line below the neck is my original "to be routed" area. However, after consideration, I decided to not move the neck down so far. The idea was to put in some compensation due to the fact that the original bridge was about 1/8" short of the scale length (which is 24 3/4") and that the action will likely be higher than the original action.

[Justin Pruitt]

Originally, the neck was square where it was within the body and at the body's edge is where they began the neck shaping. Since I've moved the neck down quite a bit, the shaping now enters the body cavity. I'm considering either filing/sanding the body down to meet the neck smoothly or simply routing that much of the body off. Would love to hear your suggestions.

Next step will be to wait for the resonator cone to arrive so that I can figure out how it will install in the body. It's just been shipped today so it will be awhile. I'm considering removing all of the finish/paint from the guitar. The wood cover is quilted maple which looks good. I'm thinking I can lightly stain it and then simply cover it with some polyurethane (NOT polycrylic!). What are your thoughts on that? I considered using this project to learn how to lacquer however finding a dust free area where I live is IMPOSSIBLE.

[Justin Pruitt]

I've just learned about the real name rule and have already sent a message to a moderator. Please forgive me!

[Freeman Keller]

Hi Justin, I will watch this with interest. I can share a few pieces of information about resonators in general - I own three, work on them and have built one (an acoustic tri cone)

First, here are two pictures of a normal biscuit cone well. The first is the well (also shows the neck stick which I'll talk about in a moment)



And here is the cone, biscuit and tailpiece in place, but without the coverplate



OK, normally the biscuit/saddle is at exactly 2X the distance to 12 - there is no compensation. Resonators intonate terrible, but you have the ultimate compensator on your pinkie. If you are building it for fretted play, add whatever compensation you normally would. Don't put the cone at 2X and assume you can turn it, it will be worse on the side that gets shorter. You can do a little bit with the saddle, but not much - most people just put the break point near the back of the saddle and call it good.

Second, the cone should be moderately snug in the well - in general you don't take all the strings off at once because it might rotate (kind of like a mando or an archtop). Some people put little brads or a tiny drop of glue on the cone, others think that is a bad idea.

The action on a reso is basically set by the neck angle, with minor tweaking on the depths of the saddle slots, You really want the slots like you would do a nut - half or a little less of the string stinking out. Remember that you have to get the cover plate over the cone so lay out your geometry carefully.

The saddle on a reso wants to be pretty flat for slide (and for your setup). Most of them have neck radius either flat or maybe 20 inches. Some PacRim inports have 16, I find those pretty hard to play slide, easy to fret. Your electric neck is going to be, what, 12 or 9 - I think that is going to make cutting the slots in the biscuit tricky (again, work out the geometry in all dimentions). Aslo normal reso's are fairly wide necks (1-3/4 to 1-7/8 at the nut) but you shouldn't have any trouble making it narrower on your electric neck.

Next, remember that a resonator really is an acoustic instrument with the top replaced by the cone. If you want it to sound reso, you need a big air volume behind it and you need to pick up the cone sound. The most natural to my ears are mics - either in front of the cone or inside the body cavity. Frankly every reso that I've heard with some sort of mag or lipstick pup sounds like, sorry, an electric guitar.

The usual cone well is 1 inch deep, with the neck angled to give the desired action. I would suggest getting your cone and biscuit and making very careful measurements of the height. The cone will load slightly when tensioned, but not very much. Remember to make the break angle to the tail piece pretty shallow - if it is too steep you'll risk crushing the cone (don't ask how I know). I would not use a ToM or thru body holes, something like a real reso tailpiece will be much better.

As I said, I'll follow this with interest.

[Justin Pruitt]

Thank you for the great tips! I'd address them in a bit. I just read, in it's entirety, your thread on building a Les Paul and I was just floored. It was such a beautiful piece and, more importantly, you're candid humor kept me clicking to see what you did next. Wonderful stuff. Having such a talented person following my work adds a bit of pressure but it will also make me more careful.

My intent is to play this finger style, which is why I was so excited when I found that people put resonator cones in an electric body. I just find electrics much easier to play than my acoustics and, especially at night, sometimes I don't want the volume to be too loud so I'll play my tele unplugged. I bought a slide 10 years ago and never really played around with it much. I might with this guitar, however, so I'll likely have the action higher than a standard electric.

All of the adjustments seem to need to be done together. Following your suggestion, I will study the cone and bridge when it arrives and plan out how high I desire the bridge to be in order to set my well depth. As an example, the fellow who crafted the inspiration for this (using an Epiphone Les Paul Jr) carved out a 1 1/4" well. A little deeper than usual but I imagine the bridge needed to be a little lower than on a typical resonator acoustic. The bridge height also effects the neck angle and I'm not really sure which should be set first. Since I have marked the original lines of where the neck met the body, I think I will follow those at first knowing that I can increase it if I need to. Using the original angle, I can attempt to set the cone/bridge and see where the action is (on the D/G strings, at least, as I won't have shaped the bridge at this point).

