BUILD A PASSENGER-SIDE SUB ENCLOSURE
V. 1.0, 2002
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HOW TO BUILD A PASSENGER-SIDE SUB ENCLOSURE |
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Original Design: Jon a.k.a. 'TampaSol' (#0033) TABLE OF CONTENTS: Note about the linked pictures: although formated for the web, some are indeed large in order to provide a detailed view. Tools you will need: If not table saw, then radial arm saw
Before you do anything, including buying speakers, make sure that the usable space you have for your del sol will comply with the "Recommended Sealed enclosure volume" of the intended speakers. First, note that for this specific design of custom enclosure, the internal volume for each side is approx 0.636 ft^3 minus approx 0.1 ft^3 for the speaker displacement. Here is how the math was figured:
Next, compare with speaker specs: For example, the Polk DX10 (which are no longer available on the market; you may be able to get them used or a demo) have a recommended sealed enclosure volume of 0.66 ft^3 +/- 15%. For the Polk EX10, it is 0.65 ft^3 +/- 15%. You can find a listing of speakers and their specs on Crutchfield's website (Look under the "Essential Info" tab and you'll find the value for sealed box volume.) Or, you could try any search engine by cross referencing "sealed box volume" with your intended speaker. Note that our del sol enclosure's volume rating is 0.51, which is a little smaller than what is required for the Polk DX10 (at least 0.56) and EX10 (at least 0.55). That's okay because you can compensate by stuffing the box with synthetic polyester textile fiber (a.k.a. "Poly-Fill," "Dacron," Nylon pillow stuffing). This material slows down the sound waves a bit which tricks the speaker into thinking it is in a slightly larger enclosure than it really is; internal volume is virtually increased by up to 10%. You can find it at most craft supply stores, typically known as "Poly-Fill," or you can find it on Crutchfield: two 10's or one 12 This design is for two 10" speakers, which will keep the box as narrow as possible since it was going behind the seats. Look for speakers (like the Polk DX10 model) that works really good in a sealed box and only requires approx .65 cubic feet of internal volume give or take 15% to work properly. Look for a specification sheet, like this example. (Bear in mind that this example is not the same as your speaker's specifications.) You can get your subs from www.crutchfield.com, or call around town and find a good deal, maybe buy one get one free. Crutchfield has decent prices and the nice thing about their website is they give all the specs for the subs so you know what you are getting. When buying speaker terminals, make sure they won't leak much air. Look for some that have a gasket which you can seal with silicone. When choosing an amp to power your subs, ask yourself the following questions: What impedance is your speakers rated? Can the amp handle the speakers? If you are going to be wiring the subs in a parallel configuration, ensure your amplifier is rated to the particular ohm level of the subs. For example "2 ohm stable" operation. Figure out where you plan to mount the amp and make sure the is sufficient space for it. You will need an amp with an internal crossover to get the most out of the subs or some sort of external crossover to filter out the high frequency sounds. Make sure you use wiring that is thick enough to handle the power output of the amp. In most cases, 4 gauge is the minimum thickness required for good power. 2 gauge is even better. Especially for multiple amp setups. An inline capacitor or Farad Cap is a good idea with an amplifier that will be used to power subs. Be sure to mount your amp according to its specifications and optimal ventilation. When wiring from your battery, be sure to install a circuit breaker to protect your car in case of a power surge. For more on electrical issues for car audio, see this greatly imformative website: Basic Car Audio Electronics Parts you will need: Poly-Fill (conditional; 1 lb. per cubic ft of internal enclosure volume) This custom enclosure was made of Medium Density Fiberboard (MDF). The other option was marine grade plywood but just the thought of making an enclosure out of plywood makes me cringe. Regular particle board should not be used because it is not dense enough and will flex under the load of the subs. WARNING: MDF makes a lot of saw dust! Cut it in a ventilated area and use a mask. To get an idea of the dimensions of the box, view the pictures: back, bottom, height, recess1, recess2, recess3, side, and speakers. A place like Home Depot can cut the MDF into 4 4x2 sheets (so you can fit them into your car just to get it home,) or you can have them custom cut. But be warned, however, that they cannot guarantee EXACT measurements, nor can they guarantee a perfect rectangle or square, which is crucial for a snug and airtight fit. If you have access to one, use a table saw to make the straightest cuts. They are much better at straight cuts that anything else. Or you can use a radial arm saw to get the cuts fairly straight. Unfortunately, some of the cuts may not end up perfectly straight and you will likely have to use a power sander. Even a millimeter or two off is enough to cause problems. BE SURE TO ACCOUNT FOR THIS IN MEASUREMENT. To make precision cuts for the speaker and terminal holes <see diagram>, use a jigsaw; you can use a regular, coarse wood cutting blade or a GP blade. You have to be careful here not to put any pressure on the board when doing so or it may snap. The narrowest edge of the bottom piece is only about a half inch or so thick. Check your speaker's manual to find the cutout diameter for its hole. For instance, Polk DX10's are 9 3/16" (233mm). The terminal holes depend on the size of your terminal gasket. You don't need to power sand these holes. At this stage it is recommended that you pre-drill for mounting of speakers. Refer to your speaker's user manual, which should provide the drill bit size. If it doesn't call your speaker company and ask for technical support to provide the recommended drill bit size for pre-drilling. For instance, (and this isn't for every speaker,) the Polk DX10 needed a 1/8th bit. To determine where to drill, slip your speaker onto the speaker hole and mark through the screw holes with a pencil. Pre-drill carefully, since these holes are so close to the large speaker hole. For a tight fit, all parts were glued together with wood glue first and screwed together (The wood screws were 6X1.5". Same length for all), but be sure not to screw through the rim of the speaker holes.) You may need to use clamps. Or you can have someone assist you in holding the pieces firmly together while you put in the screws while using a power drill. After the box is completely glued and dry, go over all of the seams with the clear 100% silicone II adhesive. Using a disposable glove, glide your finger along the seams to press the silcone into them and even the coat. Apply another coat if you like. Just make sure it is sealed and airtight.
