Question on 4-channel amp install in TJ with factory subwoofer

[Jeepin Jason 95]

I've tried searching but couldn't find exactly what I'm looking for. I'm in the process of installing a small 4-ch amp in our TJ that has the factory Mopar subwoofer and a Sony AX1000 double-din head unit. Is it OK to splice the amp in *before* the factory subwoofer? This is an amp for the regular speakers in the dash/speaker bar, NOT an amp for a subwoofer.

I know the speaker wiring goes from the head unit to the subwoofer and then back to the main harness before going out to the speakers. I don't want to cut/splice into the factory harness so I was just going to run the amp outputs to the Metra harness between Sony head unit and the factory harness (see photo below) but wasn't sure if this would cause any issues since it's all going through the factory subwoofer before going out to the speakers.

 

[NashvilleTJ]

I've tried searching but couldn't find exactly what I'm looking for. I'm in the process of installing a small 4-ch amp in our TJ that has the factory Mopar subwoofer and a Sony AX1000 double-din head unit. Is it OK to splice the amp in *before* the factory subwoofer? This is an amp for the regular speakers in the dash/speaker bar, NOT an amp for a subwoofer.

I know the speaker wiring goes from the head unit to the subwoofer and then back to the main harness before going out to the speakers. I don't want to cut/splice into the factory harness so I was just going to run the amp outputs to the Metra harness between Sony head unit and the factory harness (see photo below) but wasn't sure if this would cause any issues since it's all going through the factory subwoofer before going out to the speakers.

View attachment 568385

Have you checked out the wiring diagram? If memory serves, the feed for the sub in the stock configuration comes off of the left and right channel wiring, and then hits the sub amp in the console. I don't believe the sub feed comes out of the head unit in the stock wiring.

 

[Jeepin Jason 95]

yeah, I may have done a poor job explaining it. The factory sub wiring harness sits between the black female plug on the head unit harness and the black male plug on the vehicle harness. So the speaker wires/signals go: head unit -> subwoofer harness -> speakers. It's taking the left/right channel signals but it's doing so before the speakers, if that makes sense. Or maybe it just piggy backs off the signal, I'm not sure what the wires themselves look like in the subwoofer harness. I just know it plugs in in-between the head unit and the factory harness going to the speakers.

I don't think the subwoofer modifies the signals any, and its amp only runs the sub itself, I just wasn't sure if I was going to lose any power to the speakers by running the new amp before it goes through the subwoofer or not, of if I would damage the factory subwoofer by running higher wattage line inputs to it.

After doing a ton more reading on the factory sub setup, I may look at just replacing the speaker (currently one of those Quadratec OEM replacement woofers) with a Kicker 6.75" and adding a dedicated mono amp for it. That way the sub and speakers are properly isolated and the factory sub is apparently pretty low power anyway.

 

[NashvilleTJ]

yeah, I may have done a poor job explaining it. The factory sub wiring harness sits between the black female plug on the head unit harness and the black male plug on the vehicle harness. So the speaker wires/signals go: head unit -> subwoofer harness -> speakers. It's taking the left/right channel signals but it's doing so before the speakers, if that makes sense. Or maybe it just piggy backs off the signal, I'm not sure what the wires themselves look like in the subwoofer harness. I just know it plugs in in-between the head unit and the factory harness going to the speakers.

View attachment 568522

I don't think the subwoofer modifies the signals any, and its amp only runs the sub itself, I just wasn't sure if I was going to lose any power to the speakers by running the new amp before it goes through the subwoofer or not, of if I would damage the factory subwoofer by running higher wattage line inputs to it.

After doing a ton more reading on the factory sub setup, I may look at just replacing the speaker (currently one of those Quadratec OEM replacement woofers) with a Kicker 6.75" and adding a dedicated mono amp for it. That way the sub and speakers are properly isolated and the factory sub is apparently pretty low power anyway.

Is it too late for you to switch to a 5 channel amp?

 

[Jeepin Jason 95]

Is it too late for you to switch to a 5 channel amp?

Well, I've already got the 4ch installed and wired up. There's a compact 5ch Clarion that looks like it might fit under the steering column. At this point though it might be cheaper/easier to just get a compact mono amp, or one of those powered subwoofer units that fit in the console with a little work, like the 8" one from Sound Ordnance.

