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Old 19-04-2007, 03:16 AM   #20
TStar
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here's a real world calculation for wiring up an amp, the very same principles work for the speaker wiring.

Quote:
assume:
- the wiring material is copper (0,018 Ohm*mm²/m @ 20°C celsius).
- the amp would deliver a continous 300 RMS.
- cable length would be 6,5meters / 21.3 feet.
- chassis resistance will be ignored to keep the calculation simple.

diameter: 6mm² (about 9gauge):
cable resistance = 0,0195 Ohm
voltage drop @ 35A = 0,7V
dissipation loss = ~24 Watt = 8%

diameter 10mm² (about 7gauge):
cable resistance = 0,0117 Ohm
voltage drop @ 35A = 0,4V
dissipation loss = ~14 Watt = 3%

diameter 16mm² (about 5gauge):
cable resistance = 0,0073 Ohm
voltage drop @ 35A = 0,25V
dissipation loss = ~9 Watt = 1,7%

diameter 25mm² (about 3gauge):
cable resistance = 0,0046 Ohm
voltage drop @ 35A = 0,16V
dissipation loss = ~6 Watt = 1%

diameter 50mm² (about 0gauge):
cable resistance = 0,0023 Ohm
voltage drop @ 35A = 0,08V
dissipation loss = ~3 Watt = 0,5%
practical example:
you wire up a amp for proper subwoofer support, 300rms continous output (in reality, even with fully turned up volume, it's always a lot less than that, because after all you're listening to music and not a permanent sine wave and your amp's components will lower that as well).
the % difference of loss from a 6mm² vs. a 16mm² = 3%
the % difference of loss from a 10mm² vs. a 25mm² = 5%

fact: you need about twice the power (=100% more!) to achieve an audible volume change of +3db.
and now you can put the 3 or 5% difference into the right perspective: absolutely negligible. the amp internal's component diffusion has more impact on the output+loss than the wiring...

i know we all like the colourful cables and the idea that we actually somehow "improved" the wiring, but please: keep in touch with reality.
upgrading a speaker wire from e.g. 1,5mm² to 2,5mm² is de facto no upgrade, it's a waste of time and money. better pay attention to the things that are really imporant, for example a proper installation like the one fhrx did, THEN you will experience a gain in quality and volume.
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Last edited by TStar; 19-04-2007 at 04:41 AM.
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