My journey to rid MIM jazz fretless dead spots

yamark · #1 07-06-2009, 05:32 AM

I had the typical C C# D dead spots on the G string.

After much research on TB and elsewhere, I decided to partake in a little attempt to rid of these dead spots.

Step 1-Bought extra neck in case of major screw up.

Step 2-Threaded neck inserts. 10-32 size using a 3/8 drill bit and a tap. This proved to be much harder than I thought, but I managed to not destroy my neck.

Step 3-restrung with fresh chrome flats. This is where I did something very stupid. I somehow managed to put my D string in the E string place. It of course didn't fit the nut currectly and it rattled against the fretboard like crazy. I got pretty upset and thought I destroyed the original neck so I began to disassemble the bass for the new neck. I thought, man this E string looks a bit thin.

Step 4-Put E string in E string location. Sounded like a gem. Restrung rest of strings on modded neck.

Step 5-tuned, adjusted bridge height, retuned, adjusted intonation, retuned. Previous dead spots were about 75% gone.

Step 6-Put felt on a C clamp and placed in on my headstock. I found a spot where the it made the bass ring for days.

Step 7-I am a jeweler and had some heavy moldable metal laying around. I flattened the metal and made them perfectly circular then carved my bands logo into each of the pieces. Hot glued them in the exact locations the C clamp made contact with the bass.

It is perfect now!!

A side note on dead spots. I was curious about these natural resonances of fender basses so I did some experimenting prior to all this work. I did slides up and down my strings very slowly. There was a very noticeable increase in body vibration as I approached the C on the G string and a very noticeable decrease in body vibration as I came out of the D. This was very interesting to me as I teach physics and sound.

This will make for a good lesson next school year on destructive interference.

CDweller · #2 06-30-2010, 08:03 AM

Surprised no one commented on this. I'll be trying this with a fretless bass I have that's got a wicked dead spot issue. I can feel the body vibrate a lot when playing in the C-Eb range on the G string. That's a tremendous amount of lost energy, for sure.

longfinger · #3 06-30-2010, 08:11 AM

Yamark,

Do you have photos to show what you did?

SC Bassboy · #4 06-30-2010, 08:19 AM

I've never heard of dead spots on a fretless. Pictures of this process would be greatly appreciated!

steve_rolfeca · #5 06-30-2010, 08:25 AM

Interesting. Despite all the attention paid to neck resonance the last few years, I don't remember seeing anyone else target the neck joint for modification.

My fretted 5-string is perfectly even all across the fingerboard, but it's as far from a Fender as you can get: It's a single-cut neck-through, with carbon-fiber reinforcing rods in a multi-lam maple/bubinga neck, and a thick ebony board.

The cool thing about your approach, is that it lets you even out the response without going to exotic materials or construction.

The dead spots on my '64 P-Bass used to drive me crazy. Last year I picked up an American Vintage '62, but it soon moved on, for the same reason.

Perhaps if I had whacked some threaded inserts into either of them, I'd still have a "real" P-bass...

dmusic148 · #6 06-30-2010, 08:32 AM

While I'm glad it worked out for the OP, this should in no way be held as a cure for all basses, 'Fender style' or otherwise. I've done exactly the same things with NO improvement. The OP got lucky.
Fretless basses have dead spots as often as fretted ones do.

Eric Moesle · #7 06-30-2010, 04:10 PM

There has been a product called a "fatfinger" that's been available for years to deal with this problem. Any change in the mass of the headstock will move the deadspots.

Keep in mind that they are never truly "gone", just moved to a less offensive place....

CDweller · #8 06-30-2010, 06:14 PM

Well, I'm going to try this, and will report back once the mod is completed. I'm also going to use threaded inserts for the bridge, just for the heck of it.

I have a fretless bass that I really want to be an excellent bass. The body is an alder USA Fender Jaco tribute model that is quite light. The neck is a USCG fretless that I had Harris Thor epoxy. The tone is outstanding, but the deadspots along the G string suck. I now know a bit more about neck resonance, nodes, and anti-nodes than before. I also studied waveform analysis in some physics courses back in the day.

It's not really "adding mass". What you're doing is changing the wave behavior mechanically. The neck is essentially whistling at a certain frequency. The whistle can be stopped by interrupting the wave path. With the right imaging technology, I could probably see where to insert a pin in the headstock to stop the resonance with the greatest efficacy.

Anyway, threaded inserts are the first stop.

CDweller · #9 06-30-2010, 06:22 PM

Quote:

Originally Posted by SC Bassboy

I've never heard of dead spots on a fretless. Pictures of this process would be greatly appreciated!

A dead spot on a fretless is no different than on a fretted bass. The neck is sympathetically vibrating with the string at certain frequencies. The string's vibrational amplitude decays significantly more rapidly on a dead spot than elsewhere. You feel dead spots in the body, as the vibration from the string vibrates the neck, which in turn vibrates the body. Ideally, the neck rejects most of the string's vibration, as does the body, which keeps the energy vibrating the string- aka sustain. The amount and nature of energy absorbed by the neck and body color the tone of the bass, as does the actual vibration of the string.

Tusec · #10 06-30-2010, 06:29 PM

I wanna know the physics of how tension from machine screws is different than tension from wood screws.

