Double Bass Tendency to Sound E harmonic - Why?

[IdahoSwing58]

First, I'll say I am completely new to DB, but have some experience in guitar luthierie, and a long woodworking background. I have a science and engineering background with good knowledge of vibration/sound physics. Before I get the usual comments (I've been reading here for a couple months) - yes, I do have an instructor lined up for lessons. I'll ask here anyway...

I just got this used Cervini ply DB yesterday. The bridge needs to be replaced (see post in "Basses" section for details), but I don't think that is the source of this behavior. I put on Obligato strings, and got one of Upton's $99 bows (w/ Carlsson rosin).

Issue - the E (open) has a real tendency to sound the 1st 8va harmonic when bowed. It doesn't seem to make much difference whether the bow is pulled near the bridge or fingerboard, or in between. This does not occur on the other strings. It is possible to excite the fundamental, but it is sort of a hit-or-miss event.

Any thoughts? Maybe that middle E is a natural frequency of the body? If it's relevant, the afterlength is a bit short right now (160 mm or so - I think it should be about 175-180). I'll fix this when I replace the bridge.

Thanks in advance for your thoughts and comments.

 

[sibass89]

The octave E is an overtone it might just be possible that your bass takes better to the note E. My bass happens to love the note B (very oddly enough) and whenever I play B or some related tone of B my bass goes crazy. There isn't anything wrong, you probably just have a good enough ear to recognize the overtones from a note.

 

[jallenbass]

What kind of rosin are you using?

 

[Jeff Moote]

I think you probably just need more practice making this event less "hit or miss" and getting the fundamental to speak. I don't have experience with Obligatos, but the E can often be harder to start with the bow than the other strings.

--

What kind of rosin are you using?

and got one of Upton's $99 bows (w/ Carlsson rosin).

 

[Alex Scott]

Try holding your bow on the e string and wiggling the string back and forth without making a sound, then try popping a sound out like a pizzicatto, then try using a much slower bow stroke ( If you are currently using the whole bow during two counts, stretch it out to 4 counts.)

 

[Ludwig]

Move a little closer to the finger board with the thicker strings. The thin strings are more easily moved, to get the thick E going, it is better to start the string closer to the finger board while keeping the same bow pressure and speed.

 

[jfv]

When the speed of the bow is too fast it tends to bring out
the harmonic. Of course given that you have suspect
equipment (you mention the bridge, and this does matter),
and no training, all bets are off.

A good teacher will solve this all

Happy New Year,

 

[robobass]

How does the E pizz? In the right light you can see how the harmonics behave after you have plucked the string. A good bass should show mostly fundamental for the first second or two. If you can clearly see the node at the octave (or wherever) right away then I would say there is an acoustical problem with the bass. This is preliminary, as you said, but I have a feeling that when you show this bass to a good luthier or teacher he will confirm this. Could be that you only need a soundpost adjustment.
Good luck,
Robobass

 

[IdahoSwing58]

The octave E is an overtone...
>Obviously 1st harm.

There isn't anything wrong, you probably just have a good enough ear to recognize the overtones from a note...
>Nope. You can see the node at the string half-length - primarily the octave E being excited.

What kind of rosin are you using?
> Carlsson Bass, Upton $99 bow.

I think you probably just need more practice making this event less "hit or miss" and getting the fundamental to speak...
> My guess, but so far it seems pretty quirky

Try holding your bow on the e string and wiggling...then try popping a sound out like a pizzicatto, then try using a much slower bow stroke ( If you are currently using the whole bow during two counts, stretch it out to 4 counts.)...
> "popping a sound out" - not sure exactly how to do this. The wiggling is no problem - I can deflect the string a fair amount with not to much weight on the bow. I tried deflecting and then lifting the bow to release the string, but the note is so quiet it is hard to hear the relative amount of fundamental vs. 1st harm.

> bow stroke is quite slow. more than 8 count at 60 in one direction. Slower is better with regard to fundamental starting. You have to start the stroke very slow to excite the fundamental, before increasing speed for higher volume.

Move a little closer to the finger board with the thicker strings. The thin strings are more easily moved, to get the thick E going, it is better to start the string closer to the finger board while keeping the same bow pressure and speed. When the speed of the bow is too fast it tends to bring out the harmonic.
> Noted. this does help. Still virtually impossible to start the fundamental with the bow closer than about 1/3 distance down from fingerboard end to bridge.

Of course given that you have suspect equipment (you mention the bridge, and this does matter), and no training, all bets are off. A good teacher will solve this all...
> Hopefully that will prove to be the case. I've got a new bridge on order, and a new nut. I should get them the end of this week, and get them fitted up/set-up next weekend. I'll report back to this thread afterwards with the results. My work schedule and a long-planned winter vacation will make it about a month before I get to my next lesson.

How does the E pizz? ...A good bass should show mostly fundamental for the first second or two...
> It is so - primarily fundamental regardless of position where the string is pulled.

Could be that you only need a soundpost adjustment.
> I don't doubt this possibility. The post is slightly crooked with the back end closer to the neck by probably 5-8 mm (by eye). The top end is in a nominally "correct" position with the space from the front edge of post to back of bridge foot about 12 mm. I also suspect the post fit is too tight. I will attend to these issues when I'm working on the new bridge.

Related (?) the E and A have a duller sound and somewhat less volume than the D and G. This suggest a preference to higher frequencies in the current set-up. I'll experiment a bit and see if I can get it evened out. I was sort of limited on working the old bridge on where I could get the action height, so the strings are almost even at about 7 - 7.5 mm. I'm not too concerned about this right now, but will set it up from G @ 5 to E at 8 with the new bridge. That may help even things out as well.
~~~~

Thanks to all for your prompt replies. Once I can get this work done, and get some guidance from more experienced arco players, I'll report back.

BTW, the previous owner came to a party here last night and played it a bit (he played a jazz gig with it on Friday night, before I got it on Sat afternoon), and was amazed at the improvement in its acoustic pizz sound (he was always playing amped) by changing to the Obligatos (he was playing Velvet Animas at very low action height) and adding some height.

Also, I have read that the Obli's don't sustain very well, but they sure seem to ring well on this bass.

Thanks again to all, and to all I wish a very Happy, Healthy, and Safe New Year.