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Double Bass What about DB sound-box resonance?

#21
I think the intent is different from what the OP is saying, but in case you're not aware, Arnold's Ergonomic Contrabass has holes on the upper portion of the ribs (to project sound up to the player in addition to projecting out)

http://www.aesbass.com/handmadebasses.htm

It's also got some meat removed from the treble side upper bout to allow for more accessibility, and that's compensated for in the lower bout. If I understand it correctly.
 
#22
MingusAmongUs said:
Arnold's Ergonomic Contrabass has holes on the upper portion of the ribs (to project sound up to the player in addition to projecting out)
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Nice bass that is. And not built with consideration of Helmholz theory I'm guessing.

There is a difference between the Double Bass, a Pipe Organ, and a Speaker. The speaker is a static box (for the most part) that supports the driver which is moved by electricity. The box isn't supposed to move. The organ pipes are similar in that they are fixed and stable with air introduced to them by external means.

The Bass strings resonate in sympathy with the whole bass, both plates and the sides. It's not supposed to stand still.

It's a confounding variable when considering the application of speaker theory because it doesn't really work like a speaker or a pipe organ both of which are more similar to each other than a stringed instrument.
 
#24
Uncletoad said:
Nice bass that is. And not built with consideration of Helmholz theory I'm guessing.

There is a difference between the Double Bass, a Pipe Organ, and a Speaker. The speaker is a static box (for the most part) that supports the driver which is moved by electricity. The box isn't supposed to move. The organ pipes are similar in that they are fixed and stable with air introduced to them by external means.

The Bass strings resonate in sympathy with the whole bass, both plates and the sides. It's not supposed to stand still.

It's a confounding variable when considering the application of speaker theory because it doesn't really work like a speaker or a pipe organ both of which are more similar to each other than a stringed instrument.
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Well said. This is precisely to what I was referring when I said:


drurb said:
Therein lies the problem. As I see it, the two differ in many, many substantial ways... the fact that one is a resonant body while the other is not...
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drurb said:
...The double bass is a resonating body. The particular acoustic response, the spectral peaks and valleys, precisely how the overtone structure occurs, etc. are exactly what characterize the double bass.
Click to expand...

drurb said:
This is yet another reason that the application of Thiele-Small alignments, etc. and physical acoustics as applied to ported non-resonating enclosures is not appropriate.
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#25
To me, the most promising aspect of this idea is the ability to easily tune the ressonant frequency of the body, and to be able to change that tuning. I understand that string instruments operate differently than speaker boxes, but does that really mean that a tuned port cannot work? Luthiers like Bob Brannister tune the ressonances of the necks and the bodies to match each other, mostly by adding or subtrating mass to the neck structure because the body is too problematic to alter.

ff holes are more there to add flexability to the top, not really to let sound out or to tune the ressonance (those are more side effects), hence the responce from pollman.

I have to humbly dissagree that the design of the DB has been set for 400 years. If you take 10 basses from 10 different makers from any era, you will likely get 10 different measurements for every dimension of the bodies, and 10 different ressonating frequncies. Not to mention basses with flat/round backs, violin/gamba corners, 'cello/viol shoulders... I've never played two basses that sound the exact same, even two basses from the same factory. Differences in ressonate frequencies in pieces of wood of the same speicies make dialing in the ressonance of a design nearly impossible, that's where luthier magic comes in. These are a few reasons why I think an easy way to tune the body of a bass could be a good thing ( I don't think it would change the fundamental character of a bass at all).

That said, there's no way I'm going to cut a hole in my bass. I'm really hoping that there is someone out there with a junker that is curious enough to experiment, that is the only way to know if this idea works.
 
#26
I don't know if I believe that f-holes in a bass are there only to increase flexibility of the top.

As a Rockabilly bassist who has experimented with f-hole covers for reduction of feedback at high volumes, I can tell you that closing the f-holes on a bass changes the overall tone and volume alot. Sound is definitely escaping from the f-holes in some fashion. Sealing off the f-holes kills alot of midrange tone, too

(that's why I won't cover them unless it's an absolute last resort).
 
