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Bass frequency/waterfall plots: what they mean to rigs

Discussion in 'Amps and Cabs [BG]' started by greenboy, Jan 27, 2009.


  1. Long ago I had a pair of magnapan speakers- a roughly 4 1/2 x 2 1.2 flat diaphragm. I often wondered how this would work for a bass since it was capable of making a recording of an upright sound very real..

    I played my beloved fender bass #852 through them and heard a sound that was far truer than what I got from a cone speaker, even a EV front loaded 18". I heard more fundamental and less sustain.

    A question- an upright has all this radiating area, front and back. How much does this contribute to the amplification of the string's fundamental, vs the actual string itself? Is it possible to compensate for the electric bass's shortcomings by simply using a huge speaker ( like a magnapan) of sorts to reproduce the fundamental?
     
  2. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Yes it was. And it was vibrating at many other multiples of 41.2 Hz too. See the earlier chart I linked and the bits about subdivided string/nodes? Anyway, the string itself does vibrate at the fundamental and its subdivisions each create harmonics near-simultaneously, but as several of us said before, the body itself filters the content so that the actual acoustic output is rather weak in fundamental until you play some higher notes.
     
  3. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Just cursorily examining this, I'd say the string vibrations excite the internal air space and f-holes, which acts much like a ported speaker enclosure with the main body resonance tending to be considerably higher than low note fundamentals. And the body panels are acting much like speaker cones transmitting the vibrations cause by excitation, coupling with air to make acoustic energy at a higher level than the string itself can reproduce. It can only be so efficient at fundamental due to size and the energy levels required at the input side, but it's pretty decent at the resonant frequencies of making overtones.


    I don't think the electric bass family has shortcomings; it is what it are ; } ...To address your magnaplane question, it's perhaps more important to consider how much displacement ANY type of speaker can produce, and that's not just a function of surface area - it's also a function of movement - excursion - being translated into acoustic energy. There are plenty of cone-based systems that can go real low. It's just that they are not considered practical for high SPL portable use, generally.
     
  4. metron

    metron Fluffy does not agree

    Sep 12, 2003
    Lakewood Colorado
    Nice - fourier transforms for bass. I remember doing that crap manually in equation form for my signal analysis course. :spit::D
     
  5. wow, talk about information going over my head...

    i think this was addressed in the first couple pages here, but there doesnt seem to be much talk about human hearing.

    how audible is the difference between a true 82hz vs. 41hz?
    wouldnt any frequency have some sort of harmonic that you could not decifer? i realize this is why we have scientific data to show us via graphs, but does it matter?

    as far as audible-ility (you like that?) goes, we know our ears our more sensitive to mids. when we get to the low end dept., it seems we need those harmonics to let us know what we are hearing, if that makes any sense.

    if we were able to accurately reproduce a flat fundamental:harmonic output, would that not be mud city? maybe the bass guitar / amp / speaker designs are close to where we want them... could they be the way they are for a reason?

    i think ive gone too far here and cant organize a proper direction for my thoughts. i am going to reread this thread and continue to follow.

    carry on.
     
  6. geshel

    geshel

    Oct 2, 2001
    Seattle
    Johnny: the difference between a pure tone at 82Hz and 41Hz is very obvious. Anybody, and I mean anybody, can hear the difference. Playing with a sine-wave generator can be very enlightening in this regards. (a simple synthesizer with a "sine wave" sound is good too).
     
  7. ;)

    Bro, I appreciate what you've already done. VERY much!!

    You have done more than enough already. But I couldn't resist asking (& "no" is a fine answer).

    Wonderful to see the late 'bloom' in the electric, & the evenness of levels in the EUB's 1st few harmonics.
     
  8. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc

    Hi Johnny,

    I've talked about it in quite a few posts here, and even provided a chart that shows the relationships.

    Well, close is still no cigar. Between manufacturer and player cluelessness about the finer points of quality acoustic design, a relative dearth of superior drivers that are suitable for the bass, and the cost cutting approaches that pervade, if there is a reason, it's not because things have been optimized already ; } ...Yes, some common sense approaches have long been part of basscabdom, but I think it can get better - more diverse, more flexible, and more reliable - and I think that most players will eventually be able to hear the improvements.
     
