Mandolin Bridges

Mandolin Bridges

Does anyone know why, apart from it being the maker’s choice, are some mandolins made with a low bridge and others with the higher floating bridge. I am thinking say for example a Joe Foley which has a low bridge as opposed to say those, both vintage and newer, made with the higher bridge.Is there a volume issue? Those made with the so called "celtic" market in mind seem to have a lower bridge whilst the the bluegrass market seems to favour the higher model? I don’t know for sure but like some info if anyone had it. Thanks

Re: Mandolin Bridges

There are certainly structural reasons why you need a different soundboard construction with a higher bridge, as the sharper the angle the strings make the more downward tension there will be on the soundboard, and the more carefully it needs to be built and braced from below.
The increased tension will increase volume, but of course you then have a stronger structure underneath absorbing and losing some of the energy.
There is some argument that the Red Henry bridge design, which I keep singing the praises of, works in part because the actual area of the bridge standing on the soundboard is reduced, giving a higher compression between bridge and soundboard.
I think the european mandolins tended to be made with a lower bridge in times of yore, and this practice may have been carried-on inadvertently by some modern luthiers.

Re: Mandolin Bridges

The difference isn’t so much between high and low bridges, but fixed and floating bridges. The two work in fundamentally different ways: With a floating bridge and tailpiece the strings are pressing down on the bridge. When a string vibrates it pushes the soundboard up and down, like the cone of a loudspeaker. With a fixed bridge the strings are pulling on the top of the bridge. When a string vibrates it imparts a ‘rocking’ motion to the bridge.
Historically fixed bridges were used on gut strung instruments like the lute and vihuela, wire strung instruments like the cittern used a floating bridge. As far as mandolins are concerned, the early gut strung mandolino had a fixed bridge, but as soon as they started using wire strings they changed to a floating bridge. There is a very good reason for this: with traditional transverse-barring the soundboard won’t withstand the higher tension of wire strings on a fixed bridge, and will buckle. The use of a fixed bridge with steel strings only became possible with Martin’s invention of cross bracing in the 1920’s – steel string guitars before that time all had a floating bridge and tailpiece.
The introduction of the fixed bridge to mandolins is a fairly recent thing. In terms of which is ‘best’, a floating bridge will generally be brighter and harsher, a fixed bridge will tend to have a sweeter tone, which isn’t necessarily what you want in a session. You pay your money and take your choice

Re: Mandolin Bridges

The hight of the mandolin bridge is determined by the neck angle to give a reasonable low action on the fretboard, carved top mandolins have a greater neck angle than flat top instruments therefore require a higher bridge.

Dave H

Re: Mandolin Bridges

That’s right, but in designing an instrument the luthier works the other way - he decides what bridge height is needed first, and sets the neck angle to suit. It is perfectly possible to build a carved top with a very low bridge, or a flat top with a very high one. The reason carved tops have a higher bridge than flat tops is that the soundboard is much stiffer, and needs more energy to get it moving. Even flat tops with floating bridges don’t have the neck set parallel to the soundboard, it is typically set back by about 3 degrees to give a bridge height of about 15mm. If you built a flat top with the neck parallel to the soundboard like a guitar, but with a floating bridge, it would be very quiet as not enough energy would be transferred to the soundboard.

Re: Mandolin Bridges

I disagree with the Martin X-brace pattern comment. I understand it was a very early design of his, and he used it on his early instruments which were all gut-strung parlour models, before the steel-strung instruments which made his name.

Re: Mandolin Bridges

Sorry, I didn’t explain it very well. Yes, CF Martin developed X bracing in the 1850s on gut strung guitars, but it wasn’t until 1922 that they realised they could apply it to steel strings. Up to that point all steel string guitars had a floating bridge and tailpiece.

Re: Mandolin Bridges

Thanks everyone for the info.I certainly understand more now.I don’t find playing with a high bridge whether floating or fixed comfortable and would prefer a low set bridge but am having trouble finding anyone other than Joe Foley who makes mandolins with the low bridge. Thanks again

Re: Mandolin Bridges

There are other makers who use a fixed bridge - Tom Buchanan springs to mind.

