"Short Wave Sportfishing" wrote in message
...
On Tue, 22 Feb 2005 12:55:24 GMT, "Doug Kanter"
wrote:


"JimH" wrote in message
...

"-rick-" wrote in message
...
Ken Heaton wrote:
Basic physics: take note of the distance sound leaving the rear
surface
of
the speaker has to travel through the air to reach the front of the
speaker.
Any sound with a wavelength longer that this distance will cancel
itself
out
as the sound from the front is perfectly out of phase with the sound
from
the rear. No bass in other words. An enclosure effectively creates
an
infinite distance from front to rear as the two out of phase sound
waves
can't get to each other. they are blocked form meeting by the walls
of
the
enclosure. If the enclosure is too small the speaker ends up using up
most
of its power trying to compress the air inside the enclosure resulting
in
little low bass as well. So the enclosure has to be both well sealed
and
big enough to be effective. It is possible to vent an enclosure with
a
tuned port (often called bass reflex) allowing a smaller enclosure but
that
isn't simple physics any more...

Good explanation. It also helps to know the wavelengths. Sound
travels
about 1127 ft/second in air and wavelength = velocity/frequency so...

freq. wavelength
(Hz) (ft)

20 56
40 28
80 14


Holy cow. This ain't rocket science folks.


Actually, it's *is* science, although it's not always possible to apply it
accurately in cars & boats. You just do the best you can, using the rocket
science as a guideline. And even if you're building freestanding speaker
cabinets for home or stage use, the science assumes a perfect speaker cone
which doesn't add color of its own, which is pretty much fiction. Even so,
the science works.

Ahem - cough, cough... :)

The science is only a guide. Sound, and fidelity which is a concept
that seems to have escaped into the ether these days, is entirely
subjective. Being subjective, what may sound good to you will not
sound good to me.

I agree, for two major, recent reasons:

- As good as they are at testing some products, Consumer Reports refuses to
acknowledge that "testing" speakers is impossible. A friend of mine who
remained in the audio biz after I left says people still get excited about
Japanese speakers made of 1/4" plywood, because CR said they were a "best
buy".

- Any time you read about tests of cell phones, they're focused on network
coverage, and phone features that absolutely nobody needs, unless they
absolutely no other qualities which recommend them as a worthwhile person.
Never any mention of the audio-related design of the phones themselves. So,
we have cell phones with noise cancelling systems that play havoc with your
voice.

But, I disagree about one thing: You can come closer to theoretical
perfection with the bass frequencies than you can with higher frequencies.