[citysoundman]

12" JL Audio subwoofer install in a custom built sealed enclosure under cargo panel!

It's been a while since being active here, but I'm excited to share with the group my custom subwoofer installation! I'm an audiophile guy, and installed aftermarket speakers and a 6 channel AudioControl amp in my 2019 Limited as soon as I bought the car. I've been very happy with the setup, but I don't get good bass. Since the pandemic I've been driving much more than before, between upstate and the city, and I decided to add a subwoofer to make my listening more enjoyable

I spent a lot of time figuring out how to do this - I wanted high quality bass response, which needs a good size speaker in an enclosure with some volume, but I didn't want a box taking up valuable cargo space. So using the recommendation of the audio shop that installed my system - who said to put the sub sitting on the spare tire under the cargo panel; and with TONS of design help from experts on the DIYMA forum, I put together an enclosure that fits really well and is large enough to hold a JL Audio 12-TW3 D4. I got an AudioControl LC1.800 monoblock amp to power it.

And WOW I am thrilled with the bass! I was grinning from ear to ear on my first 3 hour drive, cranking up some tunes (probably louder than I should). Here's pics I took putting it together. It's an odd shape: a shallow trapezoid (so that the top panel becomes level), with a cutout extension on the bottom that sits in the well of the spare. This was needed for the speaker to fit and to give some additional volume. The speaker is also recessed quite a bit to allow for speaker movement without the risk of it getting too close to the grill.

This was totally a passion project of mine, something I can now check off my bucket list! Well...not quite yet check it off, cause now I realize that the sound coming out of the factory head unit is kinda crappy and I need to figure this out...but that is for another thread!

 

[citysoundman]

Where did you keep the spare?

Didn't lose the spare! The sub is sitting right on it. That's why the box is so shallow. I put a quick disconnect on the speaker wire in case I need to pull it out.

Not sure why you didn't use MDF wood, but eh it does the job. Looks like you .75 cubic feet out of it right?

Well from what I learned, even though baltic birch is not as dense as MDF the sound of the sub is not gonna be different. The birch is lighter and easier to deal with. Also my friend who cut the wood in his shop uses it all the time and basically threw it in for free. Yeah the volume is very close to .75 cuft, I added some polyfill as well which makes it seem a little bigger.

Hope to read your next thread on solving that audio problem.

What happened was in the process of tuning my audio I discovered the right side speakers connected to the head unit are polarity reversed (front out only). The speaker wiring is fine so I had no idea what was up with that. Turns out Subaru factory head units have a built in all pass filter on the fronts (not rears). I think the intention is to correct phase for the front passengers. But the result is a sound that is pretty processed. This is in addition to high pass filters to protect the OEM speakers. So the low end is seriously removed. Not great when adding a subwoofer!

 

[citysoundman]

That is badass! Very nice work. I bet that sounds awesome!

I was listening to some Aphex Twin which has probably the loudest bass on anything I've heard, and it literally shook the cabin. I was briefly scared, then realized I needed to turn down the volume!

 

[citysoundman]

@OuchDamn,
Yeah I was considering the CV at first, but was quickly talked out of it by my installer friend He said I would not be too happy.

As for the reversed polarity - that's very interesting that yours is correct. What did you use to check, did you do a speaker pop test? I'm running a speaker pop file and checking + or - results on my AudioControl app.

 

[citysoundman]

The cut out in the panel is basically my speaker hole. I have a protective grill on the sub that comes up flush with the panel, and I added that fabric to keep out dust and stuff.

I forgot to mention - even though these front speakers on the right side show negative polarity, they sound in phase. This is what's perplexing. I did some very careful listening to be sure. When I reverse the speaker wiring to give me a positive phase test result, the sound is out of phase. This leads me to believe that something like an all pass filter on the fronts, which was posted by one of the top DIYMA guys (I'm not at all familiar with these filters) may be the cause. At first I thought it was a wiring problem due to my installation (tapping in to the stock head unit to send signal to my amp). And maybe I do have a wiring issue, I'm just not sure what's going on.

 

[citysoundman]

Wow that's a seriously large screen!
Thanks so much for the Kicker info, that may be just the ticket, will definitely look into it

 

[citysoundman]

Kicker makes a device that removes the phase shift of an all-pass filter if you were interested.

Smart Line-Out Converter - KEYLOC | KICKER®

KICKER produces high-performance car audio, vehicle specific solutions, marine audio, home and personal audio, and power sports products since 1973.

www.kicker.com

Just ordered the Keyloc! I think this is going to work...

 

[citysoundman]

I'm with you on this, it's incredibly difficult to grasp - maybe working with the filters directly makes it sink in.
I was also wondering why we both don't get the same polarity results, and the big difference is I have the AudioControl amp. Pretty sure you have no external amp? So my signal is boosted or more present or something. And yeah I'm also not comfortable going with an off brand like that one.
I'll let you know how things go once I get it installed, thanks so much for you help!

 

[citysoundman]

Agreed and I've just started thinking about replacing the HU on my 2021 premium. There are a number of vehicle settings only accessible through the HU, lights, defogger, doorlocks... are these all lost with an aftermarket HU? I believe the Maestro modules only allow the retention of steering wheel audio controls.

-Dave

Good question - Crutchfield has info on Forester HU replacements. You may want to give them a call, their support is very good.

 

[citysoundman]

I like where you located those amps.

Hidden but easy to get to!

 

[citysoundman]

I have no idea whether the OBD serial bus interface connects to the center dash module which contains the clock.

I have the updated iDataLink Maestro and Pioneer head unit. Just FYI, my secondary display has always shown the correct time.

 

[citysoundman]

The Starlink Telematics Unit was removed from my car, along with the stock radio.
Does your car still have the Telematics Unit installed - and do you think it may be what's keeping your clock correct, even during DST time changes?

My telemetics unit is removed too. So it's not that.