# 2006 Lexus IS250 IB Sub, Factory integration, Amp/DSP replacement



## annoyingrob (Aug 24, 2007)

I picked up a new(ish) car a few months ago, and it's a little lacking in the stereo department. I present the guinea-pig, a 2006 Lexus IS250










Now the stock audio isn't actually THAT bad, but it has a few things I wish it did better.

What it has:

6 CD changer in dash, with MP3 support
Aux input in center console
Active 2 way in each doors, with a passive mid/high pair and midbass
factory subwoofer in the rear deck
DSP to do phase alignment for various seating positions

What it's missing

More bass. Factory sub rolls off a little high, and is a little weak for my liking
More volume. Each door's only running about 40w, and the DSP compresses the signal as volume is increased to prevent clipping, which I don't like much
Better imaging. They've done a pretty good job, but it pulls a little too much to the passenger side for my liking

So what's the plan?

Utilize equipment I have around the garage
Replace the factory amp/DSP with a mini-dsp and my own amplifiers
IB Subwoofer through the ski passthrough
Retain a factory appearance, especially the dash (No head unit replacement)
 All changes must be reversible. Plug and play would be nice.


There's just on problem. All of the audio equipment in the car is inter-connected through a communication network. There's no such thing as a fading audio signal to feed into an aftermarket amplifier. Any research on aftermarket installs in the 2nd gen IS leads to one of three options

Stock audio is fine, leave it alone. I don't agree. It's good, but not good enough.
Take all of the amplified signals, knock them back down, feed them into a DSP that can sum them, flatten them, and send them back out. I don't like this either. First there's a lot of pieces in that signal chain, and you can't bring back a lot of the <30hz information that the factory DSP filters out.
Replace EVERYTHING. That goes against my requirement to retain factory appearance

There's a fourth option too. Reverse engineer the communication protocol, build a device that can sit between in the bus and translate messages between the minisdp and rest of the audio network for a complete plug and play factory integration. That doesn't sound like an option either. Except for this silly EE degree, and extensive C/C++ experience I have........










Step one is to figure out where the bus is, and what the signals look like. It's a differential signal bus, I'm feeding it into a comparator to convert that into a TTL signal, which is then fed into my logic analyzer. Utilizing what limited information I find on the internet, I wrote a plugin for my analyzer that could decode the data packets, and present me with a timeline of the communications











I'll get back to the software in a bit, lets start making some hardware! First the subwoofer. I'm going to be using an IDMax12 


















































































Carpet wasn't picked to match, I just used whatever I had lying around









Shockingly close. The colors compliment each other quite nicely



























Painted the MDF









The result from within the car









Distro blocks were mounted to a board and carpeted despite the fact that they will never be seen.









One of the few modifications done to the vehicle, I installed two nutcserts in the rear deck for the distro block board to screw in to. This is tucked up nicely above the carpet in the trunk. Power wire was ran, but it's not interesting. I'm using my favorite power wire: Whatever I can pull out of the junkyard. This wire in particular is some 0-gauge out of a mid 90s BMW 328 for the power, and some left-over 2-gauge out of a mid 2000s BMW X5 for the ground. Cost, about 4 bucks each because it's a "Battery Cable"









The amplifiers are Elemental Designs, a Nine.1 and Nine.4. As far a modern amplifiers go, they're a little big, but they make lots of clean power. The board underneath will be the amplifier rack bolted to the top of the trunk. There's JUST enough room.










Back to factory integration. What we have is the final board, partially assembled. I tracked down the OEM connector for the communication bus (it's a 24 pin, and not commonly listed anywhere). From there we talk to an NEC UPD6708 IEBus controller. The Toyota AVC-LAN (Audio Video Communication Local Area Network) is implemented on the NEC IE-Bus. Think of AVC-Lan as layer 3, and IE-Bus as Layer 2 and 1. The UPD6708 is quite hard to come by, Renesis stopped selling individual transceiver chips after they merged with NEC around 2010, and before that nobody would really sell them unless you wanted 2500 or so. I pulled mine out of an old Toyota radio. That is then interfaced with an Arduino Nano. Specifically, a cheap $2 clone of an Arduino Nano. 









Side note, I love Arduino as a hardware platform, but hate the IDE and the hardware abstraction layer they add. Plus, as much as I love C++, I would argue that it's too bloated for a 16MIPS processor with 2k of ram. I prefer to program these things in raw C, and flash them myself. 

Going back to the amp rack, Elemental designs switched their connector blocks midway through production. My Nine.1 has the standard barrel terminals with set screws, but the Nine.4 has spade terminals. Very large spade terminals. 4ga wire doesn't fit in them nicely. I figured to see if I could make a large spade terminal out of a formed piece of copper pipe.


















Moderate successful prototype.









Finished terminals. Note that that's 4ga wire.









Test fit of the amp rack. There were actually some threaded nuts welded into the rear shelf, so I drilled a few small holes in the trunk carpet, and bolted the amp rack to those nuts. It fits, but it's too tight for my liking. I ended up replacing the bolts with some threaded rod, and dropped the rack down another inch or so. Side note, the factory subwoofer is behind this. I removed the subwoofer, and blocked off the hole from above, but I don't have pictures of that.


















