"Orchid XP v3" <voi### [at] devnull> wrote in message 
news:46dda38a@news.povray.org...
>>>> Huh?  You are saying that they deliberately make speakers less 
>>>> efficient so that a higher voltage can be used to drive them?  I've 
>>>> never heard that before.
>>>
>>> Yes.
>>
>> Interesting, how do they do that?
>
> You think *I* know?

It used to be that more efficient speakers in general had more unwanted 
resonances and lumps in their frequency responses: IOW poorer fidelity.  I 
don't particularly know why but that's how it was.  Obviously the designers 
would have overcome that if they could have, but some chose low efficiency 
in return for better sound quality.  I don't know how well they are doing 
now with that trade-off, it's been some years since I last read any reviews.

>> Hard to see how you could deliberately make the system less efficient 
>> without just plonking a huge 50W resistor in series (which would totally 
>> screw up the quality of the sound).
>
> And why would that be?

The answers lie in the way passive networks of electronic components work 
and in speaker mechanics.

Firstly, the crossover network divides the signal from the amplifier to the 
woofer and the tweeter drivers.  It must be tuned to the right frequency and 
shape the frequency falloff curves and phase so that the sound levels from 
both drivers are balanced without dips or humps or comb-filtering at the 
crossover band where both drivers transmit part of the signal.  It is also 
supposed to keep the signal phase true between the two drivers over the 
frequency range so they operate in a unison making the sound wavefront from 
both drivers combine and arrive at your ear together.  That is fekking 
difficult to design, because...

Crossovers are passive networks of resistors, capacitors and inductors. 
Networks behave much more complicatedly than isolated components because 
everything interacts with everything else, not just its immediate 
neighbours.  Speaker drivers are *also* R-L-C networks, so crossovers must 
be designed with that driver's electrical properties being integral to it.

In short, the whole thing is interbalanced, so if one resistor, capacitor or 
inductor changes, everything goes out of whack -- crossover frequency, 
frequency response, phase response, impedance response, resonances and 
ringing -- and the speaker sounds like crap.

For predictability, a speaker and its crossover also rely on the amplifier's 
output stage being very low impedance. Signal-wise, the amplifier is near to 
a short-circuit, regardless of the voltage swings it generates.  A speaker 
is a motor and when moving, it generates back-EMF through its crossover.  It 
has mechanical inertia and wants to overshoot.  It  also has natural 
resonances from driver suspension springiness, cabinet air volume, acoustic 
transmission line length, tuned acoustic port, etc.  That colouration is NOT 
part of the original signal.  If the amplifier doesn't soak up that energy 
(absorb the current), to damp the unwanted motion (overshoot and ringing) it 
will reflect back into the network and colour the sound you hear.

So if you plonk a great big resistor in series with all that, the amp can't 
damp unwanted speaker motion, the crossover detunes, the frequency response 
goes lumpy, the sound goes muddy, and you think "bleccch!"  :-)

>>> Hmm, I think my amplifier (nothing special) is rated at 60 W per 
>>> channel. (IIRC, into 8 ohms at 1 kHz.)

For listening at home, the real reason for high-powered amps is not to make 
louder noise, but for fidelity.  They have higher voltage headroom to 
faithfully reproduce the high, short sound transients (eg, snare drum 
attack, piano key strike) that would be clipped off by a low-powered amp set 
to play at the same average listening level.

>> And what happens when you actually output 60 W in your room?
>
> Well obviously I'm unlikely ever to try this. (It's like all toasters have 
> a special setting that transforms bread into charcole. We don't know why, 
> but they all have it.)

<Ahem>  Just because you didn't figure it out, doesn't automatically make 
the manufacturers into idiots.  The high setting on toasters is needed to 
get even a _little_ colour into *crumpets*.  But, as you apparently haven't 
toasted a crumpet before, they obviously don't exist and every manufacturer 
out there is stupid for gratuitously making toasters with a nuclear setting.
  :-P

> (I once tried connecting a line-level output to the phono input. Big 
> mistake...)

Ow.  :-(

>> I guess also your ears work on a logarithmic scale, so 60 W is probably 
>> not as much "louder" than 20 W as you would think just by looking at the 
>> numbers.
>
> Yeah, most human senses actually seem to work in a logarithmic way... I 
> suppose that means they work well under "all conditions" or something.

A general rule-of-thumb I got from an electronics / audio tech mag once, is 
that 10x power sounds roughly twice as loud.

>>> Wait... the *voltage* changes depending on how much you use it? That's 
>>> odd. I thought that potential difference was always constant, and it's 
>>> only *current* that changes...
>>
>> That's only true if all the cables in the whole system have precisely 
>> zero resistance, which they don't.
>
> Really? How interesting...

LOL

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