Regal Duolian Modifications

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Regal Duolian Modifications

Postby bluesmandan » Tue Jul 06, 2010 8:08 pm

Hello all. I'm new to the group and new to bottleneck. I recently purchased a Regal Duolian RC2 from Amazon for 350. I had to do a lot of mods on it to make it sound good. I tried out several nationals just before I bought the Regal, so I knew what sound I was looking for. Here's what I did:

1. Cut out the lower half of the internal wooden bracing. I just took a fine saw (bearsaw) and cut about an inch from the neck side of the soundhole. The wooden bracing was heavily damping the body's vibration. Sawed that piece, and then wiggled it a bit til it came out. So the neck is still braced, but the larger part of the body chamber is free to vibrate. By the way, this model does not have an adjustable truss rod as advertised. Glued on. If the neck comes apart, I'm gonna bolt it on myself, I think.

2. Took a dremel with a cutting wheel and cut notches in the tailpiece so that the the strings would be lowered, in order to increase pressure on the cone. This helps volume and sustain greatly.

3. With my belt grinder, I took 1/16 to 1/8" off of the saddle to lower the action so I can also play finger style

4. Changed strings to Daddario 16/56 resophonic strings.

Now the duolian sounds great, and I haven't even changed the cone or the nut yet. That may be forthcoming. So the guitar sounds good now, but I worry about the longevity of the neck joint, given its poor construction.

Has anyone else done similar modifications?
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Re: Regal Duolian Modifications

Postby zhyla » Tue Jul 06, 2010 8:48 pm

bluesmandan wrote:The wooden bracing was heavily damping the body's vibration. Sawed that piece, and then wiggled it a bit til it came out. So the neck is still braced, but the larger part of the body chamber is free to vibrate.


My understanding is resonator guitars are intentionally constructed stiffly since the cone itself vibrates.

The tail angle change sounds worthwhile, but you can always string the strings from under the tailpiece instead of on top for the same effect as your mod. Ricochet always has something say about optimal cone loading pressure - more isn't always better.

I don't understand what you're saying about the truss rod. Does it have one or not? Is it not adjustable? The truss rod cover suggests it is adjustable, is there not a little nut under there that can be adjusted?
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Re: Regal Duolian Modifications

Postby bluesmandan » Tue Jul 06, 2010 9:00 pm

I couldn't find one. It's just a bunch of wood glued together. I've got some pics, but haven't downloaded them into my computer yet. I should put them up on here...
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Re: Regal Duolian Modifications

Postby bluesmandan » Tue Jul 06, 2010 9:02 pm

Oh, and about the pressure on the cone. My guitar, as it came, was so light that I could easily lift the strings off the saddle with my fingers. Hardly any pressure at all. Now it's tight. I didn't think about running the strings backwards up under the tailpiece. I suppose that would work, too, though it might look kinda funny.
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Re: Regal Duolian Modifications

Postby bluesmandan » Wed Jul 07, 2010 6:38 pm

Here's a pic of the duolian with the coverplate and cone removed, but before I did any mods. You can see the wooden bracing.
DSC00280.JPG
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Re: Regal Duolian Modifications

Postby bluesmandan » Wed Jul 07, 2010 6:41 pm

Here's a pic of the internal bracing for the neck. No trussrod or adjustments.
DSC00281.JPG
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Re: Regal Duolian Modifications

Postby bluesmandan » Wed Jul 07, 2010 6:44 pm

Here's a pic of me cutting out the body-side of the bracing, and leaving the neck bracing in place. After I cut through that piece, I just wiggled the part on the right and pulled it out.
DSC00283.JPG
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Re: Regal Duolian Modifications

Postby bluesmandan » Wed Jul 07, 2010 6:45 pm

And last here's a pic of the tailpiece after I cut slots for the strings...
DSC00285.JPG
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Re: Regal Duolian Modifications

Postby zhyla » Wed Jul 07, 2010 8:04 pm

bluesmandan wrote:Here's a pic of the internal bracing for the neck. No trussrod or adjustments.


I don't think you understand what a truss rod is. It's a threaded rod that usually sits in a slot in the neck beneath the fretboard. If you were to separate the fretboard from the neck you would see it. The rod runs from the nut to (usually) where the neck meets the body.

It's your guitar so it's all good but just so nobody follows in your lead: no, cutting that "brace" was not a good idea. I'm not very knowledgeable about resonator design but I believe that neck stick runs the length of the body for a reason. Without it you'll probably find the neck is not held in place as stiffly and it doesn't hold a tune as well. I'd be interested in other opinions on this - where is Rico when you need him?
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Re: Regal Duolian Modifications

Postby rustyslide » Wed Jul 07, 2010 8:11 pm

zhyla wrote:My understanding is resonator guitars are intentionally constructed stiffly since the cone itself vibrates.


You want the top to be stiff and the back to be free - it's the secondary sounding board, just like on a flattop or archtop.

