You're thinking about adding an amplifier to your car stereo because you want more. You want it to go louder, you want more clarity, you want more bass. Well, good, because that's what amps do. I'm JR, Training Manager here at Crutchfield. We are constantly helping customers install amplifiers into their cars, mainly because of all of the features they're packing into factory radios these days. But how do you install an amp? Can you do it yourself? How long will it take? What tools will you need? Don't worry! Sit back, relax, and let us show you. Ken, one of our editors here at Crutchfield, has a Subaru Crosstrek with a base-level factory sound system and, well, it's not great. We've partnered with Kicker to install four new speakers and a 4-channel amp to really make those speakers sing. We'll show you step-by-step how to add an amplifier to this car, and we'll show you some other applications along the way. Here's what we're installing in this car: the Kicker 4-channel amplifier, an amp wiring kit with power and ground wire and a fuse and fuse holder, a line output converter, some speaker wires and some RCA cables. And here's the tools we'll need: basic hand tools like screwdrivers and a socket set, trim panel removal tools, a flashlight, wire strippers, a soldering iron and solder or some connectors. Is there anything I'm forgetting, Rodell? RODELL: Yeah, it'll also be helpful to have a wire insertion tool, a wire worm, a voltmeter, an ABS mounting plate, and some mounting hardware and cable ties. JR: That's Rodell, he's one of our sales managers here at Crutchfield and he's sort of our "wiring guru." He'll be taking us through a detailed look at how to do all of the wiring later on, on the bench. In Ken's car we're going to put the amplifier under the front passenger seat, which is a very common location if there's room. Once you've determined where to put the amp, it's time to start running wires. We'll start with the power wire, which goes from the battery to the amplifier. Most cars have a battery under the hood, which means you'll need to run your power wire through the firewall from the engine compartment to the passenger compartment. Our first step is to disconnect the negative battery terminal. Our next step is to find a spot in which we can run the wire through the firewall. This can be intimidating, because you'll have to create a new opening and fish the wire, but totally doable in most cars. Here's how. Look for an existing wire grommet that's large enough to house an additional wire. Make sure you can access it from inside the car. In our case, I found a grommet that I can see from under the hood as well as under the dash, right above the pedals. Pierce a hole through the grommet and run the wire through that hole. A piercing tool and wire worm will make this job much easier. Once you get the wire through the grommet, grab it from the other side and pull the wire worm and the attached wire through to the inside of the vehicle. I'll make sure to leave enough wire under the hood to get from the firewall to the battery, steering clear of the engine or any moving parts. If you can't find an accessible grommet, it's okay. You may need to drill a hole through the firewall. Look for a spot that's clear and accessible and that won't interfere with any gas lines or electrical wires. Once you've drilled the hole, you'll want to smooth the edges with a file and use a grommet to protect the wire. We'll want any extra power wire to end up near the amplifier so that we can cut it to size. I'll remove the glove compartment so that we can have access to run the wire behind the dash to the passenger seat area. For a lot of folks, that is the most difficult part of the installation. Don't get me wrong; we still have a lot of work to do, but getting the wire through the firewall is a major milestone in any amp Install the 8 gauge power wire included with the Kicker amp kit is already covered with loom. I'll route the wire away from any moving parts and anything that gets really hot, and I'll secure the cable with cable ties. Next, I'll install the fuse in the power wire as close to the battery as we can get. RODELL: Hold up, JR, we actually need to check and make sure we have the appropriate fuse installed first. Now, as a general rule of thumb, a 60-amp fuse with 8-gauge wiring will take care of you for up to about a 20-foot run, but sometimes that fuse is also protecting the amplifier. Our Kicker 4-channel amp doesn't come with its own fuse, and if you check the manual you'll see that it calls for a 40-amp fuse in the specs. That means we'll need to remove the 60-amp fuse that came pre-installed, and put our own 40-amp fuse in. From there, cut the power line, strip both ends, and go ahead and secure that fuse holder in-line to your power line. Back at the vehicle, you'll connect the power line with the ring connector to your battery on the positive terminal. JR: That takes care of our power wire, now let's move on to the ground. I'll start by removing the seat to give us easy access to mount the amp, run the wires, and secure everything. Removing the seat is pretty straightforward: simply remove the four bolts that secure the chair to the frame, disconnect any wires and connectors under the seat, and lift the seat out carefully. With the seat out, we can find our grounding