Posted by Trevor Wilson on June 17, 2009, 10:43 pm
**It doesn't work that way. Consider the situation for an orchestra: A full
orchestra delivers approximately 4 acoustic Watts into a typical hall. To
reproduce the same kinds of levels in a normal domestic environment, you
would typically require a speaker system weighing around 200kg and occupying
around 400 Litres, driven by around 1kW of amplification. HOWEVER, to
reproduce those same 4 acoustic Watts in a large hall, would require
substantially more. Figure on at least a dozen of the same speakers and
several tens of kWatts of amplification. Large areas require VERY large
power levels, since there is, effectively no 'room gain'. Most speaker
systems possess efficiency figures between 0.1% - 1%. Very high efficiency
speakers can manage considerably more, but are HUGE. Really huge. For 20Hz
reproduction, think in terms of around 8 - 10 Metres across. For a
practically sized speaker, you would require several tens of kWatts of
amplification and you'd STILL need, perhaps, 400 Litres of speaker
enclosures. Mostly because you need speakers that can cope with all the
power. All that will be a big ask for a sports car. MUCH better to just
forget the idea, or fit the whole lot into a van.
Posted by Sylvia Else on June 17, 2009, 11:52 pm
Trevor Wilson wrote:
Traditional speakers are attempting some reasonable level of fidelity.
For this application that's not required, so some improvement should be
Posted by Trevor Wilson on June 18, 2009, 12:05 am
**What would you suggest? In your suggestion, be aware that the human ear is
reasonably sensitive to certain forms of distortion, frequency linearity and
phase response. It is, for instance, a trivially simple exercise to pick the
sound difference between a 2 Litre Subaru engine and a 2 Litre Toyota one.
Posted by Sylvia Else on June 18, 2009, 12:08 am
Trevor Wilson wrote:
If you measure the actual performance of your speaker, then you can
apply reverse distortion to your sound source. What's left are
Posted by Trevor Wilson on June 18, 2009, 12:27 am
**Your suggestion was that "traditional speakers" are not appropriate. What
would you suggest? Additionally, how do you propose to apply "reverse
distortion"? Where will it be measured?
In your answer, be aware that the modern loudspeaker is not significantly
different to those developed by Rice and Kellog in the late 1920s. The only
serius change has been WRT material choice and computer aided design.
Various inertial and capacitance sensors have been (and still are) tried to
varying degrees of success. Even 'stepper motor' designs have been tried (to
disasterous effect), in an atempt to gain efficiency despite the use of a
small enclosure. The key to understanding this stuff, is to realise that
speakers, without horns, are inherently inefficient and always will be.
Horns MUST be used for efficiency to be reasonable. A horn can be looked at,
as a kind of acoustic transformer, which mates the relatively heavy mass of
the speaker to the low mass of the air. And, before you ask, direct
modulation of the air has (and still is) be tried. Ozone is a serious
problem with many such designs. Due to various factors surrounding such a
system, it is both unreliable (air must be dry and of known atmospheric
pressure) and innefficient.
Like I said: If you have something new, please let us know. Inquiring minds
want to know.