A Test Rig for Assessing Tonal Properties of Solid Body Electric Guitar Construction

[Bizman62]

3 hours ago, curtisa said:

I can't imagine you'd see anything different in the sustain readings. The string is still vibrating in the same way, the only difference is the way it's being captured - mike vs pickup.

Ahh, of course, stupid me!

 

3 hours ago, curtisa said:

changing the 'pinch point' while holding the plank may excite or dull certain harmonic overtones in the struck sound,

Pinch point, that's a good and exact expression. Thanks! The quick and dirty test indeed revealed that the harmonic overtones get affected depending on the pinch point. Or rather, there's a sweet spot where the plank really rings. But the actual pitch doesn't change. Have you ever familiarized yourself in how xylophones and the likes are tuned? The dimensions won't change much so basically tuning the planks to the same pitch might not be too much of an effort and the dimensions would still be within the margin. Not saying you should do that, though! But it would be interesting to see if there's a correlation between the pitch of the wood and the string played. For acoustic builds I've learned that having a multitude of pitches on the top depending on where you knock will result a rich sounding guitar where every note rings nicely. On the opposite side there's the wolf tones caused by the played note being too close to the natural pitch of the wood.

 

3 hours ago, curtisa said:

A guitar that apparently rings well when suspended on a wall hanger and tapped probably won't resonate anywhere near as much when in the playing position.

Most likely not, then again a much resonating guitar does interact quite some with the body before the flesh mutes it. For what I've understood this very testing process serves the purpose of finding out if some woods really tell the player things without actual audible feedback.

[curtisa]

I think it was @Gogzs who suggested this one: string-through body or top loading.

A new plank of tas oak was cut to the same dimensions as before (840mm x 65mm x 25mm) and a headstock of sorts added to one end. Instead of the headless hardware I've thrown on a single tuner from an old Strat copy and a Wilkinson WOF01 convertible bridge at the other end. This type of  bridge can be fitted as a top-loader or for string-thru body threading. The old single coil pickup was installed as per usual into a matching rebate cut into the plank and then low-E, D and high-E strings fitted and swapped between top loading and string-thru threading options. Once again the plank rests on rubber feet and the robo-picker is doing its duty:

With thru-body threading the string makes a 90-degree turn in two approximately 45-degree angular steps as it passes over the saddle:

When configured for top loading the string does a bit of a zig-zag over and under the saddle on its way to the hole drilled in the rear of the bridge plate. My gut instinct is that this reduces the amount of downforce on the saddle which may affect how much pressure the string exerts against the body, perhaps changing the way the string vibrates?

 

Audio files contain the following samples:

• Low E pluck thru-body, Low E pluck top load, pause
• Low E pluck thru-body, Low E pluck top load, pause
• Low E pluck thru-body, Low E pluck top load, pause
• D pluck thru-body, D pluck top load, pause
• D pluck thru-body, D pluck top load, pause
• D pluck thru-body, D pluck top load, pause
• High E pluck thru-body, High E pluck top load, pause
• High E pluck thru-body, High E pluck top load, pause
• High E pluck thru-body, High E pluck top load, end of file

Unprocessed and simulated amp versions for you to chose your flavour.

Like the scale length variations, I think the differences here tend to be more audible in the plugged-in recordings than the species of timber appear to have been.

Also for @Bizman62's benefit, below are the sustain comparisons between the two string threading options. The results here shouldn't be compared to the ones posted earlier comparing the different species of timber. Because the new test plank has a 'headstock' and doesn't use the headless tuners I had to crack open a new set of strings to get some extra length to reach the tuning pegs. The initial peaks of the string strikes are also not the same as the earlier tests:

09 Thru Body vs Top Load + Amp.wav 09 Thru Body vs Top Load.wav

[Bizman62]

The numbers don't lie, there's a significant difference in sustain.

This time I could also hear a difference in the sound. In my ears the top load seems to lack depth and body. Is that because of some harmonics being lost, I don't know. Anyhow, the thru body sound is beefier, at least in my ears and headphones.

[curtisa]

6 minutes ago, Bizman62 said:

The numbers don't lie, there's a significant difference in sustain.

