What is responsible for pickup "dynamics"?

[gpdb]

I've gotten this question a few times since I started my website, but I've seen it more times than I can count on internet forums. People discussing pickups and claiming that one brand/model is very "dynamic" - uncompressed, lots of headroom, etc. I would like to objectively measure this phenomenon if it actually exists (better yet, if one of the brilliant minds on this forum has done it, please share the post). My instincts tell me that this is more hyped up than what is real. But if it does exist, my hypothesis would be that the magnet would be the responsible factor, since it's the only thing that interacts with the string. Here's what I would hypothesize:

If a pickup contains a strong magnet, then the output signal will be more compressed/less dynamic, due to stronger current generation at lower string amplitudes. Conversely - if a pickup contains a weak magnet, then the output signal will be more dynamic/less compressed, due to the same factors. 

Has anyone studied this, or know of a good way to test this? Let me know if my hypothesis is garbage too. I could see more winds being a factor too as it will create more voltage, but I see switching magnets to be more impactful, given the winds stay consistent.

[gckelloch]

My understanding is there can be some level of waveform asymmetry and a difference in the level of stronger to weaker string vibrations depending on the distance from the strings, but it also makes sense that a denser coil up closer could produce the same result. It does so in my experience. String pull may also have some affect on transients along with the harmonic emphasis effect. Seems like what players deem as compressed is actually what they hear in pickups with weaker pole pieces, where there aren't emphasized harmonics. The transients/stronger-vibrations would actually be more emphasized if such a pickup is set closer to the strings to compensate for the lower output, so I'd take all the subjective terminology with a grain of salt.

[gpdb]

I wonder if a test could be performed with a sustainer to excite the string at increasing amplitudes from barely audible to maximum and then record the output voltage to create a curve, and see if that curve changes based on differences in the pickup. But like you mentioned, that wouldn't really account for what you're actually hearing. There may be a difference in sound perception vs. voltage.

[stratotarts]

Compression in the amplifier front end is the basis of "dynamics". Not in the pickup.

[gpdb]

I agree that largely the effects of compression would take place at the amp level, but are there any differences in compression within pickups? If that's the case, being able to prove that would be pretty profound. Is there no limit to how much voltage a pickup can produce?

[antigua]

Jun 20, 2022 10:52:08 GMT -5 gpdb said:

I've gotten this question a few times since I started my website, but I've seen it more times than I can count on internet forums. People discussing pickups and claiming that one brand/model is very "dynamic" - uncompressed, lots of headroom, etc. I would like to objectively measure this phenomenon if it actually exists (better yet, if one of the brilliant minds on this forum has done it, please share the post). My instincts tell me that this is more hyped up than what is real. But if it does exist, my hypothesis would be that the magnet would be the responsible factor, since it's the only thing that interacts with the string. Here's what I would hypothesize:

If a pickup contains a strong magnet, then the output signal will be more compressed/less dynamic, due to stronger current generation at lower string amplitudes. Conversely - if a pickup contains a weak magnet, then the output signal will be more dynamic/less compressed, due to the same factors. 

Has anyone studied this, or know of a good way to test this? Let me know if my hypothesis is garbage too. I could see more winds being a factor too as it will create more voltage, but I see switching magnets to be more impactful, given the winds stay consistent.

I think I have this one figured out, though you can never truly explain what people think they're hearing. The resonant peak and fall off of as passive pickups is pretty abrupt, as can be seen in bode plots. If the resonant peak cuts off at 3kHz, then all the harmonics above that are more or less chopped off, along with audio that gives the impression of dynamics, the "pick attack" sound. 

A sharp cut off at the resonant peak might not create a sense of compression by itself, but combine it with the wave form of an strummed guitar; when you first pluck the strings, there is a burst of harmonics that extend very high, maybe beyond 10kHz, whatever the guitar string is physically capable of producing (the reason why steel strings have so much more treble than nylon strings), but those high harmonics decays very immediately, most of them don't even sustain past a single cycle, and so they're technically called "transient", and it's perceived more as "pick attack" and not "treble", as "treble" would apply more to whatever survives past the pick attack. 


Here's a visualization of harmonics by frequency and time.  


Notice the higher harmonics are very short lived compared to the lower harmonics and the fundamental. The harmonics become more short lived the higher in frequency you go, (but that is not really depicted above). 

It's those short lived high harmonic transients that create the sense of dynamics in the first place, and so when a pickup has a lower resonant peak, and it filters out the transient harmonics, you're left with the impression that dynamics have been removed and that compression has been introduced, but in reality that just the perceived end result of the signal of a plucked guitar string, combined with the RLC filtering of the guitar pickup. 

