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I have just finished carving the bridge for my 2nd instrument . It is a WRC top Qld Maple back and sides, dread. My concern is that after sanding it tips the scales at 40g . It is very heavy ebony in comparison to the EIR I used on No 1. Just wondering what you folk would recommend . I would like to stay with ebony to match the fingerboard and headplate.
Thanks

Craig.

Craig buddy you are fine. Several years ago I weighed a bunch of Martin bridges and yours weighs in the range of what I saw for ebony bridges.

There will be some who will give you grief for using an ebony bridge over say a rosewood bridge but I say let them drink paddy water......

OK, let me get my prejudices out of the way first, I don't like ebony as a bridge material. Somewhere back in the archives from about four years ago or so I posted a piece about some tests we did in my lab on the sound wave transmission characteristics of various woods used for bridge material. Every sample of ebony we tried (not counting macassar here) had the highest level of damping that we measured. One thing is sure we don't want the bridge to be damping energy transmisson to the top. The best was BRW, followed very closely by Madagascan rosewood.

Now to answer the question, I usually aim at 25gm bridge weight (30gm maximum), for a steel string bridge, 20-25gm classical. So, to my way of thinking, the bridge is of the wrong wood and much too heavy.

Well you did ask .

And yes Hesh I will give grief over using an ebony bridge, why use a material that is not the best for the job, colour is the least important consideration, fitness for purpose on a musical instrument is.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

Colin my friend no argument here from me regarding the fact that ebony has higher dampening and like you I also subscribe to the school that says that we should be using woods with the highest "ping" values.

But..... many outstanding sounding guitars have been built with ebony bridges and I suspect that although the ebony bridge is indeed a less then optimal component in my way of thinking a builder's abilities to approach guitar building from a systematic approach may and often will compensate for bridge weight and material with bracing, bridge plate material/size, and top selection. In addition, a BRW bridge may weigh nearly as much as an ebony bridge depending on the specific samples of either.

Color, or colour...., never entered into it in my way of thinking.

The weight of the bridge will affect the tone. I never go higher than 30grams. You may be using a fairly large footprint as well as a dense wood. In the photo it looks to me like your design extends back from the saddle a fair bit and stays a little fat through the transition to the wings. A standard Martin bridge is 1.5" I think, and I make mine a little skinnier.

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David White, Toronto

"All my favourite singers can't sing."

A Dread. with a cedar top & Maple sides & back !
A little extra damping might be called for.

Just an opinion!

Mc

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Mike Collins

That's Queensland Maple Mike. Sounds more like Mahogany than Big Leaf Maple.

I reckon it's a bit on the heavy side Craig and I'd be trying to get another 5 grams at least off it. You'll lose half a gram when you countersink the bridge pin holes.

Colin, can you remember from those bridge studies how much attenuation and at what frequencies? I'd be interested because I'm using an ebony bridge on a guitar I'm building at present to tone it down a bit in the top end.

Cheers

Bob

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Bob Connor
Geelong, Australia

It could be argued that damping in a bridge material might be a good thing. Maybe it could help reduce some of the harsh metallic overtones that sometimes plague the steel string guitar. Maybe the damping characteristics of ebony would help EQ the tone of the instrument in a good way. Sure you might get less output overall, but maybe it would be a "better" tonal balance.

???
Mark

Colin,
I'd also be interested in knowing where the Macassar Ebony landed in your test's. Don't want to hijack this guys thread though. Maybe you could post the data in another thread?

Suggestion on the bridge weight...change the design by removing material from the outside profiles. You might have already thought of that and chose aesthetics over weight.

Chris

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There is no difference between the man that thinks he can....and the man that thinks he cannot.

Bob, I've been trying to search the archives but can't find it now ( I do find the search facility a little 'challenging') but certainly it will be the higher frequencies that are attenuated most as they are lower in initial energy, though all frequecies will be affected it will seem more marked the higher they are. I'll see if I can dig out the raw data again, though I'm about three computers down the line since then.

The point is once the damping takes place, nothing you do to the top or bracing will bring it back.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

The issue of ebony or rosewood for a SS bridge is doing a lot of circles in my head lately because i am planing on building a guitar using my classical shape and mold, but X braced and with light steel strings.