Amps test fitted.









Shot from outside. You can see that the amp is pushing up on the carpet causing it to deform a bit on the edge. That's been fixed with the amp rack dropped down an inch.









Largely finished board integrated into the minidsp. 









Test fitting a wiring harness to connect back into the factory wiring for speakers









Testing and preliminary tuning.










What's been done after pictures?

An additional harness with speaker wires and RCAs was run behind the carpet to finish the amp wiring. I don't have any pictures, I just finished it a few days ago. Software is functional, it handshakes with the head unit, receives volume commands, interprets those into an analog voltage (0-3.3v) that is feeds the MiniDSP's volume pot input, and responds back to the head unit with the current volume. Everything works as intended. 

I ran through a preliminary tune this weekend, running 2 way active to the fronts (midbass and midrange/tweeter). Subwoofer and Midbass share the same signal, and use crossovers on the amps to further split the signal.

The result?

Bass. Oh my god! The IB's LFE is incredible. No more boxes for me now. I made one mistake though. I didn't give the IDMax enough clearance for full excursion. It's not a problem for 99% of my listening, but really driving it hard around 15hz will cause the cone to push into the mounting flange. This can be remedied with an additional MDF ring though. I'll make one up whenever I get around to it. For the time being, it's been gained down, but it's still an excessive amount of bass for pretty much everything. I love it.
Now that I can adjust the phase alignment, the imaging is right where I would expect it, dead center of the windshield. Stage is a little wide, but I'm working on it. It's worlds better than "Passenger air vent" that it was before. I can't get over how much improved the staging is with a little control.
Clarity. So much more power to the front stage, and no more compression when volume is turned up. 
 Everything looks and feels like stock. The factory integration was a big success. I had actually implemented the bass/treble controls to turn on/off the amplifiers too (Bass 1 = Bass amp on, Bass 0 = Bass amp off), but I got too much noise crossing the MiniDSP's power isolator, so I removed it. 

The sound is night and day difference. I've had a few people at work ask about it, and because it's all plug and play, I can demo the old equipment compared to the new with about a 30 second cable swap (minus the factory sub, which is removed). Even people with zero audio experience are able to immediately pick up "Hey, this is really clear", and "Wow, the singer is RIGHT THERE!", and then the obvious wanging out with some really deep bass where everything seems to shake.

What's next? The MiniDSP 2x4 is going to be replaced with a 6x8 at some point. I want to split the passive mid/tw channels into a fully active 3-way, as well as have a dedicated subwoofer output rather than the midbass channel doing double duty in the processor. Plus, the 6x8 has programmable configurations which I can integrate into the head unit's dsp mode button.


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## carlr (Feb 27, 2011)

annoyingrob said:


> I prefer to program these things in raw C, and flash them myself.


+1 buddy


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## cmusic (Nov 16, 2006)

Sweet install. I've got a '06 IS250 that I've had since new. For several years I tapped into my non-ML, non navigation line level signal wires that run between the head unit and the amp. The tapped signal is ran into a JL Audio volume controller, which I mounted the knob just to the left of the steering wheel. I then ran the signal to a JBL MS-8 DSP and onto the after market amps. 

The factory speakers are made by Pioneer and are better than the generic factory amp and built in DSP let them be. I too found the sound stage pulled to the right from the driver's seat. The front doors can take a new midbass, but the speaker has to be 2-1/2" or less in depth while using a 3/4" mounting ring. 

Currently I have the factory deck moved to the glovebox. Remove the factory radio and the HVAC shuts down. Some installers have removed a circuit board in the radio and plugged it up to the factory wiring harness to get the HVAC working again. I did not want to do that since buying a replacement factory deck from my Lexus dealer was priced to me at $1500. There is now a plug in module made to allow the factory radio to be completely removed and retain HVAC function: http://www.beatsonicusa.com/slx-140l.html and Lexus IS 250 2006

In the factory location I currently have a Pioneer DEH-P99RS deck feeding Alpine PDX-F6 (150x4) and a PDX-M12 (1200 mono) mounted under the front seats. I have Scan Speak 7" Illuminators mounted in the kick panels after I relocated the factory wiring. I have a Scan D3004 tweeter in the door midrange location, but I may be replacing the tweeter or moving it to a new location in the future. In the trunk I have an Alpine Type-X 10" in a 1 cu ft sealed box firing towards the rear of the car. 

I really like your IB setup with the ski hole mounting. I had never though of doing IB in that way. 