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#28
uprightben said:
I have to humbly dissagree that the design of the DB has been set for 400 years.
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Well, I sure didn't say that.

uprightben said:
If you take 10 basses from 10 different makers from any era, you will likely get 10 different measurements for every dimension of the bodies, and 10 different ressonating frequncies. Not to mention basses with flat/round backs, violin/gamba corners, 'cello/viol shoulders...
Click to expand...

I agree, but here is where matters of degree count! One also has to look at which parameters are changing across those basses and which are remaining constant. For example, none of those 10 basses would be confused with a BG.
 
#29
I respect all your opinions and have come to view the DB a little differently. No, I am not out to create a new kind of acoustic bass, I tried that already, and found small and portable does not translate acoustically to loud and deep, the acoustic BG being a sad example. Since someone asked, I play Bluegrass and Oldtime only piz, unamplified.

I have had occasion to listen to a lot of different basses at outdoor festivals where they are not affected by room resonance. Most were old Kays or of unknown origin. Some were sweet and even, some were muddy and undefined, some were bloomy with a few notes much louder than others and a few were downright obnoxious and harsh at any sound level in any range. The contributing factors are not clear but age was not the only one.

Given that double basses like all machines are a compromise, I think the EC1, is a bargain at well less than the cost of a fair American-made guitar. A fine $10k aged, carved top it is not. There may be better ones under $1000 but THEY weren’t on Craig’s list when I got the impulse to buy

You would expect a high-production-factory bass with the Kay heritage to be acoustically optimized and close to being in design tolerance. The plywood plates should be more consistent than solid wood so it should reproducible to a large degree. But that is an assumption and I was just wondering if it could be better or better meet my expectations.

What characterizes a good DB? Is there a definable set of goals or an individualized check list? Strings themselves seem to be definable by purpose or intended useage, what about basses?

There has been empirical testing done concerning what characteristics define a high-quality instrument. For example in the research paper that I referenced earlier:

Eigenmodes and tone quality of the double bass by Askenfelt, A.

Link Removed

The author stated:
“One desirable characteristic of a double bass is a "full bass
sound" in the low register.” . . . “The term "full" here is used to describe a deep bass
sound, whose character resembles a low organ flue pipe.”

Well that was really an assumption.

And then his finding as to what contributes to it:
“ It was found that an instrument which was characterized
by a f u l l bass tone quality i n the low r e g i s t e r , radiated a stronger
fundamental than other basses. However, even the basses possessing a
full tone quality radiated a fundamental considerably weaker than the
second and t hird partials . Low values of the Helmholtz and first top
p late resonance were found t o favor the fundamental and the lower
partials.”

In other words of the basses tested those that had low cavity resonance and low top plate resonance perform better in the low register.

Cavity resonance - this is Helmholtz in action.

The noted partials are the harmonic(s) above the root, the second being the octave and the third being a perfect fifth over the second. By accident, I may know why they are important.

I know from other sources that the human ear will “construct” a perceived root from hearing the root’s partials without the root. I have a small Phillips mp3 player with 1” titanium speakers with which I perceived bass down to low G or E when I knew darn well speakers of that size could not effectively radiate those frequencies at the level I thought I was hearing it. Doing some research I found Phillips has a patent on circuitry that “fools” the ear into “hearing” low bass by stressing their overtones. I am guessing that the better DBs reinforce the weaker fundamental acoustically in much the same way thus giving a “full bass sound”.

So maybe low register roll-off can be offset with a good set of particals? Humm.

I wedged the EC1 f-holes full of foam rubber and found as Gearhead43 mentioned that mid and highs suffered. Lows MAY have improved slightly. This led me to consider that the f holes are too much vent area for optimum low resonance so I don’t need an additional hole, in fact I need less vent area for low res but that might choke the mids. A victim of the Great Compromise.

