Built-in Subwoofer Cabinets - 1st Gen 4Runner

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01-07-2006 | 10:20 PM

Bob_98SR5

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Built-in Subwoofer Cabinets - 1st Gen 4Runner

By Mark Rael

The 1st generation of 4Runner offers a great way to increase your bass levels without adding stand alone bass boxes into the bed. It requires some fabrication skills and some small interior work-arounds, but the result is very bassin', rockin', and all those other good things.

The general idea is to build out the rear sections of the bed sides enough to fit a 10" sub on each one. Using a larger diameter subwoofer than that is possible but involves building a deeper cabinet and a greater loss of cargo area. You will also need to remove the rollbar, temporarily, and then install it again minus a small amount of center section (a muffler shop can easily and cheaply do this for you.) The material for the sub baffles is merely wood; either particle board or plywood. On my 4Runner this wood is then covered with a heavy felt material held on by contact cement or other suitable glue. There are a lot of possible configurations for how you can speaker load the finished product. On mine there is a 10" Kicker sub and a 2-way ADS midrange speaker plate on each side of the bed, as shown below.

You can see that there is a wooden door back by the tailgate. Lets talk about that for a second. On the drivers side of the stock 1st gen you have your wheel jack storage area back there. On the passenger side its just a misc storage space. Those are both retained in this mod, though obviously it means an extra hour or two of work. But the result is worth the effort and I would not suggest removing the jack permanently and covering its cubby hole over with wood and felt. Heres a closer look at how the door was installed and then the area sealed off from the woofer area alongside it. Spray on foam was used to insulate the wood seams from each other.

The depth of the woofer baffles is roughly 3" more than stock, which means a loss of about 6" width to the bed of your 4Runner. But here is something else to consider- there is no need to continue towards the front of the vehicle with that much depth added to the sides. Once you have chosen your woofer location you can scale back on how deep the enclosure needs to be. In my example, by the time I got to the midrange driver mounting location the depth of the woofer baffle had been reduced already by means of a 'stairstep' made of wood and felt. It is in this potential midrange driver mounting location that you need to decide if the rear seats will be retained. If so there are limits to how you can mount midrange speakers or if you can even mount them at all. I chose to remove the rear seats and I have never regretted it. Heres a closer look at how the reduction to the width of the baffle was accomplished:

Its very possible to build a woofer baffle and not add a midrange location. Even in my example the woofer baffle itself is basically separate from the stairstep and the midrange panel. It would have been possible to stop with the woofer and retain the rear seats.

Let's spend a second on the rollbar. The top of your 4Runner needs to come off for the rollbar to be removed. Since you are narrowing the width of the bed the rollbar will not mount back to its stock bolt locations after the woofer baffle goes in. You can either not have a rollbar or you can have a muffler shop remove a 2 or 3" section from the center of it and then weld the halves back together. It sounds more drastic than it really is, and if you have one of those padded rollbar covers that some 4Runners had then nobody will know the difference. To remount the sectioned rollbar means driling new bolt holes or simply having the shop weld on the narrower unit to the bed. To each his own.

Heres a few more shots of the finished installation:

In case you were wondering, the tie down straps date from a time when I was using them to help haul cargo around. They still come in pretty handy, especially when used with the rear seat u-brackets and the two sets of stock hold down d-rings on the floor.

And finally: how does it all sound??

Well this is the best part of the write up. The sound. Its important to have enough power behind the subs of course, but these days that isnt hard to accomplish. Its also very important to have a head unit or CD player that has an adequate crossover circuit built into it. When I bought my 4Runner the previous owner had a nice but old stand alone active crossover. I kept it until it died and then replaced it with a modern CD head unit with lots of low frequency options built into it already. In particular, the new CD player lets you control subwoofer boost, the amount of boost, and the width of the bass frequencies that get the boost.

My 4Runner easily outperforms all other car stereos that I have experience with. The bass can be tailored to be smooth and not obvious or it can be boosted to give a loud and solid punch to the beats, and one that also vibrates every mirror on the truck so that you can barely see out of them. Its a great thing to consider doing if you have the inclination. Your ears will love you for it, but your neighbors will probably hate you, every time you crank up the volume.

Last edited by Bob_98SR5; 01-07-2006 at 10:26 PM.