IS 250F Subwoofer concern
I believe that the 3IS has the same setup as the 2IS. The stock Subwoofer should be a Dual Coil Subwoofer, so it has two sets of cables going to it (two Positive and two Negatives).
You have two options, you can eliminate the stock Subwoofer and use those lines to feed your aftermarket Amp (you will need an Amp that has Active Line IN to accept signals that are already amplified). This will allow you to completely control your Bass.
A second option is to tap on the signals and use it to feed your Amp while leaving the Stock Subwoofer still active (that is what I did on my setup). You loose a little bit of power on the stock Subwoofer but you really don't care as your aftermarket Subwoofer(s) will do the real job.
Your aftermarket Amp should be installed on the trunk, and you will need to run new power cables, one from the Battery Positive Terminal (place a fuse a few inches away from the Terminal) and another for the Ground (Negative) that can attach to the chassis on the trunk.
Finally, the Remote Switch to turn ON and OFF the aftermarket Amp will have to be either a manual setup (you will need to add a switch that you control) or find an aftermarket Automatic Switch that basically detects when there is a signal on the speakers (you would connect it to the Bass signal) and it will fire up the Amp whenever music is playing.
Reason to tap on the stock Amp and not on the Head Unit is simply because the signals between the two of them are digital not analog, so you would need a decoder, software... blah blah... and you would risk to damage your stock equipment.
To find out the correct wires for these projects, go to https://techinfo.toyota.com and create a subscription for 2 days, is only $15 and you will access all the diagrams for every single vehicle Toyota has, including Scion and Lexus. You will need to search for your specific vehicle and look for the wiring diagram for the Sound system. That is what I did and still do every time I get a new Lexus (I lease). I download any diagram I might need.
Good luck.
I believe that the 3IS has the same setup as the 2IS. The stock Subwoofer should be a Dual Coil Subwoofer, so it has two sets of cables going to it (two Positive and two Negatives).
You have two options, you can eliminate the stock Subwoofer and use those lines to feed your aftermarket Amp (you will need an Amp that has Active Line IN to accept signals that are already amplified). This will allow you to completely control your Bass.
A second option is to tap on the signals and use it to feed your Amp while leaving the Stock Subwoofer still active (that is what I did on my setup). You loose a little bit of power on the stock Subwoofer but you really don't care as your aftermarket Subwoofer(s) will do the real job.
Your aftermarket Amp should be installed on the trunk, and you will need to run new power cables, one from the Battery Positive Terminal (place a fuse a few inches away from the Terminal) and another for the Ground (Negative) that can attach to the chassis on the trunk.
Finally, the Remote Switch to turn ON and OFF the aftermarket Amp will have to be either a manual setup (you will need to add a switch that you control) or find an aftermarket Automatic Switch that basically detects when there is a signal on the speakers (you would connect it to the Bass signal) and it will fire up the Amp whenever music is playing.
Reason to tap on the stock Amp and not on the Head Unit is simply because the signals between the two of them are digital not analog, so you would need a decoder, software... blah blah... and you would risk to damage your stock equipment.
To find out the correct wires for these projects, go to https://techinfo.toyota.com and create a subscription for 2 days, is only $15 and you will access all the diagrams for every single vehicle Toyota has, including Scion and Lexus. You will need to search for your specific vehicle and look for the wiring diagram for the Sound system. That is what I did and still do every time I get a new Lexus (I lease). I download any diagram I might need.
Good luck.



