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What does "50 Hz and the -3db is 50 Hz" mean anyway???

Discussion in 'Amps and Cabs [BG]' started by Steelpulz, Sep 13, 2004.


  1. Steelpulz

    Steelpulz

    Nov 4, 2003
    Inglewood, CA
    I have been playing bass since the mid 70's, but I don't know what certain specs mean with regard to bass cabinets. I'd appreciate it if ANYONE would tell me what "50 Hz ...-3db is 50 Hz" means. How do I use those numbers to compare bass cabinets. Thanks in advance for your help.
     
  2. RAM

    RAM

    May 10, 2000
    Chicago, IL
    It basically means that the output is full at a higher frequency and tapers off by 3 db by the time it reaches 50 Hz.
     
  3. The -3dB point is also known as the 'half-power frequency'.

    When looking at the low -3dB point, attempting to amplify/reproduce any frequency below this (in this case 50Hz) won't have much volume. Likewise, attempting to amplify any frequency above the upper -3dB point won't have much volume.

    Being bass players, we are usually only concerned with the lower half-frequency point (especially us 5/6 string players!). Basically - the lower the -3dB point the louder those low notes will sound. :)

    If this still doesn't make too much sense (sorry - been a while since I did those amplification subjects during my electrical engineering degree), PM me or google 'frequency response' or '3dB cutoff'.
     
  4. Steelpulz

    Steelpulz

    Nov 4, 2003
    Inglewood, CA
    Thank you both for your input. I am as clear as slightly muddy water on the subject now. But, at least I have a starting point on understanding those specs.

    Thanks again
     
  5. IvanMike

    IvanMike Player Characters fear me... Staff Member Supporting Member

    Nov 10, 2002
    Middletown CT, USA
    the other point to consider is that sometimes low frequency rolloff isnt always a bad thing
    depending on the bass, sometimes cabinets that have a -3 dB rolloff at 50 hz or even a bit higher can make the bass a bit less "muddy" and sound clearer
    it all depends on the sound you're after
    and besides, specs are specs, but ears are ears, and we hear with our ears :D
     
  6. Passinwind

    Passinwind I Know Nothing Supporting Member

    Take a look here: http://www.contrabass.com/pages/frequency.html

    You can see that 50 Hz is between your G and G# on the E string, OK?

    A 3dB down point at that note means that you'll need to double the power (via EQ, or even just picking harder) available to that note to maintain equal volume to those notes a few steps above it, assuming that the note is mostly made up of the fundamental. 3dB isn't much EQ, and if you have enough power available, no worries. Even without EQ, 3dB is considered to be at the threshold of human perception, and isn't a huge loss. However, things get progressively worse on each lower note, and soon you're down 10dB, which is how many cabs are rated for useful output. At this point, you're hearing the note as half as loud as the ones above open A or so. It'd take 10 times more power to make up the lost gain. You can still EQ, but you are getting way more likely to run out of power at any reasonable volume. At some point, the speaker is going to choke on any more power too.

    Now, remember that I specified fundamental? Bass guitar has lots of other strong harmonic components, so you may not miss that low response as much as you might think. Your bass and amp may not be perfectly flat in response themselves either. Lots of old school gear is voiced to compensate for cabs that drop off fairly high. Your ears will also try to fill in missing information, as you may notice when listening to boom boxes and the like. The 10dB down point actually works fairly well for many of us as a guideline for what to expect from a cab, although you'll see plenty of resistance to it. The 3dB one is useful, but how long it takes to get from -3 to -10 is quite telling as well. That often gives a good indication of the the actual useful response of the box, in my experience.

    There are a few simplifications here that scary techs and engineers can pick on, but hopefully this gets the basic deal across.