Resophonic Guitar

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RESOPHONIC GUITAR AKA DOBRO CIRCA. 2000

I fell in love with the sound of the Dobro slide guitar back in the early 1960s and tried to mimic the sound using a Sears and Roebuck Silvertone flat top guitar.  I didn't have a clue that the strings were raised high from the fingerboard.  For whatever reason, I remember cutting the dyed black maple fingerboard area between the frets trying to level them up.  It was later that a local musician explained to me that the strings didn't contact any of the frets at all.  I purchased a metal extension nut from Crider's Jewelry here in Wadesboro, NC and attempted to get a Dobro type sound using a slide bar made by Stevens.  I watched the Lester Flatt and Earl Scruggs Show back in the black and white TV days and figured out that Josh Graves was playing in an open G chord but wasn't aware that the first string was tuned to a D pitch, therefore I broke several 1st strings trying to get it up to a high G. 

It was not until I was married and working for the North Carolina Telephone Company when I located a musician named Doc Moss in Waxhaw, NC who had an ole Mossrite Dobro and he showed me the correct open G tuning GBDGBD and I learned to play some stuff with his amateur band.  I traded him one of the Dopyera Brothers (OMI) Dobros for the Mossrite Dobro which was a 14 fret model and it didn't have a conventional sound well in it but a type of baffle construction....had good tone, but not much volume.

Without reinventing the wheel, check out my Biography page concerning my Musical Instrument Repair and mail order business from 1969 through 1978. 

Below is a copy and paste of a resophonic guitar aka Dobro that I made for myself back in April 2000 before I owned a digital camera and scanned the prints that I located and eventually posted them in my biography page.

RESOPHONIC GUITAR CURLY MAPLE "FLAMING CLAW" 2000

With some free time on my hands again, I decided to make another musical instrument and called my good friend Jim Yarboro in Gun Barrel City, Texas that still had the molds for building a resophonic aka Dobro guitar that he got from me in 1979 and he shipped them to me UPS and the fun started.  I had sold most of my wood working equipment and had only a few power hand tools left and this guitar was made by good friends letting me use critical pieces of equipment such as the band saw, table saw and jointer, etc. all of which I do have today…another grin is in order.  A few pix of that guitar under construction and Jim Yarboro and his banjo picking "bride" Carol in December 1976.

  

Pix of the guitar back with the bracing just hand planed to shape.  Most resophonic guitars (square neck) do not have any bracing but I added it since this was going to be my personal guitar and might have been just a little overkill but that is ok too.

 

Pix of semi-finished body of guitar with the holes for the sound screens not cut yet or any bindings added and bending mold and working jigs used to build the guitar. 

  Note:  Ervin Sloane's mold design.

Inlaid ebony fingerboard with the Flaming Claw mother of pearl inlays being glued to the curly maple neck blank with a pile of C clamps.  Might be another overkill on the clamps too!

Old style "neck tongue" construction.

The two upper right hand pixs above is when I removed a Fishman Classic Passive pickup from the resonator cone a number of years later.

Pix of finished resophonic Dobro guitar with all curly maple neck, back, sides and top with inlaid ebony fingerboard and peghead.  It was finished on Father’s Day in 2000 and has aged now and sounds great!  The little pc microphone doesn't accurately replicate the bass range of the guitar and the guitar sounds much mellower "in person". 

  Softly and Tenderly .mp3 file  Pee Dee River Slide .mp3 file

I'll Be All Smiles Tonight with Porter & Curtis.  Click on links to hear mp3 sound file. Fireball

Don't grin too big;  I hadn't picked on the Reso in about twenty-five (25) years and started messing with it a little after I made the above guitar and as with other things, it went back into the guitar case!

MODIFIED SOUND WELL HOLES 06-15-17

The old saying, "If it ain't broke, don't fix it", which is very sound advice, but sometimes, I do violate my own logic and thinking.  Another ole cliché, "It is better to leave well enough alone"....grin if you must!