I've printed up some free neck radius guides and will try to determine the neck radius tomorrow afternoon. That should at least allow me to determine the shape of the bridge. Since this is my first hackjob, I know very little about setting up a guitar properly, and the one thing I hate most is a guitar that doesn't play right, I will likely have the bridge fine tuning done by a professional luthier (the guy that sold it to me).

Do you think it would be in my best interest to have my friend use his plasma cutter to cut a thin metallic ring that would be epoxied to the wood in the well to insure a flat, smooth surface for the cone to make contact with? I doubt my routing ability to follow a flat plane about a circle and I'm thinking the added mass at the cone edge would mean less sound energy being wasted travelling through solid wood and more pushing air.

I do agree, mics would probably sound better. That's what my Takamine has and I love it. I'm not an EE - do you think a piezo transducer either in the air or attached to the wood of the body would be better than under the biscuit or should I get a cheap mic/preamp off Ebay? I was going to make some varitones to go with it because I have no idea which capacitor will produce a sound I like and a varitone allows for my ineptitude; I'm not sure I have the electrical know-how to wire such a device to a printed PCB board. Most conversions I have seen have a piezo under the bridge but, to me, it sounded too much like a traditional acoustic.

As for the intonation (which is most important to me; how I hate to be in tune near the nut only to have out of tune strings much further down the neck), I will have to do some math. I plan on using medium electric strings so I need to know what is the typical angle at which the bridge should be. This will allow me to determine how far past the scale length I need to go for the center of the bridge. Luckily, math and geometry are things I am good at. I just want to get it as close to right as possible and have the professional fine tune the bridge. Hell, it could all be for naught; the Hondo II's are claimed to be a considerable jump in quality from the original Hondo guitars but there's no guarantee that the frets are spaced right. I'm almost too scared to measure them, hah.

Welp, I'm sleepy. Will get some measuring done tomorrow, hopefully (building a room for my sister's house on the weekends so not much time for fun). Very glad you're interested in this project and I hope I can churn out something useful.

[Freeman Keller]

I’m glad you enjoyed the Lester build – yes, I did have my tongue firmly in cheek a couple of times, but mostly the intent of that thread was to demonstrate that Joe Average could build a fairly good LP clone with “normal” tools in a garage workshop.

Here is another build thread that might be more helpful for your conversion – this it a the wood bodied tri cone that I built a couple of years ago. I did spend quite a bit of time working out the geometry issues that I mentioned in my last post – I think that is key to your success here.

http://acapella.harmony-central.com/sho ... oa-tricone

Speaking of build threads, at one time MIMF didn’t allow the step by step construction as you are posting – they want you to wait until its finished. Posting a question about a particular step is usually OK, but I have seen the mods ask that you wait until done. I did look at your threads at the Hangout – interesting that you are not getting too many responses there. One other place you might try is OLF – they have separate Reso subforum.

I’m going to try to resist getting sucked in to this – I could easily tell you what I would do or not do, but I think you need to figure it out on your own. I will make a couple more suggestions and certainly will answer any questions. First, it looks like you are trying to build a clone of the NRP Resoelectric. I think you should get your hands on one and measure the heck out of it – where is the saddle relative to the 12th fret (you’ve asked some question at the other forum that tell me you don’t totally understand it).

http://www.nationalguitars.com/instrume ... olver.html

Next, I would carefully lay out the geometry on your body. Will the cone well even fit? The Duolian in my pictures has a cover plate that is 10-1/2 in diameter – when I super imposed that on the LP it overhangs into the waist and the route for the cone would come right up to the binding. In other words, it wouldn’t fit.

Next, I think your guitar is a carved top, right? Resonators have flat tops – the cone well is 1 inch deep all the way around. The cover plate requires a flat top to sit on. Remember that when you get ready to route.

I mentioned all the neck angle stuff in my last post and I’m not really sure what you are doing with your neck, but my suggestion is to stop until you get your cone, biscuit and cover and figure out how deep you are going to sink the cone into the top. At that point, and only at that point, should you figure out your neck angle.

Now, once you have the geometry (location of the cone, height of the biscuit, angle of the neck) can you work out fretboard radius and saddle radius. But you better be aware of this as you do the neck angle.

