THE 914 STEALTH SUBWOOFER KIT

For years we 914 owners suffered tinny stereo sound, as the air tubes behind the factory speaker grilles absorbed any bass the speakers could produce. Door speakers solved this problem - but who wanted to cut holes in pristine factory door panels? Finally a solution! Using the original foam block hidden behind the passenger bulkhead carpet, we have engineered a setup that provides the best bass, while hiding neatly behind the factory carpeting for a clean concours look!

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Instructions and illustrations by Automobile Atlanta’s own Rolf Kittlitz, 2004
    Parts List:
  • Panel #1: 1/4” thick masonite board, pre-cut
  • Panel #2: 3/4” thick M.D.F. board, pre-cut
  • 18 drywall screws (1 & 1/4”)
  • Hard foam foot rest with pre-cut hole (use Panel #1 as template)
  • 8” subwoofer
  • Amplifier
  • Set of instructions and illustrations
  • Template for cutting foam foot rest
Finally, we figured out a way to get real bass out of your 914’s stereo. For the longest time, if you were a music lover and you drove a Porsche 914, you had to put up with weak, tinny sound from the 4x6 speakers in your beloved car. Some people have tried installing either 5 & 1/4” or 6 & 1/2” speakers in their doors – somewhat of an improvement, but In the process, they ruined their factory door panels.

When I first started working here at “914 World Headquarters,” I played my 1973 914 stereo for Dr. 914. (I had purchased the car here years earlier!) He was amazed at the amount of clean, balanced sound coming from what looked like a completely stock stereo setup. What I didn’t tell him was that this great sound was the result of two years of my own research and development to add a nice subwoofer to a limited area. I had tried an oversized center console with a 10” speaker, as well as a smaller center console with two 6 & 1/2” speakers. These were either too large or provided inadequate sound – and both looked totally non-stock!

Now at last, available through us at Automobile Atlanta, is a subwoofer kit based on my latest prototype: an 8” subwoofer that resides in the passenger’s side floorboard. I have been operating this set up in my own 914 for nearly a year and have been very happy with the results.
  • Added bass impact gives nice, balanced sound to any music style.
  • Complete stealth! Take your removable faceplate off, and park your 914 with the top off. No one can tell you have a high-performance audio system in your car!
  • Takes up only one inch of passenger leg room.
  • Uses the original factory carpet and does not disturb the vintage appeal of your perfect 914.
You will love this product!


INSTALLATION INSTRUCTIONS
We’ll start by assuming a tape or CD player already exists in your dashboard, along with nice aftermarket speakers in the original 4x6 oval enclosures. To provide power to the subwoofer, an amplifier must be installed, as no radio head unit has enough power to drive our subwoofer adequately. Of course, we can supply anything you need to complete the best 914 audio system. (Please see our new, modified factory-look speaker grilles.)

    The Amplifier
  • Amplifiers need to be installed where there is plenty of cooling air and no vibrations. We suggest mounting it on the bulkhead in front of the gas tank. You can also mount a CD stacker here. Try using the small, self-tapping sheet metal screws (about 5/8” to 3/4” with a small drill-bit-like tip) and a cordless drill with a Phillips bit. Be careful; do not drill or screw into the gas tank! Check the clearance before doing anything. Mark the locations for the mounting holes, and then pre-drill the holes with the screws (with your pretty, new amplifier out of the way, so you don’t scratch it!) Remove the screws and mount the amplifier with them. The factory bulkhead carpet helps dampen vibrations as well. For you concours types, you can mount the amplifier (as well as a CD changer) in a case made of factory-match trunk carpet.

