JaySco

Short preface: I upgraded the complete audio system in my 05 LS430 (head unit, door speakers, amp, sub) and was less than pleased with the bass I was getting in the cabin. So I built yet another box and this one too slammed hard (of course it did, I made it), but yet again I was displeased with the amount of bass reaching my ears VS the amount of rattling that was going on outside the car. It seemed like most of the energy was spent vibrating the trunk lid off the hinges which would be cool in an SPL
contest but not on my smooth and refined LS430.
While researching I found that BMW owners have this same issue just because of how solid these cars are built. I also saw a disproportionate amount of Lexus IS owners with similar complaints, I guess IS owners just mod more than other Lexus folks.
So I set off on planning and executing the elusive and rare REAR SHELF ATTACHED PORTED SUBWOOFER BOX (I hope you heard a booming echo in your head when you read that). The following are some pics I snapped along the way. I’ll try to give a general description of what’s what without going into great detail or specifics since this can be applied to multiple vehicles.

Step 1) Clear all access to the rear shelf, grab a pillow, lay in the trunk and study the underside. Run your fingers over the crevices, become one with the metal, take a nap in the trunk and dream of the finished product. And decide where the lines are best to have both a good seal and strength to get cranked on. See those red lines? Those are the lines that came to me in my dream. Don’t have your car running, exhaust fumes make for a good nap but a bad headache.


Step 2) Grab the cut board you plan on using and wedge it up to the bottom surface the best you can using scrap wood, cardboard boxes, kids (yours preferably) whatever is handy. Trace out any openings, holes, odd shapes. This will help you decide where the port (if porting) and mounting points will be, it also helps to visualize if everything will fit the way it needs to. If you are asking about the sub hole already being enlarged then you are impatient. Light a candle and work on your breathing for 5 minutes. You may then come back and see step 3.


Step 3) WhY cUt ThE 8” oPeNiNg FoR a 8” SuB? Because you aren’t mounting it to the sheet metal shelf, this ain’t Disneyland so Mickey Mouse isn’t home! You will need access to the inside of the box to mount it, once it’s mounted you can drop the sub through the hole and tighten it down. I want with an 8” sub so my opening was around 9”, a 10” would require about 11”, and a 12” sub would require welding in structural support to the shelf because you’d be removing too much material and there would be too much weight. Then you could write up your own damn how-to, overachiever.



Step whatever, there’s really no specific order. Here’s the very top face of the box. Note the marks I mentioned before and the two strips of wood clamped on top. Those fit in the recesses of the sheet metal to make a level mounting surface (2 red lines from first pic are straight, other 2 are these). Once you feel everything is planned out, measured, double checked and peer reviewed you can move on.


Same thing but with holes cut, and bolts. The sealing foam is just some 1”x1” closed cell adhesive foam from Amazon, works great. This box will be in the trunk but all air and acoustics will essentially be totally sealed off from the trunk. It will also cut down on rattles.


You want to do about 30 test fits to ensure you’re not going mad and measuring using two different measuring systems. You’ll still make a mistake, it’s ok. We don’t judge. This pic has the top board of the box because I was doing no less than five things at the same time during this entire build.


So at this point the mounting face should be done and you should have exact measurements for your box size. If you’ve already gone this far then I’m presuming you know about volume size and ported vs sealed so I won’t have to give a remedial lesson is audio basics. What are you waiting for? Build the box!


Remember when I said there’s no real steps? Yeah, somewhere before completion you’ll want to get a Dynamat type material for sound deadening and vibration purposes. This is an absolute must! Note the one rectangle I left open? Port. You may use real Dynamat if you’re a baller like that.


Spacers. I shouldn’t have to tell you that any gap between sheet metal and wood should be filled with a solid spacer. That metal may feel sturdy but it will bend like an aluminum can as soon as you start to torque on those bolts. The more surface area the better, this will lead to a sturdier mount and less vibration. Are we seeing a pattern?


It’s almost complete! Here is the box attached to the mounting face and getting carpeted. My carpet job turned out crappy. I watched “how to” videos and immediately ignored everything I learned because #teamnosleep . Don’t be like me, make sure it looks nice.


Bass to the back of the dome has never been so nice.


Back inside the trunk. Trim panels as needed. I got carried away on that corner, whatever. Are you really judging this whole thread on a corner that I trimmed too much?! Fine! Go build your own and show me how it’s done!!! No really, share pics when you’re done.



Well that’s it, and just in time. This “quick” tutorial was all typed on my phone because I can’t find my computer and now my thumbs are sore. So make sure you like and subscribe…wait, that’s not how it’s done on forums
*facepalm

Mrslady

Very Nice and GREAT workman's ship.

JaySco

Thank you. I’m quite pleased with the results.