# Truck sub rear vs front firing design



## podman (Feb 20, 2010)

Doing a system upgrade to my 1993 Toyota std cab truck. These are the small trucks that put the Toy in Toyota, but they keep on running and saving me money so I can upgrade the sound system. 

Current System (about 15 years old, lacks mid-base, highs too bright and fatiguing)
- Alpine CD HU
- MB Quart 100.03 4inch in dash
- 8” inch JL Audio sub in front firing sealed box

Upgrade
- Eclipse CD7200 mkII or Pioneer DEX-P99RS HU (haven’t purchased yet)
- Boston Acoustics SPZ60 6 inch components in the doors
- 12 Rockford Fosgate P3SD410 shallow sub behind the seat
- Boston Acoustics GT-4100 4/3/2 amp

My current 2.1 setup has the 8 inch JL Audio in front firing typical setup. I have noticed how the sound gets muffled as the bench seat moves backward. Wondering about changing the direction of the subwoofer so it fires back against the back wall of the truck and not against the back of the seat for the upgrade.

Advantages
- protects the woofer more from accidental puncture
- provides an easy way to confirm enough room for driver excursion and an easy way to increase if needed 
- back wall of truck is quite uneven and this would eliminate the need to deal with that
- if enclosure is made from fibreglass there is an opportunity to gain volume as the seat has a small cavity in the lower back area and also under the seat (every bit helps going from 8 inch to 12 inch)
- woofer will be bouncing sound off the metal back of the truck rather the into the foam construction of the seat (not sure if this a plus or minus)

Disadvantages
- would set up more vibration in the cab, there is a sliding window and everything might rattle like hell
- would loose some sound absorption provided by the bench seat foam

There is some info out there about subs in car trunks that can sound way better if rear facing. My conclusion from this info is “Try it and find out” for your application. Before proceeding I wanted to float this idea with folks with experience, maybe someone has tried this before or knows there are good reasons not to do it this way.

Thanks for the great posts and sharing your knowledge!

Advice and experiences appreciated.


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## podman (Feb 20, 2010)

I've looked high and low and found little info on folks trying a rear firing sub enclosure in a truck. I did find one example and his conclusion was that it sounded great but did set up some unwanted vibration. I'm thinking about angling the sub downward a bit and place it close to the floor. That way the area directly in line of the output will be most rigid. And maybe a layer of dynamat would be in order. Does anyone think a 2 inch space between the sub and the rear wall would be too little?

Any input appreciated.


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## badmotorscooter (May 22, 2009)

You would probably have to angle it upward because of the mounting depth. Deaden that back wall and the rear fire sub should not cause a bad rattle. I have not done that in a reg. cab pickup. I always faced the seats and used 2 wood spacers on either side or top and bottom around the woofer to give it room to blow out of. The spacers need to be thick enough to account for excursion limits and long enough to keep the seat back from caving inward. I always made them from scrap mdf.


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## -Kyle- (Feb 5, 2009)

Correct me if I'm wrong, but I think the driver will need to be far enough from the wall to take into account excursion, as well as giving it enough room to load off the wall. I have no experience with it, but I know people who use plexi loading walls don't put them as close to the driver as possible with excursion taken into account. Its worth looking into though, and I feel your pain due to a small truck, because I can barely fit 8's behind my reg cab Ranger seats.


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## Lanson (Jan 9, 2007)

I built an '05 regular cab Colorado, rear fire Fi Audio 10" subs. What a monster! My build thread is in the forums in the build area.

Anyway, even with a lot of sounddeadenershowdown CLD tiles, MLV, and CCF, the back metal still shook to all hell. But the bass was impressive to say the least. I rounded off the edges of the sub box on the sides and top, to create a smooth flow of air out of the loaded area. It protects the subs, and hits very, very hard, but you must:

A: leave enough room for excursion plus a bit more for the loading effect to go somewhere.

B: deaden the hell out of that back wall

C: Tend to the plastic air flappers that are close to the back wall, as they will flutter when you are pounding away.


You should try to angle the subs back just a bit for a horn loading, which should be more effective still. I've also fired down, and that was impressive too. But the 10" subs couldn't fit that way in this particular truck.


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## -Kyle- (Feb 5, 2009)

fourthmeal said:


> I built an '05 regular cab Colorado, rear fire Fi Audio 10" subs. What a monster! My build thread is in the forums in the build area.
> 
> Anyway, even with a lot of sounddeadenershowdown CLD tiles, MLV, and CCF, the back metal still shook to all hell. But the bass was impressive to say the least. I rounded off the edges of the sub box on the sides and top, to create a smooth flow of air out of the loaded area. It protects the subs, and hits very, very hard, but you must:
> 
> ...


Is there any formula for determining the optimum space needed for this?

Also was the rear window in that truck sliding, and did it rattle like crazy? Thats a major concern for me


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## Lanson (Jan 9, 2007)

kylebigmac09 said:


> Is there any formula for determining the optimum space needed for this?
> 
> Also was the rear window in that truck sliding, and did it rattle like crazy? Thats a major concern for me



It was a solid window, but the flexing was intense. There is no formula, but you certainly are smart to experiment if possible I noticed more output when we cocked the box forward just a bit, so I'd recommend a slight angle to benefit from it. 

