Greetings from the Lace Pickups team!

[Steve Conner]

I totally agree with what Rick and Bruce are saying, except I wish they wouldn't use the word "phase response" for it.

To be sure, phase response is the half of the story that many people neglect, but it is only half of the story. The frequency response is the other half of the story and is equally important, if not more so.

The impulse response approach to instrument modelling naturally captures both the phase and frequency responses. In digital filters, they can be set independently of each other. If you removed the frequency response data, it would be an all-pass filter and would sound completely wrong. I don't know what happens when you remove the phase response data. It can be done in theory, but it's a serious mathematical undertaking and the only reason to do it would be as an experiment to see if anyone could hear a difference.

I like Bruce's wiggling wood explanation. The easy part of a digital modeller's job is superimposing the wiggles of another piece of wood onto your signal. The hard part is undoing the wiggles of the wood in whatever instrument you're actually using. I guess a piezo bridge helps a lot by giving a direct string signal.

I think when most people say "phase response" they are actually thinking of the changes in frequency response that happen when a signal gets combined with phase-shifted copies of itself.

[bbsailor]

What Rick is saying about modeling and phase response goes right along with what I've learned from 20+ years of building electric basses. The real heart of the sound of an electric bass is in how the frame of the bass springs back and reacts when the strings are plucked. It's a complex, delayed action and reaction between the strings and the frame. They are both moving and cycling, in and out of phase with each other. It's mechanical motion. The pickup has an effect, but it's mostly just reading the complex warbling that's ending up on the strings. The purpose of the digital modeling is to recreate that complex warbling that results from pieces of wiggling wood. I personally hope that they don't get too good at it. I kind of like making the sound mechanically.

Bruce,

Based on the fact that vibrating bass strings also cause the neck and frame/body of the bass to flex causing additional phase responses that add and subtract energy back into the strings, do you think that the holes placed in the body to accomodate traditional pickups affects this mechanical motion?

Thanks

Joseph Rogowski

[Rick Turner]

Bruce, you and I are in agreement on this. I'm emphasizing the phase aspect in order to get folks to pay attention to it. Of course there are frequency response issues, but if working in the frequency domain alone could EQ one sound convincingly into another that mimiced a different instrument (etc.) it would have been done years ago in the analog realm. We would have had acoustic guitar amplification (for instance) that sounded truly convincing...and we didn't because you can't just fix it in the frequency domain...you have to go deep into the time domain.

BTW, we discovered that simple impulse response capture just didn't yield the results we needed. We tried all the usual stuff...exploding wires inside the guitar bodies, light hammer taps on the bridge, piezo impulse transducers, etc. We had to use plucked strings to properly excite the guitar tops and make them do what needed to be done.

Bruce's comments about the whole instrument wiggling and shaking is spot on. That's one of the reasons why carbon fiber in a neck is such a great thing on some instruments...it really smooths things out.

And, Bruce, I'm afraid it's Pandora's box with digital. It's going to get much, much better pretty quickly. The revolution will not be as fast as with digital photography blowing away film (yeah, yeah, I know some folks love film...hey, some are still doing tin types and Daugerratypes...), but with sample rates in digital audio getting up to the 192 K range, and 32 bit processing becoming the new standard, really good digital audio is not only possible, it's happening...and I say this as a guy with two really excellent turntables, four great cassette machines, and a Nagra IV at my disposal.

I've heard the new Antares AutoTune guitar system...and it's amazing.

What all of this cannot do (and this is really important to the likes of us) is duplicate the actual physical response and feel of a guitar or bass in your hands... The thing that all those who claim that we cannot tell the difference in blind listening tests fail to take into account is the intimate relationship between player and instrument that is as much about feel as sound.

[David Schwab]

Bruce's comments about the whole instrument wiggling and shaking is spot on. That's one of the reasons why carbon fiber in a neck is such a great thing on some instruments...it really smooths things out.

This is my observation as well. Back in 1980 or so I modified a Fender P bass, turning it into an 8-string (octave pairs). It was a maple neck/fingerboard, alder body. It had a pair of DiMarzio Model Ps. I sliced a new headstock on the neck. The bass lacked some low end and had a very harsh midrange. What sounded good with 4 strings, got noisy with 8.

So I decided to make a new neck, which was 7 piece maple with walnut stringers, ebony fingerboard, two truss rods and carbon bars. I also installed a maple block into the body where the neck bolted on. This was mostly because of the neck neck heel shape and how it attached to the body (the shape of the body was modified).

The new stiffer neck made it sound like a completely different instrument. The top end was smoother, and it had more low end. It was a much more balanced tone. Even unplugged you could hear it. Then I replaced the pickups with low Z versions I wound and used a Barcus Berry acoustic preamp. Even better!