You have two options for the speaker terminals. You can omit the terminal component entirely and directly connect the wiring into the speakers. This allows you to simply drill a small hole for each side, and run enough wire for slack for the speakers when you need to remove them from the box, and seal that hole airtight with silicone. But this makes it not easy to remove the entire box from your car, as you will need tie in some male-female connectors. The other option is what we did. If you want to be able to remove the box for adjustments or if you go racing, then the terminals make it easy. Plus you don't have to worry about speaker wire hanging out in the final stages of the box construction. And you won't have to tie in male-female connectors.
Usually, your speakers have documentation on mounting them to a custom enclosure. Be sure to refer to them. You may need to afix some padding to go inbetween the speaker rim and the wood. Usually, this is provided with the speakers. Next you need to crimp or soldier wiring to the box terminals. Be sure to provide enough slack in your speaker wiring to lift the speaker out of the box so you can easily disconnect it. This is where you should stuff the box with Poly-Fill. Remember, 1 lb of polyester fabric per 1 cubic foot. A 20 ounce bag will be plenty to work with. Don't pack the stuffing; instead, line the inside of the box with the Poly-Fill evenly. If you pre-drilled, it will be easy to screw in the speakers with a power drill. For those of you who are worried that you might accidentally slip with the drill and poke a hole through their speaker, (ouch,) we suggest using a regular screw driver to tighten the screws down. It would also be wise to mount a grill over each speaker to protect them.
You should only need a philips head screw driver to take all the interior panels out. Start by taking off the long piece between the speakers off. You will need to roll the back window down and pry it off from the top. Use both hands, pry evenly. Now you should see the 2 screws a piece that are holding the speaker covers on. Remove those and take the speaker covers off. The storage compartment is held in by 8 screws. 2 in each cubby bin, one on either lower side behind the seats, and the 2 that are attached to the center console in the middle. You will need to remove the center console too however so you need to remove the 2 screws that are up near the parking brake and there is one in the cup holder area. You will also need to unplug the cigarette lighter to take it out. The upper corners of the storage compartment piece are held to the car by metal clips, you should be able to just pull them out. Use the jig saw with a general use blade to cut the plastics. Mark them first before cutting. I would suggest cutting a bit short and then cutting a bit off at a time for adjustment. You will cut the speaker cover, so it looks like this with the sub box flush. You will cut into the driver's side box, BUT MEASURE FIRST (this picture is cut a little too much, and this was corrected by adding a magazine rack to the box.) You will also cut into the middle plastic piece. As seen in the same picture, you will have to cut into the rear door jamb on the passenger side. In order for the box to be level, you will have to cut out some clearance around the bottom <see diagram>. Typically, there are four points of clearance. There is a notch starting from the driver's side of the box. This is to clear the thick black wire. The little incline cut on that same side of the enclosure was to clear the patch cords and speaker wire leading to the amp which is in the trunk. The back bottom piece on the driver's side is cut off to clear the fuel pump plate which is the silver thing that the speaker wire is laying over. These are cut with a hand held power jig saw. Add pads to prevent annoying squeeking from the wood to metal friction while driving. Here is an example, as seen from above, compartment, passenger side, other side, and speakers. The box is a one piece design with a separate compartment for each sub. If you happen to cut to far into the driver's side plastics, you can build a little magazine holder at one end. This is optional, and is seen in the example photos. The subs face down so the sound can reflect off the floor of the car for better sound. The sub is covered in black vinyl. You can buy this at fabric stores. It can be stapled onto the box. The only adhesive that worked well enough was Permatex contact cement from auto parts store. The sub's dimensions spare one storage compartment, as most of the rear storage area is cut out, including some of the bottom part of the passenger side speaker cover and the passenger side plastic by the door. If you want to keep it as "factory" looking as possible, get spare parts for the ones that you cut up. If you don't have spare parts, I would recommend you think long and hard about whether you want to do this or get spare parts to cut up so you can keep your originals. I have to say though, the sound is awesome. Top off at 90 mph and the bass still sounds great. Crystal clear at any speed with the top on. I am thinking about getting a separate amp to power the box but for now it is working out fine on the 4 channel Sony even with it's limited power output. An Amp powers élan vital's sound. A little bit of passenger seat travel is lost but not much. Driver seat travel is not affected at all. A custom enclosure for the Sol is definitely the way to go if you want good bass and you can't afford to have a shop make one for you or can't afford a JL Audio Stealthbox (I sure didn't want to drop that kind of cheese). The project (without speakers, and assuming you have access to power tools,) cost about $50 total including wood, screws and glue and other miscellaneous stuff. If you do decide to do this remember the golden rule. "Measure twice (or more for that matter), cut once." |
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