I started back trying to play my resophonic guitar this year and the above resophonic guitar is made from curly maple except for the sound well which is poplar and has a little higher resonant pitch due to the solid wood construction versus the plywood construction of the Nationals, Regals, and Dobros from the 1930s, whereas walnut, mahogany, cherry, etc., will give a somewhat lower tone.  The curly maple bodied resophonic guitars do seem to project a much brighter sound and volume with all things being equal, but can have some annoying overtones.

I viewed a number of different sound well construction resophonic guitars as well as the ones with nothing but baffles and "sound posts", whereas I decided to modify the standard round sound holes in the sound well on this guitar.  Many of the die hard traditionalists like the parallelogram shaped holes versus the round holes, but as to which one is better is still open for debate; the parallelogram shaped holes would have more area open. 

I could remove the sound well all together, but that would require extensive modification for the existing body of the guitar and present additional construction problems which I did not want to entertain.

I know, I will be taking a gamble on the modification, but don't think it would change the sound for the worse and would open up the sound well air/sound movement and maybe lower the resonant frequency which might even pump up the volume some, but this guitar has very good volume and sustain.  I know, it seems crazy to mess with it!

I didn't have any good RotoZip router bits on hand and had to wing it.  I tried to use a slotting cutter in my portable drill, but I couldn't control it freehand due to the number of teeth on the 3 inch diameter slotting cutter/saw and that was out.  I put some good gashes in the sound well which is cosmetic only.  I found a 3/32 inch diameter router bit x 1/8 inch diameter shank and used the Dremel tool and drilled close connecting holes between four (4) of the existing sound holes that I wanted to remove and ended up with four (4) very long elongated sound holes, with a regular round sound hole for the neck area and a solid section at tailpiece area.  After cutting the pieces out, I used a small 3/4 inch diameter sanding drum on the Dremel tool and 100 grit sandpaper to finish the work.  I applied some lacquer to the raw wood with a Q-Tip to seal the deal.

I put the resonator cone and spider bride assembly back onto the ledge of the sound well, attached the cover plate and tailpiece and tuned her back up.  I believe it has more volume, sustain and the tone is still sweet!.  I will let it settle down a few days and see if I can get an old Windows XP Pro system running and record some sounds and see if I can hear a difference between something that I already have on file, of which I do believe there is a difference, but there is no sure for psychological bias; e.g., we hear what we want to hear......grin if you must!  This PC here is Windows 8.1 and I don't have an audio imaging program that works on the 64 bit system.  If you cover the sound hole screens, the volume definitely goes down, therefore sound is projected from those holes for sure and they are not there just for looks in my humble opinion.  They work on the same principle as the vent hole on a drum shell as to the release of sound waves/air pressure, sound holes for the mandolin, violin and guitar, of which size does matter.  An acoustical engineer would have the data to validate the size sound holes needed for a particular sized sound chamber, but most of what was done before the invention of the PC, was trial and error until it sounded right.

The traditional Dobro sound well definitely help to keep the top from imploding and offers a secure platform to mount the lip of the resonator cone, functioning as a type of speaker cabinet.  Later designed baffle systems accomplished the same thing as does the sound post system to keep the top from imploding and the more open body cavity does change the tone, volume, overtones, etc. and seems to depart from the 1950s traditional Dobro sound in my humble opinion.  Most using this type of design, add a curved flexible polycarbonate baffle to redirect the sound.  Now, it seems like everyone wants to copy Jerry Douglas....grin if you must, but I am still an ole Uncle Josh Graves style of picking fan.

I plucked the bass string and counted one thousand one and could still hear an audible sound at one thousand twenty one count, but it was very weak at the last count.  I don't have a clue as to what the sustain on other resophonic guitars would be and what the gauge mark would be as to the number of seconds of useable sustain is, but I think the modified sound well improved the sound of this guitar.  Strumming the strings open, there is a good 8 to 10 seconds of usable sustain.

I did hear a sound improvement when the screen covers were removed.  The bass response seemed lower in tone and the volume and sustain did pick up too.  Again, it might be my own psychological bias, of which there definitely is no known cure.  Simply stated, "If one believes something sounds better, it will sound better", to that individual anyway!

