Wire efficiency?

[Ceezer 0]

Ok, I've got another question. I'm just going to copy and paste this from a thread I started at CA. I don't like to post the same question in more than one location at a time but it doesn't look like I'm going to get any kind of response there.

I was looking at the wire guide stickied above and had a few questions. The amp in question is a Dinstinct Audio by Crossfire 4-channel 700 watts A/B (not sure of the model number). I have it powered with 8 gauge, I'm pretty sure. The front channels are running my 6.5" Pioneer coaxials in stereo and the rear channels are running my (2) Alphasonik 10s bridged. The gain on the front channels is at about half-way and the rear gain is at about 3/4 way.

So...

1) If the amp is 700W, am I running a large enough power wire (provided I'm correct in thinking it's 8 gauge) or should I bump it up to 4ga in accordance with the above guide?

2) I'm running a 60amp fuse. Is that ok?

3) I was told not to have my ground wire any longer than 18". That really restricted my wiring and I had to stretch it to get it grounded, but I found one. Is there any truth to that 18" thing?

4) What does that ~50% efficiency thing mean?

5) I think I'm running 16ga from the amp to the speakers/subs. Should I increase that to 14?

Thanks for any help!

The guide in question is here

Thank you for any assistance.

[ANeonRider 3]

50% efficiency is in reference to the amp.

My rule is... run the biggest wire the amplifier will accept.

So, for the PDXs... I run 4ga., even though they are all Class D, and are over 85% efficient.

You can run 18ga. speaker cable, and it will be sufficient.... because there is not much current there.

Ground length is completely arbitrary... as long as it has very close to 0 ohms, then it doesn't matter... you have to have a 4ga. wire like 350ft. long to get over 1 ohm of resistance. It just has to be able to carry as much current as the amplifier sources... since it completes the electrical circuit.

[tejcurrent 13]

While 8 guage will most likely get you by, I'd go to 4 guage to help with any current drop that could be resulting from too small a guage of wire. If you want to know, take a digital multimeter (if you don't have one you can pick one up cheap at lowes) and measure the votage at the front (battery) of your vehicle. Then measure the voltage at the amp with it cranked up as loud as you ever listen to it. If it's much more than a few 10ths of a volt I'd definitely upgrade.

[ANeonRider 3]

It is voltage drop...

[Ceezer 0]

You guys are awesome, thank you!

[Acidburn 10]

you do want your ground wire as short as practical however, any added resistance in that wire will cause a voltage drop which means less voltage to the amplifier which means less power

[Ceezer 0]

Is my 60A inline fuse ok, then? What if I upgrade to 4ga?

Oh, and I still don't really get what the 50% efficiency means. Is it only running at half the rated power? Would larger power lines help with the efficiency?

Thanks again.

[Acidburn 10]

Is my 60A inline fuse ok, then? What if I upgrade to 4ga?

Oh, and I still don't really get what the 50% efficiency means. Is it only running at half the rated power? Would larger power lines help with the efficiency?

Thanks again.

If you haven't blown the fuse, it is acceptable. To get rid of every last bit of parasitic loss, then upgrade to a larger fuse that is matched to the 4ga.

The 50% efficiency is in reference to the amplifier's power output versus it's power input. Hypothetically, an amp is drawing in 1000 watts of power, but is only putting out 500 watts of power. That amp is only 50% efficient. The larger wires will improve the efficiency of the entire system.