On Tue, 01 Apr 2008 13:43:22 +0100, Invisible <voi### [at] devnull> wrote:

>>> The sound seems to drop off very rapidly with 
>>> distance - an effect my 8-inch Warfdales don't seem to have.
>> 
>> You have to take into account the power output of the amplifier (PC or
>> stereo) and the sensitivity of the speakers. Google it. 
>
>I think you'll find that "sensitivity" is a measure of how much sonic 
>power a speaker generates for a given amount of electrical power. It has 
>nothing to do with distance dissapation...
>

Like most things yes and no :) True "sensitivity" is a measure of how
much sonic power a speaker generates for a given amount of electrical
power but loudness is directly related to acoustic power. Therefore
the higher the sensitivity the more and thus louder the volume from
the speaker. Also below about 10 KHz the lower the frequency the less
loud it will sound to our ears. It then reverses for about 500Hz drops
off to about 12 KHz then increases again. So for the same power bass
notes will not seem to travel as far as higher ones. So why do
foghorns use low frequency? I hear you ask. Well that is because low
frequency are audible to human ears farther than higher pitched sounds
they just require more power to produce them. Confused yet? It gets
worse when you consider feedback from the inside part of the speaker.
We would ideally like an infinite baffle but that is very unlikely in
real life never mind a laptop.

>>> I notice that these speaker units are *very* heavy for such tiny 
>>> objects. Is this significant?
>> 
>> Yes the density of the speaker enclosures enhances the baffling in
>> modern designs.
>
>I was thinking more that being heavy allows the speakers to generate low 
>frequencies more easily. (Otherwise the driver might end up just 
>wiggling the cone one way and the casing the other way, and not 
>producing much sound.)

In a good speaker design the cone is quite well isolated from the
case. It is the internal pressure that is the problem. And Yes the
heaver the box the better it sounds.
The same goes for speaker stands.
-- 

Regards
     Stephen

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