I'd much sooner leave the neck stick in and think about removing the mushroom support rather than the other way around. IIRC, A lot of the early Chinese resos had too many pillars going from the neck stick to the back (especially the tricones), and removing the extras and correctly positioning the remainder was a big improvement. This is known as the 'mushroom mod'.
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Re: Regal Duolian Modifications

Postby kiwiblues » Wed Jul 07, 2010 9:16 pm

Sorry about this, I probably have a reputation around here for being a little blunt but I think you may have just stuffed your guitar!
The stick you cut was actually an integral part of the neck and responsible for stabilising the neck by partly holding the neck down when the stings exert their upward pressure on it.
Even expensive Nationals have this as an essential feature of their build.
In a resonator the body of the guitar plays little part in transmitting sound compared to the cone.
It does add some colour to the tone though.
The rear of the guitar simply acts as a sound reflector. :cry: :roll:
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Re: Regal Duolian Modifications

Postby ricbleu » Thu Jul 08, 2010 3:21 am

I know nothing about reso construction, but I do know a lot about woodwork. If Kiwi and others are correct and you have just removed an essential part of the guitar's structural integrity, then it is quite conceivable that some "reconstruction surgery" could put things right. So don't despair. Keep us posted on how you are getting on with it and if necessary, some help will be at hand. I for one would be happy to advise and suggest a solution. To that end, could you tell me whether your guitar has a tail block at the butt end ie what do/did those two braces (the lower and the one you have cut) attach to at the butt end of the guitar?

And in view of the OP, I really wonder what gives when a new instrument needs so much work by the purchaser before it's useable? In New Zealand we have a consumer protection law that states that goods must do exactly what they are advertised to do, or its money back. Sure enough with guitars, everyone does a bit of basic fine tuning set up "out of the box", but the instrument would have still worked well enough without that. But to have to go to all the trouble that you have (not including removing the brace), just to get the thing to play seems ludicrous. After all, your money "worked" perfectly well for the vendor, so the product should work satisfactorily for you (relative to the price you paid for it). It's one thing to buy a new car (even an inexpensive entry level one) and fit mag wheels etc before you drive it but quite another to buy a new car and have to replace the main bearings before you can drive it anywhere.
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Re: Regal Duolian Modifications

Postby The Breeze » Thu Jul 08, 2010 6:37 am

bluesmandan wrote:So the guitar sounds good now, but I worry about the longevity of the neck joint, given its poor construction.


Err..... And lack of bracing? I'm not sure if the steel body itself has enough resistance to twisting under the pressure of the strings, thats why the neck continues to the tailpiece. If you think of it as a long piece of wood on which the strings are attached and tensioned, then add the body and resonator cone. Which is basically a speaker cabinet with a bass port, an amplified guitar without electricity.
As mentioned in these threads before you can have too much tension on the cone with a biscuit bridge. The more you push the cone down the more energy it will take to push it down further to make it resonate, and it has to go down as well as up to resonate.
Spider cones do not suffer as much as the pressure is on the edges tending not to have as much stress transmitted on the actual cone due to string pressure.
I think... I am open to correction but this is my understanding of the construction.
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Re: Regal Duolian Modifications

Postby The Breeze » Thu Jul 08, 2010 8:10 am

I've been thinking about this a little more and think it would be useful if it was understood how a resonator works. It may help in some of the questions on the forum regarding set-up.

These are just my ideas and I would encourage the experts on this forum to correct me here.

So here goes:
I think bluesmandan has made a fundamental error in understanding that a resonator differs from a standard acoustic (sorry b'mandan). The front face of the guitar is not a soundboard as it is in a standard acoustic. It is supposed to be rigid as in a properly set-up resonator if it was allowed to resonate it may do so in the opposite direction to the cone, thus cancelling the tone from the cone (like that may use it again...). What he has done in effect is to damp out some of the movement of the cone and convert the front panel into a soundboard. I think the opposite, make the front rigid so the cone moves, I've avoided the word 'damp' cos I don't think you want to absorb any of the reflected sound from the cone.
It is in effect a speaker in a cabinet, and speakers are designed so the cone moves and not the cabinet. However in a resonator the sound reflected of the rear plays an important role in the tone of the instrument.

As for string tension on the biscuit I think the following:
The cone should resonate freely both up and down. There should be enough break angle on the strings to provide sufficient tension on the biscuit so that when the cone is on the limit of it's upward vibration there is enough pressure left to prevent rattles and buzzes, no more. Any more tension and you will begin to damp the cone and force the front panel to vibrate.
I have just checked my Duo and there is a lot less tension than you would expect to find in a standard acoustic.

The tone's from the cone...

Corrections welcomed and encouraged.
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Re: Regal Duolian Modifications

Postby kiwiblues » Thu Jul 08, 2010 10:35 am

Yep, and the more break angle you have behind the bridge the more downward force on the cone and the less in theory you can tighten the strings on the other side of the bridge before dulling the sound or damaging the cone.
On an acoustic guitar the bridge is on the most solid part of the top, on a resonator especially a biscuit bridged one, what lies under the bridge is actually relatively fragile.
The break angle on both my resos is pretty small but they sound loud and free.
As I said before, it's a compromise.
Enough pressure so the stings have a good purchase on the bridge, and transmit their vibrations without rattling or jumping out of the slots when strummed hard but not enough to stop the cone vibrating freely.
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