wire sizing

So while I'm new to the car audio world, I've been reading constantly lately and bugging everyone I can find that will listen :) I have a question pertaining to wire sizing: I'll post the two amps that I plan on using, for reference: Sub Amp: https://www.woofersetc.com/p-6040-zrs-7000d-cadence-2600-watt-1-ch-competition-amplifier.aspx Front Amp: https://www.woofersetc.com/p-10353-dpx2250-clarion-21-channel-400-watt-rms-power-amplifier.aspx The grommet in my car's firewall is particularly full..previously I was wanting to run a 1/0g wire, but I am curious as to what size I can "get away" with..I am not wanting to risk anything, this install will be done proper. Thanks

RMS input power divided by voltage gives the current. Input power can usually be approximated by output power x 1.25 (ie, 80% efficiency). Hence for your outputs of 1300 WRMS (@13.8 V; 1 Ohm sub) and 200WRMS (2x2Ohms, noting RMS = Music Power x 1/2), that's (1300+200) = 1500W x 1.25 = 1875W, or 136A @ 13.8V (and maybe less or 142A @ 14.4V), so say 150A. The experts on here use different tables (and they know better than I), but using the powerstream.com AWG table, 3G is ok ("chassis" wiring 158A, but 0G (150A) is needed if "transmission"). But I'd go by the resistance, ie, 3G is twice the resistance of 0G and hence double the voltage drop, ie, at 0.64616 mOhms per meter x 150A, that's nearly 100mV (96.9mV) per meter at 150A, or maybe 0.5V for a typical(?) installation of 5m (16') including 3G GND but excluding fuse & connection etc drops. Then I'd check that my current for that gauge does not exceed appropriate maximum ratings (hence possible fire etc). Any thinner depends on your max longish-term power output. BTW - 3G is only a 70% smaller diameter than 0G if that (it depends on insulation thickness). And OFC cable has lower resistance than the plain copper used in the powerstream AWG table which also specifies its current ratings are only a general guide and depend on various factors. But please heed what others may advise. I'm purely theoretical when it comes to practical audio.

oldspark wrote: RMS input power divided by voltage gives the current. Input power can usually be approximated by output power x 1.25 (ie, 80% efficiency). Hence for your outputs of 1300 WRMS (@13.8 V; 1 Ohm sub) and 200WRMS (2x2Ohms, noting RMS = Music Power x 1/2), that's (1300+200) = 1500W x 1.25 = 1875W, or 136A @ 13.8V (and maybe less or 142A @ 14.4V), so say 150A. The experts on here use different tables (and they know better than I), but using the powerstream.com AWG table, 3G is ok ("chassis" wiring 158A, but 0G (150A) is needed if "transmission"). But I'd go by the resistance, ie, 3G is twice the resistance of 0G and hence double the voltage drop, ie, at 0.64616 mOhms per meter x 150A, that's nearly 100mV (96.9mV) per meter at 150A, or maybe 0.5V for a typical(?) installation of 5m (16') including 3G GND but excluding fuse & connection etc drops. Then I'd check that my current for that gauge does not exceed appropriate maximum ratings (hence possible fire etc). Any thinner depends on your max longish-term power output. BTW - 3G is only a 70% smaller diameter than 0G if that (it depends on insulation thickness). And OFC cable has lower resistance than the plain copper used in the powerstream AWG table which also specifies its current ratings are only a general guide and depend on various factors. But please heed what others may advise. I'm purely theoretical when it comes to practical audio.

I'll have to mill over your response, but I certainly appreciate you taking the time to share this information with me. Where you mentioned the size difference between 0 and 3g - that fact makes me less weary of the large size. I can deal with it. My plan is to run 0g to a dist block in the hatch. From there 4g to each amp. With 50amp fuse in the smaller amp dist line and a ~250amp to the larger sub amp(I am unsure what size this fuse should be) Otherwise, can you suggest a size for my ground wires? I am going to ground the two amps within 16" of wire to one another. I've read up on proper grounds as well. Thanks!

