Threaded Inserts (Steel) - TONE A/B TEST

[SurferJoe46]

I totally agree! In fact my thought was to make your bolt-on a fixed neck by smearing gorilla glue in the joint!

Tossing this out as a thought:

How about resetting the neck-to-pocket contact with a layer of - oh, say JB Weld - then a sheet of wax paper and then another coat of JB Weld on the other side ?

Kinda a JB|WAX PAPER|JB sandwich ?

That way the wax paper would keep the neck and the body from permanent attachment and yet the air pockets and voids would be filled in completely, making a 100% footprint between the two parts.

Just a thought.

 

[mongo2]

Tossing this out as a thought:

How about resetting the neck-to-pocket contact with a layer of - oh, say JB Weld - then a sheet of wax paper and then another coat of JB Weld on the other side ?

Kinda a JB|WAX PAPER|JB sandwich ?

That way the wax paper would keep the neck and the body from permanent attachment and yet the air pockets and voids would be filled in completely, making a 100% footprint between the two parts.

Just a thought.

A similar process has been used for decades with an epoxy mix called bedding compound to improve the fit between the stock, action and barrel of rifles with the goal of improving accuracy and consistency. It's called bedding a rifle and years ago (in my pre-internet days) I saw a magazine article about applying the process to a bolt on guitar.

Long story short, on the guitar the epoxy was applied to the neck pocket and the neck heel was wrapped in a couple of layers of plastic wrap to provide a close fit while permitting subsequent easy removal of the neck.

 

[johnk_10]

Tossing this out as a thought:

How about resetting the neck-to-pocket contact with a layer of - oh, say JB Weld - then a sheet of wax paper and then another coat of JB Weld on the other side ?

Kinda a JB|WAX PAPER|JB sandwich ?

That way the wax paper would keep the neck and the body from permanent attachment and yet the air pockets and voids would be filled in completely, making a 100% footprint between the two parts.

Just a thought.

IMO, that's absolutely unnecessary. the neck pocket should be perfectly flat, as well as the heel of the neck. when the four screws (or six on a MM) pull it to the body, it should fit flush, and the screws themselves transfer the vibrations from the body to the neck by picking up the end grain. if it needs a shim, the shim should be tapered.

on a micro tilt system, if you adjust any neck tilt, the neck isn't even making full contact with the pocket, so the screws are doing the bulk of the transfer.

many people think that the 'three bolt system isn't as solid as a four bolt, however when Leo and i discussed it (he invented the micro-tilt), the micro-tilt is actually a four bolt system (counting the allen screw- and six if you count the two flat head screws that attach the metal disc plate), and can secure the neck even stronger (tighter), since the allen scew is applying pressure against the large machine scew. the method of mounting the neck and adjusting the tilt angle was to first get the two top screws snug, set the tilt, tighten the two top screws and the thrid large screw, and then go back and tighten the allen screw.

 

[mongo2]

when Leo and i discussed it (he invented the micro-tilt)

Little known factoid: Danelectro sold instruments with a micro-tilt setup about a decade before Fender.

 

[stingray69]

OK - rounded up a very nice freebie spectrum analyzer (by Blue Cat). I've never used one of these, but the application pretty much does all the work - all you have to do is play the track or in my case I highlighted a very specific single note (a G note) out of my Track 1 samples, the program will return exactly what is happening inside the waveform. It shows what frequencies are present in the waveform/note from 10Hz up through 22Khz. It also shows the amplitude (loudness) of those frequencies as they spread across that 10Hz-22Khz spectrum.

The program takes the first snapshot of the note & freezes it at it's peak, the waveform then continues to jump up & down in realtime (the second blue graph underneath the frozen peak at the top) underneath the frozen peak like a jack russell terrier in the middle of a sugar rush. So just pay attention to the top blue line in these photos - that's the frozen peak, the loudest snapshot sample of that note. What I found was pretty wild, IMO. I highlighted some areas of interest in red that changed the most and in very peculiar ways...in a nutshell, what I found was:

1. There is some low end loss, but it is isolated in a very tight band of frequency between 100-150Hz.

2. Everything else from 100Hz on down to 10Hz actually increased dramatically. That I found pretty wild. Had my bass rig been especially efficient at reproducing frequencies from 47Hz and down - I'm thinking I may have been reporting a gain in overall low end.

