Car Audio

Note: This guide was written for someone who has very little experience in car audio wiring. Please don’t be insulted at the level of detail I go into here. For you audiophiles out there, remember, you were once a beginner as well.

Head Units

First, lets talk about head units (cd players etc.) Your head unit should be able to play the type of media you most want to use. If you want to use CD’s, get a CD player. If you want to play mp3 CD’s (data CD’s full of .mp3 music files), make sure your head unit supports that. If you want to plug in your iPod or other mp3 player, your head unit should have an Auxiliary Input or something that supports your mp3 player. I believe Alpine now offers iPod compatible head units.

Of course, the more features you want in a head unit, the more you must be willing to spend. If you just want a CD player, that’s cheap. If you want a high-powered unit with iPOD support, XFM Satellite Radio, independent subwoofer controls, and a flip-down face that plays little videos, expect to pay a lot more. Generally, a basic CD player can be had for $100-200, while an absolute top of the line head unit might cost upwards of $1000 (USD).

When choosing a head unit, there are a many, many details to consider, but here are what I consider the important ones. 1) RMS power. A cheaper unit will have 15-17 Watts RMS power. If you’re an old man who doesn’t listen to music very loud, this will be fine. If you want your 240 to be a mobile party machine (meaning that you can roll down the windows and open the trunk and have enough volume to DJ a party of 300 people) you will need more power to your speakers.

This can be accomplished two ways: 1) a high-powered head unit, or 2) a separate amplifier to power your speakers. A unit with say, 22-25 Watts RMS will be good for this, but with this much power, you must be sure your speakers can handle it. The second option is a bit more challenging (i.e. you need to find a place to mount the amplifier and run a lot more wires here and there) but if you really need the volume, go for it. I have a high-powered head unit, and I have no problem with the mobile party machine scenario.

Another important decision when choosing a head unit is if it has built in, adjustable frequency filters, or “Crossovers.” A crossover allows certain frequencies of sound to get to the speakers while blocking others. Humans can hear from about 20 Hz – 20,000 Hz. A Low-Pass Filter allows frequencies below a certain setting (say, 60 Hz and below) to reach the speakers. A High-Pass filter allows frequencies above a certain setting (say, 60 Hz and above) to reach the speakers. In a typical setup, a Low-Pass filter will be setup for the Sub-Woofer (a large speaker dedicated to making bass) and a High-Pass filter will be setup for the rest of the speakers.

Making bass requires a lot of wattage, so when regular speakers do not have to replicate bass tones, they are more efficient and can be played at a higher volume without risking damage or distortion of the music.

That said, you can get both internal crossovers (built into the head unit and controlled from the head unit) or external crossovers, which have to be mounted in the speaker wire between the head unit and the speakers. External crossovers have their advantages, but for most applications, they are a pain in the but. The important message here is, if you’re going to put a subwoofer in your system, get a head unit with built in crossovers. If not, then don’t worry about the crossovers.

A third important decision when buying a head unit is if you’re going to run any external amplifiers. An external amp runs off of the car’s battery and gets its audio signal from the head unit through “RCA” patch cables, which are the red and white cables that most TV’s and VCR’s accept. If you’re going to have external amps, make sure to get a unit that has “Pre-amp Outputs.” If you’re going to have a subwoofer, make sure it has a specific Subwoofer Pre-amp Out, or Subwoofer Out. Running a subwoofer off of regular Pre-amp Outputs that were designed for speakers is a bad idea.

