BRIDGES

[GTison]

I just got a new bridge on my fern. It sounds different the saddle top is taller and maybe thicker than the old one. It seems like it has more treble now. is there any rule of thumb on standard bridges about tone. like, if it's thinner then you will get more bass or if the bridge top is not as tall you'll get more treble or anything. any EXPERIENCE here?

[Chris Baird]

The more stiffness and the less mass the higher the overtone series and conversely the more flexible and more mass the lower the modes on the bridge hence a lower overtone series. Most mandolins have e and a string overtones that are higher than humans can hear so it is, IMO, better to have a bridge that emphasizes the lower harmonic range.

[Dave Cohen]

If you fret the 1st string at the 5th fret and pick that note, it has a frequency of 880 Hz. 880 Hz is the 1st harmonic, or "fundamental". Its' 2nd harmonic (referred to above as an "overtone") is 1660 Hz, well within the range of human hearing. The 3rd harmonic would be at 2640 Hz, the 4th at 3520 Hz, and so on. According to Rossing, human hearing extends from about 100 Hz to 20 kHz, although greatly attenuated above 10 kHz (well, maybe 10 kHz and 5 kHz respectively at my age). So there are numerous audible harmonics for most of the played notes of a mandolin or violin.

At lower frequencies, the bridge acts as part of the top plate. At higher frequencies, bridges may have some vibrational modes of their own, though I don't know what their contributions to musical quality are. For that matter, the violin world does not know very much about the contributions of the bridge either. The literature of violin physics goes back into the mid 19th century; the first entry in the literature of the physics of the mandolin was in 2000. There was some literature, but not much, on guitars before about 1965. In violins, a "bridge hill" has been identified, but not much is known about its contribution to musical quality.

In a few words, I don't think that there are any "rules of thumb" about mandolin bridges. Ask anyone and you will get loads of opinion and anecdotes - all subjective. But there are no objective, repeatable, and/or verifiable measurements.

[Daniel Nestlerode]

Bowfinger, you don't say how long the bridge has been on your mandolin. #It makes a difference.

Recently (last Sunday, 6/21) I had the bridge on my Capek replaced. #I went from a standard, high quality, ill fitted thumb-wheel bridge to a Brekke bridge. # I thought I was going to have to get rags and fill the body of my mandolin because the trebles were piercing and the bass was nearly non-existant. #http://www.mandolincafe.net/iB_html/non-cgi/emoticons/wow.gif

I asked on Comando about bridges and their relationship to tone in that context and several people emailed to say a good fit is a bigger factor in tone production than the type of bridge. #They also said, give it some time and PLAY the mandolin. # http://www.mandolincafe.net/iB_html/non-cgi/emoticons/mandosmiley.gif # the tone will return.

So I did. And it did. #The bark is back, the trebles are a lot less harsh, and the tone has evened out considerably.

Having said that, I have ordered a bridge from Steve Smith which I will fit myself (luthiers worth their salt being thin on the ground in the Modesto CA area). #Once that's been on for a week and played hard I will try to compare the two. #I'm sure there will be a difference, but I think it will be fairly subtle if I ft the bridge as well as this one has been fitted. #

Best,
# # Daniel

[Luthier Vandross]

The oil content, from one piece of wood, to the next, has a great deal to do with bass/treble tilt.

More oily=dampened highs, less fundamental, more overtone.

With much of the ebony I have seen lately, it changes inch, by inch, but I prefer 'in the middle'.

I may start grading bridges, like Groove Tubes did with amp tubes.

Yeah! Boutique! (add $100!)

M

[GTison]

well I've been playing it I raised the action up, tried to get the intonation back in. I still can't get the sound of the original back. The base hasn't changed just the top. My trebles have deminished quite a bit. And it runs out of power, I can over play the strings. This was not the case before I am befuddled, and frustrated. ( I may have contradicted my first statment about the treble)

[Luthier Vandross]

Every piece of wood is as different as you could imagine..

M

[GTison]

hey luthier is it possible to sellect bridge tops for tone in setting one up, ie is this common practice.

I just took a new bridge top and put it on my old KM 1000 which is very trebley and needed more bass. It worked a little. the new top is wider and just about the same height. the new one is def. ebony but the old one may be rosewood or a real brown ebony. I'm gonna take that one and put it on my new FERN.

makes me wonder if i replaced the bottom to a wider base i would get even more bass out of the old KM1000.

