Coverplates and Tone

[robn]

I've been wondering what effect different coverplates have on guitar tone? I note that many of the better quality resos seem to have heavier cover plates which are made of machined steel or plated brass. My cheap reso has a very light pressed, chromed steel coverplate. Recently I modified the plate by adding Scotch Pressure Sensitive Tape to its underside (not over the holes), which has added weight and deepend and "cleaned up" the tone (and stopped the plate from ringing!!!)



I know that many forum members are reso builders - What have you discovered about coverplates and tone?

Robn

[snakehips]

Hi there !
I'm not a guitar builder but I'd say this - I don't believe the coverplate material or thickness makes any difference at all (well, at least compared to the rest of the body, the biscuit, the reso cone and strings).

However, I do think that the total surface area of holes would make a large impact - changing that - as it would alter the amount of air movement. Same wth the f-holes / tricone grills etc.

[mirrormist]

Hello robn

I have yet to take one apart...you have certainly done a neat job with the tape though:)

Regards

Anthony

[LouisianaGrey]

It will certainly make a difference - anything that you change on a guitar will make some difference - but I'm skeptical about whether the difference is significant enough to be really noticeable, especially on a wooden bodied instrument like the ones I build. I've never noticed any coverplate ringing but then I'm usually damping the coverplate by resting my hand on it anyway. The skeptic in me says that it's really the act of taking the guitar apart and putting it back together properly that causes the improvement in cases like this. It's a cheap experiment to make, though, and maybe it will make a difference to someone's guitar because they're all different.

Even the air hole size has a limited effect, I believe. I know that on some dobros taking the screens out makes a difference to the sound whereas on others it doesn't, so I suspect that there's an optimum size for each body shape and once you reach that then it doesn't make any difference if you make them bigger.

[Michael Messer]

I agree with Pete, that it is possibly the taking apart and putting back together that improves things. Also, the metal tape is heavy and could have a dampening effect on the tone. So possibly Robn is right too. In theory, everything affects the tone of a guitar, but how much and what it does is debatable. The good news robn is that you are happy with the results of your experiment.

Shine On,
Michael.

[Deleted]

Robn

I reckon you've probably just modifided the natural resonance of the coverplate and dampened out some unwanted overtones. Making any changes to an instrument will make some alteration to the sound, but whether you can detect it is another matter. As Pete says, changing the soundhole screens can make a difference...just strike an open chord and then cover and uncover the sundholes of your reso (biscuit or spider)..you'll notice a 'wah wah' effect as the bass overtones are cut then restored..the cone itself tends to push out more of the trebble tones, so the holes in the coverplate will contribute to shaping the overall tone (in crude terms, the body and soundholes tends to act as a 'bass reflex' chamber).

I think that what Robn has done will not make any major difference to the tone, but as I say, it probably has cut down some of the unwanted sypathetic vibrations emanating from the coverplate. A reso guitar is a complex hybrid system, and minor tweeking can either improve the tone or wreak havoc with unwanted rattles and buzzes.

By the the way Robn, good luck fitting the new maple saddle, the blanks should be with you shortly. John.

[andys]

I have made a good few solid bodied resonators all with biscuit bridges. My telecaster based ones use stock sieve chromed metal cover plates. I have made others using plastic coverplates especially on ones with small bodies where standard coverplates dont actually fit. I think that most of the change in tone comes from the size of the holes in the coverplate on these guitars rather than the material it is made from. I have made a small bodied one, which has a mirror-plastic coverplate, which has large slots cut out of it, its sound projection is great from the front, but bear in mind that unlike hollowbodied resonators, I make my guitars with soundholes in the back too. The size, and pattern of these has an effect on tone too. My first one I made I just used black plastic and because the cone stands out more from the front, because of the thin depth of the body means that there is more of a gap round the biscuit, so more sound comes out.

So my personal take is that the size of the holes seems to have more of an effect on projection and tone than the material it is made from.

When I am setting up guitars to get the action and the string spacing etc, I do this with just the cone in place, without the coverplate. This gives a great tone, and good volume and projection, trouble is it looks awful. It always seems a shame to muffle the sound, yet aesthetically you have to do it. Maybe some of us have got "recording" guitars without coverplates!!! Coverplates are mainly for a combination of protection and decoration, in my humble opinion, and other factors have more of an effect than coverplate material.

Maybe others have differing views, but these guitars have never been an exact science

Andy S

[robn]

Wow, lots of thoughts on offer - yet another area of reso playing where there are no rules, only what works in practice. I think the world of resonators must be populated by anarchistic pragmatists, if there is such a thing

ChickenboneJohn, you are right about the mod I did getting rid of unwanted overtones on that particular coverplate and on that particular guitar.