I wouldn't go quite that far. The difference in the low-Es is only half a second over 16. That's not a lot really. 0.6sec difference in the high-Es looks more significant, but it also may fall into the 'easily missed' category in a real life situation.

[Gogzs]

Now this is interesting, thanks for that, shame it came around the time my top loading bridge for the next build arrived haha. But it's something to keep in mind for future builds!

[Bizman62]

7 hours ago, curtisa said:

The difference in the low-Es is only half a second over 16. That's not a lot really.

Agreed, 3% longer isn't much. Looking at the integers only makes it look more dramatic. But it's more than what the difference in sustain of the various woods for the high-E was.

I wonder if any wood benefits more from string through than some others. Since the Tas Oak had the shortest sustain, comparing it to the longest sustaining Celery Top Pine should reveal if there's any need for further testing.

[Crusader]

Would it be a good idea to support the timber on its nodal points so it can vibrate freely?

[curtisa]

6 hours ago, Bizman62 said:

I wonder if any wood benefits more from string through than some others. Since the Tas Oak had the shortest sustain, comparing it to the longest sustaining Celery Top Pine should reveal if there's any need for further testing.

I actually have to go back through the earlier sustain table and double-check some of the values I was getting earlier. The sudden change in sustain in the most recent results with tas oak seem unusually large compared to what I was seeing earlier, almost a 2:1 change in decay length on the low-E. It could be that the new strings have made a difference, could be that the different hardware has made a difference, but it makes me suspicious that something isn't quite right in one or both sets of results.

 

6 hours ago, Crusader said:

Would it be a good idea to support the timber on its nodal points so it can vibrate freely?

They are. The positions of the rubber feet under the planks were chosen by trial and error based on how well I could get the plank to ring when knocked. Their eventual positions were then marked on each plank to help with consistency.

[Bizman62]

8 hours ago, curtisa said:

The sudden change in sustain in the most recent results with tas oak seem unusually large compared to what I was seeing earlier,

Are we talking about the very same piece of wood, or a different plank?

[curtisa]

An adjacent cut from the same slab that the first plank came from.

Just went through the files that made up the first sustain data table - nothing stands out as incorrect. The sustain appears to be exactly as it was recorded for each piece. Either the piece of tas oak that made up both sets of test planks was wildly different, the sustain differs wildly due to the second plank having different strings installed, or the sustain differences between the two pieces of tas oak are wildly different due to the different hardware and stringing methods. Scenario 1 seems pretty unlikely given the timber used came from the same slab (two planks just ripped up the middle); I'm leaning towards a combination of scenarios 2 and 3.

Either way, whether or not this still points to the possibility that the cut of the same species of timber can affect the tonal output, that's not what this particular test was trying to highlight. By necessity I was forced to change too many charateristics and parameters simultaneously that would allow us to make that particular comparison. The comparison to be made in this case is whether or not top-loading and thru-body stringing can make a difference.

[Bizman62]

Adjacent pieces, you say? Well... Wood is a living creature so there may be spots where the properties change rapidly length (or height?) wise. That may especially be true in two locations: Either at the stem where the log widens to the root system, or at the lowest branches where the growth direction changes. I guess we as guitar builders are most interested in the former as the figuration there is the strongest, the first couple of metres are what we'd like for guitar tops. Good "building lumber" can be found in the most uniform part of the trunk between the stem and the branches.

A wide quartersawn plank can also be very different from either side, the heartwood side is most likely denser than the bark side - even if all of the wood is sapwood. The closer to the center, the tighter the radius of the growth rings.

Just thinking out loud.

[Crusader]

16 hours ago, curtisa said:

They are. The positions of the rubber feet under the planks were chosen by trial and error based on how well I could get the plank to ring when knocked. Their eventual positions were then marked on each plank to help with consistency.

No worries, I thought it looked like the rubber feet in photo above are right at the end

[mistermikev]

On 5/23/2021 at 1:09 AM, curtisa said:

I wouldn't go quite that far. The difference in the low-Es is only half a second over 16. That's not a lot really. 0.6sec difference in the high-Es looks more significant, but it also may fall into the 'easily missed' category in a real life situation.

going to have to catch up on this thread but certainly taking it to some interesting heights. 

