Banjo bridge placement is a common problem. Let’s solve the mystery.

Banjo bridge placement.. What’s the mystery? Does a player really need to know this? 

Banjos differ from guitars in a number of ways, but one issue guitarists just don’t have is bridge placement. This is because the guitar’s bridge is the support for what is known as the “saddle”. To me, the terms always seemed to be backwards. The banjo’s bridge is what the strings ride on, and on guitars the bridge has a slot for the saddle to sit into and it’s the saddle which the strings ride on. I came to have to just accept what seems to be a conflict of terms, but so be it. A guitar’s saddle is equivalent to the banjo’s bridge. What is really different however is that the saddle of a guitar is fixed, and the bridge of a banjo is moveable. That is, you can place it just about anywhere. The same is true for a number of floating bridge instruments, such as the violin, the mandolin, the cello and bass and many others.Probably the true ancestor of the guitar is the lute. IT has a fixed saddle, and you might notice the term for a guitar repairman is the “luthier”, or lute-maker. It is the knowledge and craftsmanship of the luthier that is required to place the guitar’s bridge and saddle in the exact correct location, since it’s impossible for the player to move it. The banjo bridge is different, and it’s important for the player to know how to find the correct location for the banjo bridge since simply changing strings or the head will often disturb the bridge location. Mandolins also have floating bridges. The descriptions I give here are about banjo bridges, but the mandolin bridge placement procedure is exactly the same.

What happens if my bridge is not in the “correct” spot?

If your banjo bridge is not located correctly, you may be able to tune the banjo to the right notes to start with; but as soon as you begin to fret the strings the game changes and it might sound out of tune. Fretting a string on a particular fret, you would naturally expect to get a different note than played “open”. But this note may be higher or lower in pitch (sharp or flat) than what you would expect to hear. The reason for this is that the frets are placed in very specific places along the length of the string. Yes, the STRING.. And string length has to do with bridge placement. If it’s off, your fretted notes will be out of tune even if the banjo is tuned correctly.

I want to put the bridge over the “sweet spot” of the banjo head. How do I do this?

I have been asked about this. You might have heard the term “sweet spot” when talking about banjo heads. It is true, where the bridge is placed can affect tone. The tone or timbre, is not as critical as pitch. What is of absolute importance is for the instrument to play on the right pitches with each fret used. Otherwise everything sounds, well, pretty bad. So the answer to that question is generally no, the only possibility being that if you are lucky enough for the correct spot to actually be on the “sweet spot” you’ve done it. But the player has no control over this. There is truly only one spot for the bridge and that’s based on pitch.

How do I know if the bridge is too close to the tailpiece or too close to the neck?

The Tailpiece of a banjo is the metal device at the base of the banjo head that anchors the strings. The tailpiece has small hooks or pegs over which the string’s loop is on, holding the string. If the bridge is placed too close to the tailpiece the banjo will sound “flat” that is, the fretted notes will be too low. Conversely if it’s placed too close to the neck joint the fretted notes will be too low, or “flat”.
It’s pretty important for every player to understand why, so I’ll explain this and use some illustrations to help me out.

Death, Taxes, and imperfect intonation.

Intonation is the term used for what we’re talking about here. That is, how all the strings are tuned across the width of the fretboard, string to string, and also how that translates to different chord positions. When you play a stringed instrument you move your (presumably) left hand up and down the neck using different frets on the fretboard. All of the strings are all made differently- Using different gauge wire, and the fourth string is a “wound” string, so their characteristics are all slightly different from one another when they are fretted. It actually begins to get way more complicated than players need to understand, so just keep in mind the strings each behave in very slightly different ways when fretted so keeping each one of them in perfect tune no matter where you fret the strings could be considered virtually impossible. We simply have to do the best we can and accept this reality. It’s easy to become obsessed about it when you realize that not every string is in perfect tune with all the others when you’re playing. Inventions like compensated bridges are available to help out, and I’ll speak about them later- but for now just realize that it’s a fact, like death and taxes. What is the perfect bridge placement for one string may not be perfect for the one next to it and so on, across the fretboard. Using different inversions of chords (same chord, different chord shape somewhere else on the fretboard) makes it even more complicated. It’s not a problem for audiences as long as we set the bridge the best possible way.

Notes, octaves and string length

Okay so here we go.. understanding this is the key to remembering it. That’s the case for me anyway. We are going to find the middle of the strings. Not the physical middle you could measure with a tape measure, but the acoustic middle. What I mean by the “acoustic” middle is  going to be very, very near the actual mid point of the string between the nut and the bridge; that is, the free, vibrating part of the string between the nut and the bridge. Half of the string’s original length will produce a note an octave higher than the open (non- fretted) string’s note. So if you tune the third string to a G-note, the fretted mid point would produce a “G” note, an octave higher. In practice, we can actually sense the math with our ears. We perceive the octave to be different, yet in a way, the same note.

