View Full Version : Why adjustable bridge?

Nov-18-2005, 10:11am
Most of the mandolins I have seen have adjustable bridges. None of the other bluegrass instruments do. I was curious as to what the particular needs of the mandolin were to warrent an adjutable bridge, other than Loyd Loar designed one? I am truely not trying to be a smart butt, just curious. Thank you in advance,

John Flynn
Nov-18-2005, 10:39am

I think there are multiple reasons:
- They are easier to mass produce and mass market, since they don't have to be customized for a given mandolin until they are installed.
- They do allow a mando owner to more easily adjust string height to thier preferences, the weather and different string gauges.
- The Loar bridge seems to work pretty well. Solid bridges are nice too, but don't think there is any consensus or evidence that solid bridges are better.

Nov-18-2005, 10:41am
It makes it easier to change the action on your mando. Even if you don't want to change the action, humidity changes can change it for you and you have to compensate.

Nov-18-2005, 10:52am
But would those consideration not be true for all the other instruments in the bluegrass family, banjo, guitar, fiddle, bass? But they don't use them. I thought about the asymmetric design as Paul pointed out, but that would be true of the fiddle family too. There are a number of different mando designs...

Nov-18-2005, 11:15am
When did mandolins start coming out with adjustable bridges? Was it a Loar thing? Pre-Loar Gibson?

I have read in several places that a ligher, non-adjustable bridge is more efficient than the adjustable kind. For example: frets.com (http://www.frets.com/FRETSPages/Musician/Mandolin/LtMandoBr/ltmandobr.html).

Nov-18-2005, 11:49am
When the weather (humidity) changes, a plastic banjo head "just sits there". The top of a guitar, mandolin, or violin will move up with increasing humidity, and down with decreasing humidity. If you have a fixed bridge height, you must play with different action heights as the top of the instrument moves. With an adjustable bridge, you can have the same action all the time, or a different action height any time you want it.
Adjustable bridges on flat top guitars have been tried, but the general consensus is they sound bad.
I suspect adjustable violin bridges have been tried too, but imagine the indignation of a violinist at the sight of something like that! Also, the mechanics of a violin bridge in use mean you can't change it much without drastically changing the sound produced by the violin. Adjustable bridges are fairly common on basses, though, and seem to sound fine to most listeners and players.
Also, violins don't have frets, so intonation is the responsibility of the player to a greater extent, regardless of action height.

Lloyd is generally given the credid for developing the adjustable mandolin bridge, so it has a lot of credibility from the get go. Also, any sound differences between adjustable bridges and non-adjustable mandolin bridges are small, in most opinions, and the adjustable bridge is prefered by many. After all, that's what Bill used to get his sound.

So, the tradition started with the F5, and it sounds fine to most people, whereas adjustable bridges have not been thought succesfull on other bluegrass instruments, or not needed at all, in the case of the banjo.

Nov-18-2005, 4:14pm
I have read t6hat a Gibson employee named Hart had much to do with mandolin innovations at the Loar period in time. Anyone able to shed light on this?

Paul Hostetter
Nov-18-2005, 6:23pm
I'm not sure who really invented that bridge, but I doubt it was Guy Hart. He ran Gibson from 1924 until just after WWII. He was a manager, not an inventor or a hands-on kind of guy.

Big Joe
Nov-18-2005, 7:03pm
Loar did not invent the bridge. It was used before the Loar mandolins hit the market. It was first used in 1921 when the adjustable truss rod began in use. These were both Gibson innovations. The adjustable bridge is used on guitars....arch tops, which are essentially oversized mandolins (another Gibson innovation). They are also used on many upright basses and we do install them on a regular basis.

They are not easier to install or fit than the non adjustable, the same work is required on each to fit the top properly. What is different is the adjustable bridges seem to have better tone and certainly make set up adjustments very easy. Many people have tried many things over the years, but the adjustable bridge (done right) and the old Gibson style tailpiece are still being used today for one very good reason....nothing better has come down the pike. There may be fancier or more expensive options, but none that do the job better that we have found...and we experiment with everything we can.

Nov-21-2005, 8:21am
" ... nothing better has come down the pike ... "
" ... If it aint broken, break it ... " and see what happens.

The mandolin bridge is the easiest component (besides strings) that you can experiment with. A trip through Red Henry's website is a worthwhile journey.


Jim Yates
Nov-21-2005, 4:07pm
Sunburst said,"Adjustable bridges on flat top guitars have been tried, but the general consensus is they sound bad." A 1958 Gibson J-50 that my brother and I bought in the early 60s had an adjustable bridge which we eventually had replaced with a regular bone saddle. I've seen several J-50s and J-45s (the same guitar, but the 45 was sunburst and the 50 natural) since from the late 50s that have had their adjustable bridges replaced. If you look through the sound-hole they still say "Adj. bridge" on the spine.

Nov-21-2005, 7:53pm
? Since the Loar bridge has a patent stamp, Who's name is on the patent as owner or inventor? Does this open up any can-o-worms?

