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I have been reading conflicting posts on bridges and bridge material. Some posts indicate that lighter bridges are better. I have seen posts where people are using bridges in the 20 g range for steel string guitars. Other posts indicate 20 g is to light and a weight of 35 g or so would be more appropriate. I read that Trevor is using bridges that way below 20 g.

Grumpy recently posted that he had been using Brazilian rosewood for his bridges (a very a light would ) but because of export restrictions is now using African Blackwood (a very dense wood). If light is better, how come so many guitars, even from high-end makers, use ebony, a wood without a good tap tone, for bridge material.

What are your thoughts on bridge weight and bridge material?

Thanks,

EddieLee

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EddieLee

Brazillian rosewood is hardly 'very light'...

Have a look at this paper by Trevor Gore, page 17. It gives you his reasons behind his bridge designs.
http://asadl.org/poma/resource/1/pmarcw ... ypassSSO=1

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In general, no. But compared to African blkwood it is.

i wouldn't say ebony "has a poor tap tone"...

i don´t know... i guess each maker uses the bridge as part of a system. Trevor uses his own bracing design, with carbon fiber reinforcement and such, so maybe his requirements are different? i don´t build steel strings, but the requirements there are different from classical guitars. in the classical world i´m yet to come across an ebony bridge, but steel strings have more "horsepower" and much more high frequency energy present in the signal, so ebony might be an alternative if you´re chasing a particular type of sound.
at least it´s the sense i make of it - i´ve only used indian and madagascar rosewood, FWIW.

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member of the guild of professional dilettantes

Peter - Thank you for the article. I found that very informative.

I weighted different woods commonly used as bridges. I have a few species of ebony, and rosewoods, along with African Blackwood. In general the Blackwood and Ebony are much denser than the rosewoods. However, the BRW is slightly denser than the Honduras rosewood or EIR I measured.

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EddieLee

It's kind of like asking which tire is better for your car. There are some known performance characteristics about tires but it really depends on your car and how you want to drive it. The bridge is part of a complex system and it's hard to make blanket statements.

The good news is that it is relatively easy to experiment with. Glue a heavy bridge on with a glue with a low release temp, shave it down a couple of grams at a time, listen as you go. I suspect will will hear the guitar get more and more lively until the point that it looses discipline. Remove and replace with one in the weight range you like.

You can then experiment with different species to see the effect of damping.

FWIW, I designed my bridge shape so it was easy to adjust the weight by increasing or decreasing the bevel on the trailing edge. That way I can use different species but keep whatever weight I want.

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http://www.chassonguitars.com

It's unfortunate that we get caught up in 'better or worse'. It would be more correct to say 'different'. Each wood has different damping effects. Damping is not necessarily
a bad thing. If you use it to bring out the sound you want, it is a good thing. While many people feel that ebony is best for players who use a flat pick and strum and rosewood is better for note separation and players who fingerpick, some feel that Macassar Ebony gives you the best of both worlds. You really have to build a number of guitars changing that one feature before you can decide what sound YOU want to get out of the instrument.

me too - great minds think alike!

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Jim Watts
http://jameswattsguitars.com

The three factors that effect the tone implications of bridges.
1.Damping
2.Stiffness
3.Weight
And not necessarily in any particular order.

While the suitable candidates for bridges will vary in how much damping effect they have,I try to select for low damping but not at the expense of weight. Considering the thickness of the bridge and the total sandwich in that area,I don't see stiffness as a problem to consider at all especially for conventional X bracing.Trevor G. puts forth a different case for his Falcate bracing and no doubt rightly so. To me weight is the primary thing I'm concerned with and that was an eye opener a number of years back when my bridges were substantial belly bridges. Not liking what I was hearing from a certain guitar,I took the block plane to the back belly section of the bridge and also lesser so to it's overall height. I was amassed at the increase in responsivness and the change of tone. I have repeated this lightening on a number of guitars with basicly the same result.Since then I have tend more and more to trying to go light with bridges and am pleased with result.So I concur with Kent's comments.

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A person who has never made a mistake has never made anything!!!

I changed my first steel string guitar's ebony bridge for padouk because the tone was little bit too tight and lacked low end (maple back and sides definately played a big role in it).
Original bridge weighed 36g and the new bridge came out 19g.
I can't say that the difference was huge but I would say it was better after the swap.

Thanks everyone. The stories of your experiences is a real eye opener.

EddieLee

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EddieLee

Another take:
'Damping' often gets used rather loosely in these discussions, with anything that cuts down on the amplitude of vibration being called 'damping'. Technically, damping refers to how quickly the material dissipates energy: materials with low damping have long 'ring' times when tapped, and more tightly defined and 'musical' resonances. I know some folks in this discussion are using the term right, but I'm not sure everybody is, and want to clarify that point. My apologies if everybody was right all along.

