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Explain Subwoofer Boom

Discussion in 'Subwoofers' started by cjob68, Mar 12, 2003.

  1. cjob68

    cjob68
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    Can someone please give an example or explain subwoofer "boom" as opposed to having "tight" bass ?

    Thanks
    cjob68
     
  2. EvilMudge

    EvilMudge
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    Two things make a sub sound boomy.

    1) Poor subwoofer design (using a softly suspended driver to produce high SPLs) results in a cabinet resonance that causes the driver to oscillate at it's natural frequency. This is great if all you want to do is 'go loud' but pointless for music. One frequency, sometimes two or maybe three, will playback much louder than any others.

    2)Room boom, caused by a natural room mode (again a resonant frequency), selectively enhances by means of an echo (basically) between one and three fundamental frequencies, so that these appear much louder than others.

    Tight bass is the result of running a very stiffly suspended low mass cone (in an open loop - most manufacturers, car subs and DIY efforts) or a less heavily damped heavier cone in a servo feedback system. In essence the cone movement is affected more by the power of the amplifier driving it, than the reaction forces of the spring and air suspension.
     
  3. Ian J

    Ian J
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    I don't think that he wanted to know about the engineering principles but what to listen out for.
     
  4. adox

    adox
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    i think the advent of home cinema has lead to the subwoofer boom:laugh:
     
  5. alexs2

    alexs2
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    cjob68.....I think the best way of finding out is to go and listen to a few sets of speakers and subs...you'll very quickly be able to distinguish the difference.

    Basically a note played on a "tight" as opposed to "loose" system will start and stop with much better definition and to some may actually sound less extended in frequency response,as you don't have all the muddled reinforcement from upper bass overhang or looseness.

    "Boom" is the result of an underdamped system emphasizing one frequency above others...it leads to a distinctly "one note" sound to the bass.

    Tight bass doesnt have to mean a lack of depth,as any properly designed sub,or full range speaker system,with decently specc'd amps will show.
     
  6. AVMADMAN

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    i believe you can tighten bass by buying a sub cable with a very low resistance. thereby not infringing the dampening qualities of the amplifier as some cables can reduce dampening dramatically...

    also by moving a sub around the room, this sometimes helps.....
     
  7. alexs2

    alexs2
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    AVMADMAN.....damping as you refer to is a product of the output impedance of the amplifier,and the impedance of the speaker connected to it.
    i.e. an amplifier with a high output impedance(as with many valve amps)will have a low damping factor,and vice versa.
    You would have to buy a pretty awful cable to have a high resistance in the cable,and this will not affect the output stage damping,or "grip" on the speaker.

    Some cable manufacturers are making quite a thing of dedicated sub cables at present......whilst I am quite a cable fanatic in some respects,I cannot see that I need a dedicated LF cable where a good piece of XLO or Kimber would do better.

    Certainly moving a sub round the room will help in terms of ironing out room modes,or places where reinforcement of certain frequencies occurs....again,this will not make a loose sub tighter,it will only reduce it's problems to a degree.
     
  8. AVMADMAN

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    I obviously must have read it wrong then....:confused:

    i read that an amplifier/ power amplifier dampens the woofer so it reproduces a tight clean sound and that resistance in a cable reduces the dampening, making it sound looser...
     
  9. alexs2

    alexs2
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    Certainly adding resistance in the speaker cabling will decrease the damping factor,but as I said previously,it would have to be an appalingly poor cable(at either input or output)to have large levels of resistance.

    Far more significant factors are things like the cable's interference rejection,which is going to be very important in proximity to a sub,usually positioned close to other electrical equipment as well.

    After that,and certainly as far as low level full range signal interconnects go,the sound of an individual cable as price/performance rises is very important in terms of individual choice.

    I do think though that the current rash of "Sub Cables" is a bit of a marketing thing,as none do anything that a good quality audio cable shouldnt do anyway.

    I simply use an XLO Reference 1 cable for mine.....it's unshielded but very high quality and has no problems with resistance or interference.
     

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