I have put the hole saw back on the shelf for now.

Thanks for your posts, both opinions and facts were helpful.
 
#31
gbaker said:
I know from other sources that the human ear will “construct” a perceived root from hearing the root’s partials without the root. I have a small Phillips mp3 player with 1” titanium speakers with which I perceived bass down to low G or E when I knew darn well speakers of that size could not effectively radiate those frequencies at the level I thought I was hearing it. Doing some research I found Phillips has a patent on circuitry that “fools” the ear into “hearing” low bass by stressing their overtones. I am guessing that the better DBs reinforce the weaker fundamental acoustically in much the same way thus giving a “full bass sound”.
Click to expand...

Not really. What you are referring to is called "perception of the missing fundamental." It is one of the oldest phenomena studied in the psychoacoustics of pitch. What human listeners perceive in the circumstances you describe is the pitch of the fundamental even though that component may not even be present in the physical spectrum. Exactly how the auditory system achieves this has been studied for over 150 years! Notably, Helmholtz's work is fundamental (pun intended). The debate continues to this day about the details of "place" and "timing" theories. I don't recommend "internet sources" if you are interested in understanding the details and relevant phenomena.

In any case, while reinforcing the pitch of the missing or weak fundamental can be desirable (as in UltraBass devices based on Philips patent # 6134330), doing so does not, of course, provide the physical acoustic energy of that component. In my estimation, that is what is of great importance and what is preferred from a double bass.
 
#32
Well, it seems I've misspoke about ff holes.:eyebrow: What I should have said is that the design and placement of the ffs is mostly about adding flexability by cutting the arch of the top at the plane of the bridge. ffs definatly do let the sound out and tune the resonnance of the body, and you definatly need a hole in the top for an acoustic instrument to work, but bowed strings need that arch cut at the bridge to function mechanically. I'm really not clever enough to think of this on my own, I got it from a luthier when I asked him why we couldn't put the sound holes somewhere else.

I don't think plugging the ff's will give you an idea about whether a tuning port will work, I still think someone needs to take a junker and see if a tuning port can improve the sound. If I can find one, I'll do it and post sound clips.
 
#35
Jake deVilliers said:
Try taping over a small portion of the f-holes at a time.

If the opening's too big you'll tune the cavity resonance downward, which is what you want, right?
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Yep. OK I gave it a try. Duct taped a business card across one of the ff with various coverage. Result - with about 1.5 to 2 sq in covered, the peak at D went away at the expense of some highs. I think I like it. The low register (below A) did not seem to improve with any amount of coverage.

Thanks for the idea.
 
#36
uprightben said:
What I should have said is that the design and placement of the ffs is mostly about adding flexability by cutting the arch of the top at the plane of the bridge. ffs definatly do let the sound out and tune the resonnance of the body,

I don't think plugging the ff's will give you an idea about whether a tuning port will work, I still think someone needs to take a junker and see if a tuning port can improve the sound. If I can find one, I'll do it and post sound clips.
Click to expand...

Let me be clear so as to not have mislead anyone in my first post.

Don't cut too quick. For a given cavity size a smaller port reduces cavity res (Fb). Contrary to my first post, for a given cavity cutting an additional hole would raise the Fb - not desirable.

I think I effectively separated the two functions you mentioned, (plate flexibility and Fb tuning) when I revised the design of the HarpKit bass. I used the original to experiment with. When I cut a slot representing an f-hole on the bass bar side it got much louder because it allowed the top plate to move further with the same amount of string force applied. So on design II I did a single ff (which is skinny but tall and moved what was the guitar-like center hole down and right to balance the design and provide access to the SP.

I calculated the hole size to reduce the Fb to 40 hz based on volume but missed it (either because even the skinny f-hole contributes some or because my cu ft estimate was wrong due to the curved body surfaces). The round hole is easy to experiment and tune, by partially covering it I determined the proper size for a 40 hz Fb and used a port reducer to get it.