Re: Mandolin Bridges

A flat top or flat top with some arching will have a shorter bridge than an arched top. Guitars or mandolins. Flat tops/banjos will use a tail piece to attach the strings if the bridge is floating, or floating style such as an electric guitar with a tremolo bar.
Volume and tone are affected by bridge height and just about every other detail of the bridge, saddle, and tailpiece. Gibson style archtops have a target height of 3/4". Adjusters are nice to have for many reasons, including climate/humidity changes or truss rod adjustments.
The bridge height you prefer for your playing style, choice of string size and thickness of pick will be determined by the angle of the neck and fingerboard RELATIVE to the soundboard. As well there are the factors of break angle of the strings over the bridge, the length of string then to the tailpiece, and the overall scale length of the instrument which determine the perceived tension when fretting a string. Confused yet? Even though a string is tuned to pitch, a longer scale length will feel lighter to to touch.
I prefer the tone from an archtop with a carefully fitted bridge made from ebony.
Most players consider the nut width and neck shaping as the most important factor for comfort, then either a flat or radius fingerboard, and fret size/height. As for bluegrass or Celtic sound? Of course the player makes the difference, but the consensus for bluegrass is that parallel tone bar bracing with F holes can be heard over everyone else better than a sweeter round hole with X bracing. I like to play Celtic and jazz on my X braced F hole.
Blah… Have fun shopping for your new mandolin, which hopefully will have an adjustable bridge. I played a nice "Moon" mandolin recently.

Re: Mandolin Bridges

I’m sorry Screech but I can’t agree with your statement : "That’s right, but in designing an instrument the luthier works the other way - he decides what bridge height is needed first, and sets the neck angle to suit"

It would be a foolish luthier to design and build the hardest part of his instrument - ie the body and neck to suit the most easily alterable(with little effect on the results) part of the design ie the bridge.

The height of the bridge is totally decided by the relationship of the neck to the top of the sound board ie the neck "lean" angle. This in turn will be decided by the luthier when he knows/designs the height of the soundboard and it’s construction. The construction of the soundboard - in particular the stiffness will also determine the amount of energy needed to be imparted by the strings (via the bridge) into the soundboard.
ALL soundboards are raised to SOME degree - even "flat tops" - carved tops more so to give the domed/arched strength and thus less bracing is required. Flat-tops are raised to some smaller degree to allow for the deflection of the soundboard under string tension. look at badly/cheaply made/designed flat-tops that have a floating bridge arrangement and NO RAISE at manufacture and I will show you an instrument that has a sunk-top!!!

As mentioned earlier the "break angle" of the strings over the bridge has an effect on the force or energy imparted to the soundboard - given identical strings the bigger the angle the greater the force. To get a higher break-angle you need to make the neck lean back more (to allow the strings to be near the frets) and there comes a point where you can’t do that much more - so the actual design of the top ie it’s height is a crucial design factor.
You CAN have on a "Flat-top" design either a low bridge or a high bridge it depends entirely on the lean back angle ie the neck to soundboard top angle - the greater this angle leans back the higher the bridge will need to be to allow the strings to lie along the fretboard at a playable height.

Once the luthier has settled the height of his soundboard top, it’s construction/stiffness and the lean-back angle of his neck THEN he will consider the actual height of the bridge.
Personally I do not know of ANY luthier that actually cuts a bridge to finished size - a rough approximation grant you - but the actual final finished size isn’t done until it is strung up.
The vagaries of knowing exactly how high the soundboard will be (they are adjusted by thickness to suit the "Tap Tone" usually) and just where the neck angle will settle after
fixing in place plus the fact that every piece of wood behaves differently dictate that you never really KNOW where things will end up irrespective of your expertise in construction - so it is prudent to wait until the last moment to determine the EXACT height of your bridge.

Once you have strung up a new instrument it will shift shape/position due to it’s uniqueness of construction and build materials until it assumes it’s near normal playing position - THEN a good luthier will have to adjust the height of
the bridge again to suit this final position. That’s why Gibson invented the adjustable bridge - to allow easy/quick ie out of the factory quickly adjustment for all the variables before shipping and after.

Are you still awake all !!!!

Re: Mandolin Bridges

"Flat-top design either a low bridge or a high bridge it depends entirely on the lean back angle ie the neck to soundboard top angle"

Big Muddy mandolins come with three bridges i.e one fitted to the instrument + a higher and a lower one?