  9. Passinwind

    Passinwind I Know Nothing Supporting Member Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    I intend to tackle as many of these questions as I can eventually.

    I'll move away from the EUB for now; this is the BG Forum and at the least I need to get some Fender samples going ASAP. Greenboy felt that the first graph would be good enough to get the discussion going, and it looks like he was right.
     
  10. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Unfortunately a lot of favored amplification/speaker cab/driver combinations are pretty bad about obscuring low fundamentals with a cloud of harmonic distortion, and they aren't actually able to reproduce the low fundamentals at a high enough level to hear them when that cloud is present.

    We who have gear that can do better, are lucky.
     
  11. These are graphical representations of what is being sent out of a bass. Which is what we hear. I, & likely some others, find them EXTREMELY informative towards what is heard.

    The graphs are merely a different way of speaking. Like musical notation, an area I'm lousy in. Just because I can't hear music when looking at sheet music doesn't mean you can't.
     
  12. all right, i was thinking along those same lines, but everyone put it into words better than i can.

    thanks again to all the knowledgeable and who converse without being condescending.

    i guess i dont get the difference between a true flat response and an audible "flat" response that is a) desired and b) physically capable, being that speaker design doesnt seem to support the possible desired flat response.

    without trying to sound doubtful, i sincerely would like to hear such a thing... and hopefully it would sound good!

    ...trying to keep up without derailing... carry on again ;)
     
  13. Myself, I'd prefer to have lots of fundamental & ability to reproduce it cleanly. You do not HAVE to reproduce it, nor do you have to retain the cleanliness. But I feel it better to remove what you don't want than to try to add what isn't there.

    I found it VERY interesting to see what the difference is harmonically between the EB & EUB samples. That info might help me sound more EUB-like. Or it might help me sound less EUB-like.
     
  14. geshel

    geshel

    Oct 2, 2001
    Seattle
    A couple of years ago, when low C# strings were showing up on the scene, I tried to explain that very few people have ever actually heard a pure 16-ish Hz sine wave in their life. The only subwoofers that can do it without significant distortion are servo-controlled ones like Velodyne. I've never, ever, seen any bass guitar cab no matter how large that would be capable of producing 16Hz at a volume loud enough to hear without also producing so much 32Hz and 48Hz overtones that those would be what people actually hear. It turns out, this is a hard concept to explain online :)
     
  15. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    An interesting truth which I don't often see in discussions of "tone": 100% is all there is. If you want more fundamental, you need less weight in one or several other areas of the harmonic spectrum. As far as the balance of partials in the signal is concerned, this is true.

    The waterfalls Charlie is providing kind of clarify that, I think. When you see one, you are roughly seeing everything in its proper proportion for that bass, that note with that hand starting the string vibrating. That's 100%. If the 4th overtone and up were taller (more intense), the ones below wouldn't be as tall. Sum game!
     
  16. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Well, it depends on who's listening I think. Just seeing a speaker's raw response chart with maybe the 2nd and 3rd harmonic distortion plotted with it made me ask myself, "Hmmm, what's THAT?" And then I wanted to find out. And sometimes the printed lit that came with products (thanks, Peavey and others for all those great product manuals in my early years!) made a real effort to take me beyond mere dumb operation and into some deeper understanding.

    [​IMG]

    And just simplisticly, it's not so hard to understand that the cone can't entirely conform to perfect pistonic response, or that it's dead to all imperfections. So the cone vibrates and shapes in such a way as to make some content that wasn't originally in the input signal. That's maybe the simple version.

    I actually like a little of that for bass, so I favor direct radiators for the most part, as opposed to designs that can filter it out completely. But at one time I had Servodrive and ELF subwoofer stuff around, and so I could have it handling below 60 Hz and down into the nether regions. I got to hear 16 Hz and so forth.
     
  17. JAUQO III-X

    JAUQO III-X Banned

    Jan 4, 2002
    CHICAGO,IL.
    Endorsing artist:see profile.

    For many who jumped on the Low C# string band wagon it was approached kind of with a flavor of the month mentality.