3. As I (and hopefully others) are hearing it in the audio tracks, the spectral analysis graph shows the mids & highs starting at 200Hz up thru 22Khz are lifted markedly - in a very smooth, uniform & even lift across that entire band (with no resonant "spike" frequency(s) contained within those lifted frequencies). The waveform also looks likes it is carrying a much more rich, full & complex set of frequencies & overtones in that band (200Hz - 22Khz) as well.

Spectrum Analyzer BEFORE Inserts:

Spectrum Analyzer AFTER Inserts:

 

[SurferJoe46]

I recognize that the pocket should be level, smooth and all that - but even machined metal has 'tooth' and minor surface imperfections to it and on your chip in your CPU, thermal-dielectric paste is used to insure good - no, make that ALMOST perfect surface-to-surface contact for a few different but necessary reasons.

Wood can never be a solid and totally conductive surface since molecular and wood grain variations are so great.

Thinking further --- by logical extension, I wonder if the existing air pockets between the neck and pocket wood surface irregularities aren't somehow exacerbating the dead notes on the G string on many basses.

Bedding a rifle barrel is something about which I totally forgot - but it also argues a great reason why we should reconsider the possibility of needing to do the same for a bass guitar.

 

[johnk_10]

in electronics, thermal paste is used for a semi conductor's heat dissipation.

and as Leo himself stated, the body's transfer of vibration to the neck has more to do with the four long screws transferring it to the end grain than the two surfaces making contact. the same goes for the bridge.

however, as far as 'bedding' goes, the lacquer on the heel of the neck often slightly conforms and bonds with the body's neck pocket as can be seen by removing a neck that has been on a bass for a very long time. that's why i prefer to leave the neck mounted to the body and remove it only if absolutely neccesary.

 

[SurferJoe46]

johnk_ ::: .............in electronics, thermal paste is used for a semi conductor's heat dissipation.

Absolutely correct - because the surface-to-surface contact cannot be trusted and the heat build-up would kill the chip.

And that's the same thing for sound conduction. Heat or sound - they are both a flow of energy and if it's defective or not as good as it can be, there are losses to both.​

.........and as Leo himself stated, the body's transfer of vibration to the neck has more to do with the four long screws transferring it to the end grain than the two surfaces making contact. the same goes for the bridge.

I cannot see how four screws and their inherent surface contact, even under threaded tension, can be anywhere near as good as full surface-to-surface contact under superior conditions.

Without the screws, of course there can be no pressure and contact via the joint - but frankly what Leo said (if he said it) makes sense if you realize that without the screws there'd be no contact at all.​

.........however, as far as 'bedding' goes, the lacquer on the heel of the neck often slightly conforms and bonds with the body's neck pocket as can be seen by removing a neck that has been on a bass for a very long time. that's why i prefer to leave the neck mounted to the body and remove it only if absolutely neccesary.

'Punting the somnolent canine' comes to mind - but not taking the neck off is not always an acceptable solution. Many times the neck is pulled for confirmation of various aspects of authentication and shimming service not forgetting field stripping for personal recreation.

"Slightly conforms" is not be a good operand here either.

I think having one surface coated, however thickly, with lacquer or varnish or urethane, slightly conforming won't necessarily connect with all the opposing nooks and crannies and even if there was a similar coating on the opposing side - then it might not be a much more serviceable situation.

Under a 2X magnifying glass, the irregularities look like an English muffin.

Maybe I'll take the time to reset my P-bass neck and use a seating jell of some sort and see if the dead zones disappear.

Could be quite interesting. But that's gonna have to wait for an ongoing project of rebuilding my Gibson 6-string guitar first.​

<did I say the 'g-word'?
Was that an outside word or was that an inside word?
Gack! I hope I didn't say the 'g-word'> ​

 

[johnk_10]

the neck screws actually make more contact than you might think. if you figure their diameter, length and more surface area due to their threads, it's actually ALOT of surface. the neck's end grain is what is doing the transfer, not the 'bedding', and IME, any type of gel that conforms is acually going to dampen the connection. i had a customer that tried it 20 years ago, and the whole neck sounded completely dead, even with brand new roundwounds. it took me awhile to remove all of that stuff, and when i did, his came alive.

go ahead and have at it, but don't be surprised if it actually exacerbates your dead spot problem. (been there/done that).

