RE: Re: [OT] Understanding speakers & watts.

["Justin" <justin@xxxxxxx>]

Thanks for that Mark. Hope you didn't get cramp doing all that typing :-)

If I had any faith in the sales staff at Richer Sounds, I would of course
ask one of them rather than embarrass myself on this list!

Every time I have expressed an interest in an item at RS it's the same
story, "Oh yes sir, I've got one of those, absolutely brilliant!"
etc. If a
difficult technical question is posed, they will mumble, change the
subject,
then give it the "I've got one of those, brilliant" bit, and
possibly add
something about it winning an award!

Justin.

> -----Original Message-----
> From: Mark Harrison [mailto:Mark.Harrison@xxxxxxx]
> Sent: 02 January 2002 6:24 PM
> To: ukha_d@xxxxxxx
> Subject: RE: [ukha_d] Re: [OT] Understanding speakers & watts.
>
>
> The purists will probably kill me for being too simplistic here, but
> this "mental model" has been good enough for me to get
through a series
> of jobs. I'm not going to use any formulae or equations here, this is
> "plain text" ;-)
>
> The executive summary is "don't worry - the speakers will work -
just
> don't play them LOUD - Loud will be fine, though."
>
>
> Most (indeed - nearly all) domsetic amplifiers work by multiplying
> voltage. An input voltage of up to 2 volts comes in from, say, a CD
> player on the "phono" input, and an output voltage goes out
across the
> loudspeaker terminals.
>
> How high you've got the volume knob cranked determines the multiplier.
> So at _very_ low volumes, and multiplier of 1, the output voltage will
> range up to 2 volts. At high volumes, the multiplier might be 30, so
the
> output voltage will range up to 60 volts.
>
> Now, there are two monkeys:
>
> 1: CD manufacturers, particularly Sony, tend to operate outside the
> "normal" spec for the phono connectors, so _their_ CD
players might
> output up to, say, 2.4v. This is naughty, in the sense that it might
> overload your amp's input circuitry, and forces amp manufacturers to
> over-specify rather than relying on source manufacturers to stay
within
> spec.
>
> This is also cool, because on "blind" tests, most people's
emotional
> reaction is to prefer the louder source over the quieter. So, flipping
> between a Sony and a non-Sony CD player on a "which do you
prefer" means
> that Sony's sell a lot more equipment.
>
> 2: What your loudspeakers fundamentally do with this voltage is pass
it
> through some electromagnets, which causes a fluctuation in the
> electro-magnetic field around them. A normal magnet which you can
think
> of as being on a spring sitting in this field reacts to this by
> physically moving to establish a new equilibrium between the higher
(or
> lower) magnetic field pulling it one way and the spring pulling it the
> other.
>
> The magnet is attached to the centre of a paper (or aluminium, or
> kevlar, or whatever) cone. The centre of cone moves back and forth
with
> the magnet. The outside of the cone stay fixed, by virtue of being
> attached to a big bit of wood (the speaker case). This movement pushes
> air back and forth. The air pushes other air back and forth, which
> pushes more air back and forth, until we get to some air that pushes
> bits of your skin back and forth. (At normal volumes) you only notice
> this as it pertains to bits of skin inside your ear, which causes some
> electrons to flow up into your brain which then processes that
movement,
> along with the other electron flows just before it to think "ah -
that's
> Robbie Williams".
>
> The problem is that moving all this "stuff" (the skin in
your ear, by
> the expedient of moving the air, via the expedient of moving the cone,
> via the expedient of moving the magnet) takes energy.
>
> One measure of "how much energy" it requires is the
impedance figure
> quoted. The lower the figure, the more energy needed.
>
> As such, your proposed 4 ohm speakers are harder to drive, in fact,
> twice as hard to drive, as the 8 Ohm speakers that your amp
