We have a 2024 Luxury Plus and as discussed in another thread that the Mark Levinson sound system was lacking significantly in the bass department.
I’ve added subs/amps in a bunch of my prior cars (Focus RS, Subaru STU, Civic SI, etc) but am by no means a professional. There are lots of folks with better / dedicated / proper tools/skills/ etc that far surpass mine but wanted to share what it took for me to accomplish this because I’m sure others will put their own spin on it.
My wife and I have always enjoyed higher and stereo stuff and I wanted to put high-end stuff in the truck.
As most of you have eluded I’ve confirmed that the Mark Levinson amp is below the driver seat. There were some other people that indicated it was in the rear hatch, but that is not the case.
For an 1800 W amp it’s pretty small and has a factory 30 pin plug which seems to be a fairly standard Toyota/ Lexus plug used for factory amps. In order to figure out which speaker was for which wire I used a AA battery with wires taped on each end and simply applied them to any of the wires in the amplifier that were not carrying 12 V power. The 30 pin plug has 12 V power on at least two of the far ends so you need to be careful there.
You can buy this plug and a receiver from Alibaba, but it would require manual wiring if you wanted to build a feedthrough plug that you could plug in between the factory harness and then tap off those wires. I thought about going this route so I did not have to tap into a factory wire but elected to tap into the wire due to space constraints and a bit of a time crunch.
To do the install, it required me to build a box which I fit underneath the cargo cover (my choice purely), install the sub in the box and then a standard subwoofer amplifier installed kit, which had all the wiring fuses, etc.
You also need a line converter to convert a speaker level input to an RCA output that goes into the amp. Ground was simply pulled underneath the passenger seat.
The positive wire was fused within 4 inches of the battery and run through the firewall via arguably the most perfectly placed rubber grommet I’ve ever seen ha ha ha. I did not have to disassemble anything to get the wire into the cabin, but did use an electrical fish wire to pull from the inside of the cabin into the battery area in the engine bay.
I’ll add some more detail to this, but I splice into the driver’s lower door speaker which appeared to have pretty good bass range. I deliberately didn’t tie into the subwoofer line because in my experience in my last car, it only received the lowest of the Lowe’s and was missing a lot of higher and base notes. I decided to use the amp and the filters to tune there.
You basically need to tap into two wires for the speaker and run those cleanly over to the line converter. You also need to tap into the remote lead, which is also on the Mark Levinson amp. It is on the smaller plug and simply turns on or off when you turn the car on or off. It’s in one of the photos and is underneath the driver seats plugged into the far side of the amp.
Once you run your speaker and remote wires into the line converter, you then take that same remote wire into the amp, run RCA‘s from the line converter into the amp and then finish connecting power and speaker connections.
I have this set up underneath the passenger seat in the front, and did lift the seat up about a half of an inch with longer bolts and grade 8 washers.
The system really pounds now and actually needs to be adjusted to not overpower the mids and highs.
The one thing that we experienced, which is odd and maybe some experts here could help – when the truck fires up there are a series of low base tones that occur. They stop after about 10 to 20 seconds. I’m wondering if it’s related to the fake engine noise, or some other test that’s being run through the speaker that I tapped into.
Once I tuned the ground switch on my line converter to match the ground wire on my amp 80 to 90% of that went away, but you can still hear it.
Finished location under the passenger seat.
Removing some panels are required to get the carpet loose enough to get under the seat.
Lower kick panel removed for access.
This is the opening on the passenger side of the firewall that I used.
Passenger front seat footwell- before pulling the positive wire thru.
This is the fish wire pulling the positive cable thru.
Had to trim the red positive cover and drillled / screwed / double sided taped the fuse holder to a small bracket by the battery.
Finished install. Wish there was room below the floor but it is taken with other electrical devices. While not perfect- it works with the seat slightly higher now.
Screenshot of the connector from Alibaba in case someone wants to make their own feed thru plug.
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