If you can get some exact measurements and specs and such, I'll be happy to draft up a design in googlesketch.


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## Lanson (Jan 9, 2007)

I also want to comment on your speaker choice. You mentioned you do not want a fatiguing sound. I'm not saying the Bostons ARE, but you might be better off with something more mellow. Open to suggestions?


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## -Kyle- (Feb 5, 2009)

fourthmeal said:


> It was a solid window, but the flexing was intense. There is no formula, but you certainly are smart to experiment if possible I noticed more output when we cocked the box forward just a bit, so I'd recommend a slight angle to benefit from it.
> 
> If you can get some exact measurements and specs and such, I'll be happy to draft up a design in googlesketch.


Thanks, I may take you up on that. 

I was planning on running 1 8" (SA8, or 1508) behind the seats firing forward between them. The gap between seats is just a hair over 8", so no issue with firing into the seats. Any guess on whether this or the rear firing idea being discussed would be louder?


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## Lanson (Jan 9, 2007)

rear or down firing will be louder. 

You could do a pair of SI BM's, and get VERY loud, very clear, and still very small and light.

I just got my pair and they are awesome looking. Can't wait to get my build done.


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## -Kyle- (Feb 5, 2009)

fourthmeal said:


> rear or down firing will be louder.
> 
> You could do a pair of SI BM's, and get VERY loud, very clear, and still very small and light.
> 
> I just got my pair and they are awesome looking. Can't wait to get my build done.


I was very interested in them for a while but the max airspace I can fit with 12's is like .8 total. Basically I can get more airspace from a deeper, shorter box than a taller, wedge box, which is why I planned on 8's. I'm on spring break next week though so I may go confirm this.


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## Lanson (Jan 9, 2007)

Even with BM's only being a few inches deep?


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## -Kyle- (Feb 5, 2009)

fourthmeal said:


> Even with BM's only being a few inches deep?


Mmhmm. Working with a Ranger is a pain. Right now my box is approx 30" by 7" by 10" with .5 thick mdf and my seat rubs the surround slightly of my e8's. With a box for 12's it would be like 30X13X7,3 and thats pushing it on the top depth. :-\


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## yischrax (Nov 22, 2009)

Yeah from my personal experience is to downfire for best ability as for the hight you have it off the ground a inch or so higher than the narow side of your port if it's a slot port or figure you want enough area open to double that of the area of your cone


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## Lanson (Jan 9, 2007)

If you had quite a bit of available power, 6.5" subs in trio or quartet would be my suggestion. But they soak more power than a comparable 10" would, for instance. The bass is certainly impressive with 3 TB 6.5" subs for example. I did that in a 91 Sonoma, firing down and tightly packed in a 1.1 cubic foot sealed enclosure. Most impressive.


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## -Kyle- (Feb 5, 2009)

fourthmeal said:


> If you had quite a bit of available power, 6.5" subs in trio or quartet would be my suggestion. But they soak more power than a comparable 10" would, for instance. The bass is certainly impressive with 3 TB 6.5" subs for example. I did that in a 91 Sonoma, firing down and tightly packed in a 1.1 cubic foot sealed enclosure. Most impressive.


Hmm I hadn't thought about that before. I looked at the TB 6.5's on Parts Express and the RMS is only 50w. What were you feeding yours?

EDIT: Just did some looking around at 6.5's. However I have a pair of ID OEMv1's I was planning to sell. I may pick up another set and use them as sub duty. Hessdawg said they worked well in very small boxes


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## JLfan (Sep 10, 2015)

I have a rear facing sub box in my single cab ranger. I decided to build it because I couldn't find one. From my experience it seems rear facing subs sound better (with the proper sound deadening) so I wanted to ty it in my truck and it sounds amazing I think. Currently I have one ten and one twelve jlw0v2. I have the ten behind the passenger seat firing forward and the box behind the driver seat fires to the rear of the cab. It works great, all you need are standoffs so the sub doesn't hit the cab. Sound deadening is a must because it will rattle everything. I put semi soft foam in between the cab and the standoffs as well to reduce rattling and it works great.


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## drop1 (Jul 26, 2015)

I don't know how much room exactly you have but if you could get it firing towards the rear with a couple inches of space in it you get more sound. 

I think it would be fun to put like 8 six inch subs down firing on 1000 watts. Don't know how low it would go but it would get plenty loud.


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## JLfan (Sep 10, 2015)

Yeah I have about 3-4 inches now of clearance. I put expanding foam in all the empty cavities in the cab too that helped alot plus some dynamat to the metal, I can't hear rattling from the rear. I did use some silicone to seal around the inside window and any cracks or gaps. I also have 2 6x9s in boxes behind the seat jammed in there and they put pressure on my back windshield and it doesn't rattle much from the outside sounds nice and clean. Now to work on the minor dashboard rattle


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## JLfan (Sep 10, 2015)

I'm going to just go all out eventually and do a blow thru once I've saved the money. I have a few designs for 4th order boxes for either 2,4,or 6+ subs - 13.5s are what I'm going to run


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