This article was first published in 2000.
If you're putting speakers into older doors you're pretty likely to come across the problem - they won't fit. The speaker's basket and magnet will be too deep, and they'll be clashes with wound-down glass, window tracks, or even the outer door skin. Lotsa accessory stores sell vinyl-skinned door pods that will give you extra clearance, but if you're on a tight budget here's how to make your own carpeted pods. In this example we've used the mid-bass units from a set of Altronics 6.5 inch splits. These are pretty meaty speakers, with a depth of about 70mm and an actual diameter of 165mm.
This is the hole in the door trim that's been left by countless other speakers residing here over the years. The problem (one of them anyway) can be seen through the hole. The track for the window passes behind the hole - try to insert a speaker with any depth and the magnet hits it. It's not an unusual situation.
Here's the 6Â½ inch mid-bass unit for the Altronics C9302 kit. We'll do a full review on the speaker system in an upcoming AutoSpeed, but suffice to say here that the system costs only $129 and looks good value for money at that price. But check out that big magnet - how do you fit that in the door? The answer - in case you hadn't guessed - is to make a door pod. One of those curvy things that bolts to the door and houses the mid-bass driver - and sometimes also the tweeter.
The first step is to mark onto thick MDF the shape that you want the base of the door pod to take. Once you've marked it, cut it out with an electric jigsaw. The MDF being used here is a hefty 19mm in thickness. Using thick material is good because it's much less likely to vibrate and also can be screwed together with MDF screws without splitting or decent-length screws going right through to the other side.
After I'd cut out the baseplate I smoothed the edges with a belt sander, but this is also easily done by hand with some coarse emery paper and a sanding block.
With the baseplate cut out, it was then time to cut out a spacer ring. This is made from the same thickness MDF, and here the grille ring that is provided with the speaker kit is being used to mark both the inner and outer diameters.
The outer line was then cut around with the jigsaw, resulting in a disc a little larger (like, a few millimetres larger) than the outer diameter of the mid-bass driver.
Again I used a belt sander to smooth the edges. If your disc is a little wavy around the edges because the jigsaw wandered, you can also use the sander to make the disc rounder.
This handsome bugger then clamped the spacer disc onto the baseplate in the exact location that the speaker was to be mounted.
Once that had been done, the jigsaw was used to cut through both thicknesses - the baseplate and the spacer disc. Doing it in this way gives a nice neat cut through the whole mounting system, but if the jigsaw can't hack the double thickness, cut the holes separately.
Unclamp the two pieces of MDF and then check that the driver sits inside the spacer ring as it should. If the hole is a little small, sand it to a slightly larger internal diameter. The speaker must sit flat on the ring, not cocked up at one side.
Next drill four small diameter pilot holes through the spacer at even locations around the ring. These need to be sized so that four MDF screws can be easily screwed through them. (I actually used longish self tapping screws, not specialised MDF ones.)
After you've drilled the pilot holes, use a bigger drill bit (a bit larger in diameter than the heads of the screws that you're using) and drill about half way
through the ring. (Don't drill all the way through with the bigger drill bit!).
After you've done your drilling, use some sandpaper to take off any raised edges around the holes. This is so the ring will sit flat on the baseboard, and the speaker will sit flat on the ring.
Insert the four screws and screw the ring to the baseboard. You can use a nail to make starter holes for the screws in the baseboard, and make sure that you screw them all fully home, so that their heads are below the level of the ring and the ring is pulled up tight against the baseboard.
With the spacer ring screwed into place, use sandpaper to smooth the inner diameter, taking off any sharp edges and generally making it all look nice.
The speaker should then be sat in place, ensuring that it still sits flat, the magnet doesn't hit anything and there's plenty of space for air to get away from the back of the cone during speaker cone movement. The magnet can still protrude a little from the back of the assembly - you'll still need to cut a hole in the door trim.
Okay, now it's time to make it all look pretty. Mark out a piece of thin foam rubber, as has been done here. The foam rubber is available as ironing board backing, or (much more cheaply) from rubber supply shops.
Cut the foam rubber piece out with a pair of scissors (or use a sharp knife with the foam ruber laid on a backing like scrap MDF). You don't need to be terribly accurate, so don't worry if the cut wanders a little offline.
Place the MDF face down (ie so that the spacer ring is downwards) on top of the foam rubber. Wrap the edges around onto the back of the assembly, using tacks or staples from a staple gun to hold the foam in place.
As you get further around, start to stretch the foam rubber, so that it forms a tight skin over the front of the door pod.
When you've finished, from the back it should look like this. You can trim off the excess foam rubber with a sharp knife.
You'll now need a can of this stuff. Expanding space-filling foam is available in aerosol cans at most hardware stores. Note that it varies quite a lot in price, so shop around. The smallest can available will be more than adequate.
Turn the pod assembly back over. Carefully make a small hole in the foam rubber and insert the expanding foam applicator tube. Squirt the foam into the cavity between the MDF backing and the stretched foam rubber, gradually filling the void. Note that the spray stuff expands heaps, so don't overdo the fill.
Use your other hand to move the liquid foam around inside the cavity, making sure that the space is evenly filled, right to the edges of the MDF. At this point you can shape the foam and push it where you want.
Once you've done one end, move to the other end. Make another small hole and then start injecting foam around the rim of the speaker (or where the speaker will go, anyway!). Don't let the expanding foam spill over into the speaker hole.
Over the next hour or so keep a close watch on the pods. (Do both at the same time - otherwise the stuff in the spray can applicator tube goes hard.) If (when!) the pod starts to expand too much, gently press down with both hands. This will initially force some of the stuff out through the applicator holes (no problems) and then later internally compress the foam. Be ultra careful at this point - it's easy to put permanent dents into the still-hardening foam.
Once the foam has gone hard, use a sharp knife to cut off the surplus expanding foam sticking out from the applicator holes. You can then cover the door pod with carpet - a stretch carpet called Meltrim (available from auto trimmers) has been used here. The door pods are so small that you can probably get a carpet offcut for nothing. The carpet is applied in much the same way as the foam rubber was - stretched over the pod and then carefully tacked into place on the back. Note that here the spacer ring has been held in place with screws inserted from the back.
The finished product! With this speaker system, the grille retaining ring is placed on the pod first, with the speaker fitted through that. The grille is then pushed into place. Oh yeah - before you can insert the speaker, you first need to cut out the circle of carpet and foam rubber from the speaker hole! The pod can then be screwed to the door, making sure that there is a hole in the trim behind the speaker so that the door cavity can still act as a speaker enclosure.