Stereo Amplifier Wiring

[emfinite3131]

I am finishing up the final wiring on the cart and have a couple questions about the stereo wiring.

The previous owner had the amp powered directly off 2 batteries to get his 12 volts with a 40 amp fuse wired in line. He also ground directly to the frame off the batteries , which i know is a huge mistake - see pic below (its a crappy pic but i took it before i broke down the cart haha)


My question is, how do i power this thing? Do i go directly to the batteries like the previous owner and not ground to the frame? Do i connect to my 12v regulator? Specs on the amp also say to use an 8 guage wire with a 50amp fuse inline if that helps.

The amp is a rockford fosgate p4004
Heres the specs i found online
50 watts RMS x 4 at 4 ohms (100 watts RMS x 4 at 2 ohms)
200 watts RMS x 2 at 4 ohms (4-ohm stable in bridged mode)

Any help is appreciated.

[orangeman6]

https://www.crutchfield.com/S-Xudkmr...rs_faq.html#10

Scroll down to the section about “what’s the biggest amp I can hook up?” That will give you an excellent explanation.

You also need to know how many amps your reducer can put out.

Wiring to just two batteries for 12v is not good for the overall health of your pack.

How many speakers, and what type/how many watts are you running? A sub?

What head unit, and how much power does it have? Do you actually even need the amp?

Again, refer to the Crutchfield link I posted, but that’s not a particularly large amp, and your reducer should be able to handle it.

[dacheedah]

I always like separate ground wires equal in length to the power wire. Most noise in a stereo system is introduced through grounding. Put a ferrite bead around each power wire will help, if you dispose of old electronics cut those beads off and save them for future use. A lot of electronics are very sensitive to dirty power.

[emfinite3131]

Thanks for the great advise.

Im running 2 speakers and a sub.

The speakers are Kenwood kfx x166:
150 watts peak each.
I don't know what the rms rating is, couldn't find it online.

The sub is a polk momo 12" power handling:
75-400 watts RMS
peak power handling: 800 watts

The amp is a rockford fosgate p4004
50 watts RMS x 4 at 4 ohms (100 watts RMS x 4 at 2 ohms)
200 watts RMS x 2 at 4 ohms (4-ohm stable in bridged mode)

Based on the math mentioned on the cructhfield page:
multiply the number of channels by the RMS watts per channel (its a 4 channel amp but im only running 2 speakers and a sub so i think my math is 200 watts RMS x 2 ). Double it to account for amplifier inefficiency (400 watts X 2 = 800 watts), then divide by the average output Voltage, 12 volts (800 divided by 12 = 67 amps). Since the average music signal requires about 1/3rd of the average power in a test tone, divide by 3 (67 amps divided by 3 = 22.3 amps)

So i think my answer based on the advice above is 22.3 amps.

Can anybody verify that i entered roughly the correct numbers in the equation?

Heres the head unit that going in. They make some with amplifiers, mine is not one of them. The reason i went with this unit is because its android based and hopefully i can hook up my smart link to it for real time info.
https://www.carjoying.com/2017-new-d...ation-771.html


This is my first real experience with mobile audio and i'm trying to wrap my head around it.

[orangeman6]

Hmm, I think you may need to double check your plan. I know just enough to be dangerous, but I think you’ve got a couple of issues.

You need a separate channel for each speaker, including the sub. Most car audio speakers are 4 ohms (check the specs on yours). Your amp is capable of 50 Watts rms x 4 at 4 ohms. That’s going to be plenty for the kenwoods but probably not enough to get much out of a 12” sub that may be in a box, but is playing in an open air golf cart. If you bridge the amp, you can get 200 Watts per channel, but you’ll only have 2 channels at 4 ohms. That 200 Watts may be enough for the sub, but you’ll be a channel short for the kenwoods.

I installed quite a few car systems in my teens and early 20’s but that was quite awhile ago. I’ve got a 17 yo and we put a 12” JL Audio in his car. We ran a separate 500 watt rms amp just for that sub. His other speakers are all on a separate amp, which I think is the more common way to do it. When I did my cart, I wanted to put a sub, but I have to wait until the kid is gone and I will be using the cart a bit differently than I do now. For the meantime, I’m running a head unit that sends 40 Watts each to the 4 speakers in the roof of the cart. Just for reference, while sitting in the cart, it’s crazy loud at not even 3/4 volume. When I get to change it up, I’ll get a separate amp just for the sub. That amp will get it’s signal via a pre-out on the head unit, power it up, and send it to the sub. Now, I doubt you’re looking for as much bass as my 17 yo has going in his car, , but I don’t think the way you’ve currently got this figured is going to work. I think you’re going to need to find a bigger amp, run 2 separate amps, or use a head unit with an internal amp for the kenwoods.

