Again, I am just putting this information out there for any fellow 2nd Gen GX owners who might be considering upgrading their factory Non-ML sound system. I understand everyone's plans on upgrading might be different, but (myself included), want to know what all of the options are, so I'm just going to leave this write up here for anyone to view as GP.

So, for those 2nd Gen GX owners that do not have the ML sound system, depending on the year of your GX, your factory amplifier will be either one of the ones pictured below. I contacted Pioneer who makes both amplifiers and they were able to give me some info.

It is my understanding that the 17-current GX have the 86280-60451 amplifiers, those model years before 17 have the 86280-60450 amplifiers. I've read the discussions here on the forum, it seems the general consensus is that the later model years have the surround sound feature and the earlier model years do not? When I spoke to Pioneer, they mentioned that the two amplifiers are different but not by much, mostly the differences are specifications such as crossover points (which frequency within the factory amp) is sent to which speaker. Pioneer did mention that unlike manufacturers such as GM, which use a variable voltage output amplifier (the amplifier actually controls the volume level on the specific speaker), the amplifier in the 2nd Gen GX is fixed meaning the in-dash unit controls the volume of the speakers. I will add more details on info as I dig deeper into my build, but as it stands, for those who want to add an aftermarket amplifier to their factory system, they don't have to overcome too many obstacles in order to get the best sound. A lot of newer vehicles have the warning chimes and even vehicle exhaust sounds coming through the factory audio systems, from all the research I've done thus far, the 2nd GX doesn't have these types of features to overcome when upgrading to an aftermarket amplifier or aftermarket speakers. As I move along with my build, I will post up if certain chimes or notifications are being routed by the amplifier into specific speakers and a solution, but as it stands, from what I've researched, this isn't the case.

Now, I sure I will get some different opinions on this next matter, but at least for me, I would be cautious regarding which aftermarket speakers I decide to purchase and add. Again, most of this info I received from Pioneer, but no matter which year 2nd Gen GX you have (without the ML system) the factory amplifier and speakers are set up like in this way: (and please keep in mind, I may not have these channels in the correct order, but the layout is what Pioneer gave me), I will update this as I get all the specs nailed down)

channels 1&2 run the front Left Right Tweeter which are wired in parallel to the corner dash Left Right midrange speakers.
channels 3&4 run the front Left Right 6x9 door speakers.
channels 5&6 run the rear Left Right 6.5 door speakers.
channel 7 runs only the center dash speaker.

So, the factory amplifier has preset or canned crossover points for each of these channels, they have the frequency cutoff at certain points so that each of these speakers only receives a frequency signal that will work for optimum performance for each specific speaker. This means for those who might not understand all this info, that you can adjust the treble, bass, or volume level at the in dash unit however you choose, but ultimately, the amplifier is only going to allow certain ranges of frequencies and voltages go to certain speakers. The reason for this and how our systems are set up, are so that no matter what we do, we won't end up blowing the inexpensive speakers that are used in our GX's and Lexus having to replace them under warranty. So a lot of the less than stellar performance of this factory system can be attributed to Lexus designing all the specs so nothing will break under warranty. This also means that, whatever replacement speaker you decide to use, is still going to receive the same frequency/signal as the stock speaker, thus the only improvement in sound you will get is IF the replacement speaker does a better job at sound reproduction at the frequency it is given compared to the stock speaker.

Later on I will hook up a RTA (real time analyzer, I have a friend who owns one) and I will list what these frequencies are, but for now I can tell you that the front door speakers seem to serve as the subwoofers of the factory system, the front tweeters and corner dash speakers, the rear door speakers, and the center channel speaker are receiving a portion of a full range or a form of a full range signal.

Someone in this conversation has already demonstrated that the most of the factory speaker’s ohm out at right under 4ohms or around 3.5 ohms, but the center speaker ohms out close to 5 or 6 ohms. I asked Pioneer about this, and I was told that because the center dash speaker is on its own channel separate from the other speakers, it has a different impedance (resistance in ohms) and it receives a different output (voltage) as well compared to the rest of the speakers. I've read others here commenting on how the center speaker (in factory configuration) sounds a little louder or different than say the corner dash speakers, at different selected volume levels, on the in dash unit. Well, this center channel speaker which has higher/different impedance than the rest of the factory speakers, is receiving a different voltage from the factory amplifier according to Pioneer. I point this out, as I see several people are replacing the center speaker with an aftermarket speaker with an impedance of 4 ohms. Generally speaking, on a amplifier, the output (sound level) of the speaker usually gets louder the lower the impendence on the speaker is, as when you present less resistance, more power from the amplifier can go to the speaker, that is IF you have the current to deliver the power at a lower impedance and IF your amplifier can handle a lower resistance load. So, according to pioneer, this factory amp is designed to send more voltage (output) to the center channel- compared to the voltage sent out to say the channels that are driving the corner dash speaker and tweeter. I should note, I haven’t taken my vehicle apart yet to make any of these measurements, but I will in the future and update this post for those interested. I went a little further to speak with an independent shop that repairs factory audio amplifiers such as the one in our GX. In my mind, from everything I've read up on, installing a 4ohm impedance speaker on the factory center channel would present a problem as that amp is probably not designed to push a lower impedance speaker. The person I spoke with at the amplifier repair shop also agreed that he has seen several GX factory amplifiers that over time overheated and gave out due to dropping the load on this channel. He recommended at least for long term use or for someone who listens to their stereo in the upper 70% range frequently that they do not swap out the factory speakers for different impedance aftermarket speakers. Not only are the factory speakers specifically designed for this amplifier, but specs such as the sensitivity ratings and frequency responses also come into play as well. Many of the aftermarket speakers that will fit for our vehicle may not even have the same frequency response ranges or input sensitivities compared to the stock speakers which would explain why some people have commented on certain aftermarket speakers "sounding" better to them than others. For most of the speakers in our systems that have a 3.5 impedance, replacing the speakers with a 4ohm speaker shouldn't present any issues although once I (or someone) get around to figuring out exactly what frequency range and voltages are being sent out of the factory amplifier, it’s just going to be a wild guess as to what aftermarket speaker is going to sound best when paired with the factory amp. Ultimately though, it’s my opinion that replacing the center dash speaker with any 4ohm speaker will present a problem. It is also worth noting that although Crutchfield may not be the know all end all source for car audio recommendations; even their website has zero recommendations for a replacement speaker for the center dash on the GX?

