Thursday, June 6, 2013

"POWER", The Myths and Maths Series Part 2


There's been some unsolicited promotion lately by, 'independent', reviewers about the benefits of OFC over CCA wire.  The fact is that both are fine, it comes down to the capability of the wire and the application, (How you're going to use the wire).

This applies both to it's use as speaker wire and power wire... And to throw a wrench into the machine, manufacturers are developing a new type of wire that has the heft of OFC but the capacity of CCA and costs half that of CCA.  Last time I heard, it was the addition of tin, so now your wire will rust instead of just turning green.

First off, let me debunk the 'testing' that's been going on in some of these videos.  Several videos have the wire in coil, which makes for a big inductor.. Never a good idea to test wire this way. This is also not how wire is used when in the car or boat.

First, I would use a standard length that's in a kit, say 16'.  Second, identify both the wire's material and it's diameter.  After that you can actually use a chart to determine what can be used before it affects both performance and your ability to inhale large amounts of toxic smoke.

Don't worry about what is, 'spec', or what GA vs AWG mean.  Look at the material, diameter and length.  (By the way, in the wire industry there are three standards, China wire, Taiwan wire and American wire gauge. That addresses why one brand will say, 4ga and another will say 4ga but the actual wire diameter will be different.  It has nothing to do with 'quality'.  It has to do with different standards.)

Second you have to look at how the wire is applied.  Most standardized tests done are for an 'open air' test, meaning the wire is suspended in the air so that it can be cooled by methods of convection.  Then on top of that, you have to calculate what the ambient air temperature affects it.  Even more calculation if the air is moving, how fast it's moving, is it recirculating or is is coming in from a fresh source.. Just like when you want to cool your amp with a fan.

But enough of all that, most of the applications used in car or boat audio are fine with CCA.  All wire just has an ampacity.  A capability to transfer current.  For mobile audio, this is not constant power.  It's pulsed which makes a big difference.  On top of that, you'll see on many charts what the resistance of a certain gauge wire is at 1000'!  That's a big difference than the 16' to 25' that you're using.  These charts are up over 100A you can see no difference.  Take into account that speaker wire is nowhere near that type of power and is it really that important to have 10 AWG OFC?  No.

The big push of OFC is in the profit margin vs CCA.  The total volume and especially the margins of mobile audio have eroded significantly in the past 20 years.  It's no wonder brands would pay to stage an 'independent test'.  There's a good chunk of cash on the line, even after all the erosion.

In the world of audio, they can even get away with paying people with just product for good reviews instead of the usual chubby envelope given to more 'reputable' sources like magazines.  Do you really think people buy $10,000 cables?

Ok, ok... An example of power application.  Let's take the standard Taiwan spec 8ga CCA used by Metra in their Raptor line, (Just changed to 'full spec' this year).  Not getting hot enough to melt the fuse, you can still use this with a crappy, standard AGU glass 60A fuse.  This is plenty for most systems.  It may even be cheaper and have a lower profile to use multiple strands of 8ga CCA.  Of course each strand is good for up to 60A.

For 4ga CCA from Raptor, we go up to 100A AGU fuse.  Anything beyond that would require 2 or 0ga CCA or multiple runs.  Also, I recommend to many clients that get the OFC bug, to just add another run of wire rather than pull out the 'bad' CCA and go all copper.  The industry is again employing the snob tactic that you want to be superior over others.  This of course only costs you more money, that those, "poor", or "crappy", type of people won't pay.  I never agree with these tactics as they create small wars of "us vs them".  Apple is famous for using this marketing strategy.  In the end however, everyone of the unwashed masses remembers the way snobby people act and they always get taken down a notch or just taken out by an angry, poor mob.

As for OFC, if you can get a good price on it, use it.  It's not any better than CCA, it just has a greater ampacity than CCA when compared with all other things being equal.  Most of the time people never even get close to the ampacity of what the wire can do.  Now if you're competing and want to do hair tricks, that's a completely different story.  Just because they use it on a $150k demo car, does not mean that you need it for your the single 10" sub you have in your '87 Crown Vic that your grandma left you.  Use common sense, use Craigslist and always get more information than you need.

Remember that when you buy retail, from a store, you're paying for that store.  Nothing good or bad about that.  Just remember that you're paying for the store plus product, plus mark-up.

I'll take on some amp myths next in Part 3.

Patrick Chandler
Co-Founder of Robot Underground 

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