The way I see it, the primary function of the bridge is to tell the string how long it is, so that it will know what note to make. This works best when there is a very large impedance mismatch between the string and the bridge. However, as usual on the guitar, you can't have _too_ high a mismatch, because then no energy would be able to get out of the string and into the top to make sound; think of a Les Paul that's not plugged in. So, as usual, we're trying to find some sort of balance.

Of course, it's not just the bridge that's in play here; it's the top as well. For purposes of discussion I think you could consider the bridge plate to be part of the bridge, for example. Certainly the stiffness of the top bracing and the mass of the top in the bridge area come into play.

Mechanical impedance (Z) is the ratio of force over velocity at a given frequency. It will be proportional to sqrt(mass*stiffness)+resistance. Increasing mass, stiffness or damping all add to impedance, but each has different effects over the frequency range. We could look at four different cases to think about how this works. One would be a Dread with scalloped bracing and a relatively thin top, another would be a 'fingerstyle' OM with tapered bracing, a third would be a Classical guitar with light, and uniform, fans, and the fourth would be an archtop.

In the first case, owing to the thinness span of the top, , and the relatively low stiffness of the bracing in the center, the stiffness term in the impedance equation will be relatively small. To get a good 'stop' for the strings (which generally have low impedance, particularly at their resonant pitches) you might want to add some mass. Adding mass has less of an effect on the impedance at low frequencies (when it's not moving much) than at high frequencies, so this will tend to reduce the output at high frequencies relative to what you'd see with a lighter bridge. Adding mass does not _enhance_ the low end, it just cuts it down less than the high end.

The fingerstyle guitar top will probably be stiffer in the center, owing to the shorter span, and taller braces at that location. It will not need as much mass to provide a good stop for the strings, so you can make the bridge lighter. All of this will tend to favor highs: as with mass, adding stiffness increases the impedance, but has less of an effect at high frequencies than at low ones. A too-stiff top cuts down on sound output, but more in the low end.

The Classical guitar faces lower string tension, possibly a lower string height off the top (with less leverage to distort it), and a real paucity of high frequency energy in the signal, owing to the relatively high damping of the strings. The top itself needs to be as stiff as possible consistent with light weight, and a light, stiff bridge is in order. The 'brace' aspect of the bridge is more important here in general than it is in most steel string guitars, since the bridge is the only member that runs substantially across the grain of the top. Classical bridges are generally longer and narrower than steel strings, with the bridge wings being important stiffness elements at high frequencies.

The opposite holds for archtops: the arching itself is so stiff that you don't usually need to add much there, and the bridge is pretty much a simple mass element. Particularly in cases where the guitar is played amplified a lot of the time, a massive bridge is usually what's called for, if only to get some sort of treble to bass balance. It gets complicated, as well, since the tailpiece can be considered as a sort of adjunct to the bridge, particularly if the back strings are short, and with the added complication that the tailpiece can have some resonances in the range of the guitar's fundamentals.

To get back to damping: I'm just not sure what role that plays in the bridge. One problem is that it's so hard to isolate variables: finding two bridge woods that are 'the same' except for damping factor is tricky enough, but then there's no way to swap one for the other quickly and quietly enough to do a useful direct A/B listening test. You could get somewhere with recordings, but that has to be pretty tightly controlled to give useful results, as I've found recently in another set of experiments. You can, of course, look for objectively measurable changes as the damping is varied, (assuming you can isolate that variable), but that runs up against the old conundrum of instrument acoustics: some things that are easy to hear are hard to measure and some things that are easy to measure are hard to hear.

The bottom line, then, is that it comes down to 'horses for courses' as the Brits say. What works for one guitar or one system might not work for another instrument of a different type for a different customer.

I had one student who got a little carried away carving the bridge for her OM: it ended up at 22 grams. Due to time constraints, she was unable to put more than a wash of shellac on the guitar, and it ended up too 'bright' for her taste. We added (again, time..) a couple of grams of poster putty on the inside of the top at the bridge, and that took off just enough of the edge. A couple of years later, with a new baby to take up her time, she brought the guitar around to have me finish it, and I varnished it with 'Rockhard' varnish. The added mass and damping cut the edge enough that we were able to lose the poster putty. Lots of variables....

bookmarked for further digestion later on.

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member of the guild of professional dilettantes

+1

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Thank You and Best To All

To add an example of mine I have been using Brazilian bridges on many of my recent guitars with finished weights all below 20 grams. My tops are thin-ish but not overly so and I do scallop my braces but again, not to an extreme. My bridge style has long thin wings and generally is about .34-35 thick in the center with a string height of .5 for the middle strings. I would say that all of this does enhance the treble and I do love the immediate and crisp sound my guitars have been having in the upper register. It has not to my ear affected the depth of the bass negatively at all although there is still a crispness to that note as well, which I find very pleasing.