[Joe Gwinn]

Phase in Architectural Acoustics

There is also evidence on the importance of phase in music coming from the architectural acoustics field. There was a thread on this:

http://music-electronics-forum.com/t23486/

[Bruce Johnson]

Yeah, in a few more years you'll be able to buy an acoustic guitar that's made completely from molded plastic. On the touch screen on the side, you tap in 1934 Martin D-18. Hit a chord, and the little onboard computer sends out digital models to an array of piezo actuators set into the plastic at various places. The whole frame responds and reacts like an old Martin, and it sounds just like one acoustically. So, you spend a half hour trying all the sounds. Wow. Then you realize that you still can't play the danged thing, and you go back to your video game.

Meanwhile, we Luthiers, who still remain, are searching through chemical disposal yards, looking for NOS cans of vintage resin, to make perfect replicas of Steinbergers for wealthy collectors....

[Bruce Johnson]

Steve;

Yes, I agree that Rick's term "phase response" doesn't really fully describe what's going on, but a better term would be rather unwieldy. How about: Reactionary vibration with varying frequency and amplitude curves, which dynamically modifies the frequency and attack curves on the string. Burp.

The idea is that, when you pluck the string, it has a natural frequency and attack curve of its own. If you have it anchored onto a block of granite, that's what you would hear; the sound of the string by itself. But when that same string is mounted across a frame that is less than rigid, that's when things get complicated. As the string vibrates, it's yanking on the two ends of the frame, in patterns with frequency and attack curves. The frame then fights back, resisting some parts of those frequency and attack curves more than others. That reaction from the frame changes both the frequency and the attack curves sounding on the string. Most of those changes are subtractive; that is, the frame is absorbing energy as it moves and removing energy from the string. However, in some narrow areas of those curves, the frame can hit resonance points and actually add a small amount of energy to the string.

But here's where it gets really complicated: As the wood flexes, it also has a damping effect; a slight frictional drag. That slows down the frame's reaction to the pulses from the string ends. The reaction gets delayed, putting it out of phase with the original frequency and attack curves. Worse yet, the damping effect varies with frequency. So the frame's reaction is all swirled and warbling in the way that it modifies the frequency and attack curves on the string. And the little digital modeling chip emits a puff of smoke.

[Bruce Johnson]

Bruce,

Based on the fact that vibrating bass strings also cause the neck and frame/body of the bass to flex causing additional phase responses that add and subtract energy back into the strings, do you think that the holes placed in the body to accomodate traditional pickups affects this mechanical motion?

Thanks

Joseph Rogowski

Joe;

Yes, cutting holes in the body can change the way the body flexes and reacts to the strings. BUT, you have to remember that all this tone modifying stuff depends completely on physical movement of the frame. If you build the body and neck super stiff, then they can't move and therefore they don't affect the tone. If you build the body out of laminated granite (with a spalted maple top, of course), then it doesn't matter what size pickup openings you cut.

That's the part that's misunderstood in so many of the bar room arguments about whether the wooden frame of an electric guitar affects the tone. So many inexperienced builders make their instruments super stiff, in their quest for eternal sustain, frequency range, and of course, stability. They get their sustain.........along with an instrument that sounds like a steel string on a block of granite. A cold metallic twang. With lots of sustain. So, they conclude that all electric guitars sound the same, and you get "Tone" with magic pickups and tube amps. Bah.

If you want to build an instrument that has warm, rich, complex tone, you have to build it flexible enough that it can move. There's no point in gluing a sheet of Sitka Spruce on top of a block of granite. Tonewood (whatever that is) does nothing if it can't move.

The softer and more flexible the body is, the more important all the details about the body's structure become. Cutouts, chambers, and wall thicknesses all affect how the body flexes, and how it reacts against the strings.

But only if it's capable of moving.

[Rick Turner]

Bruce, and all...

What you're describing is exactly why I designed my Model 1 guitar. Alembic guitars were always described as being "too cold; too sterile", and most people thought it was because of the low (well, medium, really) impedance pickups and active electronics. I wound up thinking differently...I thought the very rigid neck-through construction, while great for bass, just didn't allow enough body tone to get back into the strings. So I kept the rigid neck for stability and sustain, went to a rosewood fingerboard (and yes, I also make them with maple or ebony 'boards...and they sound different), and mahogany body with no parallel surfaces...arched top, arched back. I wanted sustain, clarity, and warmth, and that's exactly what I got. That was the first instrument I designed where I had a very clear notion of what it would sound like when done...and it did. I'm now able to pretty much mentally predict how my new designs will sound before I build them, and it's independent of the pickup system which is a window into the instrument's tone, but not the tone generator. I know I've pissed off pickup makers in the past who want to believe that tone is in the pickup, but that's but a small part of the equation. First is the instrument, second are the hands playing it, then (maybe) you have the pickup, and lastly the amplifier with everything contributing to that from pickup(s) to jack to cable to optional effects to amp input. And I could be convinced to put the amp chain before the pickup(s). But 1 and 2 are really where it's at.

[Steve Conner]

So the frame's reaction is all swirled and warbling in the way that it modifies the frequency and attack curves on the string. And the little digital modeling chip emits a puff of smoke.

There would certainly be smoke if you started down the "physical modelling" route: creating an accurate model of the dynamical system and solving it in real time. An acoustic guitar is a pretty complicated dynamical system.

