I would like to upgrade the amp and speakers in my 2004 non-ML, non-nav LS, and install a boxed 12" subwoofer in the trunk.

I would prefer to retain the stock look and the steering wheel controls, so I am thinking of keeping the original head unit. I already have a BT45-TOY bluetooth adapter that I use with the stock system. Bluetooth is my main audio source by a wide margin. The BT45-TOY supports calling and steering wheel track advance, which is nice.

If I understand correctly from what I have read so far, the connection from the stock radio to stock amp in the trunk is a fixed level, and the radio also sends digital control signals to tell the amp the volume setting.

The PAC AmpPRO AP4-TY11 connects near the radio and decodes these inputs to produce volume-controlled analog outputs. But using this would involve running a bundle of RCA-connected signal wires from the dash to the trunk. This seems a little silly when there is already a pristine (but fixed-level) audio signal going from the radio to the trunk.

Is there some other way to replicate the functionality of the AmpPRO, but do it at the amp side of the harness instead of at the radio side?

Alternatively, are there aftermarket head units that can satisfy my criteria of 1) responds to steering wheel volume and track change, 2) has built-in bluetooth for both calls and audio, and 3) can be installed in a hidden way? I'm OK with yanking the CD changer, and I'm OK with losing the FM radio and cassette as audio inputs. I just want to keep the stock look.

 

My friends first LS430 had the "base" stereo without nav and I'm the stereo guy so I was tasked with more or less the same thing that you're asking for. The AP4-TY11 is your best bet if you want to use the factory head unit. As you've found out, the factory head unit sends a clean signal to the amp, and the volume ****/volume buttons on the wheel tell the amp to raise or lower the volume. If I remember correctly this is done via CAN, so it's not so easy to tap into and modify.

The dash kit to install an aftermarket single DIN head unit in place of the stock one doesn't look too bad, but the aftermarket head unit will be obvious. This is my personal preference as it allows you to be completely free from any of the factory audio system constraints and you can get bluetooth and android auto/apple car play if you would be interested in that. I'm not an apple guy but wireless android auto has better sound quality than bluetooth. You might not hear the difference depending on the streaming service you're using, or the quality of your local music files, but that's another topic. There are adapters that allow you to retain the use of your steering wheel controls with aftermarket head units, though the aftermarket head unit must be compatible with the adapter.

If you choose to go with an aftermarket head unit you will still need to run three sets of RCA cables to the trunk, so you likely won't be able to get away from that unless you want to use the speaker level outputs of the stock amp to feed an aftermarket amp. Though that's less than ideal and complicated because, if I remember right, the stock system independently powers the tweeters. And then you're relying on a 20 year old stock amp to keep working. No bueno.

There is information here on the forum from someone who installed a hidden aftermarket single DIN head unit behind the cd changer door. It fits rather well but that would render all of your stock radio buttons and stock volume **** non-functional. I would hate that and it sounds like you would too. However, you could at least still use the stock steering wheel controls with an appropriate adapter.

The last option I have for you today is to replace the stock head unit with a custom android head unit. I went this route with an LS430 with nav because it's one of the only routes available for those cars. You can get the same android head unit for non nav cars as well. It replaces the entire center console bezel and looks very stock, just updated with a 7 inch touch screen. If you weren't familiar with these cars you'd never know it didn't come that way. The only thing I don't like is that on cars without nav it replaces the AC controls as well, and then you control the AC with software in the head unit. In nav cars this is how they work from the factory so it's not a big deal. However, I like tactile buttons so I wouldn't like loosing the physical buttons for the AC. Maybe you don't mind though.

Below is a picture of a non nav car with the custom android head unit from some random website since I think all of the pictures here are from cars with nav.

In the end though, if you really want to keep a totally factory look and retain usability of the factory radio buttons and volume ****, your only option, at least that I know of, is the AP4-TY11.

 

Thank you for the detailed reply!

Yeah, losing the physical AC buttons would be tough for me. I want my LS to look more like an "ultimate 90s car" than a "proto-2000s car", even though it is more 2000s-like (or even 2010s-like) in reality.