Another thing I think about was something David Berkowitz mentioned a while ago regarding using ebony or not and specifically towards how many very successful makers do use ebony bridges. He noticed (and I am remembering his comments here) that the ebony (as opposed to a supposed lighter and more "resonant" rosewood) helped to cut out some of the higher end string noise that was considered bad to some players, especially those using the guitars for recording. I have noticed a bit of this myself. I like to have the option to have that extra sensitivity or not, and think of the the choice between ebony or rosewood in those terms while acknowledging of course it is never that simple. I think this correlates with Al's description, I would expect the sound of my guitars to shift away from the pure (and to my ear, crystalline) treble as the bridge weight rises (or the species changes) and I have used this before to EQ what I want to get from my guitars.

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Burton
http://www.legeytinstruments.com
Brookline, MA.

I have a preference for low mass bridges and the simple explanation is that less mass in a bridge gives more acceleration of the top for a given force supplied by the strings and more top acceleration gives more sound. F= ma (or a=F/m), according to Isaac. For those still interested, read on...

I've made steel string bridges as light as 14 grm and classical bridges as light as 10 grm. It is possible (but hard) to get lower. Even this light, I've never had problems with the strings not "knowing how long they are". However, what you immediately get is an increase in monopole mobility, (proportional to 1/SQRT (equivalent top stiffness * equivalent top mass) because the mass of the bridge forms a substantial part of the mass of the top. And monopole mobility is related directly to the loudness and responsiveness of the guitar. With less bridge mass, you need less top stiffness to achieve the same resonant frequency, so you get a double-whammy win on monopole mobility and this shows why bridge mass is so important on responsive guitars.

If you happen to want more bridge mass - easy; just change your bridge pins to something heavier. If your guitar sounds too raucous, use a different saddle material (and older strings!)

So I've yet to see a convincing technical argument for heavy bridges, or, more specifically, a bridge heavier than the lightest you can reasonably build. Polished Macassar ebony bridges or BRW bridges do look really good, mind.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

So I've yet to see a convincing technical argument for heavy bridges, or, more specifically, a bridge heavier than the lightest you can reasonably build.

One word....

Tone.

Grumpy - in a recent post on a similar topic, you indicated that your new bridge wood preference was Africa Blackwood. Based on that post I bought some African Blackwood bridge blanks. What received was 75% denser than the BRW bridge blanks I have and a littler denser than the ebony I measured. Did I receive Blackwood on the very dense side or do you trim your Blackwood bridges to get weight down, but 75% is a lot?

Thanks to all for the comments. Great stuff.

EddieLee

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EddieLee

That's not a technical argument.
There is an assumption here that more acceleration (or more sound, as you say) is better. Sometimes that might be true but, for instance, I would never say that to the banjo player.

I don't doubt that your method works with your guitars but I have direct experience to know that my guitars sound worse once I go below a certain weight (or above). And I double and triple checked that with some other ears in the room. I guess I believe that the guitar is a complex system and it rarely works to make broad generalizations about any single element.

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I can't answer anything that's specific to Mario's bridge but your stated density for ABW as compared with BRW and AE sounds about right.

Trevor, I wasn't being a smartass; while lightweight may be best for responsiveness and power, it comes at a price in tone. Not everyone wants, or needs, or can use, the tone produced by an uber-light bridge. Personally, I -want- mine to be ultra lights, like you, but it's not for everyone.

As for the ABW VS BRW, I don't know where you got your 75% figure.... Most of my BRW stash is good, dense stuff, not all that much lighter than ABW. African Blackwood is also a true rosewood, BTW. At the end of the day, I still don't have a problem getting a ABW bridge to well under 20 grams...

According to the published numbers ABW can range from about 34%-78% denser than BRW so 75%, though on the high side, is within reason.

I don't use a ton of ABW but I'd estimate that the stuff I've used has averaged around 50% denser than the average BRW I've used.
I'd agree that I've had no problem getting it down to the weight range that I'm shooting for on steel string bridges. I don't think I'll be using it on any of my classical bridges, though, unless I come across some stuff on the it's low extreme for density.

Sure, and there are plenty of ways of changing tone. I perhaps should also point out that I'm building mainly fingerpicking guitars, so I'm not usually in the 13-56 ball park with a flatpick. Remember that it's easy to get more bridge mass by using heavier bridge pins, whilst it's not quite so easy to go lighter if you started out with a heavier bridge. Just tools in the tonal tool box.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au