WHATEVER your power wire capacity is, you MUST have at least that much capacity OR MORE for the ground wire. Individually, your 2600 watt amplifier will use 115A ((2600/2)/.8)/14.4=112.84A This is perfect world numbers, BTW, and based on that amplifier being a Class D amplifier, and 80% efficiency. Your voltage will likely NOT be a real 14.4VDC, so your current requirements will go UP from there... Anyway, a #4 is rated to 150A, so the big amp will be at a minimum, a 4G, but I'd use a #2. Addressing the 400 watter: (400/.66)/14.4=43A For 45A, you could use a #8, actually, but I'd use a #6. These are wire sizes for the GROUND WIRE ONLY. These two wire gauges when added together, certainly jibe completely with oldspark's numbers, too. I am a fan of WELL overbuilding, so stick with the 1/0 for your power cable... :)It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

haemphyst wrote: WHATEVER your power wire capacity is, you MUST have at least that much capacity OR MORE for the ground wire. Individually, your 2600 watt amplifier will use 115A ((2600/2)/.8)/14.4=112.84A This is perfect world numbers, BTW, and based on that amplifier being a Class D amplifier, and 80% efficiency. Your voltage will likely NOT be a real 14.4VDC, so your current requirements will go UP from there... Anyway, a #4 is rated to 150A, so the big amp will be at a minimum, a 4G, but I'd use a #2. Addressing the 400 watter: (400/.66)/14.4=43A For 45A, you could use a #8, actually, but I'd use a #6. These are wire sizes for the GROUND WIRE ONLY. These two wire gauges when added together, certainly jibe completely with oldspark's numbers, too. I am a fan of WELL overbuilding, so stick with the 1/0 for your power cable... :)

Thank you very much. I'll take your adice with sticking with 1/0, definitely. Would there be any downside to use using 4g for the power and ground for both amps? I would assume not. So a 200amp fuse on the negative bat terminal would be sufficient for this then? And I've asked this in a couple places, but the 'big three' isn't necessary at this point, correct? I plan on just reseating the battery ground, grounding the HU and grounding the two amps together.

Also, side note question: As for power terminals, what's an acceptable option? I see many styles, from banana to binding post, spring loaded...is it necessary to us anything other than just connecting the wire to a cheap terminal cup? Thanks!

Don't fuse the negative - you must always fuse the +ve in a -ve ground system/vehicle. (Unless the GND fuse covers ALL GND/return paths.) As to cheap, what's cheaper - new amps? New car?    If a GND lets go, damage could result. If a +ve or GND goes intermittent, that too can damage. And any poor connection can end with fire. haemphyst - you used 0.66 for the Clarion which uses a Music Power Wattage rating, and I'd get... Oh - its title says " DPX2250 - Clarion 2/1-Channel 400 Watt RMS Power Amplifier", but its description says then refers to "400 Watts of Maximum Music Power"... Forget it - I have little tolerance for such contradictory or vague information (meaning woofersetc.com's page).

oldspark wrote: Don't fuse the negative - you must always fuse the +ve in a -ve ground system/vehicle. (Unless the GND fuse covers ALL GND/return paths.) As to cheap, what's cheaper - new amps? New car?    If a GND lets go, damage could result. If a +ve or GND goes intermittent, that too can damage. And any poor connection can end with fire. haemphyst - you used 0.66 for the Clarion which uses a Music Power Wattage rating, and I'd get... Oh - its title says " DPX2250 - Clarion 2/1-Channel 400 Watt RMS Power Amplifier", but its description says then refers to "400 Watts of Maximum Music Power"... Forget it - I have little tolerance for such contradictory or vague information (meaning woofersetc.com's page).

I've no desire to cheaping out on wires nor fuse size. I was specifically referring to the terminal cup. And my mistake on saying negative for the fused line.