Originally Posted by cmusic

I have been studying the audio schematics, speakers, and interior speaker locations for my IS250 over the past few days. I’ve taken the door panels off and looked at what is there. I’ve taken the trunk apart and seen what is underneath. Here is what I have found if you want to upgrade the audio system in your IS.

First off some background on myself. I work as in the outside plant-engineering department of my local telephone, Internet, and TV cable company. My dept. is responsible for the telephone, Internet, and TV cable lines from our offices to the customers. Think of my job as a cross between civil and electronic engineering. I have been in car audio since 1991 and have built many audio systems in many vehicles. I have competed in numerous sound quality competitions in the United States since 1991. I have built and helped build world championship audio systems. Major car audio electronics companies have sponsored me for a few years in these shows. There are several car stereo and electronics businesses in my region that I have worked with in sales and custom installation when needed.

Next don’t try any car audio installation unless you are sure you know what you are doing. A little slip can damage the car and cost thousands of dollars to repair. So it is probably best to leave the installation to a qualified professional (with insurance covering any damage) if you are not completely sure of what you are doing.

If you are leasing you IS, I would check with your dealer on how many changes could be made to the audio system without voiding your lease agreement. Most leases allow the direct replacement of the factory audio equipment (mostly the speakers) if no permanent alterations are done to the vehicle.

Factory system overview

The factory CD/radio is excellent. Currently there are no aftermarket dash kits that allow aftermarket radios to be installed in the IS. I have a limited edition Alpine F#1 Status CDA-7990 CD/radio that was hand built with 1% tolerance parts and cost $3,000 when brand new. It is the best CD/radio that Alpine has ever produced. I hate to leave it sitting on the shelf but the factory CD/radio (either the standard CD/radio or the ML) are so good that any sonic differences probably can’t be heard when driving. I also would lose part of the CD/radio display higher up in the dash (and navigation equipped IS’ might have the display screen problems), the factory cosmetics, the factory steering wheel controls (but I can add a custom electronic part that will allow the factory steering wheel controls to operate the aftermarket deck.), and the factory warranty might be affected. So until some company makes a suitable looking dash installation kit and the proper electronics that would allow the vehicle’s onboard computer system to ignore the missing factory CD/radio I will keep the factory unit.

The factory amplifier is located under the plastic tray on the passenger side trunk floor. There are two available amplifiers, one for the standard system and another for the ML system. The ML amplifier has fans mounted on one end of it. Going from the CD/radio to the amplifier are four signal wires (similar to RCA patch cables), a mute wire, and an amplifier turn on wire. The ML system has an extra digital wire that transmits surround sound information from DTS and DVD-A disks. I thought about cutting the four signal wires and soldering RCA plugs on them to run to the aftermarket audio equipment, but the service manual says the mute circuit wire mutes the factory amplifier when there is no audio signal being sent from the CD/radio. So that leaves me to believe the factory CD/radio can allow static and interference noises to be heard when no audio signal is being played. Most aftermarket audio equipment does not have mute circuits, so the noise could be amplified and easily heard. This requires a different scenario when hooking up aftermarket audio equipment.

The amplifiers in the IS are multi-channel and have internal active crossovers. This means each speaker is powered separately and only plays the range of sounds they are supposed to play. The only exception is the individual door mid and tweeter speakers, which are on the same amplifier channel, use the same wires coming out of the amplifier, and use a passive crossover placed on the rear of the mid to send the correct sounds to the tweeter. The standard audio system has seven channels and the ML system has eight channels.

Since I have the standard audio system I can only comment on the quality of those speakers. The speakers in the ML system are undoubtedly better. The standard audio system’s speakers are made by Pioneer and are of better than average quality. The front and rear door woofers are made from polypropylene plastic which will give many years of use without degrading. The mids are 2.5” paper cones that play from about 500 Hz and up. The tweeters are ¾” polymer domes that sound natural but have limited range above 12 KHz. However I can by the aftermarket versions of the same speakers from a regional distributor. The woofers are about $18 each, the mids are $5.25 each, and the tweeters are $9.25 each. For the standard audio system there is no center channel wiring installed and the center channel grill is not perforated to allow sound through (if you ever do install a speaker there). According to the service manuals there is also no 2.5” mids placed in the rear deck like in the ML system. The 2.5” mids are in the rear doors. There are no separate 2.5” mids in the rear doors in the ML system.

This leads me to the next conclusion about the audio system. The standard and ML systems have separate wiring harnesses. Simply changing out the CD/radio and the amplifier won’t be of any help if one wants to upgrade from the standard system to the ML system.