 

.6 sec isn't huge... but add a little amp drive/compression and that will expand exponentially.  reminded me of some testing I did a while back -I was interested in making a sampled instrument of guitar- was running through my tube setup and finding the low e would sustain for 30 seconds... reduced the gain to unity and was surprised that it brought it down to 16secs.  this was of course in a room being influenced by speakers but just pointing out the obvious i guess... that .6 seconds might be a bigger difference in the right context.

[curtisa]

21 hours ago, Bizman62 said:

Adjacent pieces, you say? Well... Wood is a living creature so there may be spots where the properties change rapidly length (or height?) wise.

That could be the case, but I don't think we should necessarily conclude that's what happened here between the two cuts of tas oak. I changed a lot more than just swapping in another plank of the same species in between the two tests. That's an experiment for another day.

[curtisa]

20 hours ago, Crusader said:

No worries, I thought it looked like the rubber feet in photo above are right at the end

The photo was merely a 'serving suggestion'.  The rubber bumpers were located in the same positions used for the earlier tests for the actual recordings. You may also notice that the closeup of the saddle for the top-loading bridge has the string quite slack too

[curtisa]

19 hours ago, mistermikev said:

6 sec isn't huge... but add a little amp drive/compression and that will expand exponentially. 

The distinction should be made however that adding amps and effects can artificially inflate the sustain of the string. That's all signal processing, not the inherent character of the instrument.

Using a zoom lens doesn't make the subject in a photo bigger

[Bizman62]

45 minutes ago, curtisa said:

swapping in another plank of the same species in between the two tests. That's an experiment for another day.

That'll be an interesting day! Gotta love your patience with my endless requests...

 

Edited May 25, 2021 by Bizman62
fixed a typo

[mistermikev]

39 minutes ago, curtisa said:

The distinction should be made however that adding amps and effects can artificially inflate the sustain of the string. That's all signal processing, not the inherent character of the instrument.

Using a zoom lens doesn't make the subject in a photo bigger

well of course... it is all signal processing... but I don't know of anyone who plays or records their guitar without some processing.  the point I'm making is that that half of a second - in a real context which undoubtedly is going to have amp gain, mic/pre gain, a compressor, etc... is going to be a much more obvious difference.  In that sense we are zooming in on the difference.

[curtisa]

14 hours ago, Bizman62 said:

That'll be an interesting day! Gotta love your patience with my endless requests...

Easy Tiger! I didn't say I'd actually do it  

[curtisa]

14 hours ago, mistermikev said:

the point I'm making is that that half of a second - in a real context which undoubtedly is going to have amp gain, mic/pre gain, a compressor, etc... is going to be a much more obvious difference.

I think unless that's actually tested that's jumping to conclusions based on an apparent small difference in the raw timing of the decays of one note and entirely dependent on whatever you run the signal through. I'm sure I could make some of those earlier 8 second tas oak sustain tests go all the way past the 20 second mark if used enough gain and compression, but that doesn't mean a guitar built from that plank has naturally good sustain because of the material itself. Nor would it mean that 15.5 seconds of sustain compared to 16 seconds (<4% difference) would translate to a sustain that somehow magnifies into a bigger difference. For all we know if you ran both string samples through the same gainy/compressed signal path the <4% difference would still remain as a <4% difference, just stretched over 30 seconds instead of 16, or even just an absolute difference of 0.5 seconds over 30..

[mistermikev]

7 hours ago, curtisa said:

I think unless that's actually tested that's jumping to conclusions based on an apparent small difference in the raw timing of the decays of one note and entirely dependent on whatever you run the signal through. I'm sure I could make some of those earlier 8 second tas oak sustain tests go all the way past the 20 second mark if used enough gain and compression, but that doesn't mean a guitar built from that plank has naturally good sustain because of the material itself. Nor would it mean that 15.5 seconds of sustain compared to 16 seconds (<4% difference) would translate to a sustain that somehow magnifies into a bigger difference. For all we know if you ran both string samples through the same gainy/compressed signal path the <4% difference would still remain as a <4% difference, just stretched over 30 seconds instead of 16, or even just an absolute difference of 0.5 seconds over 30..

yes, lets insert some math... if we assume just out of my butt my numbers were accurate and give me latitude in that respect... I went from 16ms to 30ms in my pseudo testing with and without gain.  that ratio would be applied to a bigger base so 16x = 30 x 16.5 iow x = 30.9375.  so basically that 1/2 second would become 1 second additional when gain is added (in theory).  again, not a huge difference but still 2x the original difference. 

