How does this happen?

[jazzyvee]

I have been playing by basses a lot recently and experimenting with my various amps speakers etc.
What i am puzzled by is that the sound from my Short scale series I bass seems to have slight chorus effect on it. It's really slow and sweet really. The odd thing is that it still has that sound acoustically with nothing plugged into the sockets, and when plugged through my rig it gets amplified.  It is not something i am concerned about i just wonder what the physics are that would make the bass vibrate in a way that produces that effect.
Obviously it affects the way the strings move and hence gets picked up.
I haven't noticed it on my signature shorty but will listen to my other basses hear if they have that feature.

[Moose]

Thats interesting - i've got a ric that did that "chorusy thing" even when acoustic. I think i've narrowed it down to the fact that the neck pickup is mounted a little crooked and (was) too close to the strings so whenever i use any vibrato i'm pulling the string into and out of the field of the pole piece which has a pretty narrow aperture of magnetism. This sounded very cool but was at the point where the intonation suffered in the "money zone", so i dunked'er down. The effect is less pronounced but still present and the low register intonation is good now. All this to say it might be an effect of the magnetism of the pickups altering the elliptical path of vibration of the string such that the pull biases the ellipse toward the pickup in the "ooo" part of the "woooowwwwooooowwww", for lack of a more concise description? Are yours (particularly the neck pickup) set any closer to the strings on the "chorus bass"? That might be it.

[rv_bass]

I wonder if it’s harmonics that you are hearing that are creating that effect?  That would be heard both plugged in and unplugged.

[MuseChaser]

I've heard the same thing on my bass and a few others. I agree with rv_bass .. it's caused by the interactions of the by the interactions of the upper harmonics which, by definition, contain out of tune partials of tbe fundamental. Sort of like the acoustic equivalent of TIM (transient intermodulation distortion) in audio gear. Well... not really...but kind of.

[gtrguy]

I had something like this at practice last week. It turned out the house practice bass amp was also running through the PA, which somehow caused it.

[edwardofhuncote]

I think they all do it, it's just a matter of degrees. I've had uprights in my shop drive me up the wall chasing phantom harmonics, sympathetic tones. Of course there's another set of variables on a doghouse...

My guess, -and this is purely a guess- Alembics, by virtue of their neck-through construction are bound to carry and support harmonic frequencies across the spectrum better than the average you-name-it bass or guitar, and less likely to experience a so-called 'dead' note from being cancelled out. I think where some of those harmonics and intervals fall on a short-scale like Jazzy's make this effect more evident. 

And on top of that, demographically, we're the type that are listening for it.. so it's easier for us to hear. I might just be fulla' bull-squeeze too. FWIW, I hear these things all the time, and every single one of them is a tiny bit different. My '81 Distillate is freakishly resonant. 

[JimmyJ]

I'll jump in too with no real knowledge whatsoever.    Sometimes I think a struck string will slowly rotate and cause this slight phasing or chorusing sound.  Why, I have no idea.  But when it's released from your finger it snaps back in the opposite direction and then the plane of vibration can shift to straight up and down above the pickup, the continue rotating until it's reversed phase on itself - in a way.  Factors that make that happen might include how close the pickups are and how powerful their magnetic field is, and also just how the string interacts with the instruments construction and, for all I know, which way the wood grain is running.

Jazzyvee, as an experiment, you could try lowering the pickups on your SSS-I.

Jimmy J

[jazzyvee]

Generally I hear/notice/perceive things too much. When I was growing up I was always accused, quite rightly, of observing and pointing out things that others just accepted and let pass or didn't notice.
It is a kind of curse really and over the years of being on the forum you can probably deduce the same from some of my posts. hahah. I have a passion for trying to understand what I experience through my senses and why.

One of the things Mica mentioned to me when I picked up my S2 from her was, try not to hear the 4th harmonic ( hope that is the right one), and for a while after getting home i started hearing a strong harmony note in addition to the fundamental when playing single notes which really messed my head up.
So this time i'm kind of glad to read that others have experienced the same thing. I will try lowering the pickups though the fact the sound appears when the bass is unplugged may still result in it coming through the pickups to the speakers.
Jimmy J, i do recall reading here a while back that you put a twist on the string when re-stringing your bass, was that to reduce the effect you mention above, about string rotation long it's axis?

[JimmyJ]

You do indeed have acute senses but you're "preaching to the choir" in here. 

Remember that even with no amp or preamp power the magnetic effects of the pickups are still in place and may be effecting the string's movement.  Still just my wild theory but it might be interesting to see if lowering them makes any difference.  (And you are just the guy to test it for us!)

My string twist thing is not related to this, it's an effort to keep the outermost winding tight to avoid any string rattle.  Sometimes it makes a difference, and sometimes no twist, or a twist in the other direction is quieter...  So who knows?

Jimmy J

[mica]

Its the 5th harmonic that I don't recommend you learn how to hear. I didn't mean to learn, but now that I have I can't unhear it, but it's only really evident to me when listening to a string sustain a long time in isolation.

I've never heard the chorus effect myself, but I haven't really listened for it either, and certainly Vince you've played many more hours than I have so I will trust your ears. Strings are curious things indeed.

[jazzyvee]

Thanks for that Mica, would it be correct to deduce then that when tuning low E on my basses and my clip on tuner is showing B, that it is also picking up a strong 5th harmonic? Or do i need a new tuner.

[edwardofhuncote]

All that happens on a string doing this:

[rv_bass]

That’s cool, you can see the different wave lengths for the different strings and fretted positions (notes)! 

[JimmyJ]

Jazzeevee,

Thread diversion alert... So, harmonics or overtones are just subdivisions of the vibrating string.  (Stop me if you know all this - oh, or stop reading.)  If you touch the string just above the 12th fret and pluck it with your other hand, you've divided the vibrating string in 1/2 and the note that sounds is an octave above the fundamental.  Touch the G-string above the 7th fret and you've divided the string into 1/3 and you hear an octave + a 5th above the fundamental.  Touching above the 5th fret divides the string into 1/4 so you hear 2-octaves above the fundamental.

It works pretty good until you get up to dividing the string into 7 parts (roughly fret 2.75).  The resulting "natural" 7th is what sounds terribly out of tune to our western ears as it is very flat compared to our tempered scale 7th.  Be careful if you look for it because you might end up with Mica's affliction where you can't UNHEAR it. 

I wrote about this once here in the forum and described how the Steinway Grand piano action is purposely designed to strike the string exactly at that 1/7th division spot - which inhibits the initial sounding of that overtone. 

Anyway, your clip-on tuner may have difficulty hearing the low-E fundamental of 41.2 hz. More likely it's listening to the 1st overtone of 82.4.  But sometimes it jumps to the next one which is the B at 123.5 hz.  I try to give my tuners a chance by offering them that first harmonic on the low-B string (touch over the 12th fret and pluck) so they don't have to try to decipher 30.87 hz.

Jimmy J

[garyhead]

I’m sorry, but nobody told me math would be involved in this thread!