 

[ghoulbug]

Thanks for recording these. I had a blast listening to the clips.
It really blows my mind how much of a difference the screws made. It was almost like listening to Passive vs. Active electronics.

I know the factor here is neck-body adhesion, but I wonder if a high-mass bridge or heavy body would work in the same way (by limiting string vibration).

 

[SurferJoe46]

the neck screws actually make more contact than you might think. if you figure their diameter, length and more surface area due to their threads, it's actually ALOT of surface. the neck's end grain is what is doing the transfer, not the 'bedding', and IME, any type of gel that conforms is acually going to dampen the connection. i had a customer that tried it 20 years ago, and the whole neck sounded completely dead, even with brand new roundwounds. it took me awhile to remove all of that stuff, and when i did, his came alive.

go ahead and have at it, but don't be surprised if it actually exacerbates your dead spot problem. (been there/done that).

A-haaaa! The gauntlet is thrown!

Dentu-Fix?
Silly Putty?
Dau's Good?
JB Weld?

My mind spins with the possibilities.

 

[stingray69]

Thanks for recording these. I had a blast listening to the clips.
It really blows my mind how much of a difference the screws made. It was almost like listening to Passive vs. Active electronics.

I know the factor here is neck-body adhesion, but I wonder if a high-mass bridge or heavy body would work in the same way (by limiting string vibration).

Not a problem - I'm finding these results (especially the Spectrum Analyzer) to be fascinating myself & I'm seeing these things for the first time just as anyone else reading through the thread & trying to get my mind around the data so to speak, lol. Audibly, through a bass rig, I knew immediately something had changed in the way of sensitivity, note clarity, resonance.

Regarding the bridge, I do happen to have a top-loading bridge of slightly higher mass than the stock bridge I intend to replace. Now that I found a slick little spectrum analyzer to play with, it would be pretty simple to run an A/B waveform once the bridge is replaced. But I think I see a problem, the results would not pertain to every bridge replacement due to variable factors. You know what I mean? If there were only one de-facto standard, "high mass" bridge on the market, and same de-facto standard bent-plate style bridge of exact mass and material on every bass in the world, the results would be more a "little" more applicable - more fundamentally sound in theory because at least we would have very specific mass measurements on the bridges. But even if that de-facto scenario were a reality, the bridge is transferring vibrations into the next medium - the body of the bass, so now the wood properties come into play (Alder, Ash, Mahogany) and beyond that, the unique piece your instrument is made of, the resonance quality of that specific cut of lumber (water content, grain pattern tightness, knots in the wood of various shapes & sizes & locations - density essentially) would affect the results.

Since obviously both stock & high mass bridges on the market represent all sorts of varying degrees of mass and "high mass", metal type, etc. the results can only be valid (mostly) between the two very specific bridges you are experimenting with - and only as it pertains to the exact specific instrument you are using them on. If that makes sense - at least in my mind it did, I think, lol. So I can gladly post any changes that happen in my case, with my choice of bridge on my unique instrument...I think it would be very inaccurate to imply any tone change effects would hold true to the same degree & levels on anyone else's particular instrument - even another exact make & model within my own collection of instruments. Given all the variables going on behind a simple bridge swap & any degree of tone change results - I can see why the topic swings wildly both ways on the results end of things - some will say it does not make a noticeable difference, others will say it does. But whatever it is (the degree of results), it is surely unique unto each individual instrument, as I see it.


Edit: Obviously, there is MUCH more that comes into play now that i think about it - and without doubt even more that I haven't thought about. The material, mass & length of the screw body driven into the body (and to what depth & force), etc. One could spend a LOT of time trying to measure these sorts of things, me thinks.

The bridge-related statements above would theoretically hold true for the degree of results when using threaded inserts as well. You can't get around having the bridge mass & material nor the body density and resonance qualities stated above from affecting the degree of the end results. FWIW, I've done 3 of my instruments with these threaded inserts - each exhibited similar changes & noticeable, audible results. Also fwiw, the bass in testing is sporting a standard Fender-style bent plate design.

