82.41 Hz for Low E?

[Paul Marossy]

I read in another post that an Open Low E string vibrates at a frequency of 82.41 Hz. OK, I can buy that, but doesn't it matter what kind of wood the body is made out of and what pickup you are using?

My Ibanez has a mahogany body, and when I use the neck pickup, it sure seems a heck of a lot bassier. If I use a 60 Hz notch filter (for hum), it definitely seems to thin out my guitar some. I haven't hooked up my scope to check this all out yet, but it seems to me that my guitar has tones that are lower than 82 Hz...

What is that 82.41 Hz number based on? Just the vibration of the string alone?

Just trying to understand.  

[Robin]

Hi Paul,

   The way I understand it is that a plucked guitar string creates not only a fundamental frequency, which you noted for the low E, but also harmonics, or multiples of that frequency depending on a lot of factors such as wood and string type (resonance) and types of electronics involved like pickups, filters, octave dividers, etc.. Controling even and odd order harmonics is a big part of what stompboxes do. Here's a pretty good read with a little chart on the chromatic scale frequencies in the guitar tuning range:

http://www.ee.ualberta.ca/~ee401/archive/fall2002/chromaticguitartuner/thefinalreport.pdf

It may take a while to load, but also has some interesting stuff on learning about opamp gain, rectification, PIC programming, etc.

BTW, did you ever find out what was causing your sound problems at the church?

Rob

[Paul Marossy]

Hey Rob,

Well, I sort of have it figured out. That Fender Hot Rod DeVille amp I have is a funny animal. It doesn't mind being in front of me, angled up. But if I put it behind me with a wall behind it, it loves to feedback...
It helped some when I physically lowered my pickups so that they weren't as close to the strings. I will also try standing out further in front of the amp and see if that helps.

The other problem I have is a 60 Hz HUMMMMMMMM. I just finished an adjustable notch filter (45-90 Hz) which will help with that. That is what prompted my questions about the Low E string frequency. If my guitar does have 60 Hz-ish overtones, and it grabs onto the 60 cycle hum also, maybe that is what causes the feedback to happen? Everyone was telling me that it must be how I have it EQ'd, but I knew that wasn't the problem at all.

I still think my guitar produces tones lower than 82 Hz. Anyhow, thanks for the link. I will check it out.  

[bwanasonic]

I read in another post that an Open Low E string vibrates at a frequency of 82.41 Hz.

Are you talking about a bass? If not that is WAY too low. A=440hz. Even two octaves lower is only 110hz. In general the harmonics of a plucked string are higher than the fundamental. If you think your hearing frequencies lower than 82hz, you might want to move further from the subway station :wink: Also, a notch filter is probably not the ideal way to address 60hz hum. A better idea might be to figure out where the hum is coming from.

[bwanasonic]

Are you talking about a bass? If not that is WAY too low. A=440hz.

Nevr mind. I was wrong.

 is two octaves below concert A (440Hz), so A = 440 Hz / 4 = 110 Hz.
bass-E is a perfect 4th below A, so E = 110 Hz / 1.3348399 = 82.406886 Hz.
(This accuracy is pointlessly high for the human ear, but so what!)
D is a perfect 4th above A, so D = 110 Hz * 1.3348399 = 146.83239 Hz.
G is a perfect 4th above D, so G = 146.83239 Hz * 1.3348399 = 195.99773 Hz
or it could be worked out as 2^(10/12)*110 Hz = 195.99772 Hz
B is a major 3rd above G, so B = 195.99772 Hz * 1.2599210 = 246.94164 Hz
or it could be worked out as 2^(14/12)*110 Hz = 246.94165 Hz
treble-e is two octaves above bass-E, so e = 82.406886 Hz * 4 = 329.62754 Hz
or it could be worked out as 2^(19/12)*110 Hz = 329.62756 Hz
or indeed as a perfect 4th above the B string.