If we compare a pyramid rosewood bridge with a belly ebony, the first can weight even less than 20! all the other things equal, this would make a dramatic change in tone.

My "gang" has this old overbuilt (3mm top) Carpathian spruce/maple classical with steel strings we use as campfire beater. Quite a loud beast. It originaly had a lifting maple bridge and plastic saddle which i replaced with a nicely fitted rosewood one and a bone saddle and now it is even louder and the high strings are simply ear hurting inside a room. But outside it probably is chasing away all bears within miles.

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Build log

Mark makes an excellent point... and I have certainly experienced the metallic overtone blues with BRW bridges. For the past 6 guitars, I have been making a PTME (Proulx Magic Tone Enhancer) brace that is designed to fit just behind the bridge plate. It is intended to be glued in place (or not) sometime after the guitar has been strung up and played for awhile. In each of 3 cases where the tone "just wasn't right" I installed the brace and it made a significant improvement in my assessment. (thank you Mario) Until Mark mentioned "harsh metallic overtones" I was unable to define the issue. (thank you Mark)

It was specifically due to the data from Colin, our resident seismologist, that I stopped using ebony. (thank you Colin) My weight goal for bridges has been 25-30 grams and I'm happy I bought enough BRW bridge blanks to last my lifetime of building. (thank you Zootman)

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JJ
Napa, CA
http://www.DonohueGuitars.com

I'll happily get you rid of those brash sounding Braz blanks

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Build log

Mark, what you are doing is losng information right across the spectrum of the guitar, harmonics of the lower notes are also dampened. In effect it's like putting the guitar into soft focus, while the image is still there a lot of what makes the picture is gone. Get all of the imformation into the box, then adjust the output as you want to.

Chris Macassar is a pretty good bridge wood, right alongside EIR.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

I'm with Blanchard on this. My guitars actually improved tonally after a client insisted that I use an ebony bridge on his guitar. Previously I'd been using Brazilian. The change was dramatic -- less stringy, better low-end. My bridges are closer to the 38 - 41g area (heavier for baritone bridges because of the extra saddle slope) and they don't suffer for the sonics. I can think of a lot of examples of exceptional builders who choose to use ebony for their bridges. We can discuss all the measurements we want, but the resulting guitar is the arbiter. Traugott, Manzer, Threet, Blanchard, Wingert, Matsuda, Sakashta, Beauregard, and so on all use ebony for their bridges. Some of their footprints are smaller than others. They're not suffering for using ebony.

I'd suggest that there is an argument to be made for a lighter, Brazilian rosewood bride on a classical guitar because they have so little energy and need high end.

And I am with Mark and David on this one as well.

I have two OMs that were built identically, braced the same, etc. One of the few differences is the bridge, one is ebony and one is BRW. Many folks have played these two guitars side by side and the jury is very much divided. Some feel that the ebony bridged guitar has better balance and some feel that the BRW guitar has more string noise and is a tad brighter. Personally I tend to agree with both of these assessments.

Material choice can be used to a builder's advantage - clearly.... and there are times when brightness needs to be toned down.

Being the master of psycho-acoustics here..... I have also noticed a reduction in the string noise that was problematic on an adi topped dread by nixing the bone bridge pins and replacing them with ebony pins with higher dampening.

BTW on the OM with an ebony bridge the bridge weighed in at 39 grams where the BRW bridge weighed in at 36 grams.

Again as a general rule I typically will go for any material that pings better but Mark's point is a very good one and careful material selection can help tune a sound to something more desirable.

As always, "better" is subjective.

I remember distinctly discussing some fossilized mammoth tusk with a bowmaker friend, essentially dismissing it as tonally inferior to bone because it seemed softer and more flexible across the board. His reply of course was "why is harder better?". My answer was of course less damping, more efficient transfer of vibrations, etc.
His reply again was, "yes, but why is that better?"

Of course if you want the least damping across the spectrum, most efficient path to the top, etc., ebony might be inferior toward that goal. Taking the argument that low damping and efficient transmission is invariably "better", and you'll quickly have to place BRW as inarguably inferior to any number of synthetics I'm sure.