location and run our ground wire. Ground is critical, and it should be connected to solid, bare metal. The wire run from our amp to our ground should also be as short as possible, 24 inches or less, and if there's any paint or rust at the grounding spot you want to make sure to remove that. We found some solid bolts going into bare metal in the center console near the amplifier; I'll go ahead and finish running our power wire to the same spot under the carpet. Our Tech Support team gets lots of calls about amplifier installations, and we have found that many of those problems can be alleviated or even prevented by making sure you have a good ground. The ring terminal on the end of our ground wire fit nicely over the factory bolt, and it's a short run from the ground to the amplifier under the carpet. Next, we will run signal and speaker wires. Signal wires carry the music from the stereo to the inputs of the amplifier. From there, we'll connect speaker wire to the outputs of the amp and run it out to all of the speakers. Let's take a closer look on the bench. RODELL: There's actually a few ways that we can get music from our stereo to our amplifier. If we were using an aftermarket radio, we'd actually just be able to connect these RCAs here to the preamp outputs on the aftermarket head unit, then we'll just connect the RCAs to the pre-amplifier inputs on the amplifier side. This this is generally ideal, because preamp or low-level signal is going to be cleaner than amplified or high-level signal. Because we're using a factory radio, we actually don't have any preamp outputs. Imagine we have the factory radio here, its vehicle harness, and then this connection is running to the existing speakers and sending music. We're going to interrupt that signal, steal some signal, and send it to the amplifier, and then once it's been amplified, bring it back from the amplifier, and then take advantage of that existing speaker wire so we won't have to run new wire. By far the easiest way to do this is a vehicle-specific T-harness and two lengths of 9-wire. 9-wire is great because it has positive and negative connections for all four channels, plus a connection for your remote turn-on lead. That means you can run two links next to each other at the same time, one for signal from the stereo to the amplifier, and one back to your factory connections. The vehicle-specific T-harness is great because it allows you to make all those connections behind the factory radio in your dash without cutting any factory wiring. On one side of the T-harness we have some speaker wire labeled "signal to amp" that's going to connect color-for-color to our first run of 9-wire. Then on the other side of the T-harness we have some speaker wires labeled "signal from amp" that's going to connect to the second run of 9-wire. The only connection we have left is our remote turn-on lead. That's going to be the blue wire in the 9-wire cable, and we're going to connect that to our red switched-power connection in the harness. Then you're good to go. We're constantly adding T-harnesses to the website. Go to crutchfield.com, plug your vehicle in, and see if we have something for you. we'll set aside this completed T-harness for when we get to the Crosstrek. If you don't have a T-harness, no worries, you'll do it the old fashioned way and cut your factory wiring. In theory, it's the same thing, you just don't have all the convenience of the T-harness where the connections are made for you. You're going to have to do some cutting and splicing on your own. JR: In this Crosstrek we are keeping the factory radio, which means all of the wires we need to access are in the dash, so we'll need to remove the factory radio. When you shop at Crutchfield, we provide vehicle- specific disassembly instructions for most vehicles. These will show you how to get the radio out. In this case, I'll start at the top edges to pry out the center dash vents and release six clips on each vent. Next, I'll remove two phillips screws, one on each side of the radio. Next, I'll remove this top trim strip and then remove two more phillips screws. Now there's just four clips holding the radio in. I'll pry it out of the dash, and disconnect the harnesses. Every vehicle is different, but most will require you to remove trim panels, disconnect wires, and remove some screws. With the radio out, we have access to all of the wires that we need. Fortunately, with this Crosstrek we have that T-harness that Rodell just soldered on the bench. We're going to use that. I'll plug in one end of the T-harness to the factory harness and pull the attached speaker wire down behind the glove box. I marked this length of 9-wire with a piece of tape at the other end. Now I'll plug in the other end of the T-harness to the factory radio, and pull that section of speaker wire down to the passenger footwell again. into the dash. At this point we're all done behind the radio, so I'll re-connect all of the plugs and re-install it the dash. It's important to separate our power and ground wire from our signal and speaker wire to avoid any unwanted noise. Since we ran our power and ground wire under the center console on the left side of the passenger seat, we're going to run our signal and speaker wire from the factory radio behind the glove box, behind the kick panel under the scuff plate