[250sc]

I have a solid wood Kentucky that was lacking base. I installed an original Brekke bridge and it changed the sound completely for the better. More base and nice woody tone. However, the shape of the sound board made it necessary for the Brekke to make contact with the top all the way across, not sitting up on the 'feet' with space in the center. The extra contact could be the cause of the tonal change.

[GTison]

so extra base means extra BASS?

I swapped the bridge off my old "84KM1000. on the Fern it sounds more like what I'm after more treble and not much less bass response. It seems very interesting that with arguably the cheapest part of a mando you can get some great results. (maybe as much as a tone guard to you lovers of that thing)

[GTison]

oh yeah, the bridge top of the old KM is fairly narrow and deep. It seems hard and when dropped on a counter sounds a little higher pitched than the one I took off of it. I had to file out the holes to make it fit the bridge base. It's not black either it's rather brown, could be rosewood but all the ads back then said ebony. But if it is it's not dyed or it's real brown stock.

[sam]

I just finished up a little A model, the loar type adjustable bridge was just a little disporportioned " I had an OOP's, so it looked a little funny, but the mando sounded great, if not the best one of the best, I put a solid bridge with a compensated bone insert. The bass cleared up, not that it was bad, it was awesome, the treble overtones vanished. The mando would not overdrive, this little jewel just shakes the walls. The top was a prototype , The next F will have the same carving and tap. I think I have THE SYSTEM, but the little solid bridge made an unparalelled differance. Night and Day, now I am sold on solid bridges, however I dont think customers will be convinced untill they try one. I dont think people will get the same results on mandolins which are overbuilt, they will have clearer notes but will lose some decibles. #sam

[K_D]

Here's another tid-bit of empirical data for my kit mando. Basically, I used the same set of old j74 strings and switched between a Randy Wood (RW) Loar style bridge (ebony) and a Red Henry (RH) style solid ebony bridge. To my ear the RH bridge sounds brighter and a bit louder so I used some PC spectrum analyzer software (in peak-hold mode) to record the 0-2-4-5 notes picked slowly on each string. Looking at the trends in this crude test it looks like the RH bridge has a more even response across the spectrum while the RW has more of a complex filter shape. I've also tried a solid maple bridge (brighter than the ebony RH type) as well but I keep coming back to the Loar style which seems to have the sound I prefer.

Here's a screenshot of the two spectrums overlayed:
mando scale spectrum jpg (http://www.mindspring.com/~p38/mando_br_spectrum_scale.jpg)

Keith

[AeroJoe]

I use and like the original style Brekke Bridges (not the new-model, more traditional-looking ones)...I have one on my older Flatiron F5 Master Model and the arched one that came with my new custom Weber Bitterroot (arched because the fretboard is radiused)...these two bridges came with two different saddle heights...I found that with the higher saddle installed, then the adjustment screws taken /completetly/ OUT (and securely stored in a zip-lock bag) that the mandolins sound better than with the lower saddle installed and the adjustment screws moved inward to raise the action to the exact same level. WHY this is, I have no idea...perhaps those wedge pieces make a difference in overall sound depending upon where exactly they are positioned over the top (inward, towards the center or outwards, towards the f-holes)

Just my observations...

[Dave Cohen]

K_D, a suggestion regarding your sound spectra. A difference in the force of your pluck could easily account for the difference between the two spectra which you showed. Lacking a mechanical plucker, there is an easy way to minimize the variation; take several spectra w/ each bridge, and average them. For the RW bridge, acquire 30 spectra, add them up and divide by 30. Do the same for the RH bridge.

[K_D]

Thanks for the suggestion Dave. I unfortunately didn't have the time (or patience) to do a statistically significant sampling here. It did however closely correlate to what my ear hears when using each bridge. Maybe I can get my transducer working again and do swept sine wave through the different bridges to get a better characterstic curve sometime. For what its worth here's another image comparing a d-chop between the 2 bridges.
Keith

mando bridge dchop (http://www.mindspring.com/~p38/mando_br_spectrum_dchop.jpg)

[davestem]

Funny, I notice that your spectrum analyzer mentions that it's using a "Hamming" window in the lower right corner...is that the Hanning window as protrayed by Jim Carrey?

[K_D]

Wow I didn't know Jim Carrey is a DSP expert http://www.mandolincafe.net/iB_html/non-cgi/emoticons/biggrin.gif ... Actually I believe (if memory serves) that Hamming refers to a particular shaping function that is applied to each window of sampled data so that the samples fit together a bit more cleanly. Reduces some of the artifacts caused by the digitization process if that makes any sense.