honestly, I wouldn't do it. I feel like the fact the trunk will be a resonator after the port but mostly not after the sub will make the bass feel very slow and boomy/uncontrolled. this design works well in a home or open car, a boston acoustics home sub I played with was lovely with sub front ports back, but with all the boundaries in a car I cant see it being the best idea

 

In an open air situation, it doesn't really matter what direction you face the port relative to the speaker. In a car it makes a difference because loading effects can drop effective tuning and there's other issues with resonance, noise, etc.

I don't think firing back will be an issue, and using the trunk to load the port usually works really well. I think the bigger issue is firing the subs forward. The location could lead to nodal problems above tuning where the speaker acts as a direct radiator. It might happen, might not, but from my experience the closer you move a sub to the center of the car and away from any boundary the more problems you have.

 

Thanks for the input guys. My budget is just tight enough that building a box only to find out it sucks or causes tuning issues is something I would rather avoid. I will scrap these plans for now and just go with the standard rear firing speaker and port design. Thanks again.

 

Like SPL Eclipse said - front facing subs might be a problem,....usually rear or up facing subs works best...., except in limousine type of vehicle they might do good with front facing subs

 

Instead of opening a new thread I thought I'd ask here, as I have a similar question.

I'm trying to design a slot ported box for 2 10's, firing towards the rear. I'm planning to have the slot port utilize the rear (slanted) wall which is against the rear seats.

Should the port opening be on the same baffle as the drivers (it'd be slot port, driver, driver as seen from the rear) - or - can it be on the side, with the opening towards the side of the vehicle?

Does it matter?

 

it'll be different with every vehicle. If you have a test sub and sealed box, just fire it every direction possible and see which is the loudest and fire your port there. In a hatch it could be sub up port back or sub back/up port to the side or sub up port up

 

It matters, but how much in each application, I do not know. I know that the biggest SPL monster SUVs get the most bass when the subs fire up with the ports firing to the tailgate, but that is a very different environment than a car's trunk. I have also seen rear firing subs with the port going upward through the rear deck to fire against the back window. To me this would seem like a good idea since you don't run into an issue of the tuned frequency being muffled, but I lack the actual experience to say if it is better than other placements.

 

it depends on each car. My buddy did that and lost all output due to phase cancellation issues. Its gonna be the same thing with your original idea, phase cancellation.

The only time subs foward port back is in a burp box on a honda CRX hatchback which is the famous setup for high 160b burp setups.

Other configurations that work well in trunks are:
-box pushed all the way back to the trunk lid, subs fire to the cabin, side ported.

-Port and subs firing into the cabin completely sealed and walled off from the trunk i mean you need to seal the rear deck too. Nothing can leak back into the trunk or else cancellation happens and you lose all output. This orientation gives the cleanest sounding bass imo and gets the loudest next a walled car.

-typical rear port+sub fire close to the trunk lid about port width away.

- for pure SPL purposes, box close to the trunk lid, subs up port firing to the cabin this is terry brock's 160 db trunk setup.


Now if you step away from bass reflex and go down in cone area a bit, you can do a 4th/6th(depending on subs used) order blow through the rear deck and open up many other options.

 

I had great results with 2-12's front facing in the fold down seat opening with large slot port between them. Would use it in all similar SQL applications as it eliminated trunk rattling which is an annoyance to other people trying to listen to the music as I drove down the street.

Rebounding anything off the rear trunk compartment and then back to the cabin in a coupe/sedan is asinine IMO. Hatch or completely open cabin, sure...

Unless you're driving a school bus or older jeep, front facing rebound is going to hit the windshield and be forced down to the operator in most applications based on that reflection angle.

 

port firing rear close to the trunk lid is definitely a rattle trap but if you have it further from the lid or facing in to the cabin far away from the trunk lid THIS happens. Phase cancellation where you literally lose 3-10 db easy in total output.

 

some examples of good placement and bad placement.

 

Is the red line the interior of the trunk? Black rectangles the drivers? Or the ports?

 

What having the box against the rear hatch and downfiring in an suv?

 

as long as the downfiring sub is not too close to the front, you should be fine.

Whenever you have bass in the front, it'll reflect off surfaces to the front and travel to the rear meaning the rear hatch would be the loudest spot in the vehicle if the sub was underneath the driver seat. If the downfiring sub was underneath the 3rd row seat or cargo area of an SUV that would offer the best output for people sitting in the front seats. Basically the further away the port and sub is from the listener, the fuller the 1/4 wavelength develops.

Against the rear hatch or anywhere to the rear of the vehicle offers best loading with minimal phase issues as long as the port has room to breath.

 

I'm actually thinking about putting the sub box as close to the rear of the cargo area as possible and putting stuff between box and folding back seats instead of between the sub and rear hatch. The sub would load better and I rarely pop the hatch anyway. Sure makes more sense than having the box pushed up against the back seats and putting stuff I rarely use between the sub and rear hatch.

 

Lots of activity on this thread since I last checked.

As I am a family guy (and non-animated) with two kids, options like putting the sub against the very rear, dropping the back seat or completely blocking the pass-thru aren't going to work. It's also the reason I only run a single 12" instead of two. I quite simply need to maintain some trunk space for band instruments, beach gear and other stuff. Of the positions illustrated in the above image, only #3 really works for me. The downside of this position is that I will have to build another fiberglass box. I dread this idea as three days after I built my first and last fiberglass box, my '99 Jimmy quite unexpectedly had the main bearing sieze up and kill the engine. I am not usually given to superstition, but the timing was very suspicious. This will also mean sticking with a sealed enclosure design, which is fine as I actually tend to prefer the SQ of a sealed over the SPL boost of a ported box, but every once in a while I like to play with port tuning and design just to expand my knowledge.

 

I have 2005 Toyota sequoia that built a platform with shelves underneath. I removed third row and second row seats in place. Want to install sub essentially behind driver side second row seat. I was going to seal platform and have very close to dimensions for 10” sub. Was going to install sub in up firing direction. Any problem with my plan?