Installing an amp

[jodawill]

I upgraded to the Infinity Reference speakers recently, and my head unit doesn't have enough power to drive them properly, so I'm looking into installing an amp. I talked to someone at Crutchfield and they helped me pick out the right equipment, but I'm not sure how difficult the installation job is going to be.

 

Running the speaker wire shouldn't be too difficult, but it will also require running a new power line to the battery. I have no idea how to handle that. Will it require removing the dash? If so, I'm not sure I'm ready to do a job like that. I'm afraid of messing up the speedometer and so forth.

 

Also, if anyone has had experience with these speakers, do you think they need a subwoofer, or will they produce enough low end once I get an amp hooked up to them? I'm not looking for a booming bass, but I'm not getting much on the low end right now without the amp. Going from the 4 channel amp to the 5 triples the price of the project, based on the stuff they recommended, so I'm not sure it's worth doing.

[Smokeyyank]

Running power to the amp doesn't require the dash being removed, but your deck has to come out and you have to wiggle all over to run the new wires to connect stuff for the amp. This is also all pending your deck can support an amp too. If you don't have RCA outs your limited 

You need a install kit like this to start. Bare minimum you need power wire, ground wire, amp turn on wire and RCAs. 
https://www.knukonceptz.com/product/kca-complete-8-gauge-amplifier-installation-kit/

You just need to run the power wire through the firewall. Either poke it through a hole there or a new one with a grommet.

Then from your deck you need to run the RCAs back to the amp along with the turn on wire. This is where you might need to pull some carpet and trim to hide the wires. 

You ground the amp close to it. 

Then run all your speaker wire from the amp to the speakers. 

In regards to a sub, personal preference on what you listen to. I run a 8". Most times It's turned to barley on but I like how it rounds out the system. 

[jodawill]

Thanks for the reply. The deck does have RCA line level outputs. I guess I'll have to pull the stereo out and try to figure out where its power cable leads to. Maybe I can fish another one through there.

[Pete M]

I used to have 4 speakers and a small sub (2 separate amps) but eventually got rid of the rear speakers and couldn't really tell the difference. 

[derf]

How big of an amp are you planning on running?

 

For the compact 4 channel amps at 45-50W per channel (plenty for those speakers), you can get away with a 10 gauge wire.  No matter what size wire, have a fuse near the battery.  I've seen people burn their car up by not having a fuse.  The insulation on the wire gets cut at the firewall and it shorts out.  A fuse at the battery protects you.

[jodawill]

5 minutes ago, Pete M said:

I used to have 4 speakers and a small sub (2 separate amps) but eventually got rid of the rear speakers and couldn't really tell the difference. 

 

That's interesting. Why did you remove the rear speakers?

 

4 minutes ago, derf said:

How big of an amp are you planning on running?

 

For the compact 4 channel amps at 45-50W per channel (plenty for those speakers), you can get away with a 10 gauge wire.  No matter what size wire, have a fuse near the battery.  I've seen people burn their car up by not having a fuse.  The insulation on the wire gets cut at the firewall and it shorts out.  A fuse at the battery protects you.

The sales guy recommended this one if I don't use a subwoofer, or this one if I do. I'm not sure about his recommendations because I see much more affordable options out there. I asked him why he recommended the $469 amp, and he said it's because the power output was a better match for those speakers than the cheaper ones I was looking at. I'm not convinced that's a real concern. The entire cart he quoted for me for the amp+sub was almost $900, which is a lot more than I'm looking to spend. I was hoping to pay $200-$300 for the amp now, then possibly add a subwoofer in the future if I feel it's necessary.

[derf]

11 minutes ago, jodawill said:

 

That's interesting. Why did you remove the rear speakers?

 

The sales guy recommended this one if I don't use a subwoofer, or this one if I do. I'm not sure about his recommendations because I see much more affordable options out there. I asked him why he recommended the $469 amp, and he said it's because the power output was a better match for those speakers than the cheaper ones I was looking at. I'm not convinced that's a real concern. The entire cart he quoted for me for the amp+sub was almost $900, which is a lot more than I'm looking to spend. I was hoping to pay $200-$300 for the amp now, then possibly add a subwoofer in the future if I feel it's necessary.

Yeah, I don't trust people who have a vested interest in selling me their products.

 

You don't need much to get decent sound out of the Infinity speakers.  After all, it's a regular cab truck.  There are probably better choices that would work well.

 

And they always recommend a much bigger wiring kit than you really need.  Those have a lot more profit margin.  And they're probably 2x more capable than you need for the smaller amps.

 

8 gauge wire is likely all you need.  Without a sub, you can probably get by with 10 gauge.

[derf]

As an aside, I'm planning the stereo for my MJ build.  I'm using the @boxyjeep 6.5" speaker mounts for the rear and I'll put some dedicated woofers instead of a full on subwoofer.  The fronts will be quality full range speakers.

[Pete M]

53 minutes ago, jodawill said:

 

That's interesting. Why did you remove the rear speakers?

 

space.  they were 6x9s in small boxes rather than in the wall were the factory units are.  they sounded fine and added bass... until the little 8"sub was turned on.  then they were just drowned out.   In my Liberty I use the rear channels out of the '92 radio to feed signal to the amp for the subwoofer and couldn't even tell the factory rear door speakers were disconnected. 

[ghetdjc320]

My suggestion is to ditch the b pillar speakers and run the Kicker CX 4 channel amp. It’s one of the best bang for buck options out there and is a class AB amp which has a very smooth volume response. The infinity speakers you have don’t need much power as they have fairly high sensitivity (volume output per watt of input). With that 4 channel amp, you bridge the rear two channels to a small sub. For a budget system, I’d go with a 6.5” bazooka behind one of the seats. That pairs well with the front door speakers and will give you excellent bang for buck while taking up little space and fitting nicely behind the seat on the floor.
 

What I can say is, don’t mount any subs to the center rear wall of the MJ. The frequency response there is atrocious and the rear glass will take the vibration. For your door speakers, some sound dampening around them will do wonders for how they sound. 
 

For most sub 400w 4 channel amps, they will require at least a 8awg amp kit. This will depend somewhat on amplifier type. Class D will use less power than class AB and so forth. As Derf said, always install the appropriate sized fuse near the battery. 
 

As for the B pillar speakers, swapping to a larger speaker back there meets with several issues. First, there is no baffle for the speaker there. You will loose a great deal of frequency response b cause the sound waves from the front and rear of your speaker are colliding all over the place in those b pillars. And since they are out of phase with each other, they cancel each other out. Also, they are behind your seat and throw off the front stereo sound stage. And being behind the seats, only lower frequencies will be able to make it to your ears. 

 

Amp: https://www.crutchfield.com/p_20646CX36T/Kicker-46CXA360-4T.html

 

Sub:

https://www.crutchfield.com/p_204BT6DVC/Bazooka-BT6024DVC.html

There is some simple wiring that will need to be done between the amp and sub

the amp is rated for 65w per channel at 4ohms for the fronts and the rear two channels can be bridged into a single 180w 2ohm output which perfectly matches that sub. Kicker even sells a little bass knob for that amp to control the sub gain for those two rear channels.