First Walled Off Trunk Design

[SimulatedZero 10+ year member]

Ok, so I'm looking at tackling my first trunk wall build. I'm not quite settled on building the box into the trunk or having an insert box and attaching it to a wall built into the car. Leaning towards a complete build in.

What should I do with the port?

I've read about some people firing the port through the deck and some not. I know if I have the port too close to the seats, it'll effect the tuning and the performance. So I've also thought of doing a center port and having the wall recess to it to give it some breathing room.

My goals are too limit vehicle modification as much as possible and to limit performance loss with the seats up.

I realize there will always be some loss with the seats up, but it be nice to still be able to crank the system with people in the back seat.

Click to read more...

 

[The Camry]

Opening ski hole for subwoofer

Have you considered going IB instead?

Who Has Cut Out A SKI PASS? - Car Audio | DiyMobileAudio.com | Car Stereo Forum

or if your **** good

https://www.google.com/search?q=cut+a+hole+in+ski+hole&espv=2&biw=1745&bih=890&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiMucOiw9XJAhUC8GMKHelaC8gQ_AUIBygC&dpr=1.1#tbm=isch&q=subwoofer+back+deck

 

[hispls 5,000+ posts]

Sealing off the trunk COMPLETELY from the cabin is crucial. Search on forums or youtube for Thor's Hammer's trunk build. That was an excellent example of trunk wall done properly.

 

[SimulatedZero 10+ year member]

I don't know much about IB to be honest. It's one of those things I've been curious about, but this build is for a buddy of mine and its his show. I clicked on that link and it wasn't working for me. I even googles the thread and couldn't pull it up.

I think I've seen his build a couple of times on here when I was looking for info on this. It sits a bit farther back then I am planning on which is where I'm running into the port clearance issues.

I wish I could pull that link up for diyma. But the title gives me an idea to run a PVC port into the back deck firing onto the glass with the subs forward.

 

[The Camry]

I don't know much about IB to be honest. It's one of those things I've been curious about, but this build is for a buddy of mine and its his show. I clicked on that link and it wasn't working for me. I even googles the thread and couldn't pull it up.
I think I've seen his build a couple of times on here when I was looking for info on this. It sits a bit farther back then I am planning on which is where I'm running into the port clearance issues.

I wish I could pull that link up for diyma. But the title gives me an idea to run a PVC port into the back deck firing onto the glass with the subs forward.

Who Has Cut Out A SKI PASS? - Car Audio | DiyMobileAudio.com | Car Stereo Forum

 

[The Camry]

Its really hard to make a trunk build that works and sounds good with the seats up. The only two ways ive ever seen where they sounded good was something along the lines of this.

Going sealed or IB helps tremendously if your looking to go for a ski pass build^^ because you dont need to worry about where to face the port.

again. Sealed but an excellent example of how it should look.

The issue is when you have the seats up. You get that terrible "bass trap" effect where no sound waves get to the cabin. You want to allow as much airspace to move. I took out anything i could out of the back deck and that did help alot but mostly i just drive with my seats down.

Try this, take off the plastic cover that goes over the back deck, take out any rear speakers or anything thats blocking any holes cut in the metal. Put it all back together. Face the subs towards the trunk and move the box all the way(2ins) to the trunk lid. play with the seats up. and just see how he likes it. It might just be enough for him. if not, he is gonna have to learn to drive with his seats down.

ORRRR

Do something along the lines of this.

 

[SimulatedZero 10+ year member]

Ok, I see where you're coming from on this. Couple of questions, the first is what kind of db loss would there be with an IB build. Ive read that you loose a fair chunk and then some say that if you have the right driver, you don't.

The other is that if I have the port firing into the cabin through the rear deck and the trunk completely sealed off from the cabin, would I still loose a lot of bass from the seats? I can see doing a ski pass through the back seats with out too much of a problem. If nothing else I can make a folding armrest from the seat backs. I was just curious though.

I didn't mention before, but he wants two Rockford Fosgate P3 12's in a ported enclosure. He actually wants it to sound a lot like my setup. Modeling on WinISD it looks like I can pull it off in about 4ft^3 including the port. So the goal is somewhere around 140 +-2db.

Edit: doesn't have the subs or the box yet, so no plug and play in different spots.

 

[The Camry]

Well for one. RF and any mainstream sub company isnt going to give you the best buck for your money. Shop around, ask on here what the best sub for 270$ is.
If he is going for 140db. Im doubting you care about any SQ whatsoever. If your wanting to get loud. Ported is really the only way to go. and if you want to get really loud without any musicality. Id start off by building a temporary but sturdy wall where your sub box is going to go. but a circle hole in it. Put a subwoofer in that hole in a sealed box. Run it in full rangeish 0-200hz. Make sure no eq is on, everything is set to flat, ect. Measure what the loudest frequency is. That is the peak frequency of your car. Its the frequency that gets boosted from something called the "transfer function". Then build a box thats tuned to that frequency. You will net a 3-6 db gain. It will sound like shit on music but it will get loud as **** on songs that have that freq as its bass line.

