x-bracing and full contact bridges

[David]

I recently had Steve Smith at Cumberland Acoustic install a full-contact bridge base on my x-braced Summit mandolin, and I can't tell you what an improvement it made. It was already a good sounding mandolin but it's like the thing just "woke up" to its real potential, louder chop, better sustain, improved tone esp. on the A and E strings.

Steve's theory is that a standard bridge base with feet is designed to isolate sound onto traditional tone bars, but with x-bracing the bars cross right under the bridge, so a full contact bridge is actually better for this type mandolin. Anyone else had a similar experience? All I know is, thanks to Steve, I'm smiling from ear to ear and can hardly put my instrument down.

[Tony Sz]

I have a full contact base on my Gibson Steffey. It came that way and it sounds great. Sim Daley also uses a full contact base on his mandolins. Both my Gibson and the Daley's have tone bars, so I guess this type of base works for more than just X braced mandos.

[Lee]

Bill experimented with my Old Wave oval-A and built it with a one-piece full contact bridge and it does sound exceptional.

[Kevin K]

Very interesting....

[rmartinez]

I recently took in my Collings MF to the factory to get a once over and they preferred a solid bridge instead of the standard double foot that it came with. It has tone bars though.
Anyhow, they swapped out the previous bridge because that's what they have moved to in their current mandos and I like what I hear. I can't show in any quantitative way what the difference is; however, to my ear it is VERY even. Before I felt as though (believe it or not on a Collings) there was a touch too much in the bass and not enough pop in the highs, and now it seems that there is still great volume, chop, but now better balance. Interestingly enough, I was told that the reasons were also structural. With a solid base the pressure is more evenly distributed, so the top doesn't warp over time. All that said - whatever it is that the newer bridge does, I like what I hear!!!

[Mike Black]

I have a tone bar braced Summit that I just made a full contact bridge for. I had a two foot solid maple bridge with a bone cap on top before. It was very loud, bright and crisp. It just was missing the low end that I wish it still had with an ebony bridge. So I made a adjustable bridge with a full contact ebony foot and an adjustable maple top with a bone cap. I still get a lot of the loud crispness in the highs but now have a more defined mids and lows. I'm very curious how it's going to sound with my band this weekend. I'll report back.

[Mike Black]

Sam Bush is a big supporter and promoter of the full contact bridge. That was one of the questions that I asked about for the future MandolinCafe interview.

[David]

Yeah, I actually initiated the idea of the full contact bridge with Steve because of Mike Marshall's comments in the most recent interview. I'm very glad I did.

[Rob Gerety]

What about oval holes - meaning vintage Gibson oval mandos with transverse brace?? Full contact or two foot?

[Mike Black]

What about oval holes - meaning vintage Gibson oval mandos with transverse brace?? Full contact or two foot?

They were full contact bridges originally before the two-foot adjustable bridge in the 20s.

[Fretbear]

A full-foot on conventional tone bars rocks as well. The top of John Reischman's famous Loar had started to develop a bulging-up between the bridge feet, and bassist Todd Phillips installed a full-foot bridge to settle it back down.

[Big Joe]

I often recommend a full contact bridge bass on certain mandolins and on some the gap left in between. On many mandolins the solid contact will definately increase tone and volume. This helps often on older mandolins that are beginning to show some signs of sinkage. It helps distribute the tension across the top a bit better.

Like everything, there is a place where each foot is the best. Each mandolin is different and needs to be evaluated for which is better for that instrument.

[Michael Lewis]

Yes, what Joe said.

One time I replaced an adjustable bridge on a Gibson A with a Brekke bridge, which resembles the solid bridge the factory used on their mandolins before 1921. The owner liked the result so well he had me do the same for his F model, but the result was not nearly as good, so I put the original adjustable bridge back on and the tone and volume came back. Each mandolin is at least a bit different from all others.

[David]

Yes, I guess the real answer is "it depends," like so many things. And Michael, my friend Thomas Kingsley here in Nashville plays one of your mandos, a nice blond, it's a killer instrument.

[Lefty Luthier]

I prefer the full contact bridge on mandolas and mandocellos, which I build with a Virzi. I have not observed as much improvement on parallel tone bar mandolins though I have one on my personal instrument. A benefit of the full contact bridge, in my opinion, is that it permits a bit lighter top that is more responsive at lower frequencies.

[lenf12]

So to Joe, Michael and the other luthiers in this discussion, what are the factors you evaluate when determining whether a solid contact or bi-ped bridge would be best for a particular mandolin? I have an older (1956) Gibson F-12 with a 2 footed ebony bridge (from FQMS) that I really like the sound of now that Randy Wood has done his re-voicing wonders. It does not display any sagging of the top at all. Of course, I am always looking for a bit more ooomph and wonder if there's something specific to check out or should I just get a solid contact bridge and experiment. Any opinions? I do have some bridge fitting experience and would likely get a Cumberland Acoustics bridge as a test subject.