 

[pickles]

I've been reading this and thinking ... doing the glued-in inserts that also look like they have taller threads, with machine screws, is a much better mechanical attachment than wood screws. No doubt. You're going to be able to crank much more pressure with that.

And sonically, you've traded off some high-lows for more extended low-lows, have changed the shape and quantity of the highs, and have increased sustain. More extended and clear, less punchy and fat.

Sounds like a step toward a neck-through, and if I had to guess, maybe even closer to a neck-through than a set-neck is, figuring that all that mechanical pressure probably transfers more vibration than a glue joint does.

I wonder if you could arrange some way to slack a tiny bit of the tension and see if your low mids come back.

Its very comforting to know there are people out there that are as obsessive and endlessly curious as I am

 

[stingray69]

I've been reading this and thinking ... doing the glued-in inserts that also look like they have taller threads, with machine screws, is a much better mechanical attachment than wood screws. No doubt. You're going to be able to crank much more pressure with that.

And sonically, you've traded off some high-lows for more extended low-lows, have changed the shape and quantity of the highs, and have increased sustain. More extended and clear, less punchy and fat.

Sounds like a step toward a neck-through, and if I had to guess, maybe even closer to a neck-through than a set-neck is, figuring that all that mechanical pressure probably transfers more vibration than a glue joint does.

I wonder if you could arrange some way to slack a tiny bit of the tension and see if your low mids come back.

Its very comforting to know there are people out there that are as obsessive and endlessly curious as I am

That one I had actually thought of too last night while trying to work through all this business - I will try that later tonight. That should be a fairly easy thing to try. I wonder what the spectrum analyzer will show. I'll cue up the Track 1 AFTER Inserts track (since it is played with the machine screws already under hand-tight tension) and play the same thing with an "even" but generous amount of loosening of the machine screws at the neck joint. This should be good. It should partially answer or point to indications as to whether going back to less tension at the neck pocket (wood screws) would be taking the frequency response back to stock direction along with it.

Its very comforting to know there are people out there that are as obsessive and endlessly curious as I am

No doubt about that.

 

[selowitch]

Fascinating! I love this.

 

[oyobass]

These posts have ne thinking about the drive ratios involved. Wood screws with their coarse threads represent a "higher gear" since each turn covers more distance with greater effort. Machine screws into inserts represent "low gear" - less distance per turn, so more pressure exerted onto the neck joint at the same tourque force than the wood screw. when you add in the difference in friction between a plain screw into wood vs. a lubed macine screw into an insert, it is clear to me that the difference in "hand tight" between the two would be significant.

 

[stingray69]

Alright - I loosened the machine screws and judging by the amount of creaking & complaining of the wood, I could tell a great amount of force was being relieved in the process. The tuning also (expectedly) went down in pitch and was fairly out of tune. I wasn't sure at that point how to proceed - tune it up under these conditions? Or leave it be - I decided to leave it be for the recording. Wondering how to keep an even amount of looseness on all 4 machine screws, I decided to loosen them until they were protruding an even amount of height above the neck plate. I went with 2mm protruding above the neck plate - which would be ridiculous in the real world, but I was going for very little coupling force in the neck pocket for this test. In fact the neckplate was not even being held at this point.

Track 1 with Original Wood Screws in neck:

Track 1 with Extremely Loosened Machine Screws:

Track 1 with Hand Tight Machine Screws:

What I found with very poor neck coupling:

1. The narrow band of 100-150Hz did not return to "wood screw" levels, but it did drop a little from the "fully tightened inserts" position - kinda too be expected. This little band in general still leaves me wondering if this is simply a byproduct result of the extra mass of steel inserted in the neck & affecting just this tight little band of frequencies. Unfortunately, it still leaves the question dangling out there - if that amount of steel mass (inserts) were plugged with wood & wood screws, would that tight little band re-appear?

2. Even with these ridiculously loosened machine screws, everything under 100Hz was still a little better than the wood screws levels - hmmm, not sure what to make of that one.

