Why is more power required for BASS?

Discussion in 'Pro Audio' started by Mark, May 31, 2007.

  1. Mark

    Mark Guest

    Why is more power required for BASS?

    This seems to be a common rule of thumb in PA work, most of the power
    is needed to provide the bass. This seems consistent with my limited
    experience in PA and certainly consistent with my experience listening
    at home.

    But this does not seem consistent with my limited experience mixing.

    When mixing, the bass (drum and guitar typically) are set to a nominal
    level just like anything else and per the meters they do not require
    more power than anything else. If I solo these bass parts, they do
    not move the meters any more than any other parts solo.

    So how do I reconcile these two views?

    I think the answer is the typical smiley face EQ most everyone uses
    when listening to music. Even if not intentional, many amps have a
    "loudness curve" that provides bass boost.

    So my question is: Is this "listeners EQ" the reason for more power
    needed for the bass. If we actually listened to music with a flat EQ
    would more power not be needed for the bass? Or is there a more
    fundamental reason having to do with speakers and acoustics that more
    power is needed for bass?

    thanks

    Mark
     
    Mark, May 31, 2007
    #1
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  2. "Mark" <> wrote in message
    news:...
    > Why is more power required for BASS?

    <..>
    > Or is there a more
    > fundamental reason having to do with speakers and acoustics that more
    > power is needed for bass?


    It takes a lot more power to move the air around a 12" speaker than around a
    1.5" tweeter, I guess...

    Meindert
     
    Meindert Sprang, May 31, 2007
    #2
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  3. Mark <> wrote:
    > Why is more power required for BASS?
    >
    > This seems to be a common rule of thumb in PA work, most of the power
    > is needed to provide the bass. This seems consistent with my limited
    > experience in PA and certainly consistent with my experience listening
    > at home.
    >
    > But this does not seem consistent with my limited experience mixing.
    >
    > When mixing, the bass (drum and guitar typically) are set to a nominal
    > level just like anything else and per the meters they do not require
    > more power than anything else. If I solo these bass parts, they do
    > not move the meters any more than any other parts solo.
    >
    > So how do I reconcile these two views?
    >
    > I think the answer is the typical smiley face EQ most everyone uses
    > when listening to music. Even if not intentional, many amps have a
    > "loudness curve" that provides bass boost.
    >
    > So my question is: Is this "listeners EQ" the reason for more power
    > needed for the bass. If we actually listened to music with a flat EQ
    > would more power not be needed for the bass? Or is there a more
    > fundamental reason having to do with speakers and acoustics that more
    > power is needed for bass?
    >
    > thanks
    >
    > Mark


    Maybe the clearest explanation is to say that bass production/reproduction
    moves lots of air. Here are some peak power levels of orchestral
    instruments (Tremaine):

    36" bass drum ~ 24.6 watts
    15" cymbal ~ 9.5 watts
    Snare drum ~ 11.5 watts
    Piano ~ 0.267 watts
    Piccolo ~ 0.084 watts
    French horn ~ 0.053 watts
    Violin ~ 0.025 watts

    The power is not in the mixing, where meters display voltage levels of the
    signals, but in the reproduction. Power relates to the area under the
    waveform. A 1 volt 100 Hz sine wave has a lot more area than a 1 volt 1000
    Hz sine wave. Further, power relates to the square of the voltage.

    Note: It is incorrect to say "Even if not intentional, many amps have a
    > 'loudness curve' that provides bass boost." Power amps do not have
    > loudness curves.


    --
    ~ Roy
    "If you notice the sound, it's wrong!"
     
    Roy W. Rising, May 31, 2007
    #3
  4. "Meindert Sprang" <> wrote in
    message
    news:465ed578$0$5499$4all.nl...
    > "Mark" <> wrote in message
    > news:...
    >> Why is more power required for BASS?

    > <..>
    >> Or is there a more
    >> fundamental reason having to do with speakers and acoustics
    >> that more
    >> power is needed for bass?

