This post describes the process of replacing the factory sub. First, the factory sub is mounted in a plastic enclosure right over the left rear tire. The largest sub you will fit is an 8” with a mounting depth of 3 ¾” but there is a catch: the sub enclosure curves over the wheel well, hence some subs with large magnets will not fit. I discuss how I resolved this issue with the 8” JBL sub I installed.

First you need to get to the sub enclosure. Here are the basic steps to do that:
1. Remove the rear floor in the storage compartment.
2. Remove the cover over the spare tire.
3. Remove the small 2-bin storage compartment behind the back seat by removing the 3 nuts (10mm socket) on the side facing the spare tire, then popping it straight up.
4. Remove the upper trim on the headliner (in the rear) by popping it straight down (4 clips hold it in place).
5. Remove the lower trim by the hatch latch by popping it straight up (more clips hold it in place)
6. Remove the upper and lower rear screws (torx) securing the left rear passenger seat belt.
7. Above the upper seat belt mount is an oval cap. Pry off the cap and remove the screw (7mm socket) behind it.
8. Remove the three oval shaped cargo clips (10mm socket) from the left rear panel.
9. Remove the two push pins from the left rear panel (located about mid way up on either side of the sub).
10. Pry the upper portion of the rear panel above the sub away from the car and remove it. It is held in by clips on either side of the window.
11. Remove the lower panel by prying it away from the car. Note you need to clear the metal loop that secures the rear seat in the upright position.
12. Remove the 4 screws (10mm socket) that secure the metal brace in front of the sub enclosure.
13. Disconnect the connectors going to the factory amplifier.
14. Remove the 4 (?) screws holding the sub enclosure to the car. Remove the enclosure and set it on a flat surface.
15. Remove the screw behind the sub enclosure holding the back of the sub in the enclosure.
16. Remove the 8 Phillips head screws from the sub.

You should now have something that looks like this:

 

I wanted the flexibility of being able to use my existing 12” sub in an enclosure when storage was not an issue, and the 8” in the factory enclosure when the 12” was removed. Since my amp puts out 200 watts RMS, I selected a JBL GTO804 sub due to its power rating and efficiency. This is what the JBL looks like compared to the factory sub.

 

The JBL is too deep to fit in the factory enclosure. To accommodate the extra depth I made a spacer ring from 5/8” particle board. I used RTV and 8 screws to mount the ring to the factory enclosure. The JBL has large speaker terminals that would not fit in the spacer ring. I cut a notch in the ring and the factory enclosure to make clearance for these terminals. I also drilled a small hole to run the speaker wire out of the enclosure (I did not want to use the factory’s 22 AWG wire to power my sub). Here is a picture of the spacer ring:

 

Even with the spacer ring the JBL would not fit in the enclosure; the metal basket was hitting the curved portion of the factory enclosure. This required cutting a portion of the speaker’s metal basket. Note only the basket was cut, not the magnet.

 

Finally I lightly stuffed the factory enclosure with acoustic insulation, then mounted the JBL to the spacer ring using speaker caulk (a gasket material) and 8 screws.

Note, the JBL logo does not appear in the correct orientation due to the speaker terminals hitting the factory enclosure.

 

I installed the sub enclosure back in the car, installed a metal grill over it, and fired up the system. The JBL speaker moved so far it hit the grill. I made a ¼” spacer ring out of plywood and installed it between the speaker and the grill. I then reinstalled everything in the reverse order it was removed.

I plan on using the 8” JBL when I need storage space, and a 12” Sony sub in a single enclosure when space is not an issue. I installed a ¼” audio jack in the back of the HHR for the 12” sub. When the 12” is plugged into this jack, only the 12” sub plays. When the 12” is removed, only the 8” sub plays.

Now it was time to compare the sound performance of the 8” JBL sub versus the 12” Sony sub. This JBL rocks in the car! Using a 80 Hz low pass filter, this speaker produces very tight and clean bass, better than the 12” Sony. The Sony is definitely louder and rocks the HHR more than the JBL, but the bass is not as tight. After listening to both subs for extended period of time, I actually prefer the sound of the 8” JBL sub over my 12”.

You can buy/mount subs in the HHR that will provide more bass and performance than the 8” I installed, but if you are only looking for a reasonable level of bass (read does not blow the glass out), a properly installed 8” should provide what you are looking for!

 

i have a question other then that metal bracket does anything else hold the sub in place go the sub box off ebay its off at the shop having a better sub put is but i don't want to have it all taken apart and found out i need more parts to bolt in any help?

 

The sub enclosure bolts to the frame with several bolts. The metal brace that goes across the front of the enclosure has the holes for the push pins that secure the trim panel.

 

Are you pushing your new 8" with the stock amp? Or do you have it on the same amp you push your 12" with, assuming you have an aftermarket amp for your 12"?

The way you describe that 8" sounding is exactly what I'm looking for... nothing overpowering, but more consistent and tighter, and I want to feel the 30-50hz range.

 

same amp i was pushing my 12 with no stock amp 1lt setup