So, here’s a checklist for buying a head unit:

  • Media format (CD, .mp3 CD, iPOD, cassette, satellite radio)
  • RMS power (15-17 Watts, 22-25 Watts, none if you’re using external amps only)
  • Crossovers (if you’re using a sub or planning on one later, you need ’em)
  • Pre-Amp Outs, Subwoofer Outs
  • Line inputs for plugging in a device such as an mp3 player

A word on brand names: Honestly, you get what you pay for in most cases. With some brands, like Sony, you are paying for the brand name to some degree. For car stereos, I highly recommend Alpine. I have had my Alpine for over 4 years now, and I’ve never had a single problem with it. My Sony had some problems with the click wheel, and I had to send my Pioneer back to the factory because it simply stopped working one day. This isn’t to say that Sony and Pioneer make inferior products, just that I would not buy one again after having my Alpine. Kenwood, Panasonic, and Clarion are good brands as well. Generally, Aiwa, Blaupunkt, JVC, and Sanyo make less expensive units of somewhat questionable quality, but hey you never know. The best thing to do is probably get a Consumer Reports article on car stereos at your local library if you’re interested.

Now, lets talk about getting that head unit into your 240 (1981-1993 style dashboard)! There are two places you can mount a head unit. The first is above the center console where the dash pocket (or turbo gauge cluster) is, to the right of the instrument panel. The second location (which I use) is at the bottom of the center console, right in front of the gear selector and below the ashtray. Each location has its advantages and disadvantages.

Top of Center Console Bottom of Center Console
* Nothing in the way * Gear Selector in the way
* Longer reach distance * Shorter reach distance
* Easier to see by thieves * Harder to see by thieves
* Display shaded by dash (good) * Display may be washed out by sun
Either way, you will be installing a standard size unit, known as size I, E or J. These are all the same size now-a-days. Don’t get a GM-Chrysler Perfect Fit, since it won’t fit easily and these units have a lousy resale value. No one uses the “shaft style” size anymore unless you are playing cassettes, so don’t get that size either. Finally, a “Double” I, E, or J size is available, which is about twice the size of a normal CD player. This size is found in many Toyota’s, but it won’t fit in your 240 without some *heavy* dashboard modding.

You will need an adapter to fit your head unit into the pocket. An adapter for the IEJ units is available from Crutchfield for $20 for the upper-dash opening, or for $15 for the lower-dash opening. (check under the Car Audio Accessories Section, then go to Receiver Installation, then Vehicle-specific Mounting Kits, or just call ’em up and ask for it.) Also, if you buy your receiver from Crutchfield, the appropriate mounting kit is included free. I have bought several thousand dollars of stereo equipment from these guys, and they’re great. They even gave me a free 1-year subscription to Car and Driver.

Mounting Kits:

Lower (upside down in photo) at left – Upper at right

After you get this, you are ready to install your unit. Please follow the directions in your manual. Wiring a car stereo is not hard at all, but please make sure to do these things:

  • Wire the head unit’s power cables to the fuse block using spade connectors. Don’t just splice them into some random wire; this can cause a lot of problems.
  • Choose a good solid ground point for the unit (there are tons of them on 240s)
  • When you connect two wires together, it is best to solder the ends together and then use heat-shrink tubing around the connection to protect it. The second best way is to use male and female connectors (a male on one wire and a female on the other wire) like spade connectors or bullet connectors. These are especially useful if you want to be able to easily disconnect wires later. The third best way is to use butt-connectors and heat-shrink tubing.
  • DON’T just twist the ends of the two wires together and call it good. You could short out your head unit and permanently damage it. Male/female connectors or butt connectors are cheap and easy to use.
A general order to follow when running wires:
  1. Run all of the wires into the pocket where you will install the head unit first. That is, run the wires from the speakers into the pocket. Run the wires from the fuse block into the pocket. Run the ground wire and any amplifier connections into the pocket. Find your FM antenna wire (thick and black, built into the car) and run it into the pocket if it’s not already there. Label things as you run them if need be.
  2. Unplug the wiring harness from the head unit if you can. It should be a big plastic plug that connects into the back of your head unit with a bunch of colored wires coming out of the back.
  3. Make all the wire-to-wire connections between your head-unit-wiring-harness and all the wires you ran into the pocket. If you need to, label everything as you run it into the pocket to keep things straight.
  4. Plug your wiring harness into the head unit, along with the FM antenna wire and any patch cables etc.
  5. See if it turns on and works before you put your dash back together.


