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This is for a Gibson L-O shape guitar, .110 engleman top, 1/2 x 1/4 x brace, carved POC back. The first guitar that the pictures are on has a cherry bridge, I took the picture on it for color reference. The two bridges are cherry, which has been carved down pretty far as I went too deep on the countersink and beveled to make it not look so bad, but since it is a bit messed up, I did another from my mystery stash. The cherry weighs in at 22grams, and the mystery wood at 44 grams, I can lose a bit of wood on this one.

Bridge questions: What can I expect from either of these in how it will effect the finished guitar? Is the mystery wood appropriate (when it is ID'ed) How does weight effect the performance of the bridge, I know that we are supposed to weigh them and put the info in our build log, but have not read anything on the hows and whys of weight on a bridge.

Mystery wood: Came from South East Asia, harvested in the early 1900's and used as a railroad tie, then imported to Terra Mai and sold as flooring, purchased by me to make a bar top for a South East Asian restaurant in a railroad town, pretty cool. The look on this piece is very similar to ribbon mahogany, small pores, perhaps a bit more red then hog. Once you pick it up, nothing like hog, very hard and dense, dropping the two bridges on a cast tool top, the mystery bridge gives a good TINNGGK, the cherry is a tangk, but in the end, sounds like one is heavy and the other light.
Thanks for the help,
Rob

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I would have said your mystery wood is Sapele, based on appearance alone, but not very sure frankly in view of the rest of your info.

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looks to me like ipe. i've built a few decks for people out of that stuff, and it is hard and heavy! makes a beautiful deck that outlasts redwood, and is more expensive.
don't know how it would sound.....
probably ok if you got the weight down.

Definitely not sapele, I have worked with plenty of Sapele and true hog, and looks are the only similarity, this stuff is serious hard and heavy.
From the Terramai site:
Source: Untreated railway ties, mine shoring timbers and building demolition salvage from Southeast Asia.

Species: Pterocarpus (macrocarpus and indicus), Pradu, Pyinkado and others.

Colors: Luminous burgundies to rich scarlet and rose hues.

But this may have changed, as I got the material 6 years ago and Terramai sell out an inventory and then the replacement can be different, another possiblity is Nara.
Link: http://www.terramai.com/products/displa ... px?pid=240

This is a link to a project I did when I worked there (unrelated to post):
http://www.terramai.com/pages.aspx?ID=104
All lap jointed 8 x 8 doug fir, 14' x 16'

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Grenadillo

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Never heard of it, but it sure looks the same, this material really was from Asia, what I read, Grenadillo is from this side of the globe, but it seems right from the description and pictures.

So about the weight? What are target weights for bridges, how does weight impact the final tone?

Rob

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It looks very much like a timber we use for flooring and decking in Australia called Merbau or when used in furniture it's name is Kwilla. The timber originates from Indonesia. If it is Merbau it is extremely hard on tools and when cut the saw dust will often have a yellow/mustard colour. It is very dense and heavy for it's size and comes in a veriety of colours ranging from light brown to deep rich red and everything in between. Has open pores and takes a high polish.

Bob,
That sounds familiar, this stuff is murder on blades, I just have some red stuff, it is quite heavy, I wonder how weight of the bridge effects the tone of a guitar, would this dense heavy wood be a good choice if I got it as light as possible?
Hmmmm?

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On to your other question: the bridge and sound.

It helps to remember that the bridge is the heaviest brace on the top, and one of the stiffest. A bridge can, in some cases, weigh as much as all of the other bracing put together. Usually it doesn't add as much stiffness, though. You can see this by checking the main tap tone pitch of the top before and after gluing on the bridge: usually the pitch drops because the bridge adds more mass than it does stiffness.

All that added weight and stiffness makes the top harder to move: it raises the impedance of the top. This is both good and bad. You need for the top to have a higher impedance than the strings do, so that they'll 'know' how long they are and thus what pitch to make. But if the impedance is too high, the top too hard to move, you lose sound. As usual, it ends up being a balancing act; you're trying to get the impedance high enough to cause the strings to behave, but not so high as to kill the sound.