I ordered a set of standard 1 7/8 inch diameter metal chrome screen covers, of which I will remove the screen wire from them, but leave the set of screens I have intact.  The guitar doesn't look right without the screen covers, but I think the sound is much improved with them removed on this guitar.  The covers with the screens removed should still add some eye appeal versus just the plain sound hole openings in the top in my humble opinion.

NOTE:  I went ahead and removed the screen grill from the sound hole covers I have on the ole reso guitar and it doesn't look "too off the grid", but departs away from the traditional look which doesn't seem to bother myself any.......grin if you must!  06-22-17.  Also, the imported screen covers were a little too small in diameter to snugly fit.

Web published by Bill aka Mickey Porter on 06-16-17.

REMOVED SOUND WELL 06-23-17

The tone aka timbre of the bass strings still sounded high to me and decided to completely remove the original sound well and install some support posts for the overhang aka lip of the top of the sound well.  I thought about making a wood ring support for the resonator cone, but that would take some serious routing and might damage the top.

I used a small hand held router and roughed out most of the sound well and cleaned the lower portion that was glued to the back with a sharp chisel.  I used 1/2 inch diameter poplar hardwood dowels for the support posts and ground a radius on the end that contacted the back braces.  End grain doesn't glue very well but had some tension on them when I glued them in place and hopeful they will stay in place.    

Click on thumbnail pixs below for a larger screen view:

After the sound well was removed, the support block for the neck was trimmed down and the support posts for the resonator ledge was installed. 

BLOCKS INSTALLED FOR BAFFLE ATTACHMENT

I glued a couple pieces of soft Pine wood to the guitar sides in front of the upper support posts to connect the ends of the plastic flexible baffle.  I didn't permanently attach the baffle since this is my first attempt at a flexible baffle and will see what happens, sound wise.  I used a No Trespassing plastic sign that was 11 x 14 inches and about 1/6 inch plus in thickness.  I believe the baffle was 2.5 inches in height and the inside height of this guitar is 3.250 inches.  The baffle was long enough to where it curved on the other side of the sound hole openings in an arch.   

NECK TONGUE REMOVED

Many of the 1930s Dobros had a neck tongue that was glued into the end of the neck block via a modified mortise and tenon type connection which worked pretty good.  The tenon or tongue portion actually was resting against the guitar top instead of a true mortise fitting.  This was a carry over from the open back banjo days as a means to connect the neck to the instrument body and have the ability to adjust the neck action. On this instrument, I shaped the tongue portion as part of the neck; e.g., it was one piece instead of glued into the neck heel.  The neck block and tail blocks were 3/4 inch thick Birch plywood and I had an extremely tight mortise and tenon fit for the neck tongue.  The length of the tenon needed was a little less than an inch since the sides were a little less than .125 inches in thickness and the Birch plywood neck block was slightly under 3/4 inch in thickness.  I band  sawed the "tongue" to length and installed a couple lag screws, 1/4 inch x 20 tpi, pre-drilling the holes to around .190 inches in diameter and tested the fit out on the scrap piece of tongue wood from the neck and it was a good tight fit without the danger of bursting it out.  The length of the lag screws was 2.5 inches in length and went deep enough into the neck heel, not just relying on the short tendon portion for strength.  The aluminum backer plate was 3/16 inch thick and drilled the holes a little oversize, however the neck did not move right or left or up and down due to the fit of the mortise and the short tenon......the lag bolts just held the neck tight against the body of the guitar.  I used an extension on a 1/2 inch drive ratchet to access the lag screws and bolts; tightened them down very snug.

STRUNG THE GUITAR UP FOR A TEST RUN

I installed a set of D'Addario EJ18 heavy gauge phosphor bronze strings and used a .018 string for the first string instead of the .014 string that is supplied with the set.  This reso sounds good with the medium gauge D'Addario EJ42 strings as well, but I have a quantity of the EJ18 strings on hand.  I got the guitar up to pitch and after the strings settled in stretch wise, I wasn't that pleased with the sound.  It definitely had more bass response, but everything seemed to be somewhat muted or muffled.  Since the baffle was flexible, I removed it by twisting it out through one of the sound holes, without having to take the cover plate off, tailpiece and resonator cone out .  In all probably, the baffle was far too large in height and as I said before, this is an experiment since I have not had access to a baffle guitar such one that Tim Scheerhorn makes, whereas he is the top resophonic guitar maker in the USA and has more instruments in the hands of the professionals than probably any other individual maker and/or company in my humble opinion.