Well, your 240 has speaker locations as follows: One 4″ round speaker in each front door, and two 4″ round speakers in the back dash. If you have a wagon, then you also have 4″ round speakers in the wall by the back seat. Newer wagons have the speakers in the rear doors instead; I am not sure when this change occured. Four-inch speakers are small and have very little bass response, and you’ll need custom mounting brackets to get aftermarket 4″ speakers to fit in your car.

Sounds bleak eh? Well, first off, if you order your speakers from Crutchfield, they’ll give you the mounting brackets for free. At least, for 1982+ models. If you have a 1981 240, you’ll need to get some 1982+ style speaker grills for the front (they are about twice as thick as the 1981 style.)

Second, if you have a sedan, your back dash can be modified to fit 6″ x 9″ oval speakers, some of the largest available, 6.5″ circular speakers, or many other sizes. However, to fit these, you will have to cut through metal (using some big tin snips or a hacksaw) as well as your rear dash material. My tan car and my former blue car (both 1981 240 DL’s) both had the 6×9 modification already done, so I’ve never actually done it myself. On my red car, I just stuck with the stock speaker size.

Of course, speakers need wire. If you’re going to do it right, I would recommend running new speaker wire to all of your speakers and disconnecting or removing the Volvo factory-installed wire. These old wires were not designed to be very high-performance compared to what is available today. The good news is that speaker wire is pretty cheap. The bad news is that wiring it will take you some time.

Wiring the doors:

  1. Take the door panels off.
  2. Take the kick panels off (the plastic panels next to your feet when you drive. The driver’s side kick panel probably has a vent in it, you can remove the rubber stopper from the vent lever by pushing the metal pin out of it vertically. There may also be a plastic push-in clip at the back of the driver’s kickpanel.
  3. You will need to take off the black plastic lower door sills that you step on as you get in the car. Just pull up and they’ll pop off.
  4. Take the fuzzy black dust-protectors off from underneath the dash on each side. Each one should have five black plastic turn-clip things.
  5. DISCONNECT THE BATTERY before you mess around with the fuse block!
  6. On the drivers side, unscrew the fuse block and move it out of the way, making sure not to disconnect any wires. It is held in by two phillips screws.
  7. Take the door panels off. This involves a lot of steps. First, unscrew the lock knob. Then pop out the round rubber plugs in the armrests and unscrew the phillips-head screws inside. If you have power windows, there is a third phillips screw at the front of the armrest. Rotate the armrest up or down until it comes out at the top. Don’t force it. Pop off the plastic trim ring around the handle that opens the door. If you have manual windows, pry off the plastic clip on the window crank with a flathead screwdriver and then take the crank off with a phillips screwdriver. For the door pockets (map pockets) there are three plastic flathead “screws” that hold them on. Turn them 90 degrees to loosen them. Lift up on each corner of the map pocket to get it off of the screws. Be careful not to break anything. Now remove the map pocket from the door and unscrew the two phillips screws that hold on the plastic things that the map pocket clips to. Now, get a get a flathead screwdriver and “pop” the door panel clips out of the sheet metal. They are all at the edges of the door panel. Be careful here, it is easy to break the clips or tear the door panel fiberboard. Once everything is free, lift up, and the panel should come off.
  8. You should now be able to run wires from inside the doors (where the speakers will be mounted) through the rubber sleeve that runs between the door and the car, and into the pocket where your head unit will be located.
  9. Make sure to use zip ties to keep the wires tied up under the dash and from moving around in the door panels.
  10. Check that your wires in the doors don’t get in the way of moving your windows up and down.
  11. Wire the speakers (put spade connectors on the ends of the wires and attach them to the appropriate terminals)
  12. Wire the head unit (attach the appropriate wires to the appropriate wires in your head unit as described above in the head unit wiring section – check you head unit manual for more information)
  13. Double-check to make sure your speakers are wired properly! (+) goes to (+) and (-) goes to (-), from the speaker to the head unit.
  14. Mount your speakers on the door panels and put everything back together.
Wiring the back dash:
  1. Remove either the right or left kick panels. You are going to run the wires underneath the carpet, so pick a side to work on. The passenger’s side is a bit easier because there is no fuse block.
  2. Remove the fuzzy dust-protector from under the dash.
  3. Remove the black plastic molding from the door jam(s). This is on the bottom of the door jam and is where you would step if you were getting into the car. Just tug on it gently and it will pop off.
  4. Remove the rear seat. First, stick your hand in the crack and pull up on the back of the lower cushion. It should come up fairly easily. Remove it from the car. Second, look at the bottom part of the upper cushion near the right and left doors. There are two bendable metal clasps. Detach them and remove the upper part of the rear seat from the car, or just detach them and leave the seat-back in.
  5. This is a good time to vacuum under where the seat normally goes.
  6. Run speaker wires from the trunk into the cabin so that it will be under the bottom part of the back seat.
  7. Run the wires under the carpet on the right side of the vehicle. Depending on your car, you may have to unbolt seat belts and push and pull on carpet a lot to get the wires where you want them. I had to unbolt the front seatbelt so that I could get the wires down below where the bolt goes through the carpet. Be careful here, and make sure to re-attach the seatbelt when you’re done
  8. Run the wires up under where the kick-panel goes, up under the glove box (or steering wheel) and then into the pocket where your head unit will be.
  9. Drop your speakers in the holes in the rear dash and bolt or screw them down.
  10. Use spade connectors on the ends of your wires to attach them to the speaker terminals. Again, observe proper (+) and (-) orientation; don’t get the wires mixed up. To be safe, I mark the wires with a Sharpie or with tape so I won’t get confused.
  11. Put everything back together.