    >
    > It takes a lot more power to move the air around a 12"
    > speaker than around a
    > 1.5" tweeter, I guess...
    >
    > Meindert


    Perhaps the fact that the top octave of the audio spectrum
    takes as many frequencies as exactly half the entire audio
    spectrum and the lower octave of the audio spectrum takes one
    thousandth of the audio spectrum holds a clue.


    Number of distinct frequencies/Total audible bandwidth
    Top octave 10,000 Hz to 20,000 Hz 10K/20K=.5
    Lower octave 20Hz to 40 Hz ---20/20,000=.001

    How many octaves go to the bass speakers and how many go to
    the mids/tops?


    Peace
    dawg
     
    Deputy Dumbya Dawg, May 31, 2007
    #4
  5. (Don Pearce) wrote:
    > On 31 May 2007 06:50:46 -0700, Mark <> wrote:
    >
    > >Why is more power required for BASS?
    > >

    [snip]
    > >
    > >Or is there a more fundamental reason having to do with speakers and
    > >acoustics that more power is needed for bass?
    > >
    > >thanks
    > >
    > >Mark

    >
    > No more power is needed for bass than for treble. My speakers are fed
    > by a single amp, with s single power output.
    >
    > If I filter the average music file into frequencies above or below
    > 2kHz ( a normal enough woofer/tweeter crossover frequency), I see peak
    > signals just as big in the higher frequencies as in the lower ones. So
    > just as much power is needed for reproduction in both areas.
    >
    > Listeners generally don't apply a smiley face eq to music. Most
    > amplifiers available these days have no facility for such a thing. And
    > the music sound bad if you do try that.
    >
    > d


    Don, you're looking at voltage representations of the signal. Please see
    my other respons to the OP, you're a long way off base when you say "just
    as much power is needed for reproduction in both areas (lower and higher
    frequencies)".

    --
    ~ Roy
    "If you notice the sound, it's wrong!"
     
    Roy W. Rising, May 31, 2007
    #5
  6. Mark

    Scott Dorsey Guest

    Mark <> wrote:
    > Why is more power required for BASS?


    Because conventional bass speakers are very inefficient. They are generally
    omnidirectional, throwing signal everywhere and not just where you want it.
    They have to move a lot of air.

    If you built a bass horn with the same pattern as your treble horn, it would
    take something in the same ballpark to produce the same amount of signal.
    But it would be the size of the Empire State Building.

    In general, bass devices make severe efficiency and extension compromises
    in order to get reasonable size. Life is like that. If you want to
    reproduce something whose wavelength is huge and you don't want to do it
    with a huge cabinet, you pay in efficiency.
    --scott

    --
    "C'est un Nagra. C'est suisse, et tres, tres precis."
     
    Scott Dorsey, May 31, 2007
    #6
  7. Mark

    GregS Guest

    In article <20070531105645.175$>, Roy W. Rising <rwrising@dsl[omit]extreme.com> wrote:
    >Mark <> wrote:
    >> Why is more power required for BASS?
    >>
    >> This seems to be a common rule of thumb in PA work, most of the power
    >> is needed to provide the bass. This seems consistent with my limited
    >> experience in PA and certainly consistent with my experience listening
    >> at home.
    >>
    >> But this does not seem consistent with my limited experience mixing.
    >>
    >> When mixing, the bass (drum and guitar typically) are set to a nominal
    >> level just like anything else and per the meters they do not require
    >> more power than anything else. If I solo these bass parts, they do
    >> not move the meters any more than any other parts solo.
    >>
    >> So how do I reconcile these two views?
    >>
    >> I think the answer is the typical smiley face EQ most everyone uses
    >> when listening to music. Even if not intentional, many amps have a
    >> "loudness curve" that provides bass boost.
    >>
    >> So my question is: Is this "listeners EQ" the reason for more power
    >> needed for the bass. If we actually listened to music with a flat EQ
    >> would more power not be needed for the bass? Or is there a more
    >> fundamental reason having to do with speakers and acoustics that more
    >> power is needed for bass?
    >>
    >> thanks
    >>
    >> Mark