Paul Beard resophonic guitars are also at the top as well and has many of his guitars in the professional arena too.

After the plastic baffle was removed, I immediately noticed the guitar was not muted and the bass response was great along with the high end response. 

In summation, I am well pleased with this last modification and will see what it sounds like, once everything settles in.

The only problem, without a nearby microphone and/or pickup, the resonator guitar is easily overpowered by other instruments, therefore plan B is about to manifest itself!

Updated webpage by Bill aka Mickey Porter on 06-24-17.

FISHMAN UNDER THE SADDLE PICKUP INSTALLATION

Years ago, I installed a Fishman Classic Passive Resophonic pickup to the cone of the resonator, but it was horrible sounding and took the device back to Holloway's Music in Monroe, NC for a full refund, of which they agreed to beforehand, if I wasn't pleased with the sound.  To me, the reso sounded like an amplified Ovation guitar.   

Playing the resophonic guitar in our Church, the only complaint was, I couldn't be heard loud enough and did some research on the latest Fishman under the saddle piezo ceramic pickup.  The new Jerry Douglas Nashville series pickup sounded great with the Fishman Jerry Douglas series aura imaging pedal for a realistic resophonic guitar sound.  We have input jacks in the choir area to our sound board system which should work fine.  If necessary, I can break out a 150 Watt Fender PA system which has a pretty decent sound too, which will be needed at our local nursing home monthly singing. 

I decided to install a couple more "support posts" for the resonator cone ledge and a lateral brace toward the upper bout of the guitar body and another post near the tailpiece which should have the pressure pretty much spread out from the downward force of the string tension.  All this is necessary, since I removed the sound well that was part of the original construction.

I probably would have been better off just purchasing another resophonic guitar, but I don't mind doing things the hard way, which is part of my DNA......grin if you must!

ADDITIONAL SUPPORT POST INSTALLATION

I doubt I will ever install a clear polycarbonate baffle system, since I wasn't impressed with the one I installed earlier, which muted the volume and tone in my humble opinion.  I did add a cross brace glued in place for the center support post and countersunk a 1/2 inch diameter hole for the support post.  I could have easily gotten by with a 3/8 inch diameter post or smaller, but I like to go into the overkill mode most of the time.

I glued a short block in place to support the rear post, of which I didn't glue the support post in place, since I will need access to the jack hole already drilled into the tailpiece block.  If the 1/4 inch jack is short enough, it would not be a problem, whereas the pickup should arrive tomorrow via Priority mail from Beard Guitars, LLC.  I went ahead and ordered a Beard # 14 spider bride which has four set screws to keep the Fishman bridge pickup inserts in place.

PICKUP INSTALLATION

According to Beard and Fishman, a 3/16 inch diameter hole is drilled at an angle in the rear of the ledge adjacent the resonator cone to allow the two pick up wires into the body of the guitar to solder to the 1/4 inch jack which will accommodate a balanced configuration, however only the tip and sleeve are used.  A small hole is drilled underneath the footprint of the tailpiece to allow the braided cable ground wire to contact the tailpiece, of which the braided ground wire is mounted underneath the tailpiece near the end pin screw which keeps it tight in place against the conductive metal tailpiece.

I had Nate Martin of Beard Guitars, LLC to fit the pickup inserts to the spider bridge and slot the inserts for D'Addario J42 medium gauge strings using 2.250 string spacing with the first string being .018 inches in diameter which is the same diameter as the 2nd string.  With the depth of the ledge of my guitar, the bridge insert height was specified as .582 inches which has the strings about as high as you can go without touching the resonator cover plate hand support, which puts adequate downward pressure onto the resonator cone.