Is it life changing no.  does anyone ever hold a note for 31 seconds no.  could your difference be totally chalked up to variations in air pressure not accounted for in your testing... sure.  could it be alpha particles... absolutely.  data pixies - perhaps. 

if we consider it an actual "proven difference" would marketing teams drool over it and legitimately mark it up as "our guitar has more sustain than theirs because we make it with tas oak" - without a doubt.  

 

[Gogzs]

Eh, if we argue in the same direction, one could say that the differences in tone you say to hear between different types of wood could be negated with the EQ knobs on a good amp. And we can get to the conclusion that you can build a guitar out of whatever, and make it sound/sustain as awesome and as long as you want, given the right equipment to plug the guitar in. 

But that's not the point of this whole thread IMHO, and I take what @curtisa is giving us as it arrives. Tonally, I couldn't tell differences between wood types so this gives me confidence in the bamboo build. Sustain wise, interesting results for top load vs. trough body mounting, but not significant enough to make me revisit my first build, nor to change my plans with the second one I'm building now (got plenty of sustain on the first one).

Valuable thread, looking forward for the rest of tests if there will be any (there are some good ideas still in this thread, and we love and appreciate that you basically committed to doing all of them  )

[Bizman62]

I can fully understand @mistermikev's logic as my thoughts have trotted similar paths. Half a second can be a long time, in music played at 120 bpm that'd be one full measure!

That said, sustain isn't everything. If you play staccato notes, the attack is more important. There's more than one single reason why guitarists use several guitars in different pieces of music. This testing process has shed some light to the eternal questions of guitar building mythology, at least insofar as giving confidence in trying new methods and materials as @Gogzs said.

[mistermikev]

13 minutes ago, Bizman62 said:

I can fully understand @mistermikev's logic as my thoughts have trotted similar paths. Half a second can be a long time, in music played at 120 bpm that'd be one full measure!

That said, sustain isn't everything. If you play staccato notes, the attack is more important. There's more than one single reason why guitarists use several guitars in different pieces of music. This testing process has shed some light to the eternal questions of guitar building mythology, at least insofar as giving confidence in trying new methods and materials as @Gogzs said.

for the record I totally agree that sustain is almost inconsequential. 

also, we aren't considering an important metric here which is "bloom".  folks often conflate sustain with sustained-level.  ie comparing a note that sustains 16 seconds but the apparent gain drops to 20% immediately vs a note that maintains 80% of it's initial gain over 12 seconds.  

"high performance" = paying 150% more for .0001% improvement.  Not saying I think that's wrong or right... it just IS!

[curtisa]

This wasn't meant to turn into a hotly contested argument, and I'm sorry if it's ended up that way. FWIW I'm not saying that an extra half-second of sustain translates into anything meaningful, or even does the opposite and translates into something huge in real life. I'm simply saying I don't know what will happen. At this point I'm more interested in what the unadulterated sound does when incremental changes are made to the rig. The way I'm using the test rig can't really help us predict what will happen when it's plugged in to an amp with a bunch of effects in front, and is well beyond the scope of what I'm trying to explore.

I'm also only really offering the '...+Amp' variations of the WAV files as an example of what the untreated output sounds like through some random amp. They're not what I'm personally using as my point of reference - the un-amped versions are. It's impossible to say what a third person would pass that same signal through, as that's more down to artistic usage of the raw output of the guitar, and thus nigh-impossible to make judgements on how it would sound and behave if overdrive/compressor/distortion/eq/speaker/microphone XYZ were used.

Sustain vs bloom: I'm perhaps using the technically-incorrect version of 'sustain' (I'm thinking of an old 70s analogue synthesiser and its Attack/Decay/Sustain/Release envelope), and probably lumping the 'DSR' bit of the 'ADSR' in together as one complete thing. Maybe that's right or wrong in this scenario, I dunno? 'Bloom' I would have interpreted as the way the harmonic content evolves as the note decays (or DSR's? ), which again could be an interesting angle to explore with the recordings obtained thus far. But maybe my understanding of the word is different to somebody else's and leaves things open to confusion?