Installation of aftermarket audio equipment

Starting under the hood the battery terminal has a very convenient top located bolt that a system power wire can be attached to. Space is tight around the battery but there is room for several different types and brands of fuse holders. (Always place a fuse as close as you can to the battery on the stereo system power wire.) Behind the battery is a large 4” rubber grommet with a factory wiring harness going through the middle. The stereo system power wire can be punched through the side of the grommet without affecting any of the vehicle’s wiring. Or a hole can be drilled on right side of the large grommet to insert an aftermarket grommet just for the stereo system power wire. There is plenty of room on the passenger side of the firewall for the extra grommet if care is taken when drilling. The battery does have to be removed to access the grommet area.

The power wire can be run along the passenger side door sill/floor junction. The bottom of the rear seat, and some interior trim has to be removed to run the power wire and additional speaker wires going to the front. Again, if you don’t know what you are doing, let a professional car audio installer do it.

The other scenario I talked about above to install aftermarket equipment with the factory amplifier is to use a speaker level to RCA converter. Converters can be cheap, costing under $10 for some models, but with the multi-channel amplifier one converter would be needed for each pair of outputs. And then each converted output would still only play the sounds the amplifier assigned it to play. I am planning on using an Audio Control LC8 converter. http://www.mobileaudiocontrol.com/ The LC8 will accept four stereo inputs, combine one or more amplifier channels together into one or more outputs if needed, and give a high quality noise free audio output on the RCA jacks, and provide a remote turn on wire for the aftermarket audio equipment. With this unit I can run the mid/high, woofer, and sub speaker wires to the LC8, combine them together into one full range signal, and output the signal to my equalizer, active crossover, and amplifiers. I plan on leaving the rear factory speakers playing from the factory amp, but I could run the rear speaker wires to the fourth stereo input of the LC8 to convert the rear channels to RCA level if I ever decide to install an aftermarket amp on the rear speakers.

There are several other high quality brands of speaker level converters, like JL Audio’s Cleansweep that will undo any equalization done in the factory head unit and give a flat frequency response on the RCA outputs, but it only has one set of speaker inputs and the IS’s system needs something to convert at least three sets of speaker wires if you need a full range signal. There are other companies like Alpine and Rockford Fosgate that plan on introducing converters with built in adjustable equalizers, active crossovers, time alignment, and surround sound capabilities next year.

One thing to remember if using a combining converter is the factory CD/radio’s listening position settings. The settings are Driver, Front, Rear, and All. Use the All setting. The other settings change the digitally delays the sound that is heard from each amplifier channel and speaker to optimize the sound for the particular seat. When some channels are delayed and other’s are not, it can cause the audio to sound weird when combined in the converter. The All setting turns the delays off.

I won’t recommend any brands of speakers, amplifiers, or signal processors (equalizers, active crossovers, ect..). I’ll leave that choice up to the owner. I would stick with the well-known and or high quality brands. Spend a little extra for better equipment and it will be worth it. With a nice car like the IS it would be a shame to put the cheapest stuff from Best Buy, Circuit City, or Crutchfield in it.

On the speakers the front doors can take a shallow depth 6.5” midbass at the bottom. The mounting depth available is about 2.75”. The mid location is very shallow, about 2”, unless you want to cut an extra hole in the inner door metal. The factory 2.5” mid is mounted on a bracket on top of the inner door panel. It is not in any enclosure. A tweeter can fit here but not a 4” mid. In any case a custom mounting bracket will have to be constructed to mount a new mid or tweeter there. The tweeter at the top of the door has to be small to fit inside of the tweeter pod. The rear door speakers are similarly mounted as the front speakers. The center dash location can fit up to a 3” mid without any modifications. On the standard audio system (without a center dash speaker) the center speaker grill is not perforated to allow sound to play through. I would get my Lexus dealer to order the grill for the ML center speaker if you plan on installing a center speaker. The subwoofer in the rear deck is about 7” in diameter and is weak as compared to aftermarket subs. It only plays down to about 30 Hz. I would remove it from the car and buy an aftermarket subwoofer(s) to produce some real deep bass. The rear deck 2.5” mids in the ML system could stay as they are only for surround sound effects.

If anyone has any more questions please feel free to ask me. I’ll try to help as best as I can.

Chuck Music

Originally Posted by quintonj

I have a 06 is250 and I have 3 speakers per door, two in the rear deck and I believe one in the dash. I do have the spot in the dash for one just not a hundred percent sure if there’s sound coming from it. I am just trying to figure out how many watts this system is or what system I have. Not sure if it ml or not but I do not see stamping