Double Bass Tuning problems

[sec_9]

Hello list. This is my first post here.

i took up the double bass only a couple of months ago and I'm using my university's one.
The problem is when I tune the bass.
When I tune it and play with the bow and tune it to a tuner to the open strings, everything is fine but when I play and tune with plucking the strings every string is really flat.

What would be causing this?


Thanks

 

[bejoyous]

Perhaps you are applying too much pressure with the bow, tensioning the string. A

Also, I have found, when I tune with a tuner, the machine picks up the fundamental of the note easier if I just pluck the string. It also leaves a hand free to adjust the tuning.

Plus, the bow produces more harmonics in the sound mix than pizz. Many of the harmonics are out of tune with equal temperament. This would confuse the tuner's little brain as well.

 

[sec_9]

Ok, thanks for that. I'll just stick to tuning while plucking.


Thanks


Ash

 

[RSBBass]

I am a relative newbie too, so take this with a pound of salt.

I would think that if you are getting different results when you use a bow or pizz. you should tune using the method you are going use to play.

You also may want to check why you are putting extra tension on with the bow.

BTW Have you checked you tuning against a known pitch to be sure it is not the tuner?

 

[drurb]

...Many of the harmonics are out of tune with equal temperament. This would confuse the tuner's little brain as well.

They're also out of tune in terms of perfect intervals as a result of non-linearities inherent in real strings. I wonder about how many cents the OP is worried. Sometimes there's a tendency to place too much emphasis on a small deviation.

 

[Hector Wolff]

I agree you should tune with the bow if you are going to be playing with the bow (as in orchestral music).

If you do tune with the bow you should not use much pressure.

In my experience a heavy pressure will result in the notes coming out sharp.

Then you will tune (still applying too much bow pressure) so that the note is in tune, making the open strings in reality slightly flat, which is what you are noticing when you pluck the strings.

 

[fdeck]

What kind of strings? My son's cheap Chinese cello came with strings that went noticeably (1/2 step) sharp when bowed with any vigor.

 

[tstone]

...They're also out of tune in terms of perfect intervals as a result of non-linearities inherent in real strings...​

The plucked string may exhibit inharmonicity, but the bowed string won't. The physics of the interaction between the bow and the string forces the upper partials to be integer multiples of the fundamental even if those frequencies differ from the natural frequencies of the string when plucked. It comes down to the difference between forced vibration (bowed) and free vibration (plucked). The phenomenon is called mode locking and also occurs in brass and reed instruments.

It is true that the louder a string is played, the more it tends to go sharp. Do you get the same phenomenon if you pluck and bow the string very gently?

 

[iiipopes]

Two reasons it goes sharp:
1) The string tends to vibrate like a rope over a pulley, so the top of the string actually vibrates from the center of the bridge notch, but the bottom of the string vibrates from the edge of the notch. The thicker the string, the more noticable the difference. This is more noticable on pianos, and is the origin of "bare core" strings so the overtones don't go any more sharp than they need to. Piano tuners will "pull" the octaves flat, especially on spinets, with the octave overtone of the string being tuned to the octave above, resulting in the fundamental being slightly and progressively flatter as the tuner descends in pitch. Keep this in mind when playing a piano trio with a small upright.
2) Greater dynamic equals greater string excursion and greater velocity of the string.

 

[David Potts]

Do you tune using harmonics? Try lightly bowing the D harmonic over the note D (the 7th "fret" above open G) into your tuner then playing the open G normal arco. Does the tuner indicate one or the other is sharp or flat? Do the same for each string in turn. Strings don't stretch uniformly along their length as they get older, one of the reasons for changing them. This can also put harmonics at odds with open strings. How new are your strings do you think?

Worth a try?

DP

 

[drurb]

...They're also out of tune in terms of perfect intervals as a result of non-linearities inherent in real strings...​

The plucked string may exhibit inharmonicity, but the bowed string won't. The physics of the interaction between the bow and the string forces the upper partials to be integer multiples of the fundamental even if those frequencies differ from the natural frequencies of the string when plucked. It comes down to the difference between forced vibration (bowed) and free vibration (plucked). The phenomenon is called mode locking and also occurs in brass and reed instruments.

It is true that the louder a string is played, the more it tends to go sharp. Do you get the same phenomenon if you pluck and bow the string very gently?

Indeed, I'm the one who posted about mode locking!

Piano tuners will "pull" the octaves flat, especially on spinets, with the octave overtone of the string being tuned to the octave above, resulting in the fundamental being slightly and progressively flatter as the tuner descends in pitch. Keep this in mind when playing a piano trio with a small upright.

Actually, piano tuners stretch the octaves, typically using the fourth harmonic.