Kerry M

[Paul Marossy]

No. I'm talking about an electric guitar. I know what A-440 is. Thanks.  :wink:

When I use my neck pickup, my guitar is VERY bassy. That's why I think it may be actually producing a small amount of frequencies lower than 82 Hz. If this wasn't the case, then it shouldn't make any difference to the sound of the guitar if I were to use a 60 Hz notch filter. But there is a noticeable change in the tone when I do use the notch filter. I guess I need to get out my scope and see if my notch filter really is working between 45-90 Hz.

To get rid of this hum when using high gain pedals, I have tried every possible other thing short of building a new power supply. I've never had a problem with my Boss power adapter and parallel power connectors before.

I must have a ground loop somewhere, I guess. I have even tried puttind a 1000uF filter cap across the power supply, still get a hum. Very perplexing...  

[Paul Marossy]

I just saw your reply, after I posted. Thanks for the clarification.

[Johan]

your guitar is puting out meny frequencys  beside the fundamental note, both below and above the note you're playing. its the composition of these "undertones" and "overtones" that makes up the sound of your particular instrument. if it was only puting out the fundamental, it would almost have to be a sinewave, wich wouldnt be very interesting to listen to ( unless you are into cheap analogue synths...)...as an example...hit the lowest key on a piano...the fundamental is almost sertanly to low for your ear to pick up, but you can still hear the note being played and also tell what instrument it is...its the overtones..or harmonics...

Johan

[Peter Snowberg]

Pretty much all of the direct strumming or plucking noise is well below any note you could dream of. They're super low frequency transients that stimulate resonators (aka strings) which are tens to hundreds of times higher in their resonant frequnecies.

Keep in mind that AC hum is a combination of 60, 120, 180, 240, 300, 360, etc Hz. Most of the energy is in the 60 or 120Hz spots, but the harmonics go way up the scale. Make sure you're not dealing with a ground loop too.

I recently saw a circuit for an anti-hum injector that cancels hum by mixing anti-hum with your signal. The circuit allowed you to dial in different amounts of the power line fundamental and a bunch of harmonics. Each frequency also had a phase shift to sync up with the hum. I'll see if I can find it again. If you search here for 'hum', it's somewhere in the last couple of weeks I think.

-Peter

[maarten]

As I understand it, a string will vibrate at a given frequency, but the magnitude of the swing will differ all along the string. If you sound an open string, e.g. it will vibrate less at both ends and also less halfway (at 12); it will vibrate the most at 1/4 (so at the sixth), and at 3/4, probably the place where your neck pickup is located. Though at all places the string vibrates with the same frequency, you will hear different overtones and undertones (or is it: subtones?. That is the very reason why they equipped the guitar with several pickups. The pickup at the end of the string will receive less bass tones, as the vibration (swing?) of the string is less here.

Hopefully I got the message across, I found it very difficult to describe this, as English is a foreign language to me.
Maarten.

[Mike Burgundy]

also a bassy amplifier does not mean you're generating frequencies below the fundamental harmonic of the low E, whis IS 82Hz. The frequency comes with the note and vice-versa. You cannot change frequency without changing the pitch of the note. You can change the levels of all different harmonics, thus changing the sound and affecting highs/lows/etc. Pitch does not change, therefore frequency doesn't change.
By the way: A440 is a convenient reference, since the tuning fork doesn't have to be the size of a shovel, and the human ear tends to tuning by harmonics, not fundamentals.