on the right side of the passenger seat. I'll still fish the cables under the carpet to the same side of the amplifier as the power and ground connections, but this routing keeps those wires separated to avoid unwanted noise. In many installations, we would be ready to trim our wires and connect everything to the amplifier. But in many newer vehicles, like this Crosstrek, there are other issues to consider. For example: load-generating devices and bass roll-off. We are going to address both of those problems with a line output converter. RODELL: So, technically the line output converter is optional, but I think it's a good idea. The factory radio isn't going to like it in this Crosstrek if we try to connect it directly to the speaker inputs on the amplifier. Basically, what happens is the factory radio is expecting a certain level of impedance from the factory speakers, and the amplifier's speaker inputs are going to be totally different, and the factory radio might not even recognize that. The way to fix that is a line output converter with load resistors. Now, if we weren't going to use a line output converter, something like a load-generating device would solve the problem. We could just splice this in-line on our signal run, and then we'd use these speaker-level RCA adapters to make those connections. Luckily, we won't need those today. So the other important consideration here is that our factory radio in the Crosstrek, like a lot of factory radios, has something called "bass roll-off." Basically, as you turn the volume knob up, the bass decreases. This is to make sure that at higher levels, those really cheap, sort of paper-thin factory speakers aren't distorting or maybe even blowing. But now that we're getting rid of the cheap stuff, it's time to get serious with a line output converter. We're going to be able to get full range, all of the bass, and make sure that the factory radio is still recognizes everything. You're also getting good, clean low-level signal like we talked about earlier, so we're going to get the best possible performance out of our amp. Just remember that when you're using a line output converter, make sure that you have it set to "low level" here. or if you're connecting directly to the factory radio. we'll set that to "high." JR: Time to connect everything in the car. First I'll connect this 9-wire carrying signal from our stereo to the speaker-level inputs on the LC7i Pro, then I'll plug in the power connector with the 9-wire stripped and ready to go. I'll connect each of the speaker wires to the speaker outputs of the amplifier: white is our front left speaker, gray is our front right speaker, green is rear left, and purple is rear right. The solid-colored wire is our positive wire, and each wire with a black stripe is our negative wire. Finishing the connections on this side of the amplifier, we'll connect our power, ground, and remote turn-on. RODELL: So you're probably wondering how we get power to the line output converter. we've got our 12-volt and ground connections here to the amplifier, and then for the line output converter, because it requires less power, we're actually piggy-back off of that with a power connection here. Make sure you fuse that. We've got our ground connection, and then this here is actually our remote turn-on. That way, when the factory radio turns on we've got switched power here at the line output converter and the amplifier to make sure everything is turning on and off at the same time. JR: The power wire from the battery and the small power wire that goes to the LOC get connected to the 12-volt connection, the ground wire connects with the small ground wire that goes to the LOC to the ground connection on the amplifier, and we'll run a short remote turn-on wire from the LOC to the remote input on the amp. On the opposite sides of the LOC and the amplifier, I'll connect two short RCA cables from the channels one and two outputs of the LOC to the corresponding inputs of the amplifier. Our amp and LOC both now have power, ground, and remote turn-on connections, signal wire going from the factory radio to the LOC; RCAs carry signal from the LOC to the amplifier, and speaker outputs take music from the amp back up into the dash. On the LOC, we'll set "load select" to 20 ohms to keep the factory radio from freaking out. We'll set "trigger mode" to remote in, and once we get music playing we can adjust AccuBASS to restore all that bass that the factory radio removes when you turn it up. Now it's time to set our gains let's head back to the bench. RODELL: Ooh, I love setting the gains. It's my favorite part. First off, a lot of people make the mistake of thinking the gain is a second volume knob. It's not. I want to say that again: the gain knob is not a second volume knob. What it does is, it actually matches the input stage of our amplifier to the output of whatever source we're using — our aftermarket head unit, a factory radio, or even a line output converter. First, I'm going to show you how to set the gain using a voltmeter, which is the best way, but afterwards I'll show you how to do it by ear using a slightly easier method. All right. To start, we're going to disconnect the speaker outputs from the amplifier. Next, we're going to make sure that everything's turned as low as it can. The gain, the crossovers, any