More evidence that filtering or omission of transient harmonics manifests as compression, if you turn the tone know on the guitar all the way to zero, the sharp roll off is preserved, but the resonant peak drops down well below 1kHz, and the result is a high compressed sound. If you pluck with your fingers, less transient harmonics, sounds more compressed than if you use a pick, and that's true even of an acoustic guitar. People tend to say hot pickups sound more compressed, hot pickups almost always have lower resonant peaks, and vice versa, they'll say single coils sound more dynamic, single coils tend to have a higher resonant peak. 

Note that when you turn the tone control down, the damping effect of the series resistance causes the Q factor to soften considerably, as seen here:


so the tone knob adjustment will sound most compressed at zero, where  that roll off past resonance is at it's most steep. When the rate of roll off is softer, (sometimes called a soft knee) the harmonics are still audible, so the perception that it's "compressing" by way of transient suppression is not as great. 

The rabbit hole goes farther, because a lot of guitar pickups only differ by a small amount in their relatively high resonant peak frequencies. For example a neck PAF might cut off at 3kHz while the bridge pickup cuts off at 2.5kHz, well those harmonics that touch the range of 2.5 to 4 kHz are very short lived, they're gone in under two seconds, so when you say the neck and the bridge pickups sound different, after two seconds have passed those two pickups will sound identical, and you can put that to the test by recording both, starting the recording two seconds after the pick attack and noticing that they sound indistinguishable, in contrast to what was audible two seconds prior. So it could further be said that most all pickups are set apart by what is heard within the first two seconds of the attack, after that, they're pretty much all the same. 

tl,dr; when transient harmonics are filtered or removed from the signal, it sounds as though there are less dynamics, or that the signal is compressed.

[aquin43]

Jun 22, 2022 12:17:41 GMT -5 gpdb said:

I agree that largely the effects of compression would take place at the amp level, but are there any differences in compression within pickups? If that's the case, being able to prove that would be pretty profound. Is there no limit to how much voltage a pickup can produce?

True dynamics is not a question of how much level a pickup can produce but whether the output is proportional to the string velocity from low levels right up to the clipping point of the string when it hits the frets.

Every practical guitar pickup in common use has a strong asymmetrical non linearity where the sensitivity drops off rapidly as the string recedes from the pole. For example, Zollner has measured the sensitivity of a strat pickup as being inversely proportional to the distance of the string from a point just below the pole surface.

This sort of non-linearity flattens one half of the amplitude waveform and stretches the other half. However, the pickup responds not to the amplitude of the string movement but to the velocity so any resulting distortion products are 90 degrees out of phase with the amplitude waveform. The net result, if you simulate it using Spice and a measured pickup non linearity seems to be that lots of harmonics are produced but the overall amplitude response remains quite linear up to string movements larger than the guitar itself can support.

[ms]

For this non-linearity, the maximum difference in sensitivity is between the point of furthest positive string excursion and negative excursion.  But the velocity is zero at the points of maximum excursion and so the output is zero, that is, the same.  The output is small near the points of maximum excursion as well. Highest velocities occur closer to the equilibrium position of the string, and so the positive and negative peak outputs tend to be the same.  So the effect of this non-linearity is not so large.

The asymmetry seen in the pickup output is mostly a result of even harmonics in the string motion.  For example, the test waveform sin(t) + cos(2*t) has positive and negative peaks that differ by a factor of a bit less than two. If this waveform were the output of a pickup, it would result from its integral, -cos(t) + .5*sin(2.*t).  This last waveform is symmetrical.  Thus we might have asymmetrical pickup outputs that are the result of peak string excursions that are the same in the positive and negative directions. 

[antigua]

Yeah, there's a physical limit, the strings hitting the frets, or having a large excursion away from the pickup's receptive range, but when people talk about one particular guitar pickup causing more compression than another, it can be assumed that the underlying phenomena being observed follows the pickup, and is not all pickups or all guitars, and further, when they observed changes correlates strongly with the inductance or resonance frequency, or even the Q factor of the pickups, the underlying phenomena can be related to the RLC filtering, somehow or another. How does RLC filtering manifest as perceived compression, is the question, and whatever answer someone comes up with will have to be somewhere in that domain.

The guitar pickup, as a transducer, as no compression at all (until it overheats and fails, anyway), for example, if you were to put a sufficiently strong exciter coil beside the pickup, and induce a very high voltage in the pickup, it would deliver a very high voltage output up until the point the 42AWG coil overheats and burns out. I don't know what the absolute voltage of a guitar pickup is, since in practice it couldn't matter any less. 