However if you go down the route of extracting an impulse response from a real system, it doesn't matter how complicated the system is. Provided there is no non-linearity lurking around, it all boils down to this single impulse response that you apply to an incoming signal by convolution.

Rick said that you can't make one instrument sound like another with analog EQ, and I would certainly agree. But one way of seeing the impulse response is as a filter with a frequency response that can be incredibly fine and complicated, more so than any analog EQ circuit you could practically build.

I don't know whether the Mama Bear works with impulse responses, and some trickery (I can't imagine what) was used in the lab to derive an impulse response from excitation by plucked strings, or whether the unit runs some sort of mixture of impulse responses and physical modelling. The mention of room artifacts tells me that impulse responses must be involved somewhere.

Obviously no amount of processing on the output signal will make a cheap Chinese acoustic play like a professionally set-up Martin, or make an Epiphone Casino sustain like a Les Paul. There are two transfer functions at work, one from the strings to the output jack, and another from the strings back to themselves.

[Bruce Johnson]

That's the fun of designing and building stringed musical instruments. They really are a lot more complicated technically than most people appreciate. I've spent my Luthier career concentrating on a narrow, specific type of electric basses. You'd think that, with electric basses, almost everything has already been tried and done. But, I've been doing this for about 23 years now, and I keep finding new things and improvements and areas to look at. I'm particularly fascinated with this whole field of building the frame to mechanically react to the strings. I've found all kinds of ways to work with the structure of the neck and the body, which make significant changes in the overall tone coming out of the amp. I''m a mechanical engineer by background, so I enjoy seeing how far I can push the mechanical end of the instrument. I shape the tone of my basses with the structure, and build my pickups to be clean and clear and wide range. It's the opposite of what many builders do.

The first comment I usually get from players trying one of my Scroll Basses is how it vibrates in their hands with every note. Plugged or unplugged, they can feel every thing it's doing. That's what it's supposed to do, in my opinion.

[Rick Turner]

For Mama Bear, we used a technique of deriving an impulse response from very carefully done recordings of plucked notes. I can't divulge more than that other than to say that a string imparts energy to a guitar top in a different manner than a tap, and that is important.

I believe that Fishman's manner of doing the modeling...at least in the beginning...was based on simultaneously recording each instrument with a pickup and with a mic, and then determining what the differences were. If the mic got something the pickup didn't, they added that in. If the pickup got something the mic didn't, they took that out. The downside of this comparative method is that it requires that the target instrument have a pickup in it. Our method allowed us to use some incredibly valuable vintage instruments without modification. One day I borrowed a couple of great guitars from a musician/collector/vintage dealer friend of mine, and as I was walking out of his house, I noticed the price tags on the cases: $35,000.00 for the 1923 Loar signed Gibson L-5, and $65,000.00 for the 1934 Martin D-28. I don't think he'd have appreciated our putting pickups in those guitars...

I'm totally in Bruce's camp with regard to instrument design, though I don't mind using pickups as a flavoring...spice, if you will...in the total tone recipe. But if the instrument doesn't have it unplugged, it'll never have it plugged in.

[copperheadroads]

Hey everyone! Just found this forum and am excited to get on here and start talking to fellow builders/designers about some rad pickups! Here at Lace we have a technology that no one can match, but that doesnt mean we dont like traditional pickups or helping out with information regarding our pickups and other pickups! I personally have worked for a couple different pickup companies, and know a good deal about the process of pickup building and would love to share some pickup love and knowledge, as well as receiving knowledge and being a part of an awesome community where i know my yearning for pickup information will grow immensely! Looking forward to talking to everyone out there on the interweb! And for anyone with questions regarding Lace Pickups, PM me or ask on here and ill help to the best of my ability.

I Pmailed you with a customers of yours ,that have issues with your pickups & no reply ,& thats what I expected .

[frankfalbo]

What in the crap happened to this thread?! This is the best dinner party that pickup nerds are never invited to.

First it's about Lace, then my name is brought up. This alone disturbs me more than it satisfies me. LOL. Then its about my guitars and my fretting method is called into question, by a bass pickup maker no less. But not before being called out to a cage match with the Lace guy, and the Lace guy preemptively accepts? Okay, but I get the guy who invented and sold you the Alumitone (originally copper, but I guess the name "Coppertone" was taken?) he seems like a tough dude who could hold his own. (Kidding aside he's got some great ideas)

Then the infamous Rick Turner shows up and it's about litz wire, phase correlation, the great Cliff Elion's Marshall in the computer and its like I'm in a NAMM booth in a parallel universe.

Dave that "ball peen" hammer was my grandfather's, possibly my great grandfather's, and I've been fretting with it since I was 15 years old. The face has a dime-sized flat polished into the face. The top heavy nature gives it some dead blow qualities. I've pressed frets in too. I like the hammer better. It has to do with using the shock of the blow to your advantage. But that's a different cage match for a later date.

[Bruce Johnson]

Yes, this has been a very interesting thread....We've covered a lot of ground on topics that don't get talked about very much.