Or to put it more directly -- I see no reason to think threaded inserts would make any difference. The headstock weight is interesting though.

CDweller · #11 06-30-2010, 07:23 PM

I'm thinking that maybe it's not the tension at all, although you are able to apply a lot more clamping force between the neck and body with the threaded inserts and machine screws than with the stock wood screws.

I can feel the body vibrate a lot, which means that the body is coupled to the vibrating neck just fine. I'm not sure that increasing the clamping force between the two will stop the neck from vibrating when a dead spot is played. However, inserting the threaded inserts into the heel of the neck alters the neck's physical properties- it's not the same as it was prior to installation. Maybe the resonance of the neck is changed by the inserts enough to stop the neck from vibrating so much when a dead spot is played. Maybe tugging on the heel with a lot more force, which the machine screws do, alters the nature of the neck's resonance, such that the dead spots are taken care of. I sure don't know, but I'm going to see what happens.

stflbn · #12 06-30-2010, 07:26 PM

Quote:

Originally Posted by CDweller

I'm thinking that maybe it's not the tension at all, although you are able to apply a lot more clamping force between the neck and body with the threaded inserts and machine screws than with the stock wood screws.

Yes, you can also crack the finish on the bass if your not careful with excessive tightening.

Tusec · #13 06-30-2010, 07:48 PM

Quote:

Originally Posted by CDweller

I'm thinking that maybe it's not the tension at all, although you are able to apply a lot more clamping force between the neck and body with the threaded inserts and machine screws than with the stock wood screws.

I can feel the body vibrate a lot, which means that the body is coupled to the vibrating neck just fine. I'm not sure that increasing the clamping force between the two will stop the neck from vibrating when a dead spot is played. However, inserting the threaded inserts into the heel of the neck alters the neck's physical properties- it's not the same as it was prior to installation. Maybe the resonance of the neck is changed by the inserts enough to stop the neck from vibrating so much when a dead spot is played. Maybe tugging on the heel with a lot more force, which the machine screws do, alters the nature of the neck's resonance, such that the dead spots are taken care of. I sure don't know, but I'm going to see what happens.

Yeah, I hear what what you're saying, but I don't hear a really good reason in any of that. Why would a few inserts, whose mass is insignificant, fundamentally change the way the neck vibrates? The tension argument doesn't work because once you have enough tension to achieve good coupling, adding more tension doesn't really do anything. All you're left with is, well, it might change something, but that seems pretty flimsy.

I think the inserts are a lot of work and risk for a negligible return.

On the other hand, maybe there are factors involved that aren't obvious, and it really will do something. The other things is, it's an interesting experiment. So...let us know how it works out! (but be on guard against placebo effect...)

CDweller · #14 06-30-2010, 08:12 PM

Quote:

Originally Posted by Tusec

Yeah, I hear what what you're saying, but I don't hear a really good reason in any of that. Why would a few inserts, whose mass is insignificant, fundamentally change the way the neck vibrates? The tension argument doesn't work because once you have enough tension to achieve good coupling, adding more tension doesn't really do anything. All you're left with is, well, it might change something, but that seems pretty flimsy.

I think the inserts are a lot of work and risk for a negligible return.

On the other hand, maybe there are factors involved that aren't obvious, and it really will do something. The other things is, it's an interesting experiment. So...let us know how it works out! (but be on guard against placebo effect...)

Definitely not going to accept false results (placebo effect/Emperor's new clothes).

I'm not seeing that adding mass is a solution. It seems like it's more like you're interrupting the flow of energy through a medium (the wood, graphite, epoxy, metal, etc. that comprise the neck) with an obstruction. The energy has no place to go, so it remains in the vibration of the string.

Just trying to sort out what's happening through intuition, and have no real science to back this up. I'll let you know of the results, though. I'll be having it done by Hambone, so I'll be mitigating the risk as much as I can. It'll be a little bit pricey, but as it is I'm really not happy with the neck, and this is the last stop before throwing in the towel on this neck.

JLS · #15 06-30-2010, 11:15 PM

I'm thinking that maybe it's not the tension at all, although you are able to apply a lot more clamping force between the neck and body with the threaded inserts and machine screws than with the stock wood screws.

That's my take on it, too.

koobie · #16 07-01-2010, 05:27 PM

Glad this thread got resurrected, it's interesting stuff. All my basses have a dead spot on the G string, feels weird where they're choked on one or two notes.
I've got threaded inserts on one guitar neck, but it came that way so I can't comment on a 'before-after' potential tonal change. It seems like a logical upgrade for a bolt-on instrument, wood screw are eventually gonna strip the threads of a neck that's been removed enough.

CDweller · #17 07-03-2010, 11:22 PM

Well, I sent the bass off to Hambone for the spa treatment. Two issues with the bass- the bass has no mwaa (it's a fretless), and also it dies on the G string, especially up above the 15th fret. It also has a pretty significant dead spot in the usual C#-D# area. We'll see if the treatment helps.

The bass is a Fender Jaco Tribute body with a USCG neck that was epoxied by Harris Thor. I have not been impressed with any of the four USCG necks I have purchased in the past 6 months. I gave them the benefit of the doubt, but now I'm just trying to salvage the USCG neck that Harris coated.