[ashcatlt]

Jun 23, 2022 18:44:01 GMT -5 antigua said:

The guitar pickup, as a transducer, as no compression at all (until it overheats and fails, anyway)

I agree in general with everything you’ve said, and in actual practice I’m sure no actual string movement will push a pickup into its nonlinear region. I do wonder, though, how it compares or relates to the fairly well known phenomenon of transformer saturation. That can usually be measured and heard well before the transformer burns. I know the action is not exactly the same, but like kind of, no?

[aquin43]

Synthesised waveforms with and without pickup distortion. The picture shows the attack portion.

They sound pretty much the same to me.

With distortion

Without distortion

[aquin43]

I wonder, does an electric guitar, particularly a solid, really have a starting transient in the same way as some acoustic instruments, i.e. a short higher level inharmonic burst that initiates the sound? When you look at the output on an oscilloscope it seems just to start as it intends to go on. The waveform alters soon after the start but that is mostly dispersion in the string shifting the phases of the harmonics. There doesn't seem to be any huge starting peak to clip.

[ms]

Jun 24, 2022 11:34:56 GMT -5 aquin43 said:

I wonder, does an electric guitar, particularly a solid, really have a starting transient in the same way as some acoustic instruments, i.e. a short higher level inharmonic burst that initiates the sound? When you look at the output on an oscilloscope it seems just to start as it intends to go on. The waveform alters soon after the start but that is mostly dispersion in the string shifting the phases of the harmonics. There doesn't seem to be any huge starting peak to clip.

guitarnuts2.proboards.com/thread/9073/linear-effect-decreasing-over-piece

I agree; the second plot (pickup output, velocity) in the link above is consistent with the idea that when the pick pulls the string aside and is released, the string snaps back, sending along the string a transient that bounces back and forth.

[antigua]

Jun 24, 2022 11:34:56 GMT -5 aquin43 said:

I wonder, does an electric guitar, particularly a solid, really have a starting transient in the same way as some acoustic instruments, i.e. a short higher level inharmonic burst that initiates the sound? When you look at the output on an oscilloscope it seems just to start as it intends to go on. The waveform alters soon after the start but that is mostly dispersion in the string shifting the phases of the harmonics. There doesn't seem to be any huge starting peak to clip.

Here's a spectrogram of plucks, the burst isn't inharmonic, as you can see they're evenly spaced, but there's a column of higher harmonics that are short lived compared the the lower ones.

[gpdb]

Antigua - what software were you using to create this spectrogram? This is slightly off-topic, but I think this would be a fantastic way to evaluate Dimarzio's "dual resonance" claims of creating more high harmonics by using different wire gauges. After some research, I realized their claim is simply that using two different gauges appears to cancel more 60-cycle hum in the bass but not in the treble, therefore keeping more harmonic content. I have someone sending me a few pickups to analyze to see if the harmonic content is actually greater.

[gpdb]

Oh nevermind, I found a spectrum meter plugin in Studio One 5 that I have access to. This is a great visualization. 

[antigua]

Jul 5, 2022 14:12:20 GMT -5 gpdb said:

Antigua - what software were you using to create this spectrogram? This is slightly off-topic, but I think this would be a fantastic way to evaluate Dimarzio's "dual resonance" claims of creating more high harmonics by using different wire gauges. After some research, I realized their claim is simply that using two different gauges appears to cancel more 60-cycle hum in the bass but not in the treble, therefore keeping more harmonic content. I have someone sending me a few pickups to analyze to see if the harmonic content is actually greater.

There's not even a theoretical or hypothetical basis to underpin the dual resonance claim. If you saw something different in the spectral analysis with that pickup, it would be more likely attributable to error. The effect of using different wire gauges is knowable, you can slightly different resistance / impedance with the two coils, but the resonance remains singular. I've tested several DiMarzio pickups with differing wire gauges and they show a resonant peak like that of any similar PAF type pickup.

[axetech]

Jun 20, 2022 20:40:40 GMT -5 gpdb said:

I wonder if a test could be performed with a sustainer to excite the string at increasing amplitudes from barely audible to maximum and then record the output voltage to create a curve, and see if that curve changes based on differences in the pickup. But like you mentioned, that wouldn't really account for what you're actually hearing. There may be a difference in sound perception vs. voltage.