Thanks in advance,
Len B.
Clearwater, FL

[Big Joe]

Len...it is hard to describe exactly what to look for. It is one of the things you just kind of know. There are signs one may use to help in the determination, but it is the whole more than any one thing. Of course, a sinking top is a good example of a raging sign. If that is the case you first have to determine why it is sinking and whether something else needs to be done first. Then when all else is taken care of one goes to the bridge to see what is needed. Of course the thickness of the top is a consideration, but I have seen when a full contact helps a top that is too thick as well. One of the hard things in lutherie is trying to describe how you know what to do and try to make it apply in all cases. It doesn't. I guess we have done so many of these for so long we just have an instinct that tells us this is most likely what is best for this instrument. And, yes, sometimes we try something and end up going back to the drawing board. Not often, but it does happen. I often say lutherie is half science and half art. When the two come together things just work. If you only have one you may have beauty but not function or theory and math but not a desireable end product. It is when there is a marriage of the two one finds the desired results.

I cannot speak for anyone else, but I have spoken with many of the luthiers and we have our theory why this or that works and we have had enough experience to be pretty accurate on the outcome we expect from that experience but we don't always know how to explain something to the satisfaction of others. It is hard to take 40 years of doing something and all the different things you have tried and the results and explain them in detail so a predetermined outcome will result from these actions every time. I can't do it, and it is certainly not from any lack of verbosity! I guess the best answer I can give is we just know what we expect to work and when we do it we get the desired result. If we don't we go back and redo our thinking. Sorry, it's the best explanation I can give.

[lenf12]

"It is hard to take 40 years of doing something and all the different things you have tried and the results and explain them in detail so a predetermined outcome will result from these actions every time. I can't do it, and it is certainly not from any lack of verbosity!"


Thanks for giving a try Big Joe. - Len B.

[pops1]

I am curious to ask these who have put on a full contact bridge how did the sound change in the low strings. With more mass in the bridge foot would the G string get tighter and brighter which of course makes it easier to be louder. Sound wise if you can describe the change. Thanks

[Malcolm G.]

Hopefully along the same vein - how about full contact twixt saddle and bridge base? ie: the brass adjustment screws are out of play?

I'm thinkin' same idea as full contact from base to arched top.

[Lefty Luthier]

I am curious to ask these who have put on a full contact bridge how did the sound change in the low strings. With more mass in the bridge foot would the G string get tighter and brighter which of course makes it easier to be louder. Sound wise if you can describe the change. Thanks

There is no reason to make a full contact bridge any heavier than normal, in fact, in many cases, removing sufficient bridge material to achieve full contact results in a slightly lighter bridge. Acoustic output (loudness) results from the volume of air pumped in and out of the sound chamber so increasing the flexing of the soundboard generally increases output. Keep in mind that in a small instrument like a mandolin, even minor changes to any soundboard component can have a significant effect on both output and sound quality.

[pops1]

I wasn't implying making it larger, but due to the fact that there is contact in the center instead of no wood increases mass slightly. Thanks, didn't realize how minor the changes can effect the instrument.

[grandcanyonminstrel]

If you search the back issues of Mandolin magazne, there is an artcle by Ken Cartwright ( one of the regulars around here), where he goes into good detail regarding full contact bridges and several different designs he and Monteleone use on one of the old F5 copies John made for Mandolin Brothers.

I use full contact bridges regularly, with great results. The first time I ever tried it must have been when I was about 18, on an old 40s Gibson I owned, before anyone had a chance to tell me there was a "right "way to make a new bridge.

j.
www.condino.com

[Rob Gerety]

Thinking out loud here - with zero experience - just interested in the issues. I assume that the feet on the typical two foot bridge are wider than the width of the foot on a typical single foot bridge. The total pressure on the top it would seem would be the same no matter whether a single foot or a double foot is used and no matter what the size of the foot, or feet - total pressure it seems would be a function of the string gauges and the height of the bridge or angle as the string pass over the bridge. So is it a question of varying the location of the contact on the top? Or the total square inches of the contact area? Both? Something else? Is it basically a trial and error sort of thing?

[squirrelabama]

I seem to recall the use of a full contact bridge on two Nugget A's that I had owned in the past. Both #91 and #155. I was the second owner of each of those, so I am not sure if coincidence or Mike's way of doing things. Anyone notice this on Nuggets as well? Oh, and yes they sounded amazing!

[Fretbear]

There is going to a lot less difference between a one foot or two foot bridge when you are employing a bridge of superior quality and design like Steve Smith's Cumberland Acoustic bridges, than there will be between a cheaper bridge and a CA. In other words, I'd rather have either model of Steve's than any other kind of other bridge, unless it was an exact Loar-copy like one of Darryl Wolfe's, which must be similar.

