Re: Lowest Frequency
- From: Stewart Pinkerton <stewart@xxxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Tue, 28 Mar 2006 07:31:32 +0100
On 27 Mar 2006 14:08:26 -0800, "Andre Jute" <fiultra@xxxxxxxxx> wrote:
Bassling wrote:
I am working to a lowest frequency of 40Hz for my amp and speakers, but
was wondering whether this is the lowest frequency I need. All systems
that I have heard that use this low freq range make the double bass
sound disembodied. I was wondering whether, even if the double bass
lowest note frequency is 35/40Hz, are there sub-tones that are below
this that give it its sound? Is this off-topic - I'm not sure. Its just
that 40Hz always seems to be the bottom of HiFi specs, and I want to
get some feedback on this. Thanks.
Theoretically the audio band is 20Hz to 20KHz. In practice, no one can
hear that high and there are very few recordings with material that
low.
In practice, many teenage girls can hear past 20kHz, and many
asthmatics can hear to 25kHz, while most pipe organ recordings will
have 16Hz content. Then there's the Bosendorfer 'double grand' piano
which also has an extra octave in the bass. Pluss the ambience of a
large hall 'live' recording will have content well below 20Hz, albeit
at very low level.
If cost is no object, I tune my amps for horns to 32Hz but it doesn't
really matter if you tune to 40 or even 45Hz.
More sensible audiophiles strive for 20Hz, and don't use horns. BTW,
you can't 'tune' an amplifier, it has its own bandwidth, generally set
by the quality of the iron in a tube amp, but essentially unlimited in
an SS amp. A good rule of thumb is that, to get excellent phase
linearity in your amplifier, it should extend to ten times the
required bandwidth at full power, i.e. from 2 Hz to 200kHz. This is
readily achievable by modern SS amps, but impossible for a tube amp.
If you look up the actual
energy content of each frequency played on a particular instrument, you
will discover that the fundamental represents a very small part of the
total energy. For instance, Seashore's Psychology of Music reports that
a violin tone of 196Hz has 0.1 per cent of the energy in the
fundamental, 26pc in the second harmonic, 45% in the third, 8.8pc in
the 4th, and so on.
True of the violin and other bowed strings (duhh, since the bow
*prevents* the fundamental node of the open string from playing), but
not of the piano or harp, of drums or of pipe organs. As ever, you
select your facts to shore up your false argument.
The conclusion is that the harmonic on replay creates the correct tone.
Subharmonics exist but are, by definition, less important.
They're not 'subharmonics', they are *fundamental*, and by definition,
very important. The conclusion is that reproducing *all* the
components with a *flat* response creates the correct tone. That
should be obvious, given that this is how you hear the live
performance.
There are important reasons not to tune your chain lower than your
speakers can comfortably handle. Some really sweet Lowther setups start
rolling off around 60Hz.
Sweet, perhaps, on female voice, but otherwise stunningly incompetent,
as noted by the fact that they roll off at 60Hz - and above 10kHz. And
have lots of nasty resonances in between.
The lowest note on an organ is 16Hz, which is why I tune to 32Hz.
Pretty dim of you, since the organ is putting out 16Hz at high power.
But of course, extremely difficult to reach with a tube amplifier,
almost impossible for a SET amp, although trivial for most SS amps, so
of course *you* *would* put up this false argument.
But,
more realistically, the lowest note on a piano is 27.5Hz, which means
that the major energy you want your speakers to handle starts over
50Hz.
Utter nonsense. For a truly involving and *realistic* sound, you
definitely want your whole system to be flat to 20Hz. This does of
copurse mean pretty heroic speakers an lots of power, so one can see
why *you* would make up fairy tales to pretend that it's not
necessary. To anyone who has ever experienced such a *truly*
full-range system, your suggestion is risible.
The bandwidth should be balanced. If you're going for the very low
bass, you should simultaneously go for the HF extension; if you have to
cut your top for some reason, you should reduce the bass extension as
well. If you don't, the result will sound odd.
It's much more fundamental than that - if you restrict your bass and
treble extension by using a so-called 'full range' driver typical of
horn systems, then the result certainly will sound odd - but that will
have little to do with the bandwidth of the amplifier. This is just
another of Jute's half-baked theories, and has no basis in fact.
--
Stewart Pinkerton | Music is Art - Audio is Engineering
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