View Full Version : Rear Shelf Sub Woofer in F-body???

06-15-2005, 09:01 AM
Would there be any structural harm done if I cut a 12-inch hole in the center of my rear deck shelf (between the 6x9s) for my subwoofer to mount/play through???

The thought is that the bass (although not directional) would reflect off of the rear glass giving a better bass signal to the interior... much like the 3 JL 10w6s in the back of my Mustang hatchback...



06-21-2005, 01:32 PM
Anyone have any thoughts on this???

Mount sub in rear shelf between 6x9s?
Just put in trunk in a seal enclosure??


06-21-2005, 02:31 PM
I asked about this a while back. Check it out.


The consensus was not to cut up the package tray (more than needed for the roll cage that is! :geek: ) and just build a box in the trunk.

third base
06-21-2005, 03:15 PM
I have seen it done in BMW's and other cars so I don't see what the big deal would be in your car. you could even reinforce if you wanted to. What are you running. it would have to be a free air sub if you didn't build an enclosure for it. I wouldn't use the 6x9's if you were to use the sub there. I would use a pair of 6 1/2's. this would also allow for more metal on the tray( if you haven't already cut them).

06-22-2005, 03:27 AM
I enlarged the 6x9 holes and used to have two 10" Subs in the package shelf in an 80 TA way back in the late 80's with not problems :naughty:

You will get much better sound using a box in the trunk, at the very least make sure you get a "freeair" sub, but base will not have as tight of a punch.

06-22-2005, 03:42 AM
Ahhh crap somehow I missed both threads. Here are your options for both of them.

Option 1
If you cut the hole back there it wont effect the structure enough to even worry about at all.
If you cut the rear deck shelf make sure you build a sealed box underneath it otherwise it will be worthless just sitting in the deck with nothing under it. And I mean it would have to be completely sealed to the package tray. This would be a LOT more work than the next option.

Option 2
Just put them in a box in the truck. (2) 12" subs with a mild amp will be more than enough power for what you need back there especially if the rest of your speakers arent amped inside. You could even get away with (2) 10" speakers. I personally prefer sealed boxes. I have been installing stereos into everything for over 12 years and I have the best performance out of sealed boxes with mild amps.

If you throw the subs in a box in the trunk then you can just mount 6 1/2" speakers in the rear deck shelf.

Just do NOT buy a band pass box! Unless your strictly into bass competition.
That was a quick basic explanation. If you need more detail PM me.

06-22-2005, 06:12 AM
Ive had good luck with smaller 10" bandpass enclosures. Do NOT put the sub in the package tray in a free air situation, the pressure waves from the free air sub will push the 6x9s out of phase, as they are no match for the pulling of the sub. (that compressed air must go somewhere) and it'll sound like crap. Either a sealed box, or a bandpass box is the way to go.

if you get a bandpass, make sure the ports fire tward the rear of the car, not against the back seat. same for the sealed box.

/many IASCA wins talkin.

06-22-2005, 06:32 AM
The best part about electronic components is that you have 30 days with anything. Amps, deck, speakers, subs, boxes...anything. Experimenting is the easiest way to find what you like.
If you listen to rock or heavy metal then bandpass is not the way to go. You get a much cleaner sound from sealed or ported boxes. If you do decide to try bandpass dont go anything bigger than (2) 10" in your car like Tony mentioned. Bandpass boxes generally sound better in bigger vehicles.
I want to avoid a technical debate so as I suggested, just experiment. If you dont like it return it for a full refund. Its not rocket science and the average person can have an incredible system for very very cheap.

06-22-2005, 09:56 AM
TonyL is 100% correct. Put your sub in a sealed enclosure and seal off the 6 x 9's or whatever else your gonna use. Here are a couple pics of what I did using a 1000 watt Xtant amplifer with (1) sub and components. I mounted an mdf board under the package tray using existing holes in the tray itself (someone before me had already cut huge holes in it for what reason I can't think of). An Mb Quart component system was then installed consisting of (2) 6 1/2" drivers w/1" dome tweeters. Each side was sealed underneath. I then used a Boston Pro 12.5Lf because of 1) It's high power handling capability and 2) It doesn't need a lot of space to work efficiently. 1 cubic foot of space on the inside is all you need. The key is CLEAN power to keep from blowing your speakers and the proper enclosure. Mine is not a bandpass enclosure, it's sealed. The sub box was then mounted with "L" brackets to the underside of the mdf board so as not to drill into the trunk, and possibly the gas tank. Just my long 2 cents. Hope this helps.

06-22-2005, 10:47 AM
You could put your speakers there, but you would have to use free air speakers, any woofer you put anywhere in any box in the trunk is going to distort the 6x9's. THe air needs somewhere to go and it will go up through the 6x9's. If you do put the 10's or 12 there you need to buildsomekind of frame, as a matter of fact i would cut out the package tray and build a frame out of wood to put there. Also IMO bandpass boxes SUCK, they seem to only produce one time of bass, that boom-boom-boom bass, the frequency range isnt' very good, and they are heavy and take up tons of room! I woul dbuild a board flush across the trunk and put a woofer in there, and then try to seal up behind it as good as possilbe, that way you still have access to the trunk, or just make it a box. i will try and dig up some pictures

06-22-2005, 02:24 PM
crutchfield makes drop in "enclosures" for six by nines to prevent the woofer cabnet from distorting them. they are very cheap. they look like this

https://static1.pt-content.com/images/noimg.gif simply sandwich the package tray between the speaker and these boxes. (use butel tape for a good seal)

There are many factors to consider both sides of the bandpass/sealed argument.