I've only got 102,000 miles on my IS but I have had it almost 11 years. The only things that have broken on it are: 1. the factory CD player (which was replaced under warranty), 2. the rear brake light switch on the brake pedal, the alternator (at 98,000 miles), and the mass air flow sensor (at 99,000 miles). It runs 99% as good today as when I bought it. I've always used full synthetic oil and 93 octane premium gas. I still get 33-34 mpg on the highway. I only got 26 MPG when I tried 87 octane in it one time. The engine is high compression and needs the higher octane to run properly or the engine management computer will "de-tune" the engine to stop knocking with lower octane ratings. I'm wanting to buy myself a new vehicle (looking at a 2017 GMC or Chevy truck) but my wife says I need to keep my IS until it breaks down. At this point, I don't think it ever will.


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## Knobby Digital (Aug 17, 2008)

Congrats on the car and successful sub integration! I'm also an IB convert.

Having owned the same sub, when looking through the pics, I could foresee that the following would be an issue:



annoyingrob said:


> I made one mistake though. I didn't give the IDMax enough clearance for full excursion.


They have more than 1" one-way excursion. Good thing your realized it before anything too bad happened and had to spend on a recone.


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## annoyingrob (Aug 24, 2007)

cmusic said:


> The factory speakers are made by Pioneer and are better than the generic factory amp and built in DSP let them be.


My personal opinion is that factory speakers are rarely the weakest link in any audio system, especially in a luxury vehicle like this where the manufacturer has gone a step above what would normally be found in a more cost-effective automobile. Increasing power, and limiting bandwidth will usually provide a significant improvement in sound quality. I am extremely impressed with the quality of the speakers this car has, which is why I made no mention of replacing them yet. I still need to tweak the EQ, the tuning so far has only been phase alignment and crossover (I like to get the sound as close to the curve as possible with just crossover tweaking), but RTA measurements are showing a decently flat response. 

As for the car, this one has about 110k on it, and has also been rock solid since I bought it a few months ago. I do all of my own maintenance so it was a little bit of a jump from my last vehicle which was an 86 Toyota Pickup with a Supra motor. A lot more computers in this one. 17 ECUs last time I counted. Fortunately I like computers. The only thing I needed to do to this car was replace the wheel sensors, which wasn't a big deal because I could reprogram the new ones into the computer. And yeah the motor is no joke. 12.5:1 compression. Granted the 4GR is fully direct injected, allows it to run such a high compression ratio. 

My father drives an 06 BMW 530, and still can't get over how much more solid the Lexus feels. Even after 10 years there's not a single rattle, or worn out item save for some worn text on a few of the radio buttons. Meanwhile he's spending thousands every few months on replacement everything.



Knobby Digital said:


> Congrats on the car and successful sub integration! I'm also an IB convert.
> 
> Having owned the same sub, when looking through the pics, I could foresee that the following would be an issue:
> 
> ...


Yeah, off the top of my head it's about 24mm for the V3? I knew this, but I honestly didn't think it would be a problem. I've never had the cone move significantly in its previous install ( 2.4cf ported to 32hz ). ah well, it's an easy fix, and no damage done.


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## annoyingrob (Aug 24, 2007)

carlr said:


> +1 buddy


Interesting fact, I used to just use raw ATMega328P chips for development, and then I picked up a few of these. I had to change nothing in my development process other than target an arduino bootloader as a programmer in avrdude rather than my old programmer. The old hex files still work perfectly. 

Now I have a 328p, oscillator, usb to serial converter, voltage regulator, and bootloader all pre-packaged in a DIP board for less than the cost of a raw processor. 

As for C vs C++, I develop C++ professionally so I'm extremely used to the language, but I can concede that there are advantages and disadvantages to both. Neither is "The best", it's all application specific. For an embedded system where every byte of ram, and every clock cycle is important, I want complete control over absolutely everything. 

And as for the Arduino project, yeah I see what they're doing and I applaud it, but come on man, give me access to hardware SPI, seriously.


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## mfenske (Feb 7, 2006)

Do you think you could replicate your interface? If so what would you charge for something like that? I'm looking at a 2015 GS 350 and I'd guess it has a similar setup?


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## annoyingrob (Aug 24, 2007)

The IEBus controller is really hard to find. You're either manually pulling them out of old equipment, or you're buying gray-market chips from China. That makes any sort of large-scale production impossible unless the board is re-designed to use an alternative means of IEBus interfacing, like Renesis' own controllers, or just bit-bang the whole thing in software through a CAN-Bus tranciever. The former significantly increases the cost, the latter significantly increases the complexity of the software.

Beyond that, yes I could theoretically replicate it in small quantities, but it isn't worth my time for anything under a grand, and at the point you're probably better off buying a more robust DSP, and doing some of the alternatives like a remote volume knob, or summing the factory signals. 

I'm not interested in trying to make these for profit, but rather to challenge the concept that that to obvious solutions found on the internet are not necessarily the only options. 

I wish you the best of luck on your install though. The 2015 GS is a very sexy car.


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## MatGO (Feb 19, 2017)

How did you solve the balanced to unbalanced signal conversion?


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## rakitko (Sep 19, 2017)

Great work, I sent you PM.


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## SilentWrath (May 23, 2017)

Uhhhhhhh..... wow.! 

This is one of the coolest, most innovative things I've seen in a while! 

Love seeing someone think outside the box!


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