Justin Pammer

Yes, you must run a dedicated power lead directly from the battery to the amplifier. It's usually a very heavy wire (mine is 0 Gauge). This was done correctly and so was the grounding of the amp with the initial install, so I didn't have to modify this. When I was initially troubleshooting this issue I followed this lead from front to back. It does not look that difficult to install. There is a very convenient hole in the firewall to get the lead through and running it to the trunk would just require removing the lower door jam trim on both driver's side doors. The rest of the run goes behind the back seats which you will need to remove anyway. If I had all the information up front, I might not have done it at all. I say this for a couple of reasons: I rarely work on cars and I'm a bit intimated to work on something this complex (which is why I hired someone in the first place). I always had this fear that I was going to fry the Nav or something. And it is impossible to not break some little plastic clip somewhere (I broke three during my adventure - make sure you have epoxy on hand). Lastly, I don't know what this does to my warranty, but I suspect bad things. If you're serious about doing this, let me know and I'll post more detailed instructions along with the schematic on a new thread.

I finally got this issue resolved over the weekend. Thanks to everyone for their input. It turns out there were multiple things wrong with the installation that led to this issue. I had this installed at a place called Sounds Deluxe in Clarendon Hills, IL. I wasn’t planning to disclose the installer (or the butcher as I now like to refer to him), but after what I found (and what I paid), I felt I had no choice. To answers a few questions posed earlier in this thread… • I have a 2006 Lexus IS 250 with Navigation System / Parking Assist (Rear view Monitor) / Lexus Premium 13 speaker audio. Nothing has been modified on this vehicle, except the addition of this sub. • I had a Memphis subwoofer amp (Memphis 500:1) installed, with a Memphis 12” dual voice coil sub. This is a mono amp, but requires both a right and left input signal. So, what was wrong? • The left input signal going to the Memphis amp was tied to the tweeter of the left rear door. Subwoofer amps have a very hard time amplifying frequencies in that range. • The right input signal going to the Memphis amp was tied to the woofer of the right rear door. Slightly better than the first bullet, but still incorrect as the Lexus factory amp does not send the lowest frequency ranges to the woofer’s found in the doors, it reserves those frequencies for the down firing sub found in the trunk. • The right input signal’s polarity was reversed. Yes, that’s right, reversed. Slowing turning the gain up on the amp actually REDUCED bass initially as it was cancelling out the factory sub. • The remote lead to the sub was pinched into the fuse box by a fuse. I can’t remember exactly what it was connected to, but it doesn’t matter because it was incorrect. The net affect of all of this is a very weak and unusable input signal to the Memphis amp which means the input gain and the bass enhancer (the bass enhancer can be thought of as kind of a volume control on the amp) had to be at MAX to get any bass at all. Enter the rumbling noise when the car was shut off… Any noise at all on the input end that falls in the 20-200Hz range is going to shake the earth since the amp is set to max output. The fix: Simple really. I took the car apart until I could get at the factory down firing sub in the trunk (you have to get at it from the back seat, but not really that hard). Now you know exactly which wires need to be tapped and can easily deduce the polarity since you can actually see the connections going to the speaker. The butcher spliced line after line trying to find the correct ones. Unfortunately, I found all of his damage, and some of the splice marks weren’t even taped! How could you ever figure out what the correct wires were from trial and error? There’s like 60 wires in each bundle! More than half probably aren’t even for the audio system. Madness. The second part of the fix was to tap the remote lead into the correct line. I took CrunchySkippy’s advice and used a voltmeter to test each line leading to the factory amp until I found what I was looking for. Basically, it breaks down like this: There are four connectors going to the factor amp. The first has four wires, two are “always on” 12V signals and the other two are grounds. The second connector is for speakers. The third connector (which has much finer wires leading to it) is the one of interest. And the fourth is more speakers. So back to the third connector… This connector encompasses all the leads that tell the amp what to do. For example: turn on/off, volume up/down, equalizer adjust, etc. There are two orange leads that go to this connector that will work nicely for tapping in the remote lead. After all these modifications were made, the gain on the amp is at about 5% and the bass enhancer is at 0. So the rumbling/popping is completely gone when the vehicle is shut off (or inaudible). The new remote lead tap probably helped too. And the amp sounds MUCH better as it doesn't have to struggle so hard to produce bass. In hindsight, I never would have done this if I know it was going to turn into such a mess. The butcher assured me that he knew what he was doing, but I think it’s safe to say that wasn’t the case. It’s a bit nerve racking to have a $40,000 dollar car in pieces in your garage. BTW, I was also able to obtain a schematic of most the wiring in this model IS if anyone is interested (got this just after I figured stuff out the hard way). I have it as a hard copy right now, but can scan it in if there is interest. Again, thanks to everyone for their help.

I confirmed that the remote lead does indeed run to the fuse box. This is probably not the best way to have this wired as mentioned. I found the factory amp in the trunk on the passenger side. It's very accessible. I'm trying to get my hands on a schematic, but if I can't the voltmeter route sounds like a viable option. Old Timer: The ground looks good, very solid. Overall, the installation looks professional. I had this installed at a custom car audio place and aside from this one problem, the job is quality. I believe I tested your theory by cutting off power to the remote lead connected to the amp car still on. There is no "popping", the amp shuts down quietly. In fact, this is essentially what the on/off switch does that the installer provided when he failed to resolve this issue. CrunchySkippy: In your last post, you mentioned "Let's hope its not computerized version". I'm not sure I understand what this implies. Are you saying that if it is computerized there won't be a simple on/off 12V DC lead but rather a digital signal that communicates instructions to the amp? Thanks for all the input.

Yes, the amp still has power after the head unit is turned off. My suspicion is that the installer tied the remote lead to the fuse box directly, but I don’t know because I haven’t had it apart yet. I’ll get back once I can confirm this.

Thanks for the response. Let me clarify the circumstances a bit. The noise does NOT occur when the head unit is powered off, but only when the entire car is powered off. There is still 12V supplied to the remote lead to the subwoofer amp for about a second after the engine on/off button is pressed. This is enough time to pick up this audible "signal" that is emitted. Consequently, there is still power supplied to the amp when the car stereo is off. So, turning the car stereo off and then turning the car off results in the same issue. I suppose the only way I'm going to resolve this is to get my hands on the wiring schematic as you suggest. I don't know if this is possible or not. Potentially I could purchase the complete shop manuals, but those typically cost hundreds of dollars...

Hi. I have a 2006 Lexus IS 250 AWD and had a Memphis subwoofer/amp installed in the trunk. It sounds pretty nice, but makes a terrible noise whenever the car is turned off. The installer could not figure out how to fix this and installed a toggle switch so that I could turn the sub off before turning the car off. I would like to come up with a better fix that doesn't require manual intervention. I have the luxury package that comes with the Lexus 13-speaker Premium Sound System. To my knowledge, the issue stems for the fact the amp turns off AFTER a signal is sent through the system whenever the car is turned off. It's this signal that is being picked up by the amp and amplified through the sub. Any ideas?