constant amplitude: advices needed


    Sep 24 2008 | 7:50 am
    Dears,
    I use a basic loudspeaker (mid-range) as a mechanical device acting like
    a piston engine. A sine at low frequencies (from 0. to 6. max) does the
    job.
    have a problem keeping a constant amplitude. The higher the frequency,
    the higher the amplitude on the loudspeaker. Is it normal (because i
    play LFOs in a mid-range speaker) ? If not, how does it happend that
    normalize~ doesn't do the job ? What is the smart way to keep a constant
    amplitude on my speaker ?
    Best wishes
    f.e
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    • Sep 24 2008 | 11:17 am
      I wouldn't expect a smallish (or any) loudspeaker to have a somewhat "flat" response to frequencies that low (and/or frequencies out of its designed range).
      In such case I expect "efficiency" to get lower and lower the closer you get to DC. Normalizing the signal won't help you much either because the problem lies more in how the speaker/coil/magnet assembly translate that signal (normalized or not) into movement, and it not doing it at the same efficiency at different frequencies.
      Could you just scale the amplitude of the signal down with higher frequencies, so the movement of the speaker (instead of the signal sent) to the speaker remains constant?
      I guess you could manually create a lookup for the amplitude scaling factor after testing at different frequencies, and then tweak it a bit for perceived "smoothness" when sweeping to the range, right?
      Hope this helps.
      Klaas-Jan
    • Sep 24 2008 | 2:59 pm
      >Dears,
      >
      >I use a basic loudspeaker (mid-range) as a mechanical device acting
      >like a piston engine. A sine at low frequencies (from 0. to 6. max)
      >does the job.
      >
      >have a problem keeping a constant amplitude. The higher the
      >frequency, the higher the amplitude on the loudspeaker. Is it normal
      >(because i play LFOs in a mid-range speaker) ? If not, how does it
      >happend that normalize~ doesn't do the job ? What is the smart way
      >to keep a constant amplitude on my speaker ?
      >
      >
      not sure at all but what if you over-amplify your signal in max, and
      then appply a "brickwall" limiter at the last stage????
      you would always have the same level (or so it seems to me)
      best
      kasper
    • Sep 24 2008 | 3:03 pm
      Quote: Kasper T Toeplitz wrote on Wed, 24 September 2008 16:59
      > not sure at all but what if you over-amplify your signal in max, and
      > then appply a "brickwall" limiter at the last stage????
      Wouldn't this present an even heavier load to the speaker which is already suffering "abuse"? It seems to me like a great way to burn the voicecoil.. Also, what about the harmonics generated?
      regards
      kjg
    • Sep 24 2008 | 3:31 pm
    • Sep 24 2008 | 4:27 pm
      >Quote: Kasper T Toeplitz wrote on Wed, 24 September 2008 16:59
      >
      >> not sure at all but what if you over-amplify your signal in max, and
      >> then appply a "brickwall" limiter at the last stage????
      >
      >Wouldn't this present an even heavier load to the speaker which is
      >already suffering "abuse"? It seems to me like a great way to burn
      >the voicecoil.. Also, what about the harmonics generated?
      >
      maybe maybe... but then what i said was to limit eh max output - not
      to send an hyper-amplified signal (basically to do what is often done
      in dance CD's - overcompress)
      well, that was just an idea......
      kasper
    • Sep 25 2008 | 2:35 am
      yes i see. but that would compare to just sending a square wave, right? the speaker would "pulse" x times per second with every zero crossing. lots of loud harmonics. could be cool, actually. but noisy for sure.
      and i'd be woried bout the life of the speaker. i suspect that the speaker might give in soon though, but maybe if only in short bursts... so the voice coil can cool down in between?
    • Sep 25 2008 | 4:26 pm
      f.e schrieb:
      > I use a basic loudspeaker (mid-range) as a mechanical device acting like
      > a piston engine. A sine at low frequencies (from 0. to 6. max) does the
      > job.
      >
      > have a problem keeping a constant amplitude. The higher the frequency,
      > the higher the amplitude on the loudspeaker. Is it normal (because i
      > play LFOs in a mid-range speaker) ? If not, how does it happend that
      > normalize~ doesn't do the job ? What is the smart way to keep a constant
      > amplitude on my speaker ?
      First you need an audio interface capable of putting out DC.
      Second, speakers form a physical object with their environment, and
      normalize~ doesn't know anything about it, it just pulls out the correct
      voltage and assumes it will be translated precise...
      As a speaker is a swinging resonating object, you need much less effort
      for a specific amplitude, when the speaker is "swinging". To get the
      same amplitude with DC might burn the coil of the speaker, its not
      really made for that, be careful...
      Stefan
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