Musicians use a standardized fixed frequency of 440 cycles per second (Hz) as their base tuning note, which represents an A note. Everyone in the orchestra tunes to 440 Hz. It is known as “Concert A”. Based on this standardized note, our clip-on tuners, desktop tuners and phone apps also use 440 Hz as the referenced “A” note for tuning up. They usually use the notation “A 440”. Even though the banjo doesn’t use A for any string, it’s still the reference point-  So if “A” is defined as 440 Hz, the others are standardized as well.

The music of the western hemisphere is based on scales. Every major scale has 8 notes, and the octave is the 8th note in the scale, doubling the frequency. For instance you can find a concert A at 440 Hz as I mentioned, and the next octave up, “A” will produce a frequency of 880 Hz, exactly double, To double the frequency of a string, you fret it at the 12th fret. Your ear can actually recognize the similarity of these frequencies. Because of  how the human ear perceives sound, there are some notes which are not absolutely perfect multiples of the last and they must be adjusted slightly. These slightly adjusted notes are in what is called a “tempered scale”, which I won’t expand on but it just means some notes have to be adjusted just a bit to be perceived as “in tune”. Nevertheless the general idea holds true. The key things to remember: cutting a string’s length in half will double the frequency, and will be an octave higher in pitch than the previous length. For an A note, it will go from 440 to 880 Hz and all  notes work this way.

What we’re looking for is the acoustic “middle” of the string to place the bridge. Why the middle? I want to adjust the end of the string?

We need to calibrate our string length by moving the bridge. This will let us  place the center of the string over the octave fret, #12. it’s easy to find the acoustic center point, and we use our ears- or an electronic tuner to do it. Here’s the idea behind it:
Moving the bridge relative to the fixed end (nut) will move the string’s mid-point relative to the nut also. It moves by half that distance we moved the bridge. Imagine taking a piece of cotton string and measuring out a length of 20 inches. Fold it in half, and you’ll see the middle of the string will be at ten inches. If we increase the length of the string to 21 inches, the middle of the string will now be at 10-1/2 inches from the end. The mid-point divides the length into two equal parts. The extra inch is divided equally between the left half and the right half. So the mid-point is now half that distance further from the fixed end, or nut. It’s much like marking the middle of a relaxed rubber band, measuring this from one end then stretching the band. The mark will move away from the fixed end- half the distance you’ve pulled it. This is the whole key to understanding bridge placement. They key to remember here is that moving the bridge moves the middle point of the string also, by half the amount we move the bridge.

The 12th fret needs to be exactly at the mid-point of the string. And if our string is too long, the mid-point (on the string) will be past the 12th fret. This in essence puts the 12th fret short of the mid-point, and it will sound flat. If, however, we shorten the string  more than we should (move the bridge toward the neck) the fret will be past the mid-point of the string, and the octave note we want to hear will sound sharp. What we are doing by locating the bridge then, is carefully locating the mid-point of the string to be right on top of the 12th fret, where it must be- to sound right.

What about all the other frets? I’m just aiming to tune the string on the 12th fret?

Yes you’re just moving the middle of the string to the 12th fret. All the other frets on your instrument are cut into the fretboard by the maker. They used an algorithm to place the fret cuts when the instrument was made. There is nothing we can do to change it, and it seems that they get it right.

My bridge has a tilt to it. (or) My strings have a strange buzzing sound..

Most banjo bridges have a tilt built into them. This is intentional, and the bridge should tilt toward the tailpiece. This is to keep the free vibrating part of the string in contact with the very edge of the bridge closest to the neck. If it’s put on backwards, the edge the string stops against is on the far side of the bridge’s width and it can buzz against this part of the bridge since it’s vibrating over the bridge wood. So if there’s a tilt, put it tilting away from the neck. Keep in mind too, that if- when you tune the banjo it  buzzes, try tilting the bridge toward the tailpiece and it can often eliminate the noise. But look at your bridge on a flat surface. Odds are you’ll see it’s already tilting a little bit.

The exact method we use to find the right spot

As I’ve explained, for the bridge to be in the right spot, is wherever it has to be to place the acoustic mid-point of the string right on the 12th fret. It’s like shooting a target from a distance, where we are down at the bridge aiming to put the center of the string in that spot. Think of the rubber band with the mark in the middle. We have to stretch and relax the rubber band from just one end, to get it over that spot. The method is pretty straightforward and we utilize a very interesting phenomenon called harmonics, or “chiming” the string to aid us in finding the point.

Next we’ll be putting our adjustment theory into action.

You’ll be scooting the bridge up and down a little on the head. Be careful, because some bridges are pretty thin and can snap. If you’re careful it likely won’t. In all my life I’ve broken one, and it was a bridge I sanded down to be very thin as an experiment. The bridge can also fall over, and with all that string tension pushing down on them so hard they fall- no, they SLAM over and sound like a gun going off. If you have a straight bridge tipping over probably won’t break it in spite of the huge noise it makes. But relaxing the strings a bit might be needed. Use both hands, squeeze the bridge between the thumb and finger and stabilize it, moving it just a little bit at at time. Try to keep it from slamming over on its side and try to keep if from bending too much. They will bend before they break. So keep an eye on it and straighten it if it starts to bend. And if it seems really difficult, go ahead and loosen the strings somewhat. You do not have to loosen them all the way.