    >
    >Maybe the clearest explanation is to say that bass production/reproduction
    >moves lots of air. Here are some peak power levels of orchestral
    >instruments (Tremaine):
    >
    >36" bass drum ~ 24.6 watts
    >15" cymbal ~ 9.5 watts
    >Snare drum ~ 11.5 watts
    >Piano ~ 0.267 watts
    >Piccolo ~ 0.084 watts
    >French horn ~ 0.053 watts
    >Violin ~ 0.025 watts
    >
    >The power is not in the mixing, where meters display voltage levels of the
    >signals, but in the reproduction. Power relates to the area under the
    >waveform. A 1 volt 100 Hz sine wave has a lot more area than a 1 volt 1000
    >Hz sine wave. Further, power relates to the square of the voltage.
    >
    >Note: It is incorrect to say "Even if not intentional, many amps have a
    >> 'loudness curve' that provides bass boost." Power amps do not have
    >> loudness curves.


    I was going to say something like that. Another thing is the time. HF's don't usually
    last long like a bass note.

    As a very general statement, tweeters are more efficient than woofers.

    The car audio buffs need about 100 times more power for the bass than the HF.

    greg
     
    GregS, May 31, 2007
    #7
  8. Mark

    Arny Krueger Guest

    "Mark" <> wrote in message
    news:

    > Why is more power required for BASS?


    (1) The power in most music tends to be more concentrated in the bass. This
    is at least partially due to the fact that the ear is far less sensitive in
    the bass range. In order to have well-balanced bass, it must have more
    power.

    (2) In order to produce a given amount of sound at lower frequences, a
    speaker has to be either larger or less efficient. The "make it larger"
    approach has practical limits, so efficiency is usually less in the bass
    range.
     
    Arny Krueger, May 31, 2007
    #8
  9. Mark

    jwvm Guest

    On May 31, 11:13 am, (Scott Dorsey) wrote:
    > Mark <> wrote:
    > > Why is more power required for BASS?

    >
    > Because conventional bass speakers are very inefficient. They are generally
    > omnidirectional, throwing signal everywhere and not just where you want it.
    > They have to move a lot of air.
    >
    > If you built a bass horn with the same pattern as your treble horn, it would
    > take something in the same ballpark to produce the same amount of signal.
    > But it would be the size of the Empire State Building.
    >
    > In general, bass devices make severe efficiency and extension compromises
    > in order to get reasonable size. Life is like that. If you want to
    > reproduce something whose wavelength is huge and you don't want to do it
    > with a huge cabinet, you pay in efficiency.
    > --scott
    >
    > --
    > "C'est un Nagra. C'est suisse, et tres, tres precis."


    It might also be noted that humans are not very sensitive to low
    frequencies so bass needs to be louder to be heard. Modern recordings
    of pop music tend to have exaggerated bass also. Relatively little
    bass is heard in well-recorded symphonic works since the low-frequency
    components are muted unless the kettle drums are being struck
    enthusiastically.
     
    jwvm, May 31, 2007
    #9
  10. (Don Pearce) wrote:
    > On 31 May 2007 15:02:22 GMT, Roy W. Rising
    > <rwrising@dsl[omit]extreme.com> wrote:
    >
    > > (Don Pearce) wrote:
    > >> On 31 May 2007 06:50:46 -0700, Mark <> wrote:
    > >>
    > >> >Why is more power required for BASS?
    > >> >

    > >[snip]
    > >> >
    > >> >Or is there a more fundamental reason having to do with speakers and
    > >> >acoustics that more power is needed for bass?
    > >> >
    > >> >thanks
    > >> >
    > >> >Mark
    > >>
    > >> No more power is needed for bass than for treble. My speakers are fed
    > >> by a single amp, with s single power output.
    > >>
    > >> If I filter the average music file into frequencies above or below
    > >> 2kHz ( a normal enough woofer/tweeter crossover frequency), I see peak
    > >> signals just as big in the higher frequencies as in the lower ones. So
    > >> just as much power is needed for reproduction in both areas.
    > >>
    > >> Listeners generally don't apply a smiley face eq to music. Most
    > >> amplifiers available these days have no facility for such a thing. And
    > >> the music sound bad if you do try that.
    > >>
    > >> d

    > >
    > >Don, you're looking at voltage representations of the signal. Please
    > >see my other respons to the OP, you're a long way off base when you say
    > >"just as much power is needed for reproduction in both areas (lower and
    > >higher frequencies)".