manufacturer
> was expecting.
>
> The rating of your amp is a rating of how fast it can put out energy.
If
> it's operating within its tolerance, then it'll do it gracefully. If
> it's not, then something will give - generally loudly with a sort of
> bangy noise, and expensively.
>
> However, don't worry. The reason that amp manufacturers quote a figure
> into 8 Ohms is that, historically, this was the most common sort of
> loudspeaker, and if everyone quotes the figures in the same way, then
> it's possible to make an objective comparison.
>
> The amp will still work with your speakers. However, don't turn it up
> stupidly high, and if you notice the sound distorting, then it
probably
> means it's turned up too loud.
>
> Mark Harrison
> Head of Systems, eKingfisher
>
>
> -----Original Message-----
> From: jcom10 [mailto:jcom10@xxxxxxx]
> Sent: 2 January 2002 17:14
> To: ukha_d@xxxxxxx
> Subject: [ukha_d] Re: [OT] Understanding speakers & watts.
>
>
> Thanks for the info guys!
> Just went in to buy them, then noticed they say 4 Ohms. I'm sure my
> amp says 8 Ohms. What's that all about?
>
> Justin.
>
> --- In ukha_d@y..., "Phil Harris"
<phillip.harris1@v...> wrote:
> > I had great success in my "in car audio" days using
good quality and
> > high(ish) powered amps on line fit speakers. I had used 4 x 40w
> Rockford
> > Fosgate amps on speakers which were supposedly rated at 8w and
never
> > blew one of them - even though they were used quite hard. They
were
> > filtered to restrict the lower end of the frequency range as too
> much
> > bottom end through them would kill them as it ripped apart the
> > suspensions but that was about it.
> >
> > On the other hand I have seen loads of speakers destroyed by
using
> cheap
> > and crappy amps which when driven into clipping simply spend most
of
> > their life putting out almost square wave DC (clipped AC
waveforms)
> > which - as Keith has said - destroys tweeters in seconds and mid
> bass /
> > subwoofers in hours!
> >
> > Phil
> >
> > > -----Original Message-----
> > > From: Keith Doxey [mailto:ukha@xxxxxxx...]
> > > Sent: 02 January 2002 14:01
> > > To: ukha_d@y...
> > > Subject: RE: [ukha_d] [OT] Understanding speakers &
watts.
> > >
> > >
> > > If you turn it up way too high then you can damage the
> > > speakers, but an amp that is too small can damage the
> > > speakers because when an amp is overdriven the resultant
> > > clipping causes an excessive amount of high frequency energy
> > > that kills tweeters pretty damn quick.
> > >
> > > On overpowered amp driven sensibly is much less dangerous.
> > >
> > > Mordant Short normally have "Positec" protection
which are
> > > self resetting fuses that cut out if they are overdriven.
(My
> > > MS3.10's do anyway)
> > >
> > > HTH
> > >
> > > Keith
> > >
> > > -----Original Message-----
> > > From: jcom10 [mailto:jcom10@xxxxxxx...]
> > > Sent: 02 January 2002 13:46
> > > To: ukha_d@y...
> > > Subject: [ukha_d] [OT] Understanding speakers & watts.
> > >
> > >
> > > I have been looking for some new surround speakers, and
> > > recently saw a Mordaunt Short "Premier" package in
Richer
> > > Sounds. SWMBO was with me and insists we get them because,
> > > they are unobtrusive and "they look nice"! I would
have to
> > > agree, but I don't think they are man enough for the job.
> > >
> > > The speakers are rated at 50W but my AV amp is, IIRC, 80W.
> > > My assumption is that the speakers will be knackered if the
> > > volume is turned up too loud. Is that correct?
> > >
> > > They aren't on the MS site (strange) & I can find very
little
> > > information about them on the web. Anyone have any
experience
> > > of these?
> > >
> > > Any recommendations for other speakers? The keyword here is
> > > SMALL. I fancy the Bose Acoustimass ones but they are a bit
> pricey.
> > >
> > > Cheers,
> > >
> > > Justin.
> > >
> > > PS: Happy new year to everyone!
> > >
> > >
> > >
> > >
> > >
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