Electro magnetic sustainers (like Ebow) are not quite suitable for such measurements, as signal/noise ratio is excessively in the negative territory - the signal from exciter coil caught by guitar pickup usually exceeds the one produced by the string being excited by the sustainer. I ran the "compression detection" experiment with a specially built coil driver back in a day: even with the driver placed at around 5th fret the signal/noice was at 6db, which effectively invalidated any measurements.

I guess using mechanical exciter might be a better approach. I am using Dayton acoustic exciter to spot rattling components in guitars. Here is the picture of sample setup:



So I tried to profile a couple of pickups this afternoon using the above setup, here are the results:


Blue is Strat with Dmarzio Area 58, neck position. Green - Schecter Solo with Fralin Unbucker, neck position, humbucker mode. For Strat I placed exciter at the headstock, Schecter Solo had exciter on a body, as pictured. Both X and Y are in db. 

Frankly I did not run studies on how exciter placement affects string amplitude, whether exciter amplitude translates into string amplitude linearly and if yes, what are the limits of that linearity - the -6db input level is set to "just below" the fret buzz level for Strat. The Unbucker is hotter than Area 58, also exciter body placement is more efficient than headstock, so I adjusted exciter volume to match starting point readings, hence the graphs are useless for comparison these two guitars/pickups.

Just wanted to share the method rather than outcome.

[roadtonever]

IMO how you hear the 2000Hz frequency range in the room or through monitors. It if sits balanced to adjacent freuencies your playing will be expressive. Elevated or sucked out it will cause your dynamics to be more monotonous. This relates to he voicing of the pickup, sensing position/s and magnetic width.

[aquin43]

Jul 12, 2022 15:11:20 GMT -5 axetech said:

Jun 20, 2022 20:40:40 GMT -5 gpdb said:

I wonder if a test could be performed with a sustainer to excite the string at increasing amplitudes from barely audible to maximum and then record the output voltage to create a curve, and see if that curve changes based on differences in the pickup. But like you mentioned, that wouldn't really account for what you're actually hearing. There may be a difference in sound perception vs. voltage.

Electro magnetic sustainers (like Ebow) are not quite suitable for such measurements, as signal/noise ratio is excessively in the negative territory - the signal from exciter coil caught by guitar pickup usually exceeds the one produced by the string being excited by the sustainer. I ran the "compression detection" experiment with a specially built coil driver back in a day: even with the driver placed at around 5th fret the signal/noice was at 6db, which effectively invalidated any measurements.

I guess using mechanical exciter might be a better approach. I am using Dayton acoustic exciter to spot rattling components in guitars. Here is the picture of sample setup:



So I tried to profile a couple of pickups this afternoon using the above setup, here are the results:


Blue is Strat with Dmarzio Area 58, neck position. Green - Schecter Solo with Fralin Unbucker, neck position, humbucker mode. For Strat I placed exciter at the headstock, Schecter Solo had exciter on a body, as pictured. Both X and Y are in db. 

Frankly I did not run studies on how exciter placement affects string amplitude, whether exciter amplitude translates into string amplitude linearly and if yes, what are the limits of that linearity - the -6db input level is set to "just below" the fret buzz level for Strat. The Unbucker is hotter than Area 58, also exciter body placement is more efficient than headstock, so I adjusted exciter volume to match starting point readings, hence the graphs are useless for comparison these two guitars/pickups.

Just wanted to share the method rather than outcome.

A pointer to a good experiment, but too many things varied at once. The obvious non linearity in the blue trace needs to be explained, but may be caused by saturation of the driver or detuning of the string at larger amplitudes. Do you drive the string open loop or do you make it part of an oscillator? An accelerometer or contact mic bear the bridge would be a useful addition.

[axetech]

Jul 13, 2022 9:11:28 GMT -5 aquin43 said:

Jul 12, 2022 15:11:20 GMT -5 axetech said:

A pointer to a good experiment, but too many things varied at once. The obvious non linearity in the blue trace needs to be explained, but may be caused by saturation of the driver or detuning of the string at larger amplitudes. Do you drive the string open loop or do you make it part of an oscillator? An accelerometer or contact mic bear the bridge would be a useful addition.

Like I said, it's not quite an experiment report. Just an illustration of an idea of exciting a string using mechanical resonance.

Answering your questions: there is no feedback loop at all, just a generator plugin and input meter using out of the box Logic Pro plugins. In practice this means I had to find the exact tuning of the G string by adjusting the generator frequency in small steps. The feedback based system a la ebow would do it automatically, but would be useless for the experiments.

Not sure about contact microphone applicability - the signal it is going to pick up will be almost 100% the one of the exciter, rather than string.

One interesting observation: a string excited by electromagnetic or mechanical device without a feedback produces almost pure sine signal. Which might be helpful for measurements.