    >
    > OK, a better answer for you. There is generally the same power in both
    > high and low frequencies as you will see if you do the filtering
    > experiment, but there is more energy at low frequencies. This is
    > because the low notes tend to go on for longer, while the higher
    > frequencies are found in transients. So if you do an FFT of a whole
    > piece of music, you will generally see a curve that slopes downwards
    > as the frequency rises.
    >
    > That is all fine, but it is a representation of power multiplied by
    > time - in other words, energy. The power requirements of an amplifier
    > are determined by the instantaneous amplitude of the signal, which you
    > will find is pretty similar all the way up the spectrum for most
    > music. I can post examples if you like.
    >
    > d


    Good clarification. The temporal aspect isimplicit in my note that power
    relates to the area under the curve.

    --
    ~ Roy
    "If you notice the sound, it's wrong!"
     
    Roy W. Rising, May 31, 2007
    #10
  11. Mark

    jwvm Guest

    On May 31, 10:56 am, Roy W. Rising <rwrising@dsl[omit]extreme.com>
    wrote:
    <snip>
    > The power is not in the mixing, where meters display voltage levels of the
    > signals, but in the reproduction. Power relates to the area under the
    > waveform. A 1 volt 100 Hz sine wave has a lot more area than a 1 volt 1000
    > Hz sine wave. Further, power relates to the square of the voltage.


    You might want to rethink your power statement. There is no
    relationship between power and frequency for a purely resistive load.
    The areas are the same for any 1 volt sinusoidal waveform regardless
    of frequency assuming some reasonable number of cycles are applied to
    the load. Also note that power is energy/time. The energy in one cycle
    of a 1 kHz waveform is the same as 10 cycles of a 100 Hz. waveform and
    both would require the same time interval.
     
    jwvm, May 31, 2007
    #11
  12. On Thu, 31 May 2007 14:59:34 GMT, "Deputy Dumbya Dawg"
    <> wrote:

    >> It takes a lot more power to move the air around a 12"
    >> speaker than around a
    >> 1.5" tweeter, I guess...
    >>
    >> Meindert

    >
    >Perhaps the fact that the top octave of the audio spectrum
    >takes as many frequencies as exactly half the entire audio
    >spectrum and the lower octave of the audio spectrum takes one
    >thousandth of the audio spectrum holds a clue.
    >
    >
    >Number of distinct frequencies/Total audible bandwidth
    >Top octave 10,000 Hz to 20,000 Hz 10K/20K=.5
    >Lower octave 20Hz to 40 Hz ---20/20,000=.001
    >
    >How many octaves go to the bass speakers and how many go to
    >the mids/tops?


    If that meant anything, it would mean the treble end, with all its
    frequencies, required MORE power than the bass, surely? :)
     
    Laurence Payne, May 31, 2007
    #12
  13. Mark

    hank alrich Guest

    Laurence Payne wrote:

    > "Deputy Dumbya Dawg" wrote:
    >
    > >> It takes a lot more power to move the air around a 12"
    > >> speaker than around a
    > >> 1.5" tweeter, I guess...
    > >>
    > >> Meindert

    > >
    > >Perhaps the fact that the top octave of the audio spectrum
    > >takes as many frequencies as exactly half the entire audio
    > >spectrum and the lower octave of the audio spectrum takes one
    > >thousandth of the audio spectrum holds a clue.
    > >
    > >
    > >Number of distinct frequencies/Total audible bandwidth
    > >Top octave 10,000 Hz to 20,000 Hz 10K/20K=.5
    > >Lower octave 20Hz to 40 Hz ---20/20,000=.001
    > >
    > >How many octaves go to the bass speakers and how many go to
    > >the mids/tops?

    >
    > If that meant anything, it would mean the treble end, with all its
    > frequencies, required MORE power than the bass, surely? :)


    But he's not talking "frequencies", he's talking _octaves_.