Now all that, you might have known. Back to the subject.

IB = +0db

Sealed = +3db

Ported = +6db

Bandpass = +6-10db

ported box vs infinite baffle - Car Audio | DiyMobileAudio.com | Car Stereo Forum

im sure you googled that but short, sweet. to the point.

The issue with firing into the seats and then having a port firing into the cabin through the back deck is that you create a very weird frequency response because what your essentially doing is making a shotty 4th order bandpass.

Imagine this. The area with the dark blue is the area between your sub and your seats. The side with the port is the one firing into the cabin. 4th order and as most people on here would tell you. dont **** with 4th orders unless you know what you're doing.

when porting rear deck - Subwoofers / Enclosures - SMD Forum

Rear Deck ports vs. Forward firing ports [Archive] - MobileAudioForum

Are you starting to see why trunk builds are so **** difficult?

I think your best bet is too find a better choice of subs and do something like the 2nd to last pic on my prev post. then try to cut a hole in the ski pass. Getting loud with your seats up is just..not gonna happen.

 

[ciaonzo 5,000+ posts]

Well for one. RF and any mainstream sub company isnt going to give you the best buck for your money. Shop around, ask on here what the best sub for 270$ is. If he is going for 140db. Im doubting you care about any SQ whatsoever. If your wanting to get loud. Ported is really the only way to go. and if you want to get really loud without any musicality. Id start off by building a temporary but sturdy wall where your sub box is going to go. but a circle hole in it. Put a subwoofer in that hole in a sealed box. Run it in full rangeish 0-200hz. Make sure no eq is on, everything is set to flat, ect. Measure what the loudest frequency is. That is the peak frequency of your car. Its the frequency that gets boosted from something called the "transfer function". Then build a box thats tuned to that frequency. You will net a 3-6 db gain. It will sound like shit on music but it will get loud as **** on songs that have that freq as its bass line.

Now all that, you might have known. Back to the subject.

IB = +0db

Sealed = +3db

Ported = +6db

Bandpass = +6-10db

ported box vs infinite baffle - Car Audio | DiyMobileAudio.com | Car Stereo Forum

im sure you googled that but short, sweet. to the point.

The issue with firing into the seats and then having a port firing into the cabin through the back deck is that you create a very weird frequency response because what your essentially doing is making a shotty 4th order bandpass.

Imagine this. The area with the dark blue is the area between your sub and your seats. The side with the port is the one firing into the cabin. 4th order and as most people on here would tell you. dont **** with 4th orders unless you know what you're doing.

when porting rear deck - Subwoofers / Enclosures - SMD Forum

Rear Deck ports vs. Forward firing ports [Archive] - MobileAudioForum

Are you starting to see why trunk builds are so **** difficult?

I think your best bet is too find a better choice of subs and do something like the 2nd to last pic on my prev post. then try to cut a hole in the ski pass. Getting loud with your seats up is just..not gonna happen.

Dude, Camry. You came through with that post. Thanks for the effort.

 

[SimulatedZero 10+ year member]

Well for one. RF and any mainstream sub company isnt going to give you the best buck for your money. Shop around, ask on here what the best sub for 270$ is. If he is going for 140db. Im doubting you care about any SQ whatsoever. If your wanting to get loud. Ported is really the only way to go. and if you want to get really loud without any musicality. Id start off by building a temporary but sturdy wall where your sub box is going to go. but a circle hole in it. Put a subwoofer in that hole in a sealed box. Run it in full rangeish 0-200hz. Make sure no eq is on, everything is set to flat, ect. Measure what the loudest frequency is. That is the peak frequency of your car. Its the frequency that gets boosted from something called the "transfer function". Then build a box thats tuned to that frequency. You will net a 3-6 db gain. It will sound like shit on music but it will get loud as **** on songs that have that freq as its bass line.

Now all that, you might have known. Back to the subject.

IB = +0db

Sealed = +3db

Ported = +6db

Bandpass = +6-10db

ported box vs infinite baffle - Car Audio | DiyMobileAudio.com | Car Stereo Forum

im sure you googled that but short, sweet. to the point.

The issue with firing into the seats and then having a port firing into the cabin through the back deck is that you create a very weird frequency response because what your essentially doing is making a shotty 4th order bandpass.

Imagine this. The area with the dark blue is the area between your sub and your seats. The side with the port is the one firing into the cabin. 4th order and as most people on here would tell you. dont **** with 4th orders unless you know what you're doing.

when porting rear deck - Subwoofers / Enclosures - SMD Forum

Rear Deck ports vs. Forward firing ports [Archive] - MobileAudioForum

Are you starting to see why trunk builds are so **** difficult?

