Fiberglass Rear Cushion Enclosure

[Foxhound547]

Hello all. First time poster here. I have a 2001 Forester and I'm looking to design a box. I'm relatively active and want to reserve as much usable space as possible. I have looked into a couple placement and sub options. First, I considered a custom fiberglass enclosure in the passenger cargo window then inside the spare tire well, but air space was a problem. So, I started thinking if it were possible to convert the rear cushions into the box itself, leaving the bench fully functional. I've settled on 2 10" JL audio W3 shallow mounts because they seem to offer the best frequency response and require little air space. Initially, I considered p3 shallow mounts but their frequency response just isn't low enough.

I understand how to lay the fiberglass but I'm lost how to execute all my steps. I purchased a salvaged rear cushion for tests and measurements then marked the area needed at the base for the closest air space. When I receive the speaker rings, I planned to mark their area and cut a recessed pocket where they could best fit. It looks like they'll have to be angled slightly to the rear to avoid the cross member near the front. I'll cover and prep the area on the base of the cushiom for fiberglass and exceed the area needed by a bit.

Here's where I get lost. Upholstery removal, foam cutting, and support brackets within the seat. How are these assembled and constructed? How do I deconstruct them? How much of the support wire is needed? Could I cut the brackets from the old seat and bond them to the new shell? How do I make clean, horizontal cuts to remove the foam for the enclosures cavity? Is that even necessary or is there a better way?

I planned on hollowing out the area needed, making the upper part of the shell, then bonding them together. Will that work? Will I need any supports within the shell? Any help would be appreciated. I've nevet played around with fiberglass enclosures and I'm excited to solve this puzzle.

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[hispls 5,000+ posts]

I can't quite wrap my head around how you plan to mount subs within seat cushions but my biggest issue that pops to mind is that centrally located sub(s) in a vehicle generally don't sound very good. You really want it in a corner or against a wall somewhere.

Can you perhaps use some painter's tape to show where you aim to mount things and take some pictures of it in the vehicle?

I'm thinking if you want to gut the seats and rebuild them somehow you might want to find someone who does upholstery and try to quiz them on how much and what material you can sacrifice or change and still have as much functionality as a seat as you want to keep.

 

[OldFartAudio]

I think that using the spare tire well would be better than the seat. If you are concerned about air space it is easier to raise the hatch floor a few inches than to gut the seat, build a box to fit and protect the subs from the weight of people who might sit in the back seat on top of them. It might even be easier to cut a hole in the floor and go infinite baffle. Seriously, depending on what is underneath the vehicle. Also consider a subwoofer box that is removable, or one that is designed to fit inside the spare tire. JBL makes versions of both, any box can be made so you can remove it and Stinger and NVX both have quick disconnects for amps now.

 

[Foxhound547]

I had approached the local audio shop with the idea and concerns about stability. They said they've done it and it works. But they didn't disclose any more information than that. They had a bit of a line and I didn't expect them to take a whole lot of time explaining to someone that wasn't spending any money. Anyway, I digress. I can't take a picture of the concept just yet, but once I receive the rings I can provide a visual.

To try to describe it further: the woofers will be angled towards the rear and downward firing. I don't expect a whole lot of space between the grille and body of the vehicle. Maybe an inch. They will be angled to compensate for the design of the cushion and to avoid the cross member that runs under the seat. The base of the shell will be moulded around the base of the cushion. The rings will be mounted to the fiberglass shell and to woofers mounted to those. I'm mostly confused as to how I'd construct the upper portion of the enclosure and whether or not to use MDF, and if I did, what would be the best way to measure it.

 

[Foxhound547]

I think that using the spare tire well would be better than the seat. If you are concerned about air space it is easier to raise the hatch floor a few inches than to gut the seat, build a box to fit and protect the subs from the weight of people who might sit in the back seat on top of them. It might even be easier to cut a hole in the floor and go infinite baffle. Seriously, depending on what is underneath the vehicle. Also consider a subwoofer box that is removable, or one that is designed to fit inside the spare tire. JBL makes versions of both, any box can be made so you can remove it and Stinger and NVX both have quick disconnects for amps now.

