I'm pretty new to building and would love to hear from anyone who has encountered what I just did. Here's the story...
I built an electric 3 string fretless using an Undercrown box, oak neck, CB Gitty snake oil humbucker and chrome hardtail bridge. It's a 25" scale with the bridge far back on the box resulting in 17 "frets". It also has a volume pot. Build came out great--sounds great--fairly loud even without plugging in, great tone. It's the build on the right in the photo.
A friend asked me to build him the same basic guitar except he wanted a longer neck so I got the same box and parts and built it up. The only differences from the first build is that this build doesn't have the volume pot and the bridge is moved farther from the box edge so he could have a longer neck (20 frets) at the same 25" scale.
The puzzle is that the second build sounds substantially different. Very low acoustic volume and a different tone, not as "bright" I'd say.
Any ideas why the sound would be so different? Is the neck length difference and resulting change of bridge location the culprit?
First, Moving the hardtail farther into the center of the box on the second build is likely to impact acoustic volume. It will dampen the ability of the box top to vibrate. Some nice F holes might help improve acoustic volume.
Second, the pickup is not in the same relative position from one guitar to the other. The second build has the pickup at a lower percentage of scale length than than the first.Measure from the bridge to the pickup on each guitar, then divide that by the scale length. That will telly the percent of scale each is located. They are different.
If you look at a commercial six string electric with two pickups, one is called "Bridge" pickup because it is closer to the bridge the other is called the "Neck" pickup because it is closer to the neck. The reason commercial guitars do this is that the two pickups will sound different because of their location. That is essentially what you have with you two guitars. Yours has more of a bridge position pickup which typically sounds more mellow that a pickup positioned closer to the bridge.
So your guitar should sound more mellow (electrically) than the second build. That being said, I wonder if the pot on your guitar is actually a tone pot and not a volume pot. Based on what I see, your guitar should be more mellow and the second guitar more bright (when electrically amplified).
Since you didn't describe how the two guitars sounded different, I have to go on what I'm seeing. I guess the question becomes "Is there a problem here or just a difference?"
By the way, nice looking gits.......
Thanks, Tom. Everything you said makes sense. I particularly like the comment "Is there a problem here or just a difference?". I'm hoping it's just a difference to my buddy!
I suspect having the hardtail nearer the middle reduces the lid vibrations, especially if there is a wooden block under the lid into which you have screwed the hardtail bridge.
The difference in tone when plugged into an amp is explained here https://www.amplifiedparts.com/tech-articles/basic-electric-guitar-...
"The actual value of the pot itself does not affect the input to output voltage ratio, but it does alter the peak frequency of the pickup. If you want a brighter sound from your pickups, use a pot with a larger total resistance. If you want a darker sound, use a smaller total resistance. In general, 250kΩ pots are used with single-coil pickups and 500kΩ pots are used with humbucking pickups."
With no volume pot there is no resistance added and so a darker tone.
You have built two CBGs to be proud of. The difference in tone can be modified via the amplifier controls and had you not built two very similar you probably wouldn't have noticed the acoustic difference. I am sure your friend will be very pleased.
Usually I use a hardtail near the edge of the box and a free floating bridge if the neck length/scale means it will be nearer the centre.
Acoustically the left one is louder as the strings vibrate the lower middle lid strongly due to the downwards pressure of the vibrating strings via the floating bridge (the bridge is only held in place by the string pressure).
The right one is screwed into a thick block of wood which is needed so the six string pressure doesn't pull the box apart. Also as it was the first ever one I made I drilled a big hole in the box lid so not much soundboard to vibrate. Even so I find I can play it acoustically and the volume is perfect - I can hear every note but my family don't get disturbed :0).
Thanks David. You are right that the hardtail is screwed into a block and that makes sense that it's limiting the vibration of the lid dramatically since the bridge is more centrally located. I'll have to digest the info on the pots... a bit confusing to me!
Having played around with it I am hoping that the amp will allow him to adjust the sound the way he wants it.
And love the look of your guitars!
Hi, my first thoughts on the differences of the two guitars that will effect tone and volume was.
one bridge is closer to the rim of the box so a stiffer mounting point.
the pickup is under a different portion of the strings length.....and
Are the pickups The same? Good pickups are wound to suit the position they are placed under the string, bridge-middle-neck.
just a thought. Taff
Thanks for all your help. As you all pointed out, the sound is different but it still sounds great and an amp adjusts for the volume. My buddy was thrilled with it so it's all good!
Mounting a bridge closer to the center of the box will dampen the sustain(how long the string vibrates), but the strings being closer to the middle increases the acoustic waves which increases the acoustic volume and gives the guitar a fuller tone(bass/midrange/treble) compared to a bridge mounted closer to the edgethat has more treble influence.
I'm guessing the pickups are the Gitty SnakeOil pickups that have the same output specs and not designated for neck or bridge positions. The placement of the pickups relative to the fretboard position has a effect on the output tone. The edge mounted bridge guitar has the pickup mounted where the 19th or 20th fret would be while the center bridge guitar has the pickup mounted where the 22nd or 23rd fret would be. That has a influence on the tone too because of the string vibration node points(vibration wave intensity).
So the git with edge mounted bridge should have more treble tone acoustically, but the placement of the pickup further up the fretboard would add more bass tone from the pickup. It probably has a mellow tone to it overall.
The git with more centered bridge and pickup closer to the end of the fretboard would likely be louder acoustically and electrically with good harmonics and a more balanced tone.