sort of bass boost. So we're good there. Now if you haven't already, go ahead and download the test tone appropriate for your amplifier. For this Kicker 4-channel, we're going to use a 0dB 1khz test tone that we got from kicker.com. Once you've got that on your source, we're going to go ahead and make sure that our volume is set to about 75%, and let's go ahead and turn our voltmeter on to A/C voltage. All right. Next we're going to connect our positive and negative voltmeter leads. All right. From there, we're going to play our test tone. And now that we're playing, we are going to adjust the gain — slowly — until we hit, in this case, 16.12 volts. [Humming softly as he works] All right. So we've got it set as close to 16.12 as we could without going over, and we didn't just pull that number out of thin air. What's going on is we got a 65 watts RMS amplifier, and it's connected to 4-ohm speakers. So multiply 65 * 4, take the square root of that, and you've got 16.12. You can also just check the specs manual that came with your amplifier; there'll usually be some sort of conversion guide. From there, you're going to do the same thing for the rear stage: set in the set in the gain again, and disconnect your voltmeter leads, reattach your speaker outputs, and never touch the gain knob again. All right, now let's check out how to do this by ear. For a quick and easy setup without a voltmeter, go ahead and leave your speakers connected to the output of the amplifier, and make sure that everything's zeroed out on the gain side. From there, we're going to turn up our source head unit to about 75%, hit play, and I picked a song that I know pretty well. The idea is that you hear something that's going to be nice and clean, and you're going to be able to hear if anything changes pretty quickly. So from there, we are going to turn the gain up slowly. All right. And we're listening, we're listening for any crackling or distortion, and once we start to hear it we're going to back off there, and leave it. We'll do the same thing for the rear stage, and congratulations, you set your gains. Next, we're going to set our crossovers. For the front 6x9s we want them set to full range, or off. For those rear speakers, we're going to set a high-pass filter at about 80 Hz. Make sure your input level is set to low, and then we're going to make sure our bass boost is set all the way down to zero. Now that everything on the amp is set, it's time to set the AccuBASS on the LC7i Pro. Easiest way to do this is just follow the manual. You're going to set the threshold control all the way down, and then on your stereo, start to turn the radio up until you start to hear that bass roll-off where, specifically, those bass frequencies drop out in relation to the rest of the music. Leave the volume there, and then slowly start turning the threshold control until you start to hear the bass come back. Leave the threshold control there, and then use the level adjustment to fine-tune exactly how much bass restoration you want, and with that, we're done. JR: Wow, that sounds so much better than before. It's clearer at all volume levels, and we can now turn it up so much louder. It's time to button everything back up. We're going to secure the amp and the LOC under the seat. Rodell, back to you. RODELL: Here's what I would do now in our Crosstrek. There's not quite enough room to mount the line output converter next to the amplifier, but we can mount it on top. Because the amplifier's heat sinks are on the side, we don't have to worry about any transfer, so a little bit of heavy-duty velcro and we are good to go. From there, to get as clean of a factory look as possible, I'm actually going to take that ABS mounting board that I mentioned earlier and slide it underneath the factory carpet, sandwiching that carpet in between. From there you've got your screws that you're going to mount the amp's feet to the board, now if those screws extend past, make sure you file down any exposed metal and tape that metal off so we don't have any sort of grounding issues. Once you're done with that, a little bit of cable management and this thing will look like it came with your Crosstrek. We're talking clean, we're talking smooth, we're talking immaculate. JR: Um, that may be how a professional would do it, however, many non-professionals might just use some velcro to attach the bottom of the amp to the carpet. Is that okay? RODELL: I mean, if you use some heavy-duty velcro it'll be fine, but... JR: Cool, that's what we're going to do. Velcro to the rescue. Now I'm going to position the amplifier under the seat in a way that we can access the controls, even after the seat is back in. Controls like gains and crossovers, bass boost, etc. Next, we'll tidy up the wires and we'll put the seat back in, reconnecting any harness we disconnected earlier. We'll secure the seat using the same four brackets and bolts that we removed before. Okay, all the tools are put away and Ken's car is put back together, and it looks just like it did before we started. The factory radio is still in the dash, the new speakers are hidden behind those factory grills, and the amp is tucked away under the passenger seat, cranking out power to those new speakers. If you have any questions about how to improve the sound in your car, visit us here at Crutchfield.