Wanted to fill out the lower end a bit in my 2018. Wanted an underseat sub, not wanting to give up cargo space or take on a custom setup between the trunk the floor and the spare. I read that the kicker underseat didn't fit, and have used a Kenwood KSC-SW11 in a previous car and wanted a similar sound with just a little more oomph. Looked like the Infinity Basslink SM just might fit under the seat (spoiler: sorta does) and got good reviews.
TL;DR
Mounting
Under the driver's seat, horizontally with the controls and inputs at the front. As noted above, it basically fits, but part of the seat mechanism does catch (and scratch) the back left of the sub. Haven't investigated options for avoiding that yet, but note the interference is independent of seat height. Support is needed under the front side of the sub, as the rear sits on a raised section under the seat. I 3D printed support feet for that job, but you could use anything about 3/4" thick.
Disadvantages:
Wiring
Ran a power lead as described in this install video. The wire loom that runs under the door sill goes through a plastic housing under the sill itself. That housing was annoying to pry open, but had enough room inside to run an 8 gauge power wire. There are a couple of good existing exit points from the housing and carpet. Ground was to the bolt shown in the photo, which worked fine without needing to remove any additional paint. Ran a turn-on wire using an add-a-fuse from the existing fuse panel behind the glovebox.
For speaker taps I ran one set to the B-pillar to pickup the rear left speaker, and another set from behind the glovebox to pick up the front right using the wiring colors detailed in this thread. The wires headed from the head unit to passenger side door are pretty accessible on the head unit side with the glove box removed, and the tap wire can be run down the transmission tunnel to the sub and hidden under the plastic. The sub has speaker level inputs for two channels, so both can be used together. I'd intended to tap only one set and started with the rear because it was easiest, and only added the second after getting underwhelming results and reading various threads talking about high pass filtering on the rear channels.
Results
Initially results were completely underwhelming using the speaker-level inputs on the Basslink. Tried lots of combinations of the inbuilt controls on the Basslink for level, bass boost etc. without noticeable improvement. Read a bit about line out converters with processing and decided to try the AudioControl LC2i (and RCA connection) for the AccuBass feature. That made all the difference, which surprised me since I'd expected the speaker level inputs and adjustments on the sub itself to take care of all that.
Had to adjust the bass output level of the LC2i way down -- the Basslink expects 2V on the RCA inputs, and the LC2i goes up to nearly 10V. Used a 50Hz test tone with an RMS AC multimeter and the head unit set at about 75% to set the level on the Bass output, shown in the picture below. No idea how consistent those controls are across units, so that's only to indicate that "surprisingly low" is where I had the output set on the LC2i.
Still playing with the combination of AccuBass, sub crossover and output level etc. But I'm getting what I was after: good fill at the bottom of the factory system with healthy -- not window-shaking -- bass.
TL;DR
- Sounds good, but required AudioControl LC2i adapter to do so
- Fits under the seat, but snags a little on the seat base
Mounting
Under the driver's seat, horizontally with the controls and inputs at the front. As noted above, it basically fits, but part of the seat mechanism does catch (and scratch) the back left of the sub. Haven't investigated options for avoiding that yet, but note the interference is independent of seat height. Support is needed under the front side of the sub, as the rear sits on a raised section under the seat. I 3D printed support feet for that job, but you could use anything about 3/4" thick.
Disadvantages:
- Under seat vent blows onto the sub. I'll likely add something to deflect that airflow at some point.
- Takes up rear seat foot room.
- Requires cutting the factory rear floor mat for best fit.
- You can reach the controls with only minor contortions once the seat is installed.
- With the seat reasonably far back the sub is hidden from view.
- Handy grounding point at bolt on driveline tunnel.
Wiring
Ran a power lead as described in this install video. The wire loom that runs under the door sill goes through a plastic housing under the sill itself. That housing was annoying to pry open, but had enough room inside to run an 8 gauge power wire. There are a couple of good existing exit points from the housing and carpet. Ground was to the bolt shown in the photo, which worked fine without needing to remove any additional paint. Ran a turn-on wire using an add-a-fuse from the existing fuse panel behind the glovebox.
For speaker taps I ran one set to the B-pillar to pickup the rear left speaker, and another set from behind the glovebox to pick up the front right using the wiring colors detailed in this thread. The wires headed from the head unit to passenger side door are pretty accessible on the head unit side with the glove box removed, and the tap wire can be run down the transmission tunnel to the sub and hidden under the plastic. The sub has speaker level inputs for two channels, so both can be used together. I'd intended to tap only one set and started with the rear because it was easiest, and only added the second after getting underwhelming results and reading various threads talking about high pass filtering on the rear channels.
Results
Initially results were completely underwhelming using the speaker-level inputs on the Basslink. Tried lots of combinations of the inbuilt controls on the Basslink for level, bass boost etc. without noticeable improvement. Read a bit about line out converters with processing and decided to try the AudioControl LC2i (and RCA connection) for the AccuBass feature. That made all the difference, which surprised me since I'd expected the speaker level inputs and adjustments on the sub itself to take care of all that.
Had to adjust the bass output level of the LC2i way down -- the Basslink expects 2V on the RCA inputs, and the LC2i goes up to nearly 10V. Used a 50Hz test tone with an RMS AC multimeter and the head unit set at about 75% to set the level on the Bass output, shown in the picture below. No idea how consistent those controls are across units, so that's only to indicate that "surprisingly low" is where I had the output set on the LC2i.
Still playing with the combination of AccuBass, sub crossover and output level etc. But I'm getting what I was after: good fill at the bottom of the factory system with healthy -- not window-shaking -- bass.
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