I received the maple saddle blanks yesterday - Thanks

I shaped and fitted one to replace the ebony capped saddle I had on my Resound Blues. The bass tone improved dramatically on the bottom 4 strings but I was dissapointed in the loss of sustain on a couple of the strings - and the 1st string was completely dead. Then, as I was making some adjustments, I brought the 1st string to pitch out of the saddle slot I had cut and suddenly I had great sustain and sweet treble I had a little lea way so recut the 1st and second string slots - Magic ;D

I slightly adjusted all the slots and recon that I can get even more sustain across all the strings on my next attempt - Any tips on cutting slots that will save me some trial and error? I can't belive the significant difference in volume and sustain that such fractional adjustments in the slots seems to make

Incidently - the tone difference between an all maple and an ebony capped saddle is conciderable on my guitar. I'm getting more bass, sweeter treble, more individual note clarity and less slide noise using maple. My guitar certainly doesn't need the the added "briliance" of an ebony capped saddle.

I should have a piece of boxwood comming from Dave King in a few days so I'll be giving that a try as well.

Robn

[Deleted]

I usually cut the slots using a straightblade scalpel rather than a file, and put a little backslope on the slots, running down towards the tailpiece so the strings are breaking right over the front edge of the saddle. Sounds like on your first try the strings may have been damped slightly in the slot, and not vibrating from the leading edge of the slot. If the string is bearing in the middle or back of the saddle, the string can make contact with sides at the front of the slot, causing this damping effect. As you've discovered, the diferences between getting a clear tone and a muffled one can depend on really tiny variations in the saddle slot. Also getting the saddle closely fitted in the biscuit is essential for proper transfer of vibrations from string to the cone. Sounds like on balance you've got it pretty well OK, it can be a frustrating thing to do if its not right first time - and yes, it can be a handy comparision to just pop the string out of the slot onto the top of the saddle to check the sound.

[robn]

Thanks for the tip John,

I can see the benifit of using a blade to get a clean finnish on the slots. Three of the slots on my first effort could be greatly improved with a blade

The original bridge saddle had the strings resting at the rear with the slots sloping down and widened towards the front of the saddle - I think that this was to improve intonation. I've seen pictures on the web of saddle slots cut with the slope to the rear, as you sugest, and to the front (the Stewmac resonator guitar assembly instructions). Confusing or what! I think I need as much scale length as I can muster to help the intonation on my guitar.

What about depth - are you looking for about half the string to be proud of the saddle? I think that some of mine on my first effort may be a bit deep.

Robn

[marshcat]

John,

Interesting about the "backslope" on the slots. For the last 20 years, I've been doing the opposite - cutting a "frontslope" running towards the neck, avoiding string contact with the sides by giving the slots a V profile. It was once explained to me that as a result, the string is still vibrating over most of the saddle, imparting more vibration to it. It works for me, but just goes to show once again that there are no hard and fast rules...

[Michael Messer]

Most people working on Nationals and Dobros these days do a 'frontslope' on the string slots as Marshcat has described. This has become accepted among luthiers & repairers as the correct way of setting up a resophonic guitar.

Shine On,
Michael.

[Deleted]

Interesting point about which way you cut the slope on the saddle..one thing about doing the 'frontslope' is you get a very clean break off the back of the saddle, and I can see it being marginally more stable and efficient as it will put more of the cross section of the saddle under compression. Whichever way you do it, you do need to be careful about getting the right shape for the notch so that the string doesn't foul the side of the notch when vibrating..giving you that muffled tone (or a buzz).

[robn]

New maple saddle shaped and fitted ;D

I cut the forward slanting slots with a small, sharp triangular file (I didn't have a steady enough hand to use a knife!) and used different size needle files to seat the strings to half depth. All the strings are singing cleanly and I'm getting better sustain than from my old ebony capped saddle - which I didn't expect. It looks like getting the saddle slots right really helps volume and sustain.



I'll be interested what difference a boxwood saddle makes to the tone compaired to this maple saddle. The cone is a Quarterman - I may try a National but will have to use the biscuit you can see in the picture as the saddle slot is offset about 4mm to the rear of centre to get the intonation right (the sign of a cheap guitar!).

[Michael Messer]

Robn, you have done a great job (Nice photo too!). It really does make a difference to do these things correctly.

I hate to tell you but the offset bridge-saddle will eventually collapse your cone and it can't be helping the sound. So while you are doing this work I recommend you change the biscuit for one with a centre slot for the bridge.

To get the intonation in tune one should move the cone around in its well, not move the bridge off-centre on its biscuit. Luckily your Quaterman cone is too thick and rigid, so it may hold up, but with a National Reso-Phonic cone I do not believe it would be good to leave the offset bridge-saddle.

One thing’s for sure – by doing this you are learning a lot about the value of a correct set-up, even on a budget-priced guitar it makes all the difference.

Shine On,
Michael.