Author Topic: I'm sure it's logical physics....... but what is happening here? (Read 378 times)

jazzyvee · « **on:** March 10, 2010, 05:20:59 AM »

Today whilst in the middle of a song I was practicing I noticed a mark on the fretboard near the inlays on my Europa 5 so I rotated the bass from the playing position by 90 degrees so i could look at the fretboard and thats when I noticed that the plucked string got louder in volume and richer in sound which I thought was wierd.

Hmm... i thought so I tried it again, plucked the string finger style as normal so that the string was moving mostly parallel to the top of the pickup, rotated the bass by 90 degrees so that the fretboard was face up and parallel to the floor and indeed the sound got louder and richer.

So then i decided to pop the G string so it was moving mainly at 90 degrees to the pickup cover as you would do when slapping and popping then rotated the bass in the same way and the volume reduced and tone of the string got less rich. I wonder what is the reason for that?

I can imagine that when you pluck the string so that it moves across and parallel to the pickup, then turn the bass horizontal, with the back of the bass to the floor, the effect of gravity and the weight of the neck would bring the string closer to the pickup slightly giving it a slightly more dense magnetic field to move through and generate more, output but then the same should happen when the string is popped at 90 degrees to the pickup as gravity would move it closer to the magnet in the same way although it would still be crossing the magnetic field in a different axis. But in this case, doing so the volume of the vibrating string was reduced.

I know this is a pointless observation as the only guitarist I know of who held his guitar with the back of the guitar facing the floor was T-Bone Walker.

I guess it's just one of those momentary conscious observations of physics at work that got me thinking.

Jazzyvee

adriaan · « **Reply #1 on:** March 10, 2010, 09:13:49 AM »

If you start rotating the instrument around its axis, gravity might kick in to change the orientation of the vibrations along the string, perhaps bringing them into the focus of the pickup.

Perhaps it makes the string hit a fret ever so slightly, which would excite the string again, and might accentuate harmonics.

The body of the bass may also be reflecting more sound coming out of the speakers, going into your ears (it is a pretty hard surface after all).

You may also be increasing the coupling between your body and the instrument, which would increase the contact sound entering your inner ears.

Hm - perhaps the second theory is the best of the bunch.

dadabass2001 · « **Reply #2 on:** March 10, 2010, 11:28:14 AM »

Does this suggest I'll get better tone recording while laying on my back and playing (like the motown story about James Jamerson)?

Mike

benson_murrensun · « **Reply #3 on:** March 10, 2010, 01:56:25 PM »

You will get the best tone by playing behind your head, a la Hendrix. The instrument contacts your skull and your entire cranium becomes a soundboard, radiating sonic vibrations 360 degrees.
Wha? No? You don't think so?

gtrguy · « **Reply #4 on:** March 17, 2010, 10:43:24 AM »

If you really want to hear it, try putting your bare teeth into the body (lightly) to really feel the vibrations in your skull bone. Works well unplugged!

jazzyvee · « **Reply #5 on:** March 18, 2010, 12:40:29 AM »

I'll try that on my gig tonight. hahaha
jazzyvee

benson_murrensun · « **Reply #6 on:** March 18, 2010, 09:32:12 AM »

Your instrument will be personalized with your bite marks! You won't need those ID chips or other identifying marks anymore.

terryc · « **Reply #7 on:** April 12, 2010, 06:43:12 AM »

You could always play it like a lap steel..maybe that is why they sound so loud!!!

JimmyJ · « **Reply #8 on:** April 12, 2010, 01:10:56 PM »

Hey Jazzyvee,

Once the string starts vibrating back and forth I think it's inertia that keeps it moving roughly in the same plane even if you rotate the axis points.

So if you're finger releases the string towards the ground, the plane of vibration is basically across the pickup surface. If you turn the bass 90 degrees while the string is ringing (so the pickup faces the sky) the string is now vibrating more directly towards and away from the pickup. Make sense?

But if you lay down and pluck the string, unless you've change your hand position and picking style, you're release will again send the string across the face of the pickup. Stand up while it's ringing and it will get louder. Ha!

Time to write a song which takes advantage of this technique. Can't wait to see the video!
Jimmy J

David Houck · « **Reply #9 on:** April 22, 2010, 05:07:11 PM »

Jimmy's statement didn't make sense to me, so I ran a search but couldn't find anything. So I picked up the bass, unplugged, and started plucking an open A. I tried to watch the vibration of the string as I rotated the bass on its axis, but my eyes just aren't that good; however I thought I did notice a difference watching the string vibrate when the bass was lying flat on my lap, and when I plucked the string in normal position and quickly rotated to flat on my lap. But then I noticed the buzz. Whether in normal position or flat on my lap, if I plucked the string, there was a nice even tone; but if I plucked the string and then started to rotate the bass I heard a buzz. It happened every time. And I'm guessing that this confirms Jimmy's statement. The string is wanting to continue vibrating in a stationary plane, but the bridge saddle groove, over and within which the string is stretched, is being rotated. The relationship between the vibrating string and it's saddle, the contact, is changing; and as the contact point moves relative to the vibration, the string is essentially bouncing on the saddle; thus the buzz.

Or at least that's my guess.

dadabass2001 · « **Reply #10 on:** April 23, 2010, 09:23:48 AM »

Jimmy,
Would that mean writing a bass part that requires one of those hanging inversion-therapy stands (wish I could remember their name) to be set up in the studio? I'm guessing the label accountant and A & R guy might have something to say to the Producer about that expense showing up on a session sheet.

This is also triggering my memory of Keith Emerson's rotating piano from the 70's (California Jam?).
Mike

JimmyJ · « **Reply #11 on:** April 23, 2010, 10:01:45 AM »

Mike, that's it. It would need to be a midi-controllable tilt table...

Dave, I have not observed this visually either (even tried the low-b under fluorescent light). We would need some very high-speed video to observe what's really happening. But the results do seem to indicate what we're talking about. If I pluck my low-b hard and turn the bass it rattles against the frets, so...

I theorize that the string starts moving in a single plane which then rotates on its own - again I'm no physics guy. But this could explain the growl that some fretless or low action acoustic basses have where the note seems to grow louder after it's played. I suppose the exact way you release the string has an effect on this too so your own technique is part of the equation.

Interesting stuff!
JJ

lbpesq · « **Reply #12 on:** April 23, 2010, 05:24:40 PM »

Sounds almost like a gyroscopic effect. Makes sense to me.

Bill, tgo

jakebass · « **Reply #13 on:** April 24, 2010, 02:52:00 PM »

I don't know whether this observation would reveal the plane of the string but I have noticed that if you watch a string vibrate with a crt TV in the background of your vision, the string appears to vibrate very slowly and the oscillation is visible. I guess this is due to the strobe effect of the frames in film (that really is a guess) but it may mean you can see the direction...
Give it a try...!
Jake

lenny_d · « **Reply #14 on:** February 19, 2011, 01:16:19 PM »

I agree with JJ's assessment. I've noticed that same effect after plucking a note then moving the instrument in a different orientation causing the string growl/buzz. I always just thought it was something I did wrong! ;-)