Using harmonics

To begin, you should string up the instrument with the bridge in the closest correct approximation you can put it. Normally on a standard banjo it’s somewhere around 4 inches from the bottom of the rim, or the same distance your banjo has from the nut to the 12th fret, the bridge should also be from the 12th fret. For most banjos that’s about 15.5 inches. So just put the bridge up there, be sure the tilt is downward, away from the neck, then tune up the instrument. You’ll need to play a “harmonic” on one string at a time starting with the first string. To do this, place your finger very gently- just touching, but not depressing the string right over the 12th fret. Pick the string and you’ll get a pretty sounding bell-like tone that is an octave above the tuned string note. What you’re doing is forcing the string to vibrate on each side of the center, while the center is almost still. This is the harmonic center of the string, and it will automatically snap to this harmonic even if your finger is a little off of the exact point. This is why it works so well, this note is the natural harmonic point of the string and it is prohibited by the laws of physics to chime incorrectly. Next press the string onto the fretboard at the 12th fret. Compare that note with the harmonic note. Try to hear the pitch change, if it does. You can use an electronic tuner to help out if you can’t tell by ear alone. If the note sharpens when fretted, the center of the string is behind the 12th fret and you need to move the bridge a little bit toward the tailpiece. If it’s flat, the center of the string is past the fret and you need to move the bridge (and the center of the string) back up toward the nut. Do this until the two notes are the same. Do this also with the fourth string and try to move only that end of the bridge, since you know the first string is already good. Then see if the second and third strings are accurate, too. Because of tempering and imperfect intonation you may have to compromise just a little, leaving one a tiny bit sharp and another a tiny bit flat. Just do the best you can. Once the strings ring a harmonic on the same note as fretting on the 12th fret, the bridge is placed.

A quick note:

Most people will tell you that you have to re-tune the banjo every time you move the bridge. I don’t do this. I just continue to compare the notes, whatever they are- Maybe it’s a little flat or sharp, I match the harmonic note and the fretted note and continue adjusting the bridge. Whether the string is tuned back to the original starting note is up to you and it might make it easier for you. It won’t really make any difference if you do or if you don’t re-tune. In other words, The two notes should be the same, even if they are not tuned correctly to standard pitch. You will re-tune when you’re done anyway.

My bridge doesn’t look straight, it’s angled!

Go back over this process at least twice. Moving one end always moves the other a little. Have you noticed that the bridge ended up looking crooked? Here’s another one of those “live with it” notions. It probably won’t be perfectly straight. Guitars of all types have slanted saddles to compensate for intonation differences. You might end up with a bridge in a similar position. Remember we’re just looking for the best compromise between sharp and flat on each string. I’ll often end up with a bridge that looks a bit crooked. Sometimes on a different banjo, or with a different string brand, it will look straight. Let the pitch be your guide and don’t pay any attention to that odd bridge angle. It’s okay.. And not entirely unexpected. I’ll always sight down the string from the tailpiece to see if the bridge is centered left and right also. The third string should come straight out of the tailpiece and straight down the center of the frets.

How Compensated bridges don’t work.. and they do work.. and the problems of intonation

Compensated bridges are one way of attempting to fix the whole angled bridge/intonation/tempered scale problem.  I’ve seen many designs from half moon shaped bridges, stair stepped bridges, other odd looking types.. They actually are effective at reducing intonation problems. None of them cure it completely. This is because of the various chord inversions possible, with the tonic note on any given string it’s like trying to nail jello to the wall. But they can, and do help. We have the Golden Gate compensated bridges from Saga and I like them not only for the compensation factor but they also have a very good timbre. I recall the Shubb company many years ago used to have one like that, perhaps Saga bought it from them.. I don’t know, but they do seem to help out. Then there’s the moon bridge. I’ve tried it. It seems to be an improvement too. In essence, they really do the same t hing A curve, or a stair step, the third string is longer than the others. Interestingly both of these bridges seem to have a big effect on one banjo and not seem to do anything to the next. It’s something worth experimenting with if you want to, as long as you never expect things to be perfect. Guitar builders have worked on this problem for ages. Many have individual saddle adjustment devices used to apply a contact point that is adjustable for each string. This is a great idea, you can see many electric guitars with them. They use a screw and bracket to adjust the string length, and there’s at least one, likely more you can purchase for use on an acoustic guitar. To me it’s such a minor thing the slant the guitar luthier built into the bridge when he  put the guitar together is okay with me. (But I’m just an old banjo picker and accustomed to imperfection).

That’s about it!

I do hope my concepts have helped you to further understand what we’re trying to do here to put the bridge in the right place. If you have any questions of comments please post them here and we can talk more about it. But most of all, keep on pickin!