[s1m0n]

I hear full contact bridge is all the rage in some of the tougher retirement communities.

[David]

^ haw! ^

[Larry Simonson]

I am thinking that Dr. Michael Kasha (Florida State Univ.) was right in the late '60's when he suggested that the bridge of a stringed instrument behaves something like a transformer and that for maximum power transfer from the strings to the top (and back) there was a need to match the impedances of the source and destination of the power. If Kasha's suggestion is true, I can imagine how a subtle change in the bridge could lead to a significant change in the performance of a stringed instrument and would explain the various results described in earlier posts.

[Michael Gowell]

I finally took my 5-year old and acquired-nearly-new Sumi to a luthier for a setup. Jack O'Brien in Jaffrey NH was well recommended on this board and in private. After years of experimenting with saddle heights & different strings it became clear to me that the original owner must have substituted a new, higher bridge for the original despite his very brief ownership. At its lowest, this saddle was still too high. Instead of mail-ordering a bridge, Mr. O'Brien prefers to make his own. He recommended a full contact rosewood base (and defended its choice when I inquired about ebony) and a bone saddle. He returned a much improved mandolin - the new base is a fairly subtle change visually but the pencil-thick shaped, machined and compensated bone saddle isn't... powerful to see as well as hear. Anyway, since I presumably got two physical changes - bridge and saddle - plus perhaps some tone improvement from the set-up and the Sumi's increased playbility - I can't give all the credit to the full contact base. But certainly some of it. I think of my mandolin now as a lap full of chimes.

[grandcanyonminstrel]

I am thinking that Dr. Michael Kasha (Florida State Univ.) was right in the late '60's........

Ever actually play a kasha based instrument? I've played close to 50 based on his designs, have been to some of Richard Schneider's workshops building by his designs, am great frends with Richard's most successful apprentice, built a bunch of instruments based on the ideas, and yet have NEVER played one of the instruments that I felt like I had to have. They have some attributes which like, and I love the ideas from an intellectual standpoint, but my ears have a dfferent opinion....

All that said, I still morph a little bit of it into my own bridge designs...the wider bass foot and narrow treble, but I also change the mass to compensate for it.

j.
www.condino.com

[Larry Simonson]

I have not played one of Kasha's instruments. I was a grad student when he was experimenting with his ideas. But the point I was trying to make is that from the many posts about bridges over the last decade on how minor changes in bridges have lead to significant changes in performance must involve some hidden explanation. Kasha's suggestion of impedance matching may very well be true. That is not to imply we know how to measure and/or balance these properties.

[Rob Gerety]

I'd rather have either model of Steve's than any other kind of other bridge, unless it was an exact Loar-copy like one of Darryl Wolfe's, which must be similar.

Also bridges by Randy Smith.

[Dobe]

I seem to recall the use of a full contact bridge on two Nugget A's that I had owned in the past. Both #91 and #155. I was the second owner of each of those, so I am not sure if coincidence or Mike's way of doing things. Anyone notice this on Nuggets as well? Oh, and yes they sounded amazing!

I remember asking when my A was on order , Mike said he usually goes through 3-or 4 bridges before he gets one he's happy with. I guess that goes to show that every piece of wood is different. My A had the standard 2-foot bridge but I played one of the nicest older Nug A's a few years back with just the smallest mass saddle & base (2-foot) I'd ever seen. Guy said that's the way it came. Go figure !:popcorn:

[david blair]

Yes every piece of wood, bone, or ivory is different. Workmanship is another variable.

Lewis #162, F5 tone bar braced, came with a single footed bridge. After fitting at least 4 new bridges (while learning how) and even more saddles with different pickup experiments I use a two footer from Siminoff. The posts are about an 1/8" wider apart than Fishman or Cumberland bridges which is interesting.

[Steve Hinde]

I would expect that some builders use the full contact base to reduce warrantee repairs. There is always a risk for deflection of the top piece under string tension and vibration over time, resulting in rotation of the posts, causing the 2 footed bridge to dig in to the mandolin top. Especially if you try different ways to reduce the mass of the bridge, or have material variations in the bridge. The surface area on the 2 footed bridge on either side of the post may not be equal, resulting in a different defection distance under load. Plus deflection in the top plate at the bridge contact areas. The full base almost eliminates those possibilities. Anyone else shape the 2 footed bridge base to contact the outside edges slightly before the center, without load, to compensate for that? And I do mean very slightly.

Steve

[Jan Ellefsen]

After reading the Mike Marshall interview I found this thread and would like to ask the experienced builders: Could it cause any problems to take a little off of my two-footed Cumberland bridge base so that it makes full contact? Now it only has an area about 15 mm wide that is not touching, and about 1 mm from the top to the middle of the bridge.