It is important to understand that the vast majority of bandpass enclosures on the market suck. they are not "tuned" or properly ported. Basicly a bandpass box produces "perfect" bass within a specific range. especially tight, quick bass. Ported bandpass boxes remove all distortion even if the woofer is blowing itself up. (so be careful)

note that bose's subwoofers are ported bandpass enclosures. Most show winners (sound quality) use some sort of ported bandpass enclosure. High db systems tend to use sealed boxes. Again, this is mostly preference stuff. you can get awsome performance from one ten inch sub in a one cubic foot box, if built correctly.

dont forget the "polyfill" in a sealed box.

Pro-touring towncar
06-22-2005, 03:34 PM
Well I'll throw in my $.02. I would just run 2 10" under the shelf firing through the 6x9 holes. In all the compititon cars I have built I haven't used rear speakers. just draws the sound stage to the rear of the car.
Are you looking to use a box for the sub or run it free air? What kind of bass are you looking for? Plus you really don't need big woofers to get great sound. I have used 8" for 95% of my systems. I used a 12" in my world champion, but got better sound out of an 8.
In the town car I am looking at going with 5.1 surround sound running 4 8" in the rear deck.

06-24-2005, 09:04 AM
Wow!! I hadn't checked this post for a couple days b/c it initially didn't get any replies... Thanks guys!!!

Put a Pioneer 6300 CD changer in the dash... (6 disc will go in the trunk once I find the brackets to mount it). For now I just wired up the 6x9s in the back... planning to make an MDF panel for under the rear (metal) shelf to mount the speakers to... I do have the 6x9 boxes already too if I need to use them to separate everything... so, box the 6x9s or free air the 6x9s into the trunk?

The plan (or questions) was about mounting a 12" sub in the center of the rear shelf between the 6x9s in a sealed enclosure and bouncing the bass off the back glass... what do you think? (I prefer sealed boxes!)

Or should I just put it (in a sealed enclosure) in the trunk??

Either way this quick little "tunes" install has me scraping the old factory sound deadener off the rear metal shelf and replacing it with Dynomat! I've also order a ($6) factory trunk divider for behind the back seat.

The plan this weekend is to finish the stereo install and put the rear seat and panels back in... then I have to figure out what to do for front speakers next!! LOL Use the 4x6s I have or get the aftermarket
dual 4" setup for the front center of the dash?

I had all the stereo stuff already setting on shelves in the garage...
Pioneer 6300 head unit, 6 disc, Pioneer 6x9s, 6.5s, 4x6s and a 12" sub.

The rear deck shelf still has just the factory 6x9 cutouts...

Should I mount the 6.5s in the rear seat panels too or is that overkill?

Thanks for all the input!


06-24-2005, 09:22 AM
Oh yeah...

The amp is a JBL 400w with built in cross overs...

I'll run the 6x9s at 100w RMS each and then the sub at 200w mono.

The front speakers will run off the head unit's 50w x 4 RMS.

Should I put the 6.5s I have in the rear seat panels too?
Run them off the heads unit's rear 50w's each...

I have another JBL 400w amp running two JBL 10s in a sealed enclosure in my daily driver 04 Grand Cherokee with the factory Infinity system... sounds great!!!

I'm not looking for a competition sound in the Firebird or to blow the back glass out of the car... just thought that bouncing the bass off the back glass would sound good. I have 3 JL Audio 10w6s running 200w each in the back of my 93 Mustang Cobra and they hit REALLY HARD!!!

I'm just looking for some good strong tight bass fill in the Firebird...
I'd run two 10s but I already have the 12" sub laying around from a previous car... as with all the other Pioneer stuff...

Just wanted to put a good system in the Firebird with what I had...

Your thoughts/advice are appreciated!

06-24-2005, 12:09 PM
Most systems Ive heard that had the bass firing into a window sounded distorted and there were lots of resonance problems. you'll probably be better off putting in a box in the trunk and firing rearward.

06-30-2005, 06:46 AM
Thanks for all the input!!

I've decided just to run the single 12" sub in a sealed box in the trunk.

Do I need to put the 6x9s in boxes (I have them) to prevent the bass in the trunk from blowing up through the 6x9s?

Should I put the 6.5s I have in the rear seat panels (next to your hip if you're setting in the back seat) or is that overkill since I'll have the 6x9s in the rear shelf?

I can run the fronts and 6.5s in the back seat off the head unit and the 6x9s and the sub off the amp.

Please let me know your thoughts as I'd like to get this wrapped up over the long weekend.

Happy 4th of July everyone!


06-30-2005, 10:02 AM
Yes you should seal the 6x9 off one way or another otherwise the air from the 12" sub could fight the 6x9 speakers especially if you have a really tight sealed trunk. There are many ways to seal the 6x9 speakers.
To answer your question about the 6.5 next to your hip in the rear facing forward. You could do it if you want but its not necessary at all.\
I try to keep up with this thread as much as I can but cant catch everyones questions.

06-30-2005, 10:30 AM
agreed that the mid bass needs will be met by the 6x9s. That should do fine.

07-02-2005, 07:53 AM
Thanks for your replies... I plan to get the stereo install complete this weekend. Still don't know about putting the 6.5s in the rear seat panels though... I've got them... and already have the wires run from the head unit so I might as well I guess... maybe I'll put bass blockers on them too since I'll have the 12" sub in the trunk in a seal enclosure.
I'll try the 6x9s (full range) with and without the boxes and see how they sound...