Okay, so the human ear actually responds to harmonics more than fundamentals? Pluck your low E, regular style, on a clean setting. Now carefully pluck it *exacly* over the twelfth fret, parallel to the front face of the guitar. This sounds, weird, hollow, boxy. Not at all a full bodied note. It is however the closest you can get to a fundamental on a guitar.
Why does the note seem warmer, fatter even when plucked a little more towards the bridge? Harmonics. The TRUE fundamental is hardly picked up, actually.
There's also a phenomenon that's related to this that can also increase percieved low-frequency content. It's used in church organs (the size-of-a-minivan windpipe type, not a Hammond). The bass pipes for these are so bl**dy large (9 meters, maybe more) that it's just too impractical (and expensive) to fit those. But the organ player wants a full register. Here comes the trick (watch the hat for a fluffy bunny): They fit several pipes that are in harmonic  and dynamic relation to the desired note. This means when put together, they more or less make every tone and overtone that the "real" pipe would make, and exactly as loud, except for the fundamental. Our ears get confused, confer with our brain, and they settle on the fundamental actually being there even when it's not.
This is also why even on a (well-designed) bass amp that doesn't really go below 45 Hz, a low B (31Hz) can still roll out with authority and serious low-end rumble. The fundamental's (partly) gone, but the harmonics aren't.
This whole frequency business can be rather confusing and counter-intuitive. If, for instance, as an engineer I want to increase the "growl" or "roar" or what you want to call it of a bass guitar in a loud, crowded live setting, I go for.... lo and behold, somewhere between 800Hz and 2Kdepending on the situation. No where near the actual notes played, "fundamentally". This increases hi-mid content, but you end up with an agressive, roaring bass cutting through the mix and actually *seeming* a lot lower.

[Paul Marossy]

Thanks for the responses.

That's what I was thinking, undertones. Everyone always talks about overtones - second and third harmonics, etc. I know that there are others, too. Some below makes sense to me.

The little circuit that I have built really helps cut it down, and I think it's adequate for my purposes at this point. It helps to make my neck pickup a lot less boomy as well. Now I think I understand how all of this is working together.

Peter, if you find that schematic I would like to see it. Anyone have suggestions on how to kill ground loops in a guitar effects pedal board? I don't want to use batteries, I have 10 things on my board. With batteries being like $5.00 each these days, it's just too expensive. I guess I need to look into a different power supply. Which means I would have to possibly build a new pedal board.

[Mike Burgundy]

one more addition: a guitar does put out frequency content below the E's fundamental, but these are not resonant frequencies in any way and will be very, very short lived. a thump on the strings might have a 10Hz or lower ramp, but it wont do more than a couple of cycles before it's completely gone. This will not add to bassier sound.

If this guitar is significantly darker than a guitar with similar pickups (no point trying to compare a Tele to an ES345), there might be a fault in the guitar?

[Paul Marossy]

Thanks Mike, what you say also makes sense. I guess my ears, as good as they are, aren't a perfect guide...  my amp at church is very bassy, even with the bass and mids turned all the way down. My Twin Reverb can compensate by turning up the bass a little bit, which is fine. I'll see how the one at church sounds tomorrow morning.

I found this article the other day about guitar frequency stuff:
http://www.gmi.edu/~drussell/guitars/electric.html
I'm not sure how to interpret all of it, but is interesting nonetheless. It talks about the vibrations of the guitar itself. It seems to me that some of that must also be picked up by the pickups, too. I think that is what I am getting at.

[Paul Marossy]

I found the source of my problem last night. I just moved the power transformer to the other side of the pedalboard. Took care of the problem. Apparently, one of my patch cords was running too close to the transformer, and it was picking up hum as it went by. Not perceptible with a clean sound, but definitely very noticeable with a high gain pedal such as a Boss Metal Zone.

About the patch cord: It's one of those long patch cords that, yep, RadioShack sells. Apparently, they must have skimped on the shielding, or it was just too close for any patch cord to keep quiet.

The hum filter that I built is cool as a notch filter, kind of gives a low cut effect when you dial it to 90Hz. As we all know, the open low E on a guitar is 82.41Hz. So, this little box might help out with my very bassy amplifier. I still do wonder about resonant frequencies below 82.41 Hz and if they last longer than just a few milliseconds on my guitar, though. The feedback problem I was having seems to almost be in the 60Hz range... but maybe that has nothing to with the guitar itself.