    They dived in with ears were not even developed enough to pick up the 23hz of a low F# string,let alone the 17hz of the low C# string and to their astonishment all they could do was complain that it couldn't even be heard and logically resorted to using the string as nothing more than a thumb rest.

    It takes more than the string alone to capture the 17hz properly and that's what many do not seem to be aware of.



    I never relied on cabinets to begin with(and that's the mistake that most seem to make).

    What makes it so hard to explain online is that those who don't believe it or don't want to believe will simply not believe it even when they are actually hearing it for themselves with their very own ears :)
     
  18. joelc1319

    joelc1319

    Sep 12, 2007
    Jauqo, I read the Low C# Theory page on your website (great read). I'm curious, do you think the most strength comes from the 34Hz harmonic, or do you think the most energy comes from even the 68Hz harmonic? I guess my question is, as the fundamental gets lower, is the strongest harmonic always the first harmonic (34Hz in this case)?
     
  19. Kindness

    Kindness

    Oct 1, 2003
    Chicago
    First, thanks to GB and PIW for the informative graphics that broaden the understanding of many members of the forum. Thanks also to the contributors that add to the knowledge base.

    greenboy - This quote jumped out at me. You know I'm on board with you as far as making use of systems that are essentially flat throughout the bass regions . However, I wonder what you mean by compensating for the ear's lack of sensitivity. I am well versed in understanding the F-M curves and the phenomenon they describe; however, these ears are part of us and our listening experience. Compensating for them would be an extraneous and, in my view, superfluous move unless you are looking to create an unnatural (un)balance of the harmonic content. Here's my example. When I listen to a pipe organ, I hear the notes (from fundamental through all of the harmonic content) as they exist in the environment, through the filter of my insensitivity to the lowest octaves. If I were to look for a faithful reproduction of the live sound and had a faithful recording, I would need a system that is essentially flat throughout the bass regions, but I wouldn't want to compensate for my ear's insensitivity because that would shape the reproduction away from what I'd hear in a live performance.

    It does makes sense to me to compensate for your hearing if you are looking to take the sound away from what's in the graphs you've posted towards a distorted, bass heavy version. (distorted meaning revoiced, not clipped)

    Also, just for fun and on a moderately related note, since our last discussion about use of different pickup positions to emphasize various harmonics, I've looked more closely at also changing the types of pickups used: specifically magnetic, piezo and optical. I've been working with a fairly well known pickup manufacturer and have been learning quite a bit about the technical details. I have yet to implement any optical pickups, but it seems to me that they may be more capable of capturing higher energy from the fundamental than the more common magnetic and piezo pickups. Just another tool for voicing our instruments.
     
  20. alexclaber

    alexclaber Commercial User

    Jun 19, 2001
    Brighton, UK
    Director - Barefaced Ltd
    The string will be vibrating at 41Hz, but also at 82, 123, 164, 205, and so on. However, the body of the double bass is too small to amplify the 41Hz harmonic well and thus the higher harmonics dominate. Play the same note an octave higher and you will get a similar energy balance across the frequencies but the note will sound an octave higher because of the implied fundamental from the harmonic series being an octave higher.

    Note that you've referred to the pipe organ vibrating air. Well that's what the double bass has to do too - we do not hear the string vibrating, we hear the air vibrating that the instrument has excited. It starts with the string but that energy has to be transformed into air vibrations and doing this hugely changes the harmonic balance.

    Actually the longer strings produce a more accurate (in tune) harmonic series. The additional strings (if tuned correctly) should not add additional harmonics because they should all be in tune with each other, but they are there to attempt to make up for even the largest piano's defiency in tuning that string vibration into air vibrations that we can hear.

    A large grand piano will tend to sound better on low notes not really because you get more fundamental but because you get a more accurate harmonic series which helps your brain determine the fundamental more accurately - just as a longer scale bass will.

    You don't need any fundamental at all. In fact the vast majority of low B notes that you have heard will have so little fundamental that the human ear cannot detect it (due to a combination of the bass guitar producing less fundamental than second harmonic, the speakers being down many dB by 31Hz, the human ear being much less sensitive at 31Hz than 62Hz and finally the 31Hz output being masked by the higher frequency output).

    Alex