The problem with the spare well is space. I'm pretty stuck on not compromising any storage. I don't want to remove the spare, and even though I there's enough space to mount even a full size 15" in the area inside the tire, air space is still a concern. I originally wanted to use that space, and even considered just making mount for the woofer, then sealing the area completely to be the enclosure. Local audio guys advised against it and that's when I came up with the idea for the seat. I don't really carry very many passengers often but still wanted the versatility. Fiberglass is pretty strong, so I figured it could be layered to withstand some use. As far as removable enclosures go, I just can't justify putting the money into a system I can't use 100% of the time. If I go on a long haul cross country, I don't want to have to leave behind my subwoofers just for the occasion.

If you have any links to the sub boxes you mentioned, I'd like to check them out.

Thanks for replying.

 

[Foxhound547]

• #4

I had approached the local audio shop with the idea and concerns about stability. They said they've done it and it works. But they didn't disclose any more information than that. They had a bit of a line and I didn't expect them to take a whole lot of time explaining to someone that wasn't spending any money. Anyway, I digress. I can't take a picture of the concept just yet, but once I receive the rings I can provide a visual.

To try to describe it further: the woofers will be angled towards the rear and downward firing. I don't expect a whole lot of space between the grille and body of the vehicle. Maybe an inch. They will be angled to compensate for the design of the cushion and to avoid the cross member that runs under the seat. The base of the shell will be moulded around the base of the cushion. The rings will be mounted to the fiberglass shell and to woofers mounted to those. I'm mostly confused as to how I'd construct the upper portion of the enclosure and whether or not to use MDF, and if I did, what would be the best way to measure it.

 

[Foxhound547]

I can't quite wrap my head around how you plan to mount subs within seat cushions but my biggest issue that pops to mind is that centrally located sub(s) in a vehicle generally don't sound very good. You really want it in a corner or against a wall somewhere.

Can you perhaps use some painter's tape to show where you aim to mount things and take some pictures of it in the vehicle?

I'm thinking if you want to gut the seats and rebuild them somehow you might want to find someone who does upholstery and try to quiz them on how much and what material you can sacrifice or change and still have as much functionality as a seat as you want to keep.

I had approached the local audio shop with the idea and concerns about stability. They said they've done it and it works. But they didn't disclose any more information than that. They had a bit of a line and I didn't expect them to take a whole lot of time explaining to someone that wasn't spending any money. Anyway, I digress. I can't take a picture of the concept just yet, but once I receive the rings I can provide a visual.

To try to describe it further: the woofers will be angled towards the rear and downward firing. I don't expect a whole lot of space between the grille and body of the vehicle. Maybe an inch. They will be angled to compensate for the design of the cushion and to avoid the cross member that runs under the seat. The base of the shell will be moulded around the base of the cushion. The rings will be mounted to the fiberglass shell and to woofers mounted to those. I'm mostly confused as to how I'd construct the upper portion of the enclosure and whether or not to use MDF, and if I did, what would be the best way to measure it.

Thanks for responding. As you can probably see, I'm having a rough time figuring out how use this forum.

 

[hispls 5,000+ posts]

To try to describe it further: the woofers will be angled towards the rear and downward firing.

So you're talking about the part of the seat that your back would rest against? Really I wouldn't think you could carve out much meat from that before sitting in the back became uncomfortable and you'd probably want to build that out a little bit which would hose you if you wanted to fold the seats down and keep a long flat cargo area.

As far as not having low extension with shallow mounts you're not going to be that much better off trying to shoehorn anything else into such small space. You will need to do a few layers of fiberglass to build something strong enough to not flex and generally people use MDF for the baffle and really for anything else you can as it's far cheaper and easier than fiberglass. Are you quite sure you can't do something along a side in the cargo area?