    --
    ha
    Iraq is Arabic for Vietnam
     
    hank alrich, May 31, 2007
    #13
  14. Mark

    Arny Krueger Guest

    "Deputy Dumbya Dawg" <>
    wrote in message
    news:qpB7i.20969$

    > Perhaps the fact that the top octave of the audio spectrum
    > takes as many frequencies as exactly half the entire audio
    > spectrum and the lower octave of the audio spectrum takes
    > one thousandth of the audio spectrum holds a clue.


    That would be relevant if music usually contained equal power per frequency.
    That can happen, but it is relatively rare.

    Speaker builders and system designers would be wise to assume that music has
    about the same power content as red or brown noise. Pink noise has equal
    power per octave, but red or brown noise takes things to the next step. As
    the frequency goes down, each octave has twice the power.


    > Number of distinct frequencies/Total audible bandwidth
    > Top octave 10,000 Hz to 20,000 Hz 10K/20K=.5
    > Lower octave 20Hz to 40 Hz ---20/20,000=.001


    > How many octaves go to the bass speakers and how many go
    > to the mids/tops?


    That varies quite a bit from speaker to speaker.
     
    Arny Krueger, May 31, 2007
    #14
  15. Mark

    Mark Guest


    > The power is not in the mixing, where meters display voltage levels of the
    > signals, but in the reproduction. Power relates to the area under the
    > waveform. A 1 volt 100 Hz sine wave has a lot more area than a 1 volt 1000
    > Hz sine wave.


    There are a lot of interesting answers to think about but this one is
    wrong.

    I am 100% positive that a 100Hz 1 Volt RMS sine wave has the same
    power as 1 kHz a 1 Volt RMS sine wave or 10 kHz or any other frequency
    (into a fixed load resistance).

    Mark
     
    Mark, May 31, 2007
    #15
  16. "Mark" <> wrote in message
    news:...
    >
    >> The power is not in the mixing, where meters display
    >> voltage levels of the
    >> signals, but in the reproduction. Power relates to the
    >> area under the
    >> waveform. A 1 volt 100 Hz sine wave has a lot more area
    >> than a 1 volt 1000
    >> Hz sine wave.

    >
    > There are a lot of interesting answers to think about but
    > this one is
    > wrong.
    >
    > I am 100% positive that a 100Hz 1 Volt RMS sine wave has
    > the same
    > power as 1 kHz a 1 Volt RMS sine wave or 10 kHz or any other
    > frequency
    > (into a fixed load resistance).
    >
    > Mark


    But is that ratio musical? If not then is it realistic for
    anyone listening to mistake those tones for something they
    want to listen too?

    peace
    dawg
    >
     
    Deputy Dumbya Dawg, May 31, 2007
    #16
  17. jwvm <> wrote:
    > On May 31, 10:56 am, Roy W. Rising <rwrising@dsl[omit]extreme.com>
    > wrote:
    > <snip>
    > > The power is not in the mixing, where meters display voltage levels of
    > > the signals, but in the reproduction. Power relates to the area under
    > > the waveform. A 1 volt 100 Hz sine wave has a lot more area than a 1
    > > volt 1000 Hz sine wave. Further, power relates to the square of the
    > > voltage.

    >
    > You might want to rethink your power statement. There is no
    > relationship between power and frequency for a purely resistive load.
    > The areas are the same for any 1 volt sinusoidal waveform regardless
    > of frequency assuming some reasonable number of cycles are applied to
    > the load. Also note that power is energy/time. The energy in one cycle
    > of a 1 kHz waveform is the same as 10 cycles of a 100 Hz. waveform and
    > both would require the same time interval.


    I might be mistaken, but I think you have that backwards.

    --
    ~ Roy
    "If you notice the sound, it's wrong!"
     