Finally, once you know this is even possible, should you start thinking about the pups and wiring and all the little details that you seem to be worrying about. Not trying to be critical, just think this through a little more carefully.

btw - a fairly common mod is to put a cone and well in a standard acoustic flat top. I know there were some articles in the MIMF archive - you might want to do some searching

[Justin Pruitt]

Thank you so much for the tips, I will try my best! As it's my first foray into guitar modification of any kind, I don't expect it to be perfect. Or great. Hell, if it's just "playable" then I will consider this a success. On the other hand, I want to do as good a job as I can! Hopefully, with a few years of experience, I can make something half as nice as yours. They are beautiful.

From our previous conversation, I have measured the neck radius and it is a 12" neck (or at least it fits my 12" template whose accuracy is taken at face value). At the least, I will be able to determine the bridge radius from this template as it fits well. I'll worry about it later, as per your suggestion.

I admit, trying to understand bridge location before hand seems beyond me because quite a bit of it seems like voodoo (which is before even considering nut compensation which I'm going to pretend doesn't exist for now). Every maker seems to use a different method, all with reasonably equal amounts of success. Which one to use? Throw a dart at a dartboard with methods, I suppose.

The cone center (I haven't routed, just marked a preliminary center), as I measured earlier, is 24 15/16". Given the 24 3/4" scale length, this leaves me with 3/16" (0.185") compensation at bridge center which seems to be too much. From what I can find online, some say "I use 1/8 of an inch" and some say "it's 0.100 inches at the high E and 0.125" at the low E". They're all for acoustic, of course, which should require more compensation due to thicker cored strings.

For reference, I'm planning on using Ernie Ball "Skinny top heavy bottom" which range from 0.10 to 0.52. Every electric I own has an adjustable bridge. Following the acoustic pattern of 0.100 to 0.125, I need to have the bridge center at 0.1125". My measure only goes down to 32nds, so I'm hoping 3/32nds (0.0938") compensation for the first string and 7/64ths (0.1094") for the 6th string should be "close enough" while also accounting for the thinner strings. "Close enough" meaning that when the shop tech carves the nut he can set relatively good intonation. The nut is 1/8" thick which I guesstimate gives me 1/16th of an inch to be "off".

Going to take a break from trying to figure out where to center the bridge and move on to some good, and simple, news. The guitar is not a carved top. Being an inexpensive Korean copy of a LP Jr, the Hondo II features a beautifully simple flat top. What's more, at the cone's current planned center location, I have 1 1/8" clearance between the cone well and the edge of the body. Fitting a 10.5" cover plate should be no problem although I will likely fashion my own cover plate. I plan to use a short trapeze tailpiece.

It is my hope to get the cone well routed, bridge carved and placed, and get it strung in the next week. I'll play it acoustic for a week or so and give it time to settle in before doing any fine tuning. I just want it to play well and feel right in my hands. Everything beyond that (electronics, finishing) is fluff.

Sorry if I over think it a bit. I have entirely too much time to think about possibilities. I'll try to stay focuses on the next step

[Freeman Keller]

I seem to be the only one following this but I'll throw a few more comments out.

As far as your saddle location, as I said before, the "normal" position is 2X distance to the 12th fret (which is the definition of scale length). That is for a slide guitar and will be very sharp when fretted. If I was going to build strickly a fretted guitar I would either copy the location of the saddles on your ToM before you removed it or use the handy calculator at StewMac (it was very close to the measurements given on my LP plans)

http://www.stewmac.com/FretCalculator

With the ToM you obviously get a chance to tweak the intonation, with an acoustic you get a small chance by the way you shape your saddle (see the thread currently running on the MIMF Acoustic forum). With a reso you get very little chance, but again, it normally doesn't matter because (1) most people play slide and (2) most people never fret them very high on the neck. You have to decide, because that will set the center of your cone route.

On your ResoHangout thread you mention making the cone well 1-3/4 or so deep - In my humble that is too deep. I think that 1 inch is normal, that will fit normal cover plates and will give the correct neck angle and fretboard height off the top. Remember that you will be shaping the top of the biscuit a little and will be cutting slots - that will lower your action somewhat. Most people run their 12th fret action just a hair higher than normal - if you like 5/64 high E you might go to 6/64, maybe 7/64 on the low.

Don't forget that you are building an acoustic guitar with a couple of pups - you need some string tension, break angle and action height to drive the cone. Remember also to make the slots deep enough that you don't pop the strings out if you plan to do 2 step bends. I hate to keep saying "most resonators...." but the most common string gauges are somewhere around 13-56 tuned to open D or G, lighter will probably sound kind of wimpy.

I don't understand your comment about compensating the nut. Cut the slots as normal, maybe a hair higher. Set the relief as you normally would.