I agree, there are lots of moving parts in play. But it all depends on a problem we are trying to solve. For me it is an answer to the question whether "pickup dynamics" is nothing but snake-oil-ish marketing gimmick, rather than something that really exists. Running the above experiment on two pickups from the same vendor claiming that one model exhibits "better dynamics" using same setup (same guitar, same equipment) would yield a definitive answer. If the experiment shows there indeed is a difference (meaning at least one pickup exhibits compression), then I would look into refining the methodology to allow reliable measurements of the proven-to-exist compression.

 

[aquin43]

Driving the string with an external oscillator will certainly have problems with detuning at larger amplitudes because the effective Q of the string is very high so the bandwidth of the string is very narrow. The best arrangement with a standard guitar would be to drive the head and put a contact mic on the bridge. With luck, any direct feed from head to bridge via the neck will be small enough that the contact mic output will be a direct measure of the string amplitude, bypassing the effects  of detuning and linearity in the driver. This could be checked by stopping the string motion. Otherwise, a special test rig with the bridge and pickup isolated by extra mass would be required.

[heardsoundcircuits]

I always assumed pickup "headroom" referred to the difference in output voltage between the loudest strum (say, at the 12 fret treble strings) and the smallest "perceptible" picking, more or less.

[stratotarts]

No, "headroom" refers to the safety margin in the dynamic range of a signal channel, that allows transient peaks to pass without significant distortion, above the average or nominal signal level. What you are talking about is just "dynamic range". But since all pickups are basically linear transponders, the dynamic range you describe pertains to the actions of the player, rather than the pickup itself. The pickup itself has no dynamic range that is a useful metric. Technically, the dynamic range would be the ratio of the thermal noise in the wire, to the limit reached when the voltage in the wire is high enough to break through the insulation, or the current is enough to melt the wire, whichever comes first. Obviously this is not a useful metric since it never happens.

[heardsoundcircuits]

Thank you! That is incredibly helpful.

[timtam]

Interesting empirical example of apparent restoration of pickup attack dynamics by rewinding a tele neck pickup (43 ?) with thicker wire (42) ... from 27:37 ...

[antigua]

Oct 11, 2022 1:38:43 GMT -5 timtam said:

Interesting empirical example of apparent restoration of pickup attack dynamics by rewinding a tele neck pickup (43 ?) with thicker wire (42) ... from 27:37 ...

 The DC resistance ends up being 5.3k ohms, so to me anyway, it's pretty clear that a much lower inductance is at play in any difference they might notice. A low resonant peak will make pick attack sound muted because transient harmonics are of very high frequencies, above 4kHz. 

I don't think the rust around the pole pieces eating into the enamel is really an issue. One might assume it should be based on the optics alone, but first they didn't check to see if there was continuity against the rusted out part of the coil to see if a short even existed, but even if a short was found to exist, it only shorts the first layer of the coil, which will have an extremely negligible impact on the Q factor, and we know this because we can see what happens when you short a tapped single coil. The effect is extreme with a tapped coil, but a coil tap is many layers of depth, and this potential short is only one layer of depth. Bill Lawrence talked about these shorts too, and one of his fans on another forum was insisting they're a big deal, but any short within the coil is going to jump across a very small segment of the coil. It's somewhere between unlikely and impossible for a coil short to jump a large portion of the coil.

[gckelloch]

To be fair, Bill discussed with me how cracks in PE insulation around bobbin edges can align closely enough for substantial losses to occur if they aren't patched via post wind heating, but isn't it also possible that any wind in the first layer shorting to the poles could completely drain the signal to ground?

[reTrEaD]

Oct 13, 2022 1:19:31 GMT -5 gckelloch said:

To be fair, Bill discussed with me how cracks in PE insulation around bobbin edges can align closely enough for substantial losses to occur if they aren't patched via post wind heating, but isn't it also possible that any wind in the first layer shorting to the poles could completely drain the signal to ground?

In a typical HB, the bobbin is plastic so damaged insulation can only result in shorts between winds. The windings have no physical contact with the pole pieces.

For a Strat pickup, there is no bobbin. Flatwork is placed on the ends of the pole pieces (magnets) so if tape is not applied, there is a danger of the winding shorting to the pole pieces, if the insulation is damaged. The pole pieces aren't typically connected to ground, but even if they were, a short to the pole piece would only shunt the signal created in the first layer to ground. The start of the wind is connected to ground. Of course if a phase switch is in the circuit of a compromised pickup, the finish of the winding is connected to ground, when out-of-phase.