This will be the thread in which I'll be posting a complete design for an MDF-based subwoofer box that fits into the factory Blose location. Here is what I posted in response to other questions about custom boxes in that location:

My wonderful lady blessed me with a new Rockford Fosgate amp, 10" Punch Z Series Sub, and wiring kit for Christmas.

I started working on a design immediately. What I found through measurement is that for a squared, trapezoidal shaped box to fit, the dimensions are very constrained. So, I measured and measured, and finally settled on a box design. Matched it up to the acoustic design I did specific to my subwoofer, and it worked perfectly. Here's where the problems began.

Got the car torn apart, and started building the box. Somewhere, I made a mistake in measuring the clearance required for my subwoofer in the box, and found that the box wasn't tall enough to clear the sub frame and still match the factory angle for the bracketry. I don't want to go into details, but I burned over 6 hours adapting the box I had built to make it work, and keep it able to fit into the space and sealed. My problem is, it's not a very clean installation, and I don't want to publish it if it won't end up looking perfect. It's installed, braced into the front mounting bracket, and sounds great, but I don't think it's classy enough to give its design out to the public. It's more of a pride thing than anything. Also, I used a Blose factory cover to finish the space off (sanding down the Blose logo, of course).

Needless to say, I want to stress something. Subwoofers MUST be checked dimensionally to ensure they would fit into the type of box that would work in the factory space. This will limit many of the subs that will work. My design will be based on the Rockford Fosgate Punch RFZ3410 subwoofer, and will use the dimensions of this woofer. It definitely "rounds out" the sound of the factory system, and is perfect if that's what you're looking for. If you want competition-level SPL or extreme thump, you'll have to spend $$$ for a fiberglass enclosure that allows for more volume (cu. ft.).

Keep in mind, another challenge of this location is that you have a seat belt tensioner, as well as the fuel tank sending unit access located within this space. Because of this, I think the box must be removable.

My design will fit the Fosgate 10. As an alternate design, I'll try to create one using a JL Audio 8" (model TBD), because it will (1) fit within the stock speaker bracket opening better than the Fosgate 10 (which didn't), and (2) you should be able to work within the space constraints better with the 8, and most likely get a sub with a bigger magnet.

So, please be patient. I'm trying to work out a design that anyone with access to tools and time can do for a clean, good-looking install in the factory space. Feel free to ask any questions. I'm trying to fit this into my life around my 12-hour a day work days, so please bear with me.

My goal for completing this is no later than January 31, although I'm pushing to have it completed by January 24. As soon as it's done, I'll publish it.

Design will be available in AutoCAD and *.pdf files.

 

Could you give us a pretty detailed drawing of your sub as well. Things like Mounting depth, motor diameter, cutout diameter, length and approximate angle of basket, etc.... so we can compare other amps. Some amps like Boston Pros have very short mounting depths (4.75" for a 10") while some are over 6" long.

When I say 'we' I mean the 'board members' since I'm 100% fully decided my sub is going else where.

 

Detailed information about the sub will be on the drawings. This should help those that are looking at other subs to put in the space.

 

Excellent - I'm sure you are going to make a lot of people happy.

My compliments in advance .

 

Update:

The base drawing is completed, and test fitting will be completed hopefully tomorrow.

Then, addition of construction and installation notes will be added, and the package released hopefully by Sunday.

Here's a preview:

 

Nice. Keep up up-to-date on the progress! I want to put two 8's in that location if possible.

Thanks for the drawings!

 

I am so looking forward to this! Keep us posted. Since the 10" sub doesn't fit in the factory sub cutout.. what are you going to do to make it look clean? Or am I getting ahead of your complete explanation and pics?

Looking forward to seeing this!

 

During the test fitting, I'll check to ensure that the box can attach via bolts/locking nuts through the metal bracket. Obviously, the hole for the sub within the metal bracket will have to be widened, but if you're going to be cutting MDF with a jig saw, it's easy to just open the hole up on the bracket.

All of the questions are good ones, and I'm trying to anticipate the problems so I can provide decent construction and installation instructions. I'm getting in serious trouble at home with the lady over the amount of time spent at work (~12hrs) and working on the design (~3-4 hours/night, at the office where I have a faster CAD machine.)

I'm still shooting for Sunday. Saturday may be a very busy day for me.

 

Another Update:

Test-fitting will happen today/tonight (dependent on weather and light availability). After seeing the box in live 3D instead of on CAD, it looks like it might be a better fit then my previous box.

Here's some pictures. The first one is resting relative to how the box will actually sit within the enclosure, to match the 45 degree angle of the mounting plate. The second is of how the box is oriented at its minimum height. I'll try to take more pictures of the test-fitting as I go along. When this is confirmed, I'll finish the drawings and release them with instructions.

Also note that I've placed the templates for the exterior and cut-out ring for the Rockford Fosgate sub. There's room, but it's tight, and has to be to make everything work.

Enjoy!

 

Picture 2:

 

Another Update:

Test fitting was interesting. The box would fit in the space provided, but I couldn't clear it to get it completely into the space. As such, I'm back to tweaking the design. I have another one done, but I need everyone's opinions.