That's not to say I don't personally agree in a preference of rosewoods over ebony, but it's tough to make an argument that all damping of frequencies is "bad" in shaping an instrument's tone.

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Eschew obfuscation, espouse elucidation.

I've noticed that heavier, stiffer bridges also dampen the metalic string noise. My favorite bridges are BRW or Cocobolo in the 40g range. Gives me the clarity without the brashness. But my bridge patches are often smaller than average too and that also plays into the equation.

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http://www.chassonguitars.com

I think Colin is absolutely right for classical guitar bridges; there's less energy to waste, and you can't afford to lose any treble.

Steel strings have some energy to burn, and as some have said, it can be pleasing to attenuate some high frequencies, especially string noise that is not in the note's overtone series.

One thing not yet mentioned is the bridge's function as a device for mismatching impedance. If there were a perfect impedance match, the energy of the string would transfer instantly and then die--a kind of "wolf" note (this is an important way that a guitar differs from a loudspeaker, which has constant power input and gains in volume for a given power input with a good impedance (electrical) match; it's also one of the major errors that Kasha made in his approach to bridge design). If damping is not also increased, an impedance mismatch will not cost any energy, but will spread out its transfer over time--in other words, increase sustain, and more so in the treble than the bass. The difference this makes can be readily heard in the long sustain (and powerful trebles) but very low acoustic volume of a solid body electric guitar (of course, the acoustic is also losing energy to the air, internal losses throughout the box, etc.).

Next, mass has a relatively greater effect on impedance in the treble frequencies, and damping a relatively greater effect on it in the bass. But damping causes a loss of vibrational energy--it's converted to heat by internal friction. If you wanted to smooth out harsh transients in the treble but not lose the initial volume of the bass, you could get this by raising bridge mass without raising damping. With wood you can't add one without the other, but a more massive bridge of lower damping material would come closer to this than using a material with both more mass and more damping.

Which brings us to ebony--high mass and high damping. An increase in impedance all around. More sustain with loss of the quick transient in the treble; some increase in sustain with an overall loss of energy in the bass, but probably heard mostly as a slower rise in the volume. The effect compared with a rosewood bridge is a guitar that has less harsh pick and finger noise (relatively sweeter trebles) and more treble relative to the bass as the note rings, plus an overall increase in sustain (even though the transfer of energy to the air is less in total, it is not so front-end loaded). A classical can't afford the losses; a steel string can, if you like the sound.

Which is not to say ebony is an improvement on rosewood. It's a different envelope. My own preference is BR, with less concern for keeping the mass down on a steel string than on a classical. A little more mass will sweeten the treble without causing as much loss to damping as with ebony. BTW, I've used African Blackwood on a couple of very successful steel strings. I haven't done any testing on damping, but it's heavier than BR, and my conjecture is that the damping is a lot lower than with ebony.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

Well there's allot of opinions !

BUT-Is this a "fingerpicker"-or a "flatpicker"-or a all around Bluegrass
screamer????
let's start back at the beginning !
Cedar top-how thick & stiff?
How did you brace it????
How deep is the box (and loose)
What were you trying to make????

Then decide what bridge to put on it!!!!

I decide every aspect of my guitars BEFORE I make them !


Mike

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Mike Collins

If we want to maximize efficiency and minimize damping, we shouldn't even be considering wood soundboards.

Everyone should be playing 6 string banjo guitars with tight clear heads and massive tone rings - there's your maximum horsepower right there.

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Eschew obfuscation, espouse elucidation.

Didn't I just say that?

Thanks for the physics lesson. Gotta love those rare moments when theory jibes with experience in the guitar world.

One question though. When you say...If damping is not also increased, an impedance mismatch will not cost any energy, what is the "also"? Are you just saying an impedence mismatch alone doesn't cost energy unless you increase damping?

Fortunately, this is also one of the few things in lutherie that's easy to test. Just add or remove some mass from an existing bridge or pull off one bridge and put on another. And unlike tweaking the bracing, the effects on tone are fairly universal. It just becomes a matter of deciding what sound you're after.

Also, one reason my bridges are shaped the way they are is so I can easily adjust the weight for different species without changing the thickness at the saddle or the footprint. Something to think about in bridge design and a good reason not to jig up too much in bridge production.