OK, thanks for confirming. I wonder if it's possible to hack up the AP4-TY11's harness to connect it at the amp end of the data cable instead of the radio end? I am also tempted to make an electronics project out of this - surely it can't be too hard to set up a microcontroller that decodes the volume messages from the CAN bus with a voltage-controlled amplifier. Famous last words...

 

Capturing the CAN bus messages and decoding them is very, very difficult. In fact, I only personally know one person capable of doing that. Obviously there are others, but I've never crossed paths with any. If you look at the wiring harnesses for the AP4-TY11, they are mostly very nicely done splices into the factory wiring going into the back of the stock head unit. They intercept audio and CAN signals, sending them to the AP4-TY11 where it does its magic of decoding CAN messages. It also splits the two channel audio signals into six channels and adjusts them for volume, fade and balance according to the intercepted CAN messages.

Now for the complicated parts and unknowns. CAN is Controller Area Network, with a network there is always a host controller, aka ecu, bcm, ecm, etc. In the LS430 I believe there are several separate CAN networks. Somewhere in the car is a CAN controller for the audio system. I don't know if it's in the head unit, in the amp, or in some other module hidden somewhere in the car. I also don't know if CAN messages are addressed like Internet Protocol packets are but I believe they are (someone more knowledgeable in CAN can correct me if I'm wrong). Messages or packets that are addressed will be seen by everything on the network but only read and carried out by the device they're addressed to. CAN devices also talk back and confirm receipt of the message. The factory amp is required to be left in the car and remain connected while using the AP4-TY11. This means the amp and the head unit are talking to each other via CAN and is why I believe the CAN messages are addressed. I'm not entirely sure, but I believe the AP4-TY11 is hijacking the CAN messages going to and from the head unit, reading them, modifying them and sending them on their way, both to the head unit, and from the head unit, in addition to using them to make adjustments to its own audio output. This is why I don't think it's possible to create a device similar to the AP4-TY11 on the amplifier side of things, because the messages need to be intercepted and changed for the head unit.

I could be entirely wrong about the AP4-TY11 modifying CAN messages, however, another reason I don't think it's possible to rewire the AP4-TY11 to live on the amplifier side is that in networking you have transmit (tx) and receive (rx) lines. If you spliced the AP4-TY11 in on the amplifier side it would be expecting to see messages coming from the head unit as tx, but since it would now be downstream of the CAN controller, on the receiving end at the amplifier, and so the messages would now be on the rx line instead. Also, I don't believe the AP4-TY11 is its own independent CAN device because the LS430 was not designed to allow extra CAN devices on its network, because why would it be? That would be a lot of extra software coding for nothing. So it must intercept the messages as I described above, and therefore it is expecting to see a specific message format on the tx and rx lines at the head unit.

Anyways, that's my lengthy theory (theories?) on why the AP4-TY11 has to live behind the head unit and not in the trunk with the amp.

Can you create and code your own device that operates like the AP4-TY11 and have it live on the amplifier side of things? I don't know, maybe? But, if you have the knowledge and ability to work with a CAN network on that level, that's a question for you to answer. For me, I'd just run some nice shielded RCA cables back to the trunk. At least you don't have a UL model.

 

I wrote this thread on aftermarket HU + amp on a 2004 nav LS - the wiring and photos might be helpful for your project. Steering wheel controls are tough. For your other requirements - have you considered using a bluetooth amplifier if you're doing the streaming and calling from your phone?

 

Yes, that does seem to be the simplest option if I am willing to give up on steering wheel controls. I can live without radio, cassette, CD. I'm thinking about it...

 

Don't forget, if you go the route of a bluetooth amp, you loose all factory controls, including the factory volume ****, all radio buttons and AM/FM functionality. 100% of your music selection and volume control will be through your phone. You will achieve your goal of retaining the factory appearance, but at that point I feel like, what for? It will all be dead and non functional. Personally that would drive me nuts. I want every single button on my car to work.

Why not go with the AP4-TY11 like you mentioned originally and retain not only the factory appearance, but also all factory functions? If it's the job of running RCA cables from the dash to the trunk that you're worried about, that's much... I won't say easy, but much less difficult than you would think. The only reason I don't say it's easy is because it's tedious. Nothing about it is actually difficult because disassembling the trim panels and rear seats on the LS430 is very straight forward. And, Mr. Car Care Nut just did a video where he runs the wire for a backup camera from the trunk up to the dash. RCA cables are larger than a camera wire, but they will take the same path. Here's a link to the timestamp where he starts pulling the back seats to pull in the wire from the trunk if you haven't seen the video already.