Wiring the back speakers in a wagon is similar, except you don’t have to remove the rear seat. Rather, you just run the speaker wires under the carpet and up into the little pockets below the C-pillars. If your wagon has speakers in the doors, wiring the rear doors is going to be similar to wiring the front doors.

I recently installed a CD player, two 4″ speakers in the doors, and two 6×9″ speakers in the rear deck of The Blue Car. We ran fresh wires for everything, basically as I have described above. My friend went with medium quality components, using a Sanyo CD-Player with Line-in ($130 on sale at Wal-Mart) and Pioneer 4″ and 6×9″ speakers. All told, including wire and stuff, the bill came to about $300 USD. Including the time it took to drive to 2 different Wal-Marts and another audio store, it took us about seven hours to complete.

A Few Words on Amplifiers and Subwoofers

You can do a lot with subwoofers, like annoy your neighbors and get your car broken into repeatedly. No really, they can be fun, but here are some things to consider.

  • Subwoofers are expensive, and it’s easy to hear if you have one. You probably want to get a security system for your car.
  • All you need is a screwdriver and a crescent wrench to open the trunk of almost any car, including 240’s. To prove it, just get a big flathead screwdriver with a square shaft. Jam it in the trunk lock of a car at a junkyard. Put the crescent wrench on the shaft of the screwdriver and turn it. Abracadabra, the trunk lock has been easily forced open in under 30 seconds. Get a security system and garage your car.
  • You probably should bolt down your subwoofer and amplifier(s) as well, not only to prevent theft but to keep them from sliding around.
  • The sub should go in the trunk of your 240, against the back seat.
  • 240’s are Rear Wheel Drive, so they have little trunk space next to the back seat. Make sure your subwoofer box will fit.
  • The sub you select should be able to take more than the amp can dish out. For example, if your amp supplies 300W RMS and 900W peak, you sub should be rated for something like 350W RMS and 1000W peak.
  • You can mount most amps under the front seat(s) of 240’s. This saves on wiring costs (RCA patch cables from head unit to amp are more expensive than speaker cables from the amp to the sub).
  • Wire the amp power cable directly to the (+) battery terminal. The thickness of the wires you use will depend on how powerful the amp is. You can buy whole kits to do this at many audio stores.
  • You may need to buy a bigger/better battery for your car to supply the necessary juice to power a sub.