The result was apparently good, in fact it led to me to wonder why my new much larger DB wasn't louder below A. As someone said "It is what it is". Maybe I should check that the SP is not too tight.:hmm:

Anyway, please, measure twice, saw once (or none).
 
#37
I am currently on vacation and won't be available to answer any reply for a couple of weeks. However, as many of you know, I have been working for several years with matching the resonance frequency of the neck assembly (B0) with that of the body cavity (A0). In doing this, I have had the opportunity to determine the body resonance frequency of many basses. Some have had an A0 as low as 58 Hz and some as high as 92 Hz. I have found NO evidence that a lower body resonance improves either the sound quality or volume of an otherwise well made instrument. I've had basses in my shop at either end of the frequency range (A0) that would knock your socks off. Making the body cavity larger or the A0 frequency lower is no guarantee that the bass will sound any better than one with smaller cavity size and higher A0.
 
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#38
Thank you, Bob, for sharing your experience with us, I was hoping you would chime in and strighten me out. The OP got me thinking "hey, here's a way to make a complete POS sound better", but now I'm thinking "a POS will be a POS no matter how you shine it". For the record, I'm very happy with the sound of my bass and never considered cutting it or modifying it in any way, I just really wanted to see how far we could take this.

gbaker, if you are unhappy with the sound/volume you are getting from yuor e string, you can try a heavier gauge string, or have someone move the soundpost slightly outwards (away from the bridge). You should also be aware that it is hard to hear the lowest notes from a playing position, have someone else play your bass and stand about 5 to 10 feet away and see how it sounds (if your helper doesn't play bass, make sure you show him how to dig in and use plenty of finger meat to pluck). When I think of englehart and kay, I think big bottom sound as the most common character.
 
#39
drurb said:
It seems to me that what gbaker is really doing is designing another instrument with acoustic properties that he may find more desirable. Whatever the result, it will not be what we think of as a double bass. The acoustic characteristics of the instrument that have evolved over the centuries are precisely what define the instrument.

gbaker said, "I began to wonder why bass manufacturers do not lower the resonance to smooth the mid response and increase the loudness of the lower register." The answer is simple. It is because to do so would produce an instrument that does not sound like a double bass.

The goal is not at all to produce a "flat" or "smooth" response. The goal is not necessarily to produce an instrument that radiates more acoustic power in the "lower register." The double bass is a resonating body. The particular acoustic response, the spectral peaks and valleys, precisely how the overtone structure occurs, etc. are exactly what characterize the double bass.

To be sure, there are differences in personal preference in terms of desired sound. Still, there is pretty good agreement on what are particularly good exemplars of different "classes" of the double bass sound (e.g., the French sound, Italian sound, powerful orchestral depth, more delicate solo sound).

This is not to suggest that gbaker's project is folly. He may produce an interesting sounding instrument. I doubt, however, with the goals he has defined, that he will produce an instrument that has sonic characteristics that will be recognized as that of a fine double bass. Rather, he will likely produce an instrument with a different sound, however interesting it may be.
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I agree with this posting. It is a complex problem and you need to know what you are trying to do. The port in a reflex speaker box is there to extend the lower frequencies below the resonance of the speaker, not to make it more 'boomey'. Coming to the double bass, it seems to me that the mid and higher harmonics give an impression of a bass note which might not be actually as loud as it sounds. You can find this in many modern speakers where the bass guitar sound is implied beautifully by loudspeakers that are incapable, (according to the laws of physics), from actually creating that frequency. Large wavelengths cannot, (again in theory), exist in a room that is smaller than its wavelength, however very acceptable sounds are created by small speakers, especially where there are two as in stereo where bass is often in phase. Another thing to think about is that the double bass sound is not a harmonically 'flat' sound. It peaks in many areas, due to the different places form which the double bass will radiate sound. I do find this thread very interesting and look foward to more comments.
 
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