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RE: Whole House Audio
- To: <ukha_d@xxxxxxx>
- Subject: RE: Whole House Audio
- From: "James Hoye" <james.hoye@xxxxxxx>
- Date: Wed, 20 Jun 2001 22:22:20 +0100
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> Unfortunately running an amp from 12v is pretty inefficient ... I used
to
> have an Orion 2100HCCA that we tested once at 1,280w RMS bridged
> into a 2ohm
> load without clipping and at that it was drawing slightly less
> that 220Amps
> at 13.8v.
<really_sad_mode>
Given that R=pl/A and the resistivity (p) for copper is 1.7E-8 (at 20 deg
C), 1 metre of 35mm^2 copper cable is going to have a resistance of
approximately 1.7E-8 x 1 / 0.000035 or 0.000486 ohms/metre
The heating effect of a cable is I^2R, so 220^2 x 0.000486 = 23w/metre.
For
a boot mounted amp. with 4m of power cable each way you're going to be
losing nearly 200w in the supply cable alone!
Of course with that sort of current draw you'd go for a split-charging
system with additional batteries in the boot, thus keeping the distance
between the batteries and amps minimal.
</really_sad_mode>
Sorry - just reviving my A level physics (with textbook - can't remember
the
all formulae from that long ago).
James H
____________________________________
Automated Home UK
http://www.automatedhome.co.uk
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