RE: speaker frequency response - technical stuff

["Paul Weissman" <paul@nioterra.com>]

another thing to keep in mind, although i'm not sure how much this comes
into play here, are psycho acoustic effects based on harmonics.

as may be already more than apparent to you, when you play a low E on a 
bass
you not only have energy at your fundamental frequency, 41hz, but tons of
different energy levels at multiples of the fundamental frequency that are
based on the modes of the plucked bass string.  these will be at integer
multiples of the fundamental... 41, 82, 123, 164, 205, etc.  the
distribution and attack/decay behavior of the energy at each of these
harmonic frequencies is what gives the bass it's signature tone.  pardon me
if i'm boring you.

so what happens if you completely remove energy from the first fundamental?
(so instead of the series starting off with 41, the sequences begins 82,
123, 164, 205, ...)   well, even if there is no energy present at the first
fundamental, your brain does a sort of interpolation of the frequencies 
that
are present and gives you a sense that you're hearing the missing
fundamental, allowing you to perceive the starting point of the complete
harmonic series.  you can try it with any synth that has a few sine
oscillators... it's neat.

and then there's also the fact that speakers have response below what they
are 'rated', just not as accurate a response.

hope that made sense...

paul








> -----Original Message-----
> From: Bill Fox [mailto:billfox@fast.net]
> Sent: Saturday, May 25, 2002 9:50 PM
> To: Loopers-Delight@loopers-delight.com
> Subject: Re: speaker frequency response - technical stuff
>
>
> ----- Original Message -----
> From: <JIMFOWLER@prodigy.net>
> > why
> > or how is it that i see plenty of bass cabs rated 50Hz-
> > XkHz? doesn't speaker X need to be rated at least as
> > low as the fundamental of the lowest note produced on
> > instrument Y?
>
> Frequency response is often specified from the half power points;
> -3dB down at
> the low and high ends of the audio spectrum.  Unless otherwise
> specified.  (CD
> players might specify 20-20kHz +/- 0.1Hz for example.)  A
> response that is down
> by 3dB at 50 Hz means that at 41 Hz the response has dropped off
> a little more,
> but it's still there.  There will be a response at 20Hz, too.  But if the
> response is falling at 6dB per octave (10dB per decade), that
> means the response
> is half that of 40Hz, given equal levels at the input.
>
> Cheers,
>
> Bill
>