I received the Fishman pickup, spider bride and the Fishman Jerry Douglas Nashville Series Aura Imaging Pedal and it didn't take too long to install the pickup.  I planned to install a rear vertical support post in front of the tailpiece block, but the 1/4 inch jack was too long for that.  That post probably would have been my normal overkill, therefore everything worked out OK nevertheless.

A couple holes were drilled into the body of the guitar; one for the pickup leads from the bridge inserts and one under the tailpiece footprint for the braided ground wire to attach beneath the tailpiece.

Beard Guitars, LLC definitely knows more than a thing or two about shipping parts, etc.  The # 14 spider bridge and pickup inserts were totally isolated with packing materials, of which you definitely need it like that when dealing with any of our US Shipping carriers.........grin if you must!

The 1/4 inch jack has a detachable sleeve that goes over the exposed threads in case you want to install a sling.  I already have a sling base for a detachable sling attached to the tailpiece screw, but installed the sleeve anyway since it looks better and offers additional protection to the jack.

I double checked with the multi-meter to be certain I had continuity between tip portion, aka signal lead and had a good solid ground between the sleeve portion of the jack to the tailpiece before reassembly.

According to Padellara of Fishman, there is no normal resistance on a capacitive device. It will test as an open circuit, but I wanted to make certain there was no short between the hot lead from the passive pickup to the shield ground wire.

READY FOR THE ACID TEST

In summation, I am totally stoked with the way the Fishman Jerry Douglas Series, Under Saddle  pickup performs.  The reso sounds great without plugged into an amplifier/PA system and is light years ahead of Fishman's older model piezo pickup disk that attached to the resonator cone via a pressure sensitive adhesive strip.

I am having a problem with the high G string, which seems to be producing overtones or harmonics and sounding wiry when played open, but not as noticeable when played away from the nut.  I checked the nut slot and everything looked ok.

I talked with a resophonic legend named Bobby Wolfe at Davidson, NC on 07-19-17 who has been making resophonic guitars for many decades and discussed what I had done removing the sound well and he said I needed to beef up the area around the tailpiece since there is at least 200 psi pressure there due to the string tension.  Bobby also gave some recommendations as to the set-up.  He said he had never run into a problem with the high G string producing those wiry overtones or harmonics played open and will have to keep checking until I can find a cure for it.  Whatever it is, it definitely isn't obvious. 

When running the guitar straight into the PA system, it was excellent, however the Jerry Douglas Signature Series Aura Imaging Pedal gives that authentic microphone sound of the resophonic guitar and is a must if you wish to stay away from a microphone and still be heard with that resophonic signature sound.

Now, to get some serious practice aka "Practising" in as Gary Cooper stated in the movie, Sgt. York.

BEEFED UP THE TAILPIECE BLOCK SECTION

I removed the tailpiece, cover plate, bride and resonator cone after releasing tension from the strings.  I placed masking tape around the tailpiece to keep the strings in place at the tailpiece when planning to use the same strings when setting everything back up.

In my spare resophonic parts box from the year 2000, which consisted of an extra steel fan pattern cover plate chrome plated, an OMI brass chrome plated tailpiece, 1930s # 14 spider bride with the narrow slot which I believe came out of Ray Atkins "white face" Dobro and several tailpiece blocks that were 3 1/4 inches square x 3/4 inch birch plywood which would be ideal to glue in alongside the existing tailpiece block which will strengthen the top at the tailpiece and help prevent the top from caving in due to the 200 lbs. plus pressure there.  I had to grind a small radius on one edge of the lower block where it could be angled into place and then pushed into a vertical orientation as the original tailpiece block.  I used Titebond Ultimate III glue.  The block on the left was very tight and the block on the right wasn't as tight but tight enough for the glue to do its job.  I put a couple guitar makers clamp in place for some extra force, of which I don't think it moved the top/bottom to the blocks if any, because of the two angular upright posts installed. 

I also added a couple angular supports after the additional tailpiece blocks between the top resonator cone ledge to the small block I glued in place before installing the Fishman under the bridge pickup.  Their placement, will allow access to the pickup jack in case I decide to remove the pickup at some point in time.