3. Without question, the complexity of the mids and highs dropped off tremendously throughout the 200Hz thru 22Khz range under the poor coupling condition (see extremely loosened image). Take a look at the extreme nose dive the mids & highs & harmonic complexity took under this poor coupling test. You can see that the frequencies at roughly 3Khz really started to tank - and by about 5-6Khz, they literally fell off the graph completely.

4. Although the low-lows (47Hz and down) were still a little louder than they were with wood screws. The Extremely Loosened Machine Screws waveform shows that the bigger band of 200Hz-22Khz fell well under the wood screws level and they fell in a fixed straight-line, linear fashion. The amount of loosening was kind of ridiculous - very likely well under wood screw strength. It even started to kill off high end frequencies that were present in the wood screw waveform. So there is strong indication that if I played with a more realistic tension with the machine screws I could raise that overall 200-22Khz band to almost exactly where the wood screws frequencies were hitting in amplitude and harmonic content. The entire degree of threaded insert changes/"benefits" & results is starting to look controllable (by tensioning force) with exception to that tiny 100-150Hz band - still trying to figure that one out.

My conclusion on this one is that since I have no earthly idea exactly how much force the hand-tight wood screws were applying in the first place - I cannot even begin match it by loosening the machine screws. But the general, poor coupling test here still had volumes to show us. All I can state with absolute certainty from this particular test is that there is no question left in my mind that a stronger coupling of the neck in its pocket will have a very real & resounding effect on the tone, sustain, frequency range & harmonic content of the instrument. Taking any more than that from this poor coupling test would be too far-stretching and most likely just flat out incorrect. Interesting stuff.

 

[ghoulbug]

[snip]

Regarding the bridge, I do happen to have a top-loading bridge of slightly higher mass than the stock bridge I intend to replace. Now that I found a slick little spectrum analyzer to play with, it would be pretty simple to run an A/B waveform once the bridge is replaced.

[snip]

I see what you mean. All the different variables would make it impossible to state for sure what factors would contribute to which tonal changes.

But as your threaded insert clips alone have shown, it would still be another useful clue towards solving the great mystery of the bass tone equation. With enough solid experimentation, we could make our theories the accepted truth. Consider yourself a pioneer in this field by recording the tonal changes with high-mass bridge installations!

If all else fails, we'd still be able to have some fun from it all.

 

[stingray69]

I see what you mean. All the different variables would make it impossible to state for sure what factors would contribute to which tonal changes.

But as your threaded insert clips alone have shown, it would still be another useful clue towards solving the great mystery of the bass tone equation. With enough solid experimentation, we could make our theories the accepted truth. Consider yourself a pioneer in this field by recording the tonal changes with high-mass bridge installations!

If all else fails, we'd still be able to have some fun from it all.

LOL - I don't know about pioneer, but I'm doing what I can with what I've got. I just find these kind of experiments fascinating, and wanted to do it. But now that you mention it, I suppose I haven't really seen any spectrum analysis of threaded inserts or bridge replacement before, lol. I will get to the bridge experiment just as soon as I can, but being in a gigging band and family duties takes time too. Although I am looking forward to that myself very much. I will gladly post the results here in this thread as they pertain to the 2 bridges I'm using. I'm digging the spectrum analyzer a lot for visual confirmation of what is happening in the audio. I hope to have the high mass test up within a week or two. Thanks for the encouragement.

 

[ghoulbug]

LOL - I don't know about pioneer, but I'm doing what I can with what I've got. I just find these kind of experiments fascinating, and wanted to do it. But now that you mention it, I suppose I haven't really seen any spectrum analysis of threaded inserts or bridge replacement before, lol. I will get to the bridge experiment just as soon as I can, but being in a gigging band and family duties takes time too. Although I am looking forward to that myself very much. I will gladly post the results here in this thread as they pertain to the 2 bridges I'm using. I'm digging the spectrum analyzer a lot for visual confirmation of what is happening in the audio. I hope to have the high mass test up within a week or two. Thanks for the encouragement.

You sound like a man on a mission.
I'm sure the least you could do would be getting listed on the FAQ, considering how many people love to argue about these things.
Take all the time you need with these, though. I'm sure we're all still mulling over the significance of your threaded insert clips.
And we should be the ones thanking you. They may not be perfect, but fun scientific threads like this are what keep me on TB. (that, and maybe the "Post your pets with basses" thread)