 

Yeah, I considered a Bluetooth amp but mostly dropped the idea after thinking about the issues you raise. The main point in favor would be no superfluous digital-analog-digital round trips ahead of the amp DSP. Initially I thought using the AP4-TY11 on top of my bluetooth adapter will cause *two* such round trips (one between phone and the AP4-TY11's DSP, another between the AP4-TY11 and the amplifier DSP). But I learned that the AP4-TY11 also has an optional TOSLink module, so if I get an amp/DSP with a TOSLink input, I can send a digital signal from the dash to the trunk. That seems really attractive to me. It will also help avoid noise from running near the amp power cable.

 

Using a TOSLink cable is a good idea, but there are some down sides. The APA-TOS1 module for the AP4-TY11 only has one TOSLink connection for digital output which an optical output. Being an optical cable means you must be very careful not to squish or pinch the cable and it also can not make extremely tight 90 degree bends. If you do, it ruins the cable and light will not pass through. Less importantly, you will loose the ability to control front/rear fade at the head unit and will have to do this at the amp. You will also loose the subwoofer level control feature of the AP4-TY11. The reason for both of these is because the APA-TOS1 puts out "S/PDIF 2 channel uncompressed PCM audio," which is fantastic for sound quality. But, lastly, that means your amp will have to have the ability to take in 2 channel audio and split it into 4, 5, or 6 channels, depending on how you intend to set things up. None of this is particularly difficult, just some things to keep in mind. If you run a separate DSP that has a TOSLink input, it should be plenty capable of multiplying channels. The more I think about it, the more I like this idea.

 

Thanks so much for your detailed responses!!

yeah, I guess I should look at some photos/videos of LS 430 cable routing and see if the bend radius will be an issue. I am surprised PAC doesn't offer a second add-on module for electrical digital output alongside the optical one.

Is this a big deal? I know some people prefer to have no rear speakers at all when there are no passengers in the car. But with the stock system, the rear speakers give a nice feeling of being enveloped by the music. I honestly *never* adjust the balance and fade with the stock system. But maybe that will change with a better system?

But if I get a remote volume control for the subwoofer amp it will be just as good, right?

Yeah, I'm currently leaning towards a 6-channel DSP amp such as the Helix M Six DSP, with a separate subwoofer amp. I thought about separate DSP too, but it seems to end up more expensive and will take up more trunk space.

Me too, I am close to pulling the trigger. Now to pick the amps and speakers...

 

Problem with an all in one amp/DSP is you're married to it can't upgrade the amp without tossing the entire thing. And the more integrated something is the more compromise you get generally speaking so consider a separate amp and DSP.

 

Check the video I linked, at the timestamp Ahmed, aka AMD, aka Car Care Nut, does exactly what you'll need to do in order to run a wire from the trunk to the radio. You can see the entire wire path very well as his videos are always excellent. It may be a good idea to protect the TOSLink cable by putting it in a length of rubber tubing to protect it. Something like a thick walled vacuum hose or small gauge fuel line. Slit the tubing along its length and carefully fit the TOSLink wire inside. That'll at least help protect it from being damaged when reassembling the interior panels around it. When a sharp 90 degree bend is needed, you can sometimes mitigate that by making a loop or coil if there's room.

I don't think loosing fade ability is a big deal. It'll just be slightly annoying to set the fade properly the first time because you'll have to keep returning to the trunk to adjust it. Stock systems are usually set up with proper speaker levels and that's why they don't really need any fade or balance adjustments. Aftermarket components often require some fade tweaking.

If your sub amplifier has a remote level control then yes it'll be just as good as the one on the AP4-TY11.

I don't have any suggestions for amps or a DSP, but for speakers I'm a fan of Morel and JL. Also, you're going to need to go mid to high end on the speakers even with a higher end brand like JL because the LS430 stereo system is/was rather good from the factory, even the non-ML stereo. So, for example, something like a JL C1 may not be an upgrade, or may not be much of an upgrade from stock. You'd likely want to go with C2s or C3s in the JL lineup as an example.