Should I:

1. Do another Scale Mockup of the new design, and test-fit it

or:

2. Don't worry about it. The CAD file indicates that the box should be able to fit into the allowable space if it's turned properly (I'll show this in the drawings), and I don't need to do a mockup. What I've done is depress the top of the box and reconfigure it so that I can insert the back first, tilt it until it will clear the front, then slide the rest into the enclosure.

I need to know from everyone that's interested in this. The box design has gone from an easy-construction to one that will require some skill and tools to ensure proper angles and fitment.

I'll continue to complete this, but it might take another week or so to build another mockup and test-fit. Then, some more time to finalize the drawings and release them.

Please post here what your preference is. If there are any questions, please feel free to post them here, and I'll try to answer as I can.

Thanks to everyone for your patience. I'm trying to make this work, and still be easy enough for someone to do in a weekend.

 

I am interested in this, as I had contemplated a similar idea for my car (when I get it). Perhaps I am jumping the gun by trying to plan the system out a few months before the car's in my garage.
The pictures of the prototype that you posted definitely look promising.

What amount of airspace can be expected out of your design?

 

The box is custom for the Rockford Fosgate RFZ-3410 10" sub. This particular sub requires 0.75ft3 of airspace, and the box design I do is ideal for this volume requirement.

In my design, I'll attach links to the AJ Box Designer freeware program that will help fine-tune your box design based on your sub specs.

So, 3/4 of a cubic foot is the volume I'm shooting for.

Thanks for your patience. I'm working as fast as I can to make sure it will work for everyone.

 

The .75 cubic feet will work nicely for many 10" subs, like:

Infinity Perfect 10
Polk Momo 10
Probably a few JLs too but I can't remember specs.

I understand the area is pretty limited, but do you think it would be possible to get more airspace, like somewhere around a foot or a little more with a few modifications of your design?

 

Making the box either wider and/or deeper is more difficult, as strong modifications would be necessary to the box to enable it to fit around the beginning of the rear driver's side wheelwell. This element is the only thing that prevents someone from making a box up to 2+ cubic feet if they wanted to.

To "notch" a box design for the purpose of making it fit is possible, but I don't think I'm going to design it. When I do provide my drawings and build notes, I'll make the CAD files available, so that the design can be modified.

I will warn, however, that because of this space constraint, I have cut the clearances for the sub to the absolute minimum while still allowing for minor angular miscuts and/or mismeasurements. The sub I'm using is only 4 7/8" deep, so this will be another driving factor in the box design.

The goal is to provide a baseline design that can be modified relative to each sub's specs. What I'm trying to say is, the overall design of the box will be critical to actually getting it to fit within the space, but some of the dimensions (except the height) can be finessed to hopefully fit larger subs. The box I've designed is narrower than the enclosure space, so deeper is a possibility. However, if you run numbers and find that wider is the only way to go, then you'll have to deal with the wheel well issue.

Hope this helps. I'm working on the drawings right now. I did a mock "test-fit" on CAD using the absolute clearances present in the enclosure space, and it seems to work. I'm going to try one more time, and if it works, I'm finishing the drawings. The build notes may take longer, and I may wait until people ask the questions before I include the information in build notes.

 

I struggled myself with how to utilize this space. My stereo installer was kind enough to allow me an A/B comparison of a forward facing sub (firing into the cabin), or an upward facing sub. The box design I went with was upward facing, firing into the space twards the roof. You will have to place more emphasis on the door speakers as some more directional bass frequencies are not transfered into the cabin well. However, lower bass is abundant and sounds very clean and tight. I am not saying what I did is the right way, I just offer the alternative for design consideration.

 

Your mockup looks about the same as my metal box I made for my car. From the cardboard mockups I can cut the steel pieces and make a box in an hour or two. Good luck with the complex angles of the MDF. The metal type is much easier due to no need to figure saw cut angles to join the edges with. I just use a very hot glue gun (MIG) to put the steel together.

 

Another update:

The test fitting was a lousy experience. The design I had was too difficult to execute on a weekend, and the sound quality out of the box was bad when I tested it.

Instead, I'm going to a box with an upward-firing sub, like some of the ones I've seen. I want to give credit to whomever came up with the idea, but couldn't find them. You know who you are, and it ended up that your idea proved best for the space.

Regardless, I'll continue to work on the CAD drawings for the new design, and work more on attachment to the body and easy measurements for building the box. I've become extremely busy, but will do everything not to disappoint when I do release a complete design package.

The new box will appear more standard, and fit better into the factory location than my other design. It won't be the loudest, but will sound good when tuned properly.

Thanks to all for being patient. Progress is slow, but I want a quality package to be released when it's ready.

 

I just found this thread while searching the archive. I am interested in putting a subwoofer in the stock location in my convertible when I get it. (I am assuming that it will have a comparable space to the coupe, but I could be wrong).

Did you ever finish this project?

Got anyother suggestions for how to add a sub in this location?

AndyB

 

I can tell you from experince no matter what you do behind the seat it will not sound right. It will need to be in the hatch area or in the trunk if you get to convertible.