Hopefully this helps at least some. Again, I’m far from an expert, but pretty sure I’m on track here. Maybe Dacheedah will chime back in. He seems to have some knowledge.

If you want to, call Crutchfield, or peruse their website. You don’t necessarily have to purchase from them but they have advisors that, in my experience, have been very helpful in getting you lined out.

Good luck, and post what you come up with.

By the way, cool head unit with the 8” screen, but where are you mounting that thing?

[emfinite3131]

Thanks for the response. you are waaaay more knowledgeable than me on car audio. To be honest, i have zero interest in car audio and this is the "chore" part of the project for me. Funny enough ive really enjoyed re-wiring the cart so maybe ill learn to like the audio stuff as well once i can start to conceptually understand it.

Everything was installed by the previous owner so im trying to make heads or tails of it all. The sound system was running before i took the cart apart and the sub was actually really loud - loud enough that my wife was wondering why the garage was shaking hahaha so good enough for me.

as far as the amp goes, im kinda married to it. It looks like the previous owner had some brackets welded to the frame to mount the amp to and it fits so perfect so id kinda rather not switch it up so much.

For the screen, i bought a dash kit and in my trial test fit, fit really good. Its not going to be mounted flush, think tablet style like the mecedes cla or the tesla model 3

[orangeman6]

That screen will be very cool. Looks like you could watch movies on that thing.

If you enjoyed wiring the cart, you’ll enjoy the audio too. It’s kinda fun figuring it out, then hearing it actually work. I’m big on music, so I especially enjoy it. As long as it ends up working correctly. Ha ha.

So, was that head unit already in the cart? I ask as much for my own learning. Again, definitely not a legitimate audio guy, and I can’t understand how that combination would work well together, but I’d like to.

Sounds like I threw you off course, if everything was already good and you just wanted to move the power supply to the reducer. I didn’t check your math when you calculated above, but it looks like you’re in good shape. To be sure, however, add the draw for any other 12v accessories, and reference the specs on your particular reducer.

[emfinite3131]

The head unit was not in the cart, all they had was a audio jack to plug into your phone that went directly to the amp.

I tested everything last night and it worked. screen powered up, stereo thumped pretty loud and all appears to be good.

i ended up using some 10 gauge wire i had laying around just to test it but will probably end up swapping out to 8 gauge.

a few other issues remain like the unit switching off when its put into neutral - need to do some research on that one. also the headlight switch isnt working and the lights are stuck on so i need to figure out that one as well. overall nothing major.

Thanks for all the help.

[orangeman6]

That’s good!

Are you running just 50 Watts to the sub, then?

Which cart do you have?

How did you wire the reducer? Does yours have a trigger wire to turn it on/off?

Were your lights factory lights, with the three position key switch? There’s quite a few threads on installing reducers, and if you want them turned on with the key or a separate switch. A quick search should find what you need. FWIW, everything in mine has a separate switch, including the reducer, but that’s because I use the stereo, etc often when the cart is stationary and I don’t want to worry about someone accidentally hitting the go pedal. It all depends on how you use your cart.

Post which cart you have, 3 position key switch?, which reducer (separate trigger wire?) and how you wired it.

[mtbman1016]

This is a fairly simple setup for the amp. You can run the two Kenwoods off two of the channels, the bridge the sub of the other two which will have it run at 4ohm mono. You’ll want to see which channels, typically 3&4, have the low pass filter. Use those for the sub to filter out anything usually 80 MHz and above. Amp should run fine with 8awg wiring.

For the head unit, unless your completely concerned with maintaining the correct time, twist the yellow and red wires off the radio harness together. Wire them to a source that gets 12v with key on. Utilize the blue remote turn on lead from the head unit to turn the amp on when power to the head unit is active.
You’ll need to check that power source that the unit is currently wired to as the cart being in neutral shouldn’t turn the unit off. Typically with a 3-position switch, you’ll have a 12v feed to power the lights that would be sufficient enough to power the head since you’re not utilizing the internal amp.

Hope this helps


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