 

[ChasUGC]

If they are regular speakers you will likely blow them out if you put an amp on them. Trying to tune down an amp kind of defeats the purpose of having an amp, and I found it doesn't really work even with good speakers. Plus, if you amp the speakers and don't have a loud enough subwoofer, it will defeat the subwoofer, eventually blowing out the subwoofer trying to compensate. The stock subwoofer is really limited, but good enough for regular speakers. Luckily, I didn't have to worry about the stock subwoofer as my 97 Wrangler never came with one. I put in 4 CDT-5.25 powerful 150 RMS speakers($400)($200/pr) with a 5 channel Alpine PDX-v9 amp($1000), Clarion EQ($100), and a removable dual 10" subwoofer box in the rear($500). My Amp is just too powerful without the Clarion to tame it. I've used Clarion EQ's for 40 years. The Clarion has separate dials for my sub and Alpine, so I can quickly dial everything in and only occasionally need to change the subwoofer output. No problems in ten years. But, the cost was over 2G with installation. I also had a professional do it.

For a cheap sound upgrade, I would ditch the 4x6 front speakers and put in the same 5.25 speakers all around. If you get good RMS capable speakers, then you can reliably amp them. The problem then becomes the inadequate subwoofer. You can probably spend around $300-$600 for the speakers. Good Luck.

 

[ChasUGC]

Well, I've already got the 4ch installed and wired up. There's a compact 5ch Clarion that looks like it might fit under the steering column. At this point though it might be cheaper/easier to just get a compact mono amp, or one of those powered subwoofer units that fit in the console with a little work, like the 8" one from Sound Ordnance.

My Alpine PDX-v9 is under the dash. It is way up there around the steering column. There is a special mounting kit for it, and its only about $60 dollars. But, your 400 watt amp is likely going to be too powerful for regular stock speakers. They are probably about 25-30 watts RMS, and less for the front 4x6 speaker. Your amp is 100 watts per speaker. I wouldn't even settle for 100RMS speakers because distortion is what blows the speakers. But, you may get away with 100RMS speakers if you are careful. Regular stock speakers won't work at all.

I also tried the cheap route, and it didn't work. Those amps get really hot really fast, and they shut off. I spent like $400-500 for a five channel amp and the specs were good, but it kept overheating. My Alpine never shuts off or overheats. Of course they all need space. I wouldn't try to mount any amp under your seat.

 

[Jeepin Jason 95]

We've had 5.25s in the dash for over 20 years now actually. The speakers were the very first thing we ever upgraded sound system-wise. Started with Boston Acoustics all around and recently replaced those with Kicker 46CSC54 5.25s in the dash and sound bar. They're rated at 75W RMS. My Kenwood amp is 45W RMS.

We've also got a set of SelectIncrements ModPods on the floor with another set of the same Kicker 5.25s, wired in parallel to the dash speakers. I may take those speakers out of the scenario though.

 

[ChasUGC]

Well, I've already got the 4ch installed and wired up. There's a compact 5ch Clarion that looks like it might fit under the steering column. At this point though it might be cheaper/easier to just get a compact mono amp, or one of those powered subwoofer units that fit in the console with a little work, like the 8" one from Sound Ordnance.

You've got the 4 channel 45w/channel amp wired to the 4 kicker speakers? You didn't power the subwoofer from the amp, right?
If so, how does it sound? Because, I keep my amp well below half power and it is plenty loud. The only concern I can think of is maybe your subwoofer power.
It is strange, somewhere I saw a 400watt amp. I thought that was your amp. Maybe that was just an ad on the page.

 

[GaTechTJ]

To answer the original question, you will need to measure the resistance of the speakers that the amplifier sees with the factory sub in line with the rear speakers. If the resistance is in the range of what your amp is rated for, then no harm. Most 4 channel amps are looking for 4 ohms per channel.

 

[JustDandee]

Maybe they are wired different through the years. Not understanding how you wire in a 4 channel and run that amplification through a factory amp. I am wondering if you would not burn out the factory amp. 05 schematic below

 

[AdelaideTJ]

Well, I've already got the 4ch installed and wired up. There's a compact 5ch Clarion that looks like it might fit under the steering column. At this point though it might be cheaper/easier to just get a compact mono amp, or one of those powered subwoofer units that fit in the console with a little work, like the 8" one from Sound Ordnance.

depending on budget, the Kicker KEY500.1 is a pretty tidy little compact mono amp. Quite small, but it is pricey. I have the Kicker 360.4 for the front and rear and the KEY500.1 for the subs

 

[Jeepin Jason 95]

You've got the 4 channel 45w/channel amp wired to the 4 kicker speakers? You didn't power the subwoofer from the amp, right?
If so, how does it sound? Because, I keep my amp well below half power and it is plenty loud. The only concern I can think of is maybe your subwoofer power.
It is strange, somewhere I saw a 400watt amp. I thought that was your amp. Maybe that was just an ad on the page.