I also followed your questions on cones on the Hangout. My experience has been that the acoustic sound of the new NRP "hot rod" cones were better than the stock spun cone in my Duolian but it is very hard to put into words. I run the hot rods in my tricone and a Quarterman in my 1932 Dobro.

Last comment on electronics and wiring. There are wiring diagrams all over the internet of every pup out there - StewMac, SD, everyone who makes them tells you how to wire them. Melvyn Hiscock's great book has a very good chapter on electronics - he discusses theory of all the standard wiring systems.

Carry on, report back.

[Justin Pruitt]

Yah, I'm gong to have to decide. I've read up on a plethora of different methods, numbers, equations, blah blah blah. They all seem to work. What I think I need to do now is just pick one and get it done.

I was going to make the well 1.5" deep; this would leave 1/2" of the cone sticking up. I could do 1" or 1.25", that would just mean I have to carve more off of the bridge. I may go with 1.25", that would give me 3/4" of bridge sticking above the face of the guitar which should be enough BUT I will go with 1" first and see what it looks like there. If it looks good with a 1" well, I can do some preliminary shaping of the bridge and set the neck angle temporarily with a shim and see how that works. If I don't like such a large neck angle, I can lower the cone later but I think it would be best to follow your suggestion first and just see how it turns out. Better to do that since I can always adjust the well depth later but it would be hard to make it less deep.

Well, that's enough talking. I've spent the past 48 hours reading hundreds of differing "this is how *I* do it" and I'm going to go nuts if I do it any more. If I screw it up, I screw it up, no big deal. Make a new body, buy a new one, doesn't matter. Lets see what happens... for science! Muahahaha

[Justin Pruitt]

Well, I've routed the cone well and it seems to have come out well. It's a perfect fit! Measure's ok, too, but I'll have to wait for my tailpiece to arrive and have the nut carved before knowing how the intonation is. I also want to route out the inside some more and find a way to allow the air to escape.

[Justin Pruitt]

The bridge currently sticks out about 1", as predicted. I will get the bridge carved to match the fret board radius and dips for the strings to go in. After that, and after my tailpiece arrives, I can check neck angle and then intonation. I don't know how much the cone will settle while under the tension of the strings so I'll let it sit a week before deciding whether the bridge is too high.

[Mark Swanson]

You can check the layout of the neck and the angle by using a straightedge placed along the frets and over the bridge. This will tell you a lot about your neck angle.

[Justin Pruitt]

Thanks, Mark! I had considered that although I wasn't sure I could get my neck perfectly flat as it's supposed to be. The reason is that it's 30 years old and the frets are pretty worn down. Can't hurt to look, right?

I'll use your tip and give it a check!

I will still wait until it's strung before making a decision, however. I don't know how much the cone will settle or go down until it's strung.

[Freeman Keller]

Sweet - looks like it was made to have a cone. Carry on.

[Justin Pruitt]

Used a straight edge from the neck and it just hit the base of the biscuit. The bridge is 5/8" tall and its center is 24 13/16" from the nut (putting it 1/16" past the scale length). It's about 1/32" shorter than where I wanted it but after sanding the cone well it should be able to move back that much. I have 5/8" of bridge height so plenty of room for adjustment. I could probably route the cone well another 1/4" deeper but I'm going to carve the bridge and see what happens. Perhaps I will only need to carve an extra 1/8" off the bridge and increase the neck angle to have good action. On the other hand, the cone stand well past the front of the guitar (est 5/8") which may make fashioning a cover plate more difficult.

One other area of concern is where the original electronics went. Their previous location was partially where the current cone well is. Because of this, there is an area (circumference length est. around 4 inches) for which the cone rim is unsupported. With a 9.5" diameter, that's around 13.4% of the cone rim unsupported. I worry that this will cause the cone to fail in the future; what do you think?

[Mark Swanson]

(circumference length est. around 4 inches) for which the cone rim is unsupported.

Too bad, you should have made a wood piece to glue in there before you routed, and then you would have had a perfect section in there to support it over that span. Right now, I'd see if I could build a piece like that in and then re-route it to fit. After that you can figure out where the new electronics will fit in, but first you'd need to give the cone a full support. That's my opinion, others might say that you could leave it as-is but I'd feel better with it supported.

[Justin Pruitt]

I shaped a piece of plywood that would fit the cavity and will glue that in place before stringing. It only took a few minutes, no big deal although it was nothing but curves hah. Chisled the neck joint of the body down a bit to increase the angle by about 2 degrees (which is about 1 degree more than original). Once I finish sanding the cone well, I'll fit it together and check that it all matches up. Tailpiece is in Indianapolis so it should be here in a couple of days.