Bertram Henze
Nov-22-2005, 6:07am
But would those consideration not be true for all the other instruments in the bluegrass family, banjo...
Just my 2 cents worth of facts:
Banjos usually have adjustable necks (not by the truss rod, by the screw that holds the neck to the body), so action can be adjusted there.
Fiddles are not frettet, so a considerably low standard action cannot lead to rattling; on the other hand, fiddle strings are rather soft, so action does not have to be too low.
These are the only instruments on your list I have played myself, so I can't say anything about guitars...


Bob DeVellis
Nov-22-2005, 10:21am
Banjos also have adjustable heads. To a degree, bridge height can be raised or lowered by means of head tension, although there's obviously an upper limit. As Bertram pointed out, the coordinator rods can also adjust the neck angle by forcing a slight warp into the rim, compressing the bottom opening of the rim while expanding the top. The banjo tailpiece is also adjustable, so in theory, you can change neck angle or increase head tension (creating more downforce) but offset it by raising the tailpiece (reducing downforce). Guitars, of course, have a different bridge system using bridge pins. So, really, fiddle is the only instrument consistently without a means of adjusting string height and tension, but I suspect fiddlers would find the tone changes unacceptable, as also noted earlier.

Bob A
Nov-22-2005, 11:21am
I suspect the sound post in the fiddle would help keep the action more nearly constant, within limits, of course.

Nov-22-2005, 12:02pm
I have a mandolin without adjustable bridge, and i live in a place where relative humidity varies a lot (Chicago). I try to keep the instrument humidified, within reasonable limits. There is no noticeable change in the action throughout the year. I'm not convinced tinkering with the action is necessary; once it's adjusted correctly, it can be left alone.

Note: this is a flat-top mandolin, but why would arch tops move any more than flat tops?

Note 2: I'm not saying the adjustable bridge is a bad idea. It allows you to make the adjustment without having to cut wood or make a new bridge (which for most of us would mean sending the instrument to a luthier).

Nov-22-2005, 5:28pm
Glauber, I certainly notice changes in my mandolins over the seasons. Also, over long periods of time, bridges often need to be moved away from the neck to maintain intonation.

As for violin, they do have a sound post under the treble side, but also, the violin action is much higher and the tension lower, so a minor change in string height on the violin is not that noticable. Also, since the violin has no frets, a minor change in action will not cause a fret buzz as it would on a low action mandolin.

Jim D. in Rochester NY

Paul Hostetter
Nov-23-2005, 6:54pm
If anyone's still wondering who invented the "Loar" bridge, it wasn't Lloyd Loar. I asked Cumberland Acoustics' Steve Smith (who also explained his interesting history with Daniel Smith, and no, they're not at all related) who in turn asked Charlie Derringer (one step away from Walter Carter) who offered the following: Ted McHugh was the proud daddy of the adjustable compensated bridge and also invented the elevated pickguard and the truss rod. #All during his tenure at Gibson, and all during the time that Lloyd Loar was there. I wonder about this slightly because if Big Joe's right, and I think he is, the adjustable bridge was in evidence slightly before LL got on the payroll.

Big Joe
Nov-24-2005, 1:15am
Actually Paul, it was Charlie Derrington, not derringer. Also, Loar was on the payroll before some of these came into effect but he was not the acoustical engineer....whatever that meant...until the 22-24 period. When it comes to mandolins Charlie takes a back seat to no one. Walter is a great guy and a good historian, but that is Charlie's speciality (though Walter is a good mandola player and a great guy).

Paul Hostetter
Nov-24-2005, 1:53am
Derrington, Derringer - shoot me. Duh!

So what was Lloyd Loar doing there before he got a title?


Michael Lewis
Nov-24-2005, 2:13am
Lloyd was busy playing and demonstrating Gibson mandolins. http://www.mandolincafe.net/iB_html/non-cgi/emoticons/mandosmiley.gif

fred d
Nov-25-2005, 1:49am

I've read these coments with great amusment I think that like a lot of other areas in life people are like sheep What ever they see better players use is what they must have If adjustable bridges were better then WHY arn't all string instruments usuing them? Check the amount of changes,listed in the US patten office on mndolins in the lAST 15 years I made a new bridge for a cheap mandolin I was given Granted I,m new here and to music playing BUT sometimes NEW eyes see clearer JUST A THOUGHT. ANYWAY I think the CHEAP mandolin sounds a lot better and MY wife
A concert marimba player thinks so also she even thinks It
sounds slightly simmilar to a brealove

Nov-25-2005, 2:55am
The thing about those adjustable bridges (I am talking about superior one's) is they really shouldn't work very well, but the fact is they do work as well or better than everything else that has been tried (I've done the experiments myself and am not just taking someone else's word for it) and the fact that they can be easily adjusted is just a nice bonus...

Nov-25-2005, 11:11am
I've seen upright basses with Adjustable bridges.