Impedance is frequency dependant, and adding weight to the bridge has a different effect on the tone than adding stiffness, even if both of them do increase the impedance of the top. Basically, adding weight has very little effect on low frequencies, but cuts down on highs, while adding stiffness has the opposite effect of cutting lows. So, all else equal, adding weight to the bridge will tend to make the sound less loud, particularly in the trebles, so the timbre will become more 'bass balanced'. Note that you didn't add to the bass, you cut treble. Making the bridge lighter makes the guitar louder overall, but particularly in the trebles. Stiffness works the other way.

Many people feel that the damping factor of the wood used is important. I can see where it could be, but so far have not found any major effects that I could attribute to that with any confidence. It's a case of there being so many other variables that it's difficult to isolate that one: are you absolutely sure that the new bridge you put on has exactly the same mass and stiffness, as well as size and shape and height, and only differs in it's damping factor? If you are sure of that, then you need to get some objective data: 'sounds like' is nice, but doesn't cut the mustard in a debate on physics.

At any rate, damping has more of an effect in the higher frequency ranges, so it's possible that a lighter and stiffer bridge with higher damping could, in the end, give you better trebles than a heavy low-damping one. You could easily see that effect when swapping out a rosewood bridge for a walnut one that is slightly larger.

The bottom line is that weight is one of the more important properties of the bridge, and one of the easiest to keep track of, so it makes a lot of sense to do so. You can do a fair amount of fine tuning of sound with the bridge, but most of us don't really like to remove them if we can help it, so there's a premium on getting it more or less right the first time. Too light or floppy (especially too light) can contribute to 'wolf' notes, and too heavy or stiff costs tone. So long as you stay within the 'normal' range for weight you probably won't have too many complaints, but knowing a bit about how the bridge effects tone can help you pick one that will enhance the sound, rather than just not killing it.

I'm not sure what you're saying here. If it's Pterocarpus, that's Padauk. Narra is another name for the same thing.

Take a small shaving if you can Padauk/Narra will be bright reddish orange when cut, give off a nice rose smell and the dust is pretty fine. The mystery piece does look like narra.

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Alan,
Thank you for the answer, as usual, more then one can digest in a sitting, I really appreciate the time that you put into this and your other very informative posts.


That info was copied from another site where the wood was purchased from. They sell their flooring products as color sorted mixes, so there are a variety of species within a color mix, this one being the "rose mix" This is from a railroad tie, I have other pieces with the spike holes in it. Come to think of it, railroad tie lumber, that's what I call a tonerite.

What is interesting on this material, the railroads were build with material harvested on site, so as they cut through the jungle, they used the trees for the ties, it was never dried or treated, just a railroad tie in the jungle for almost a hundred years, they pulled up milled and shipped to Terramai, so the wood has a ton of checking, and most is garbage, but some is sound.


Hmmm, we definitely had the rose smelling dust at Terramai in some of the mixes, but I don't think this is it, but I will double check with your test, I do have plenty to play with, as most is checked and useless, and this is the fall down from a project, so the good stuff went to the customer.

As we know, some of this tropical material can vary from irritant, to toxic, and at Terramai, with the material in color mixes, we did not know what we were cutting, even with masks and respirators, we had some nasty days there.
Rob

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To me it looks like a wood I used when I lived in Jamaica (West Indies) called 'Tamarind'. It's kind of an orangey color, very hard and heavy, but has a great ring to it. It also dulls blades like you're cutting stone, very high silica content. I still have a few small pieces I'm going to make bridges out of.
Tamarind comes from Southeast Asia and came to Jamaica with Indian and Chinese workers brought to work in the sugarcane fields.

If not too far off topic, I would sure appreciate everyone's input on how the stiffness of the bridge wings affects tone. What changes if the wings are made thinner and floppier? How about if I leave them thicker and thus stiffer? I'm guessing it affects tone in other ways besides just increasing/decreasing the overall weight of the bridge, true? I've read that thinning the perimeter of the soundboard at the sides of the lower bout (where the bridge wings point) will increase the treble response. Will thinning the bridge wings give the same result?

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Darryl, that's a good question and probably deserves it's own thread where others can see it. I'd sure like to hear some of experienced folks weigh in on this one.

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Ok, I'll start another thread so we don't take this one off topic.

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