    Neatly install the following wires to ground your system:
  • Power wire – must lead directly from the battery to the amplifier. Our enclosed kit provides a wire of sufficient thickness for the power it needs to support. Remember to install the fuse holder within the first few inches of the power wire, and use rubber grommets when passing the wire through any holes in the sheet metal (engine compartment to passenger compartment, passenger compartment to trunk).
    If you route the power line correctly, there is no need to drill any holes in your precious 914. Starting at the battery (and remember: do not connect to the battery until the complete system is installed!), run the power cable down along the front shelf (along with the original factory harness), beside the bulkhead harness, and into the top center tunnel well under the center armrest and center tunnel carpet. Finally, route the cable under the passenger bulkhead carpet and out the antenna hole behind the original radio. In the trunk, use the same hole that the windshield washer pressure hose uses (the air line from the spare tire) to pass under the gas tank and through the bulkhead.
  • Ground wire – must not exceed 18 inches. Make sure it has good contact with bare metal. An eyelet on the end and another self-tapping screw work well here.
  • Remote turn-on lead – (the blue, small-diameter wire.) This wire goes from the radio head unit to the amplifier and tells the amplifier to turn on and off, so your battery doesn’t run down.
  • Low level leads (AKA high impedance leads) – This paired cable plugs into the radio head unit, and the other end goes into the amplifier. This transmits the music to the amplifier at a low power and distortion level. Remember to keep the left and right cables separated.
  • Speaker wires – You may have a single-channel amplifier (only has outputs for one subwoofer), or a multi-channel amplifier (has speaker outputs for the subwoofer and the mid-range/high-frequency speakers). In either case, always consult the component’s instructions manual. (See Illustration #3.)
  • Make sure you read, thoroughly, all the instruction manuals for all the stereo components you purchase. Don’t forget to fill out any warranty cards and send them to their respective manufacturers.
    The 914 Stealth Subwoofer
  1. Carefully remove the four Phillips screws, securing the right side 4x6 oval speaker panel, and unplug the speaker.
  2. Next, peel up the carpet in the passenger’s floor board – both the carpet lying flat on the floor and that on the inclined foot rest (on cars with a moveable passenger seat. Early 1970-early 1972 914 and 914-6 owners can call us to obtain the appropriate parts.)
  3. Pull out the hard foam footrest (Jan. 72-76 914s; we can provide this needed part for early 914s) and set aside. Place the speaker template on the face of the foam wedge. Trace around the inside of the circle with a felt-tipped marker. Next, completely hollow out the foam wedge within the circle. This will make room for the back side of the speaker. (See Illustrations #1 and 2.)
  4. Neatly run the speaker wires from the amplifier to the subwoofer. To avoid drilling extra holes again, we suggest using the hole behind the dash radio, where the antenna enters, as well as the hole in the bulkhead, where the washer hose enters the spare tire compartment. Make sure to pay attention to the polarity (+ and -). It should match both the amplifier and the subwoofer.
  5. Spread glue evenly across the face of the foam wedge (we recommend contact cement or weather strip adhesive). An old paint roller may work well here. Finally, mount the pre-assembled speaker panel… It’s that easy! (The protruding screws will help keep the panel in place.)
  6. You will notice that there is no protective grill supplied with the kit. I first tried it with a metal grill in my car, but the carpet buzzed like crazy. Next I glued the carpet to the grill, but this only muffled the sound, as if the subwoofer wasn’t even there. So I simply re-glued the carpet tightly over the subwoofer panel. The tension of the carpet and the fact that the subwoofer is so far recessed protect it from harm, should your passenger unknowingly put his or her feet on it.
  7. After reinstalling the bulkhead carpeting and the 4x6 enclosure, enjoy! With a little tuning of the bass and treble controls and the gain (volume) on the amplifier, you will enjoy rich, full, balanced sound that you never thought possible in the small confines of your 914’s interior.
    Notes:
  • Some fitting may be necessary on 914s with a center console (914s with the appearance group). You may need to cut off a small corner of the plate.
  • For even bigger sound, increase the air space behind the subwoofer by cutting the foam wedge just to the left of where the subwoofer mounting hole is. Discard the larger portion of the foam, using the driver’s side piece (the side toward the center of the car) for bracing and to make the carpet lie correctly. Use silicone caulking all the way around the enclosure to seal and hold it in place. This is how I have mine installed.
  • If you have questions concerning wiring, consult a local automotive stereo shop, or make an appointment and bring your 914 to Automobile Atlanta for installation.
  • Make sure your amplifier has a “low-pass” crossover for subwoofers.
  • A small piece of old carpet or soft foam padding (about 8x8”) glued to the floor and bulkhead underneath the subwoofer’s magnet will help keep it from vibrating. The magnet is very close to the chassis here.