"Ron" wrote in message
...
On Wed, 15 Oct 2003 15:02:01 -0400, "Robert Morein"
wrote:
"Ron" wrote in message
.. .
On Wed, 15 Oct 2003 04:06:08 -0400, "Robert Morein"
wrote:
"Ron" wrote in message
news
On Tue, 14 Oct 2003 20:47:00 -0400, "Robert Morein"
wrote:
"WindsorFox[SS]" wrote in message
news:Je0jb.73317$AH4.43019@lakeread06...
Nexxon wrote:
NEXXON_CAR_AUDIO - The Best for Less
Over 19,000+ Car Audio, 7,000+ Home Electronics Products, Free
Shipping Satisfaction Guaranteed, 276+ Brands, Amps, Woofers,
Equalizers, CD Players, Speakers, DVD, Etc. If we don't have
it -
you don't want it. Please visit the website:
You don't have Eclipse, that surely does not mean I do not
want
it. Even IF you could produce a 3000 watt amp for any price, let
alone $179, exactly what automotive electrical system do you
expect
to power it??
Obviously there's hype in the advertising.
what's 'hype' to a seller, is ripoff to a buyer. Even if
that rating is for instantaneous power, the current
delivered to the speakers would be 250A, meaning that the
current drawn from the battery would be 360A (best case).
If anyone believes this $179 amp comes even close, I have a
wonderful bridge for sale. No, really...
-- Ron
You may be right, but there is no physical reason it can't be done.
Installers frequently use multiple banks of 1 Farad capacitors to
stiffen
the car power.
At 12V, a 1 Farad capacitor stores 12 Couloumbs of charge.
A single capacitor could provide 120 amperes for 1/10 of a second.
Ten capacitors could provide 120 amperes for about one second. Of
course
the
voltage goes to zero during this interval, but it gives the idea, and
the
amplifier spec is for a one ohm load.
Right. So, to provide 360A you would need 3.6Farad and to
maintain reasonable voltage while doing so you'd need at
least 10Farads. The Rockford Fosgate CPC10 1 Farad Capacitor
costs about $100 each -- about $1000 for the bank to feed
the $179 amp...
True.
And, BTW, do you really believe the $179 amp output stage
is up to the task of driving 360A for 100mSec?
In a design I'm working on, I'm using little International Rectifoer
TO-220
MOSFETS which have an Imax of 40 amperes each.
And how much are 18 of these FETs, along with the
required heatsinks and mandatory protection circuit?
Can you build an amp around them for $90 (so it can
sell for $179)?
MOSFETS don't require thermal protection, other than a thermal breaker.
I paid about $4.00 each from Digikey, so I suspect the quantity price is
around $0.50 each.
MOSFETs are not subject to thermal runaway, but they sure
require protection if you want a 350A stage to be trouble
free. Putting a circuit breaker in the signal path is not
a good idea, even in a $179 amplifier. However, we're
getting to the nit-picking stage real fast here...
I guess my point is that at this price point, it's highly
likely the 3KW spec is a lie. Don't you agree with that?
-- Ron
You are probably right. I certainly haven't checked the car stereo scene, so
I'm not informed on the level of misrepresentation out there. Personally, I
long for the days when the FTC enforced brutal RMS standards.
But the typical buyer in this market, who is usually a blue-collar, not
terribly smart young male who is the modern version of the glass-packing
hotrodder, is not really educable. It doesn't matter what we tell him; he is
going to buy from this market, and be half deaf by the age of 23.
It seems to me that the important thing is that during the short lifetime of
his inner ear, he be made to feel as happy as possible. The principle form
of protection he needs is to receive the product he ordered, and the usual
90 day warranty.
Judging fraud by audiophile or engineering standards will, quite literally,
fall on deaf ears.