I think your best bet is too find a better choice of subs and do something like the 2nd to last pic on my prev post. then try to cut a hole in the ski pass. Getting loud with your seats up is just..not gonna happen.

Holy crap. I'll be honest, I was not expecting quite this much of a pain in the but. As much as I would love to tackle a 6th order for the hell of it, I'd only do that on one of my own cars, not for a requested build.

Yeah, RF wouldn't be my first choice either, but its not my show so... He wants a clean look to the install, almost show quality and that's his brand of choice.

I think I'm going to go for a ski pass design and he'll have to have the seats down to show off. The other option is to build a ported enclosure into the rear deck, which I have no issues with fabricating if he wants. I did read in one of your links about some tuning issues off of the glass though. I want to do a build like in my girls car so I guess I'll find out soon enough.

About how far back should I have the subs from the seats? I was thinking 4 inches for the front of the drivers and 8 or so inches for the port with the ski pass in front. Trying to save some space in the trunk for storage, per request.

 

[germanyt 10+ year member]

I built this box.



And installed it like this.

I installed some beauty panels in the trunk to cover the amp which was mounted on top of the box and make it look like a flat wall. Other than that I didn't do anything special to seal off the trunk from the cabin. It sounded terrific and was loud even without folding the seats down.

 

[The Camry]

Holy crap. I'll be honest, I was not expecting quite this much of a pain in the but. As much as I would love to tackle a 6th order for the hell of it, I'd only do that on one of my own cars, not for a requested build.
Yeah, RF wouldn't be my first choice either, but its not my show so... He wants a clean look to the install, almost show quality and that's his brand of choice.

I think I'm going to go for a ski pass design and he'll have to have the seats down to show off. The other option is to build a ported enclosure into the rear deck, which I have no issues with fabricating if he wants. I did read in one of your links about some tuning issues off of the glass though. I want to do a build like in my girls car so I guess I'll find out soon enough.

About how far back should I have the subs from the seats? I was thinking 4 inches for the front of the drivers and 8 or so inches for the port with the ski pass in front. Trying to save some space in the trunk for storage, per request.

Honestly, thats something you will have to experiment with yourself. I can still get pretty decent bass with my seats up, so do keep that in mind. I say screw it and just build a walled off trunk design.

That^^ but with the ski pass hole cut. Really its just about having as much as airflow as possible.

Do keep in mind that freq response will be different with seats up vs down so if you do any EQ'ing. Do it with whatever he gonna be driving around most with. Also, like anything else. Once you get loud subs, you are gonna want a frontstage that can keep up so when your installing all this for him. Leave yourself room(with hardware like 4 or 6 channel head unit and install wise like maybe building an amp rack and not mounting your sub amp in the middle. ) for future improvements.

For your girls car. i assume shes gonna want a good sounding system (vs a louddd one) so get her a good 12 on 1000rms and either run her an IB wall or brace the **** out of the back deck and run an IB set up in the back deck.

 

[The Camry]

I built this box.


And installed it like this.

I installed some beauty panels in the trunk to cover the amp which was mounted on top of the box and make it look like a flat wall. Other than that I didn't do anything special to seal off the trunk from the cabin. It sounded terrific and was loud even without folding the seats down.

your box size does that for you. Im jealous of your perfectly square trunk hole. Mine doesnt allow for anything near that.

 

[SimulatedZero 10+ year member]

Honestly, thats something you will have to experiment with yourself. I can still get pretty decent bass with my seats up, so do keep that in mind. I say screw it and just build a walled off trunk design.

That^^ but with the ski pass hole cut. Really its just about having as much as airflow as possible.

Do keep in mind that freq response will be different with seats up vs down so if you do any EQ'ing. Do it with whatever he gonna be driving around most with. Also, like anything else. Once you get loud subs, you are gonna want a frontstage that can keep up so when your installing all this for him. Leave yourself room(with hardware like 4 or 6 channel head unit and install wise like maybe building an amp rack and not mounting your sub amp in the middle. ) for future improvements.

For your girls car. i assume shes gonna want a good sounding system (vs a louddd one) so get her a good 12 on 1000rms and either run her an IB wall or brace the **** out of the back deck and run an IB set up in the back deck.

Sorry for the late response, I've had a hell of a weekend.

Yeah, his next step is going to be mids and highs, along with an entire CCF / MLV and dampening treatment. I like to do most of my EQing through the box build and let it be from there to be honest. The exception is if I'm going for a high quality SQ build.

Yeah, she's as much of a bass head as I am. I'd probably get shot if I put something in her car that into the mid 130's at least, lol. I might try building a t-line into the back deck if I can, just to see what happens.

Thanks again for all your help dude, seriously

 

[mlstrass 5,000+ posts]

If you must keep seats up then 4th order with port firing thru ski pass...otherwise reg ported with trim panels to seal it off. I also use foil tape since it's not a show car. Don't overthink it, it's speakers in a vehicle designed to make some noise....