I put everything back in place and brought the strings up to pitch, which should exert some downward pressure on the two additional tailpiece blocks and upright support posts.

The open G string overtones will no doubt be a "dawg" to find and hopefully will find and fix the problem.  It could be some weird resonant frequency of the entire guitar or might even be the resonator cone, but doubt it is the resonator cone.

FISHMAN PICKUP FAILURE - 07-21-17

I tried everything I could to locate the source of the G string overtones without success.  A few days ago, I noticed that the low B string sounded muted and was hoping that it wasn't the guitar body remodeling causing the issues.  I decided to take the Fishman pickup out along with the Beard # 14 spider and put my original spider bridge which had the ebony/maple inserts back in the reso and go from there.  I originally had the ebony portion under the strings, but the tone was too bright and slotted the maple portion of the bridge inserts and had the ebony portion in the bridge slots and the tone was much better; not as bright.

Upon removing the cover plate, I noticed that the top black portion of the insert for strings 6,5,4, the top portion of the insert had just about come totally unglued from the maple bottom section with the piezo ceramic sandwiched in the bottom half as it appears to me.  It appeared to be a glue failure!

I called Beard Guitars, LLC and talked to Nate Martin and we decided to send the entire spider bridge and pickup back to them, of which they would send the pickup back to Fishman for analysis and Beard would replace the pickup and fit it to my specifications to the Beard # 14 special spider bridge as originally ordered.

Nate emailed me a Priority 1-Day shipping prepaid label and I got the package in our Post Office in short order this afternoon.

I plan to install my original spider bridge back into the guitar to ascertain that the above issues have disappeared.

I didn't take the time to get a pix of the broken Fishman pickup.....my bad!

Beard, LLC received the mailed packed on 07-24-17.

INSTALLED ORIGINAL SPIDER BRIDGE AND INSERTS

I installed the original spider with the ebony/maple bridge, of which I had the ebony portion on the bottom of the spider bridge slot, since with the ebony under the strings, the reso sounded a little too bright for my ears.  The maple under the strings sounded better to me.

I still had the wiry overtones on the 3rd aka high G string, but not as bad as with the Fishman under the saddle pickup installed.

My very good friend Jim Yarboro of Gun Barrel City, Texas calls that wiry sound a rattle.  To quote him, "I called it a Rattle, it makes you Rattled when you can't get it to stop."  And that is a fact for sure!

I plan to make a set of solid maple inserts and make a temporary nut for the 3rd string to try and isolate the problem.  There are several variables that have to be eliminated; one at a time to get to the bottom of what is causing the wiry overtones and/or harmonics for that string only.  Hopefully, it will not be the modification that I did to the sound well.

I found a piece of 40 year old plus hard tight grained maple in my Kennedy machinists tool box big enough for the spider bridge inserts and will install them at a later date: the Lord willing of course.

I have learned a valuable lesson from all this, "If it ain't broke, don't fix it."

Web page updated by Bill aka Mickey Porter on 07-19-17, 07-21-17 and 07-22-17.  

LEAVING ON A SPIRITUAL NOTE

If you do not know Jesus Christ as your Lord and Savior, please take this moment to accept him by Faith into your Life, whereby Salvation will be attained.   

Romans 10:9 “That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved.”

Open this link of Bible Verses About Salvation, King James Version Bible (KJV).

Hebrews 4:12 “For the word of God is quick, and powerful, and sharper than any two edged sword, piercing even to the dividing asunder of soul and spirit, and of the joints and marrow, and is a discerner of the thoughts and intents of the heart.”

Romans 6:23 “For the wages of sin is death; but the gift of God is eternal life through Jesus Christ our Lord.”

Romans 3:23 “For all have sinned, and come short of the glory of God;”
 

IN GOD WE TRUST - GOD BLESS AMERICA - "FOR GOD SO LOVED THE WORLD, THAT HE GAVE HIS ONLY BEGOTTEN SON, THAT WHOSOEVER BELIEVETH IN HIM SHOULD NOT PERISH, BUT HAVE EVERLASTING LIFE"   JOHN 3:16 KJV 

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