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http://www.chassonguitars.com

Sorry for the lack of clarity. I meant if only mass is increased, without any increase in damping. Yes, it will not cost energy; just spread its release from the string to the guitar out over time. Since all wood has some damping, changing one without changing the other by adding or taking off wood is not going to happen in practice; it's more like you can change the relation by the choice of materials--e.g., adding mass by using African blackwood allows a mass increase with proportionally less of a damping increase than you would have adding the same mass by using ebony.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

Thanks everyone for your help on this one. I had an idea that the bridge specs were an important part of shaping the response and tone of the instrument but I can see from your responses that it is probably more important than I first imagined.
Hesh thanks for the reassurance , I'v managed to knock another gram off and I'm planning on slotting the bridge so should be around 38g final weight. It is a reasonably large footprint 6.5 inches x 1.55in at the widest point.
Mike the top finished up at just under .125 .Felt reasonably stiff compared to the ADI top on my first instrument. Bracing was all 1/4 sitka . Just under 3/4 high at the X and tapering down to .4 in about 3in from the sides. Tone bars tapered from .450 down to .300. Finger braces were .350. I wanted it to be a bit of an all rounder. Strum and fingerpicking.
Bob is correct in that QLD Maple is not a true maple and to me it has it's own unique sound .Definately closer to a mahogany sound than maple though.
Thanks again folks for your detailed and thoughtful responses. This info will go into my reference folder.

Regards

Craig

Howard Klepper wrote:
"Next, mass has a relatively greater effect on impedance in the treble frequencies, and damping a relatively greater effect on it in the bass. "

It took me a long time to find the handle on impedance, so I may be wrong, but I disagree with you on that one point. One way I found helpful to think about it is to use the electrical analogy.

First: 'impedance' is the AC equivalent of 'resistance' in a DC circuit. DC resistance is a measure of how difficult it is to pass a current through a wire. Impedance measures how hard it is to pass an AC signal through a circuit at a particular frequency. The frequency dependance is important.

Several things can add to the impedance of an electrical circuit. We all know that putting a current through a wire creats a magnetic field: as the current builds up some of the energy is taken out of the current and stored in the magnetic field, to be 'given back' as the current dies down. Thus 'inductance' resists changes in current. Similarly, a capacitor stores some energy in the form of an electrical field ('static electricity') when there's a voltage change, and so a large capacitance opposes changes in voltage within a circuit. Good ol' resistance opposes the current all the time. Generally speaking the effect of a given inductance will be small at low frequencies, and larger as you go up. Capacitance has a large impedance effect at low frequencies, which drops off as you go up.

If you use the analogy that voltage>force and current>velocity, then inductance>mass and capacitance>1/stiffness (a large capacitor is like a soft spring). Resistance>friction, or damping in wood. Using this analogy a heavy bridge should block high frequencies, while a stiff one should block low ones.

The usual measures of damping in wood (or in electrical circuits, for that matter) involve either the 'Q-value' or 'log decrement'. These are actually inverse numbers: Q=1/log dec, iirc(sometimes you see 'pi' in there, depending on whether they're talking about frequency in Hz or radians per second). In log dec you figure out how many cycles it takes for the thing to lose half it's energy at resonance once the power is turned off, in Q value you look at how far off resonance you have to get, driving with a constsnt power, to drop the driven amplitude in half. Q gives you the proportion of energy lost per cycle: a top that has a Q value of 50 loses 1/50th of the energy in it for every cycle of vibration.

If the Q value of a material is inherent, and the same at all frequencies (neither of which is likely to be strictly true, but probably close), then the higher you go in frequency the faster the vibrations die out. Thus a low Q material (high losses) will tend to 'eat' high frequency energy faster. Cardboard is 'deader' than Brazilian rosewood, which is 'deader' than glass.

It is not at all clear to me how the damping factor of a bridge wood would effect the tone of the guitar. Sure it 'ought to' if there's enough of it, and it's bending enough, but the bridge does so little compared with the top, or even the back, that it's hard to assign a definite role, in my mind. I tend to think the mass and stiffness are pretty important, and pay less attention to the damping. I could be wrong: it wouldn't be the first time.