    Roy W. Rising, Jun 1, 2007
    #17
  18. "Laurence Payne" <lpayne1NOSPAM@dslDOTpipexDOTcom> wrote in
    message news:p...
    > On Thu, 31 May 2007 14:59:34 GMT, "Deputy Dumbya Dawg"
    > <> wrote:
    >
    >>> It takes a lot more power to move the air around a 12"
    >>> speaker than around a
    >>> 1.5" tweeter, I guess...
    >>>
    >>> Meindert

    >>
    >>Perhaps the fact that the top octave of the audio spectrum
    >>takes as many frequencies as exactly half the entire audio
    >>spectrum and the lower octave of the audio spectrum takes
    >>one
    >>thousandth of the audio spectrum holds a clue.
    >>
    >>
    >>Number of distinct frequencies/Total audible bandwidth
    >>Top octave 10,000 Hz to 20,000 Hz 10K/20K=.5
    >>Lower octave 20Hz to 40 Hz ---20/20,000=.001
    >>
    >>How many octaves go to the bass speakers and how many go to
    >>the mids/tops?

    >
    > If that meant anything, it would mean the treble end, with
    > all its
    > frequencies, required MORE power than the bass, surely?
    > :)


    Maybe I could have expanded on that a little more. Sorry!

    Not that I believe this is "the answer" but perhaps if one
    spreads out a little bit of power over an octave with 10,000
    individual frequencies and averages it out ....... that would
    be the same number as averaging a 20 frequency octave with
    proportionally higher power for each frequency.


    Another consideration is looking at a spectrum analyzer
    playing music over a period of thousands of hours of music
    listening. Any decent sounding program will show a distinct
    downward amplitude slope from bass to treble. Good sounding
    music spectrum naturally has more power in the low
    frequencies.

    peace
    dawg
     
    Deputy Dumbya Dawg, Jun 1, 2007
    #18
  19. On Fri, 01 Jun 2007 03:37:07 GMT, "Deputy Dumbya Dawg"
    <> wrote:

    >
    >Another consideration is looking at a spectrum analyzer
    >playing music over a period of thousands of hours of music
    >listening. Any decent sounding program will show a distinct
    >downward amplitude slope from bass to treble. Good sounding
    >music spectrum naturally has more power in the low
    >frequencies.


    It shows the sound levels. It doesn't show the power required to
    produce those sound levels. You're chasing the wrong rabbit :)
     
    Laurence Payne, Jun 1, 2007
    #19
  20. "Laurence Payne" <lpayne1NOSPAM@dslDOTpipexDOTcom> wrote in
    message news:...
    > On Fri, 01 Jun 2007 03:37:07 GMT, "Deputy Dumbya Dawg"
    > <> wrote:
    >
    >>
    >>Another consideration is looking at a spectrum analyzer
    >>playing music over a period of thousands of hours of music
    >>listening. Any decent sounding program will show a distinct
    >>downward amplitude slope from bass to treble. Good sounding
    >>music spectrum naturally has more power in the low
    >>frequencies.

    >
    > It shows the sound levels. It doesn't show the power
    > required to
    > produce those sound levels. You're chasing the wrong rabbit
    > :)


    Perhaps not we are changing the question from...Why is more
    power required for the bass? To : Does it take the same power
    to produce nSPL at low freq x than nSPL at high frequency y?

    The new question would have to cover.
    1) the radiation space of the SPL - and ways to hold them
    equal for comparisons.
    2) the driver efficiencies and sensitivities scaled back to
    the amplifier power.
    3) measurement techniques which remove any room effects from
    the acoustic measurements.
    4) differences caused by measurement distance
    5 ????


    I suggest that the answer to the OP question falls into these
    boundaries.

    Why do you need a bigger amp on the bottom of a bi amp PA
    system than on the top?

    1) there are usually more low frequency octaves in the low end
    than the high therefore more program to be reproduce by the
    lows.
    2) the program (usually and especially in rock music) requires
    more low frequency energy to sound natural.
    3) High frequencies are usually reproduce with comparatively
    sensitive compression drivers mounted on horns that beam the
    energy where you need it .
    4) Low frequencies are usually produced by comparatively less
    sensitive cone drives mounted in boxes which radiate the
    sound all around the box where a lot of it is wasted and only
    some if it goes where the HF frequencies are beamed by the
    horns--that is at the listener(s) are listening.


    peace
    dawg
    5)
    3)
     
    Deputy Dumbya Dawg, Jun 1, 2007
    #20
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