17 replies to this topic

[TittySprinklez]

hey peeps so iv just got my hands on a memphis mojo cm12d2 sub and a nakamichi ngtd1200 monoblock, and im wondering if the power cable i have in place at the moment (4awg aerpro stuff) for my current sub will do the job for this new gear, i suspect not and im guessing ill have to get like 1/2 guage wire? anyway just wanted to get your input on what you think would be a smart next move. cheers luke

[patttyfox]

I'm going to be running a 1500 watt RMS amp and sub plus a second amp for the door speakers off of a 2 awg incoming.

Is the amp for the sub the only amp you have in the car?

Are you going to run a capacitor?

[allpaw4]

For wattages like that I would be running a cap for sure. You won't be pulling massive currents all the time, so the cap will help the peaks on beats and such. Basically the bigger the better when talking high power amps. Plus, it would be a good idea to upgrade the standard battery. The stock gen 3 battery is tiny.

[Grahama]

I like this question.

Quick bit of research, and these are just the first bits of info I found so I don't know if accurate.

Nak ngtd1200 = WRMS@Ohms: 400@4, 800@2, 1200@1
Sub, couldn't find VC specs, but I guess a D2 means dual 2 ohm VC so parallel wired for 1 Ohm, putting max load on amp & max power.
Amps fuses are 4x30A so it should have a max draw of 120A. (Don't forget to fuse your power line @ the battery > 120A )

At this crutchfield page, I found this equation and table:
"Total RMS Wattage x 2 (Inverse of Amp Efficiency) ÷ 13.8 Volts = Current Draw in Amperes"
1200x2/13.8=173A.

http://www.crutchfie...auge_chart.html



So your current draw might be 170A instead of just 120A.

According to the table, 120A would be fine with 4WG up to a length of 5m, but 170A needs 2WG with cable lengths of 3m +.

My last thoughts, the Amp is class D so a lot more efficient than the above calculation. At 90% efficiency, 1200W/.9/13.8= 100A.
This seems to match the fuses much better so makes me think 4WG is fine for this amp. But go bigger if you're adding other amp(s).

[Matty_Lib]

Capacitors are a waste of money. Upgrade your battery to a decent deep cycle and do the 'Big 3' upgrade. I'd probably run 2awg wiring.

[TittySprinklez]

cheers guys, made me realize how much i left out of my question lol 
i have an MB quart OA800.4 running my door speakers which are polk db6501's, the idea was to simple take my existing sub and sub amp out and replace with the new gear keeping the 4guage wire in, might rethink that and grab some 2 guage power cable, get a yellow top, and do the big 3 ? 

thoughts? 

[patttyfox]

What's the big 3?

[Matty_Lib]

That sounds good, having a good battery is the most important. I used to run 2 15's on 2k RMS with a single deep cycle battery and no Capacitor, voltage drop was never an issue.

The big 3 is an upgrade for the charging system. Basically upgrading cable size to charge more efficiently. There's no point running 2awg cable to your amp if the negative is still standard 8awg. Do a quick Google search and you'll find more info on it.

[patttyfox]

Sorry in advance for hijacking the the thread..

So just read up on the big 3, what size cable would you suggests as a minimum to upgrade the Big 3 too?

[Matty_Lib]

I'd run 0awg, though you could probably get away with 2awg.

[TittySprinklez]

how much should i be looking at per meter for 0awg ?

iv seen that stuff by stinger and the like going in the 30's per meter? that sounds like its gonna get expensive :/

[allpaw4]

You don't need to get audio branded cable for power cable. 35mm2 or 50mm2 welding cable (flexible) will do the same job and may be cheaper. Check it out. You may be paying for the name with audio stuff. At the end of the day prices will be high for big cable, purely because of the amount of copper.
I can't remember what the comparison is between mm2 and awg. You can look it up online if you need.

[TittySprinklez]

yea was thinking about using welding cable cause i mate has abit i might be able to get for cheap

one last question 

what size yellow top fits an 02 RX liberty ? D34?

[Matty_Lib]

Jaycar sell cable at a reasonable price per metre. I have this years catalogue here somewhere, if I can find it I will let you know how much it is.

 

A D34 battery should fit, I'm not 100% though.

[Grahama]

Good news, Jaycar appears to have 0G on special , save $5 per m, making it same price as their 2G at $14.50/m.
http://jaycar.com.au...&SUBCATID=995#1
http://jaycar.com.au...&SUBCATID=995#1


Just remember 0G is going to be harder to get around corners and through firewalls, etc.

[Tim.]

Feel free to ignore this, but I though it was interesting and not many people may know about efficiency of drivers.

The efficiency of that Memphis sub is quite low, so most of that 1200W is going to go to waste.

For every 3db of efficiency you only need half the power, so if you had a sub which has an efficiency of 95db/1w/1m, you would only need 150W to produce the same SPL as that Memphis sub (86db efficiency).

[TittySprinklez]

Feel free to ignore this, but I though it was interesting and not many people may know about efficiency of drivers.

The efficiency of that Memphis sub is quite low, so most of that 1200W is going to go to waste.

For every 3db of efficiency you only need half the power, so if you had a sub which has an efficiency of 95db/1w/1m, you would only need 150W to produce the same SPL as that Memphis sub (86db efficiency).

...... does this mean i should of bought a type R and saved monies ? lol 

 

also cheers for that jaycar link

[Tim.]

Not at all. Type R's are between 82 and 85db efficiency which is worse.

+1 for Jaycar cable. If you are able to sign up for a trade card, you get the next price break on the 2 Gauge cable ie. $12/m instead of $14.50