So…for those GX owners that are wanting to just upgrade their factory speakers only, I would say your best option is to

1), Know exactly what the sensitivity rating is on the factory speakers: example, if the factory speaker is rated at a sensitivity of let’s say 96db and you replace it with a speaker that has a sensitivity rating of 86db, you are going to notice a sharp drop off in the performance of the replacement speaker, a lower sensitivity rating is going to require more (especially at lower volume/output/voltage levels to achieve the same output volume compared to the higher sensitivity rated speaker. My opinion here: since the factory amplifier is not that powerful to begin with, if you are replacing just the factory speakers, I would opt for a speaker with a higher sensitivity rating as a general rule of thumb. Some people in this group have commented on how the JBL speakers they placed in the dash were almost too bright for their taste- JBL’s are known for having a higher sensitivity rating, and are designed to work with lower power systems.

2). Know exactly what frequencies are being sent to each speaker. As I mentioned before, the factory front 6x9 door speakers serve as the “subwoofers” in this system as they seem to be the only speakers being sent low frequencies. Now these factory 6x9’s might be cheap Chinese made speakers, but they also might be designed to play a certain range of frequencies, it should also be noted, that these 6x9 speakers are basically drivers not coaxial. They are basically a 6x9 woofer. So when you go and purchase a set of aftermarket 6x9 2 way or 3 way speakers, the tweeters in the replacement speakers aren’t even going to receive a frequency that they can play at, and the woofers may be designed to only play down to say 40 hertz, where as the factory speakers play down to 20 or 30 hertz. The factory speakers are going to play lower and cover more of the frequency being sent to them, thus they may not sound louder per say, but they will sound better if that makes sense as they will be able to reproduce every frequency that is being sent to them.

3). Know the power that is being sent to each speaker. A huge mistake in car audio is pairing up a speaker designed to perform at a certain power range with an amplifier that comes nowhere near that power level. A lot of aftermarket speakers that say can handle up to 50 or 60 watts rms require a minimum of 10 watts rms to begin with. Again, I haven’t taken my vehicle apart as of yet, but I can almost assure you, the factory amplifier is more than likely putting out somewhere in the neighborhood of 15 up to 30 watt rms of power into any given speaker in the factory system. So again if you want the best bang for your buck and the best results, it will be important to select aftermarket speakers that closely match the factory amplifiers capabilities- installing a aftermarket speaker such as say the Infinities (I believe I saw someone was trying out), yes they have a high sensitivity rating, but those speakers require a bit more power to reach their potential, more than what the factory amplifier can offer.



Moving along, for those of us who want to go with an aftermarket amplifier and new speakers, such as myself we have a few options that I've found so far. Again, I will let those who interested in this topic respond if they want me to post pictures of the entire build from start to finish, but for the time being, I'm just putting this info out as GP. From all my research, the best option for getting the best improvement in sound over the stock system is to add an aftermarket amplifier. And in the case of our GX's the most simple way to accomplish this without cutting or splicing wires and keeping everything in a form that would allow transfer back to factory, adding an aftermarket amp and retaining the factory amplifier to provide an output signal is going to be the best route.

Now, out of all the amplifiers that are out there, our factory system presents one big issue and that is all the frequencies are crossed over at the amp and sent to the different speakers. So, using just a line output converter (while that might work) depending on which speaker output from the factory amp you tap into, is only going to give you part of the full range of frequencies. To overcome this, the best solution is to purchase a DSP or an amplifier that has DSP in it. Audio Control (I don’t work for Audio Control) makes products such as the LC2-LC7i that can take your factory amp's outputs and sum them together to create a complete full range signal to send to your aftermarket amplifier which is a great option, but you'll be forced to run a separate power, ground, remote turn on for this unit, and once its installed, unless you have a RTA to tune everything, it's just going to be a best guess by ear of what frequencies are coming into the aftermarket amp and going out to whatever speakers you're going to be installing. If you're like me, where space is a concern and keeping the vehicle as close to factory as possible is a priority, adding a separate DSP then Amplifier(s) will present running a bunch of new wiring, finding a place to mount everything and so on.

With a DSP, again (Audio Control now makes amplifiers with DSP built in) you can have all the software for your laptop that can serve as a RTA, which will let you see exactly what's coming in and going out and it will allow you to sum the appropriate channels and adjust everything all in one package. You can go onto youtube and check out Car Audio Fabrication’s review of the D.1200 amplifier to see an in depth look at how all of this works.

JL audio also makes an amplifier with built in DSP and can do the same thing. Either of these two manufacturers also makes these amplifiers in a compact chassis that can still fit under the passenger seat with the factory amp which is a plus. I think I'm going to go the Audio Control route, run just a 2 way component set in the front, co-axial in the rear doors, and a small subwoofer, Audio Control is supposed to introduce a new 5 channel DSP amplifier soon which will work with this sort of set up. I'm going to just disconnect and remove the corner dash speakers and the center speaker. I will be happy to post up all the details of this build once I get all the gear together if this group is interested.