Correct - the 4 channel, 45W RMS amp is running the 4 (technically 6) Kicker speakers. The sub is currently the factory powered sub which has its own built-in amp.

I think it sounds fine, but I also think it sounded fine before the amp. I'm far from an audiophile, and rarely crank the volume to even 50% max, but my teenage son however, who drives the TJ now, likes his music at teenage boy levels, lol. Even with the amp there's still noticeable distortion during certain songs, particularly those with lots of bass lines, with the volume at like 80% max. Some of that is likely due to the lower power output of this compact amp. Some is likely due to running full frequency through the Kicker speakers vs limiting the low end. And some of it in the front speakers could be from having 2 'dash' speakers in parallel on each side. And some could be from the dash speakers just being in open 5.25" adapter plates vs closed pods (I'm going to be getting some pods for them soon).

The 400W you saw was in the illustration of the amp in the installation instructions in my initial photo. 400W is the max output of the amp, kinda like how lots of aftermarket head units advertise max power output vs rms power output.

 

[Jeepin Jason 95]

Maybe they are wired different through the years. Not understanding how you wire in a 4 channel and run that amplification through a factory amp. I am wondering if you would not burn out the factory amp. 05 schematic below

Yeah, the wiring harness for the stereo and subwoofer changed in 2003. Our TJ is a 2000, but I installed a 2001 subwoofer center console in it back in 2002. It's got a 6pin connector at the subwoofer and and a flat 7-pin connector that plugs in in-between the black plug from the head unit and the back plug in the factory harness. '02 and older TJs have a 2-plug harness (see my original photo) from the radio, vs '03+ that have a single plug.

Based on the pin outs of the plugs on both the early and late model subwoofers, and the schematic you posted, the signals have to be splitting off the main harness, like inline taps, vs going into the sub and then back out to the speakers. Other than running higher wattage inputs than the factory amp may be expecting, I think things should be fine with having the amp before the subwoofer harness.

 

[ChasUGC]

Correct - the 4 channel, 45W RMS amp is running the 4 (technically 6) Kicker speakers. The sub is currently the factory powered sub which has its own built-in amp.

I think it sounds fine, but I also think it sounded fine before the amp. I'm far from an audiophile, and rarely crank the volume to even 50% max, but my teenage son however, who drives the TJ now, likes his music at teenage boy levels, lol. Even with the amp there's still noticeable distortion during certain songs, particularly those with lots of bass lines, with the volume at like 80% max. Some of that is likely due to the lower power output of this compact amp. Some is likely due to running full frequency through the Kicker speakers vs limiting the low end. And some of it in the front speakers could be from having 2 'dash' speakers in parallel on each side. And some could be from the dash speakers just being in open 5.25" adapter plates vs closed pods (I'm going to be getting some pods for them soon).

The 400W you saw was in the illustration of the amp in the installation instructions in my initial photo. 400W is the max output of the amp, kinda like how lots of aftermarket head units advertise max power output vs rms power output.

Okay, gotcha. But, this distortion you are talking about if from phone files could be caused by the file itself. Especially, if it only happens on some files. I had that problem on a few of my most popular songs, especially the Hip Hop ones. Just load them in any waveform program, like Sound Forge. If the wave if clipped or cut off on the top, that is the distortion. Sometimes, normalizing the file can fix it. You should only see sharp peaks, no cut off peaks or heavy flattening on top and bottom. It is caused by bad ripping or noisy recording, what we call over saturation of the waveform.

If you have a stereo and amp with low THD, you really shouldn't be hearing any distortion. That is the point of the THD rating. My Alpine is like 0.1% THD. My stereo is like 1% THD. It is when you get stuff with like 10% THD is when you start to hear it. I've only had one stereo like that in have life, it was 8.8%, and you could definitely hear the distortion at high levels. I just amped it, and kept the stereo volume low and boosted the amp level. It was a rare super cool stereo that had a removable remote control. You could remove the stereo itself too. It folded down too. That was before I got the Wrangler.

I hope you aren't using the amp for the subwoofer signal. The amp should be getting signal from the four speakers. And the subwoofer should be getting signal from the stereo via the subwoofer out. I assume the Metra has sub out and you plug that to your stock subwoofer. You might also want to check that your polarity is good, especially if you are running one channel in parallel for four speakers. If it is badly out of phase that could sound kind of wonky at high levels.