Proper way to screw in subwoofer

Hi, I am designing a rectangular sealed 15''-subwoofer box for my first do-it-yourself car audio endeavor. What is the proper way mount a subwoofer to the box? I have heard recommendations of using bolts, but then how would you get a nut onto the bolt from the inside of the box?

Similarly, what is the proper way to secure the box to the car's trunk? I have heard people recommend L-brackets. However, I am thinking about just making the bottom floor piece of the box larger so as to create a margin around the box, which I think would serve the same purpose as L-brackets. Would this work, and again if I use bolts here how would I get a nut on the other side?

I have also heard of a no-drilling alternative of using industrial grade velcro to secure the box to the trunk. How would this work, does one side of the velcro get glued to the bottom of the box and the other side glued to the metal floor of the trunk? (meaning I would have to cut a hole the size of the box's footprint in the trunk carpeting?) Don't worry about saying that this option is easier for thieves to steal my sub, that's not an issue for me.

I would appreciate it if some people could explain these as clearly as possible, even though it may seem stupid or obvious to anybody who has done this before. I just like to be sure of what I want to do before I start doing anything.

Thanks in advance! Much respect to this forum.
Ray

T-nuts...here you go.

https://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=260-778

That would be a no to the velcro route. You have the right idea to build a false floor but instead of trying to bolt it down, screw it down taking care that the screws are not too long and will not puncture a wire or fuel tank etc.

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Top Secret, I can tell you but then my wife will kill me.

i drilled some holes into my gas tank once, my car smelled like gas when ever it was filled up, it was not a good feeling lol

Securing the woofer to the box:

• Position the box so that you can install the sub on the top;  that is, don't try to secure the sub while in the firing-sideways position.
• Center the sub over the mounting hole.  Move it slightly in all directions to ensure that it clears the hole on every side.  Look through the sub's mounting holes to see that there is wood at every hole location.
• Using a sharp awl or thin nail, tap with a hammer at each of the hole locations to mark the starter holes.

If you are going to carpet the box, now is the time to mark the subwoofer frame location.  Draw a pencil line around the sub.  Carpet the box and cut the carpet on the line.  This will allow the sub to fit against the wood, not against the carpet.

• Remove the sub from the box and put it out of harm's way.
• Use a drill bit that is slightly smaller than the shaft of the wood screws that you will use to secure the sub.  Use a drill that has a plumb level (bubble in a window) to guide the drill straight down into the wood.
• Install speaker sealing gasket tape around the circumference.  Cut an X with a sharp razor blade across every hole.
• Push round toothpicks into at least 3 of the holes, which will serve as guides for placing the subwoofer into position.  After the sub has been settled into position, press a toothpick into the starter hole at every mounting location to make sure the starter hole is centered under the sub mounting hole.  Once satisfied, remove the toothpicks.
• Use a good quality screwdriver that fits the mounting screw.  It's best to practice one into some scrap wood to make sure it doesn't slip in the threads.  Screw the sub into place using coarse-thread high quality wood screws.  Select the screws so that they fit nicely onto the subwoofer frame (usually pan head).  If your sub came shipped with mounting screws that take an allen head wrench, use those.
• Position your hand between the screwdriver tip and the sub cone/surround.  You want the gouge (if there is one) in your hand, not the speaker, should the screwdriver slip.  Blood washes up nicely if done right away.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

Thanks everybody who answered. And stevdart that was a great response, thanks for taking the time to write it out. Can you also provide some advice for securing the box to the trunk? I know forbidden addressed it but you seem like you would offer more on the subject.

Also, another question that I don't think deserves a new thread: I'm also going to install Diamond HEX component speakers in my front doors and I was wondering if anybody has good ideas about where/how to mount the crossover since it is sort of big. I heard that you shouldn't put crossovers in the doors because it can get wet, so I'm not sure where else to put it. Possibly under the front seats somehow?

Ray

Velcro couldn't hold the sub in the event of a sudden stop (read: crash).  Securely bolted to the chassis, however you want to do it.  As for the crossovers, look into the glove compartment for an answer to where to put them.

Not much more to add to it than that.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

Is it perfectly fine to use the same gauge speaker wire for the door speakers as for the subwoofer, ie 12 gauge?

Yes.

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My ex once told me I have a perfect face for radio.

Regarding the crossovers you can put them where the kickpanels are located and run the wires straight up and through the door runner boot. As far as the wiring goes no harm will come from using 12 gauge wire but it is overkill for components, plus smaller wire will be easier to hide and run.

now this is just from personal use. we did an install in a 94 ranger extended cab with a 13w7 in a ported enclosure. we built a small false floor in the rear just to flatten out the hump of where the driveshaft goes through the middle of the truck. and then to hold the box on the false floor we did use some STRONG velcro. and from my experience it worked. it takes everything me and my install has in us to get the veclro to come apart. now not every install is the same so use your better judgement of the vehicle before using this method. But im just here to say its not that bad of an idea

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2007 Acura TSX
SQ setup in the works

as it was mentioned before